Patent Publication Number: US-2022227086-A1

Title: Injection molding system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation in part of U.S. application Ser. No. 17/147,417 filed Jan. 12, 2021, which is a non-provisional of U.S. Application No. 62/992,764 filed Mar. 20, 2020 each of which are hereby incorporated by reference as if fully cited herein. 
    
    
     TECHNICAL FIELD 
     The present invention is related to an injection molding system and an injection molding method, and, in particular, to an injection molding system and a method of injection molding for injecting molding an article including a plurality of layers. 
     BACKGROUND 
     Foamed polymeric material has many advantages, such as high strength, low weight, impact resistance, thermal insulation, and others. Foamed articles can be made by injection molding or extrusion molding. For example, after the polymeric material is melted and mixed with a blowing agent to form a mixture, a force or pressure is applied to the mixture to inject or extrude the mixture into a cavity of a mold, and the mixture is foamed and cooled in the cavity to form the foamed article. 
     However, it is necessary to improve the properties of the foamed article made by the injection molding system, such as causing different portions of the foamed article to have different properties. Therefore, there is a need for improvements to structures of the injection-molding system and the method for making foamed articles. 
     BRIEF SUMMARY OF THE INVENTION 
     One purpose of the present invention is to provide an extruding system and a method of extruding a mixture. 
     According to one embodiment of the present disclosure, an injection molding method is disclosed. The injection molding method includes providing a molding device including a first mold, a second mold over the first mold and a first mold cavity defined by the first mold and the second mold; injecting a first material into the first mold cavity; forming a first layer from the first material; replacing the second mold by a third mold; injecting a second material into a second mold cavity defined by the first mold and the third mold; and forming a second layer from the second material, wherein the second layer at least partially contacts the first layer. The first material is same as the second material. 
     According to one embodiment of the present disclosure, an assembly of polymeric components is disclosed. The assembly of polymeric components includes a first polymeric component and a second polymeric component. The second polymeric component is directly attached to the first polymeric component. A material of the first polymeric component is same as a material of the second polymeric component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a flowchart illustrating an injection molding method according to one embodiment of the present invention. 
         FIGS. 2-13  are schematic cross-sectional views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIGS. 14A-14C  are schematic views illustrating exemplary articles in an injection molding method according to one embodiment of the present disclosure. 
         FIGS. 15-17  are schematic cross-sectional views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 18  is a schematic view illustrating exemplary article in an injection molding method according to one embodiment of the present disclosure. 
         FIGS. 19-22  are schematic cross-sectional views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 23  is a schematic view illustrating exemplary article in an injection molding method according to one embodiment of the present disclosure. 
         FIGS. 24-28  are schematic cross-sectional views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 29  is a schematic view illustrating exemplary article in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 30  is a schematic cross-sectional view illustrating exemplary operation in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 31  is a schematic view illustrating exemplary article in an injection molding method according to one embodiment of the present disclosure. 
         FIGS. 32-36  are schematic cross-sectional views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 37-38  are a schematic views illustrating exemplary articles in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 39  is a flowchart illustrating an injection molding method according to one embodiment of the present invention. 
         FIGS. 40-52  are schematic views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 53  is a flowchart showing a method of injection molding method in accordance with some embodiments of the present disclosure. 
         FIGS. 54-64  are schematic cross-sectional views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 65  is a schematic view illustrating exemplary article in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 66  is a perspective view illustrating an assembly of polymeric components according to one embodiment of the present disclosure. 
         FIG. 67  is a side view of the assembly of  FIG. 66 . 
         FIGS. 68-69  are schematic cross-sectional views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 70  is a schematic view illustrating exemplary article in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 71  is a side view illustrating an assembly of polymeric components according to one embodiment of the present disclosure. 
         FIG. 72  is a perspective and exploded view of the assembly of  FIG. 71 . 
         FIGS. 73-77  are schematic cross-sectional views illustrating exemplary operations in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 78  is a schematic view illustrating exemplary article in an injection molding method according to one embodiment of the present disclosure. 
         FIG. 79  is a side view illustrating an assembly of polymeric components according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in the respective testing measurements. Also, as used herein, the term “about” generally means within 10%, 5%, 1%, or 0.5% of a given value or range. Alternatively, the term “about” means within an acceptable standard error of the mean when considered by one of ordinary skill in the art. Other than in the operating/working examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages, such as those for quantities of materials, durations of times, temperatures, operating conditions, ratios of amounts, and the likes thereof disclosed herein, should be understood as modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the present disclosure and the attached claims are approximations that can vary as desired. At the very least, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Ranges can be expressed herein as from one endpoint to another endpoint or between two endpoints. All ranges disclosed herein are inclusive of the endpoints, unless specified otherwise. 
       FIG. 1  is a flowchart showing a method M 10  of injection molding method in accordance with some embodiments of the present disclosure. The method M 10  includes several operations: (O 101 ) providing a molding device including a first mold, a second mold over the first mold and a first mold cavity defined by the first mold and the second mold; (O 102 ) injecting a first material into the first mold cavity; (O 103 ) forming a first layer from the first material; (O 104 ) replacing the second mold by a third mold; (O 105 ) injecting a second material into a second mold cavity defined by the first mold and the third mold; and (O 106 ) forming a second layer from the second material disposed over the first layer, wherein the first material is different from the second material. 
     In order to illustrate concepts and the method M 10  of the present disclosure, various embodiments are provided below. However, the present disclosure is not intended to be limited to specific embodiments. In addition, elements, conditions or parameters illustrated in different embodiments can be combined or modified to form different combinations of embodiments as long as the elements, parameters or conditions used are not in conflict. For ease of illustration, reference numerals with similar or same functions and properties are repeated in different embodiments and figures. The various operations and the thus formed articles of the injection molding method can be in various configurations as shown in any of  FIGS. 2 to 38 . 
       FIGS. 2 to 5  are schematic cross-sectional views illustrating a first molding device  100  of the operation O 101  of the method M 10  in accordance with some embodiments of the present disclosure. In some embodiments, the method M 10  of injection molding method includes step O 101 , which includes providing a first molding device  100  including a first mold, a second mold over the first mold and a first mold cavity defined by the first mold and the second mold. In some embodiments, a first molding device  100  is provided or received as shown in  FIG. 2 or 3 . In some embodiments, the first molding device  100  is configured to forming an article. In some embodiments, the first mold is a lower mold  102 , and the second mold is a first upper mold  101 . 
     In some embodiments, the first molding device  100  includes the first upper mold  101  and the lower mold  102 . In some embodiments, the first upper mold  101  corresponds to the lower mold  102  in some configurations such as dimension, shape or the like. The first upper mold  101  can be placed on and engaged with the lower mold  102 . In some embodiments, the provision of the first molding device  100  includes conveying the lower mold  102  towards the first upper mold  101 . As such, the lower mold  102  would be disposed under the first upper mold  101  for subsequent steps. In some embodiments, the first upper mold  101  is aligned with the lower mold  102 . In some embodiments as shown in  FIG. 2 , the first molding device  100  is in an open configuration. 
     In some embodiments, the first upper mold  101  includes a protrusion  101   a  protruded from the first upper mold  101 . In some embodiments, the lower mold  102  includes a recess  102   a  indented into the lower mold  102 . The protrusion  101   a  is receivable by the recess  102   a . In some embodiments, the protrusion  101   a  and the recess  102   a  are configured complementary with each other, such that the first upper mold  101  is engageable with the lower mold  102  when the first molding device  100  is in a closed configuration as shown in  FIG. 3 . In some embodiments, a first mold cavity  103 - 1  is formed when the first molding device  100  is in the closed configuration as shown in  FIG. 3 . Although  FIGS. 2 and 3  illustrate only one recess  102   a  at the lower mold  102 , it can be understood that any suitable numbers of the recess  102   a  can be configured at the lower mold  102 . 
     In some embodiments, the first upper mold  101  includes a first passage  101   b  extending through the first upper mold  101 . In some embodiments, the first passage  101   b  is communicable with the first mold cavity  103 - 1  when the first molding device  100  is in the closed configuration as shown in  FIG. 3 . The first mold cavity  103 - 1  is accessible through the first passage  101   b . For simplicity and clarity, only one first passage  101   b  is illustrated, however, it can be understood that any suitable numbers of the first passage  101   b  can be configured at the first upper mold  101 . In some embodiments, the number of the first passage  101   b  is identical to the number of the recess  102   a . In some embodiments, the number of the recess  102   a  is more than the number of the first passages  101   b . In some embodiments, the number of the first passages  101   b  is more than the number of the recess  102   a . In some embodiments, the first passage  101   b  corresponds to the recess  102   a . In some embodiments, each of the first passages  101   b  corresponds to one or more of the recesses  102   a.    
     In some embodiments, instead of configuring the first passage  101   b  at the first upper mold  101 , the first passage  101   b  can be configured at the lower mold  102  for accessing the recess  102   a  or the first mold cavity  103 - 1 . In some embodiments, the first passage  101   b  can be configured at a sidewall of the lower mold  102  or any other suitable positions as long as the first passage  101   b  is communicable with the recess  102   a  or the first mold cavity  103 - 1 . 
     In some embodiments, the first upper mold  101  may not include any protrusion. In some embodiments as shown in  FIGS. 4 and 5 , the first upper mold  101  does not include the protrusion  101   a  as described above or illustrated in  FIGS. 2 and 3 . For simplicity and clarity, only the first molding device  100  having the protrusion  101   a  as shown in  FIGS. 2 and 3  is illustrated for describing the injection molding method below. However, it can be understood that the first molding device  100  without the protrusion  101   a  as shown in  FIGS. 4 and 5  can also be used for the injection molding method described below. 
     In some embodiments, instead of configuring the protrusion  101   a  integrally formed with the first upper mold  101 , a removable plate (not shown) can be used. In some embodiments, the removable plate can be placed between the first upper mold  101  and the lower mold  102  for adjusting a volume of the first mold cavity  103 - 1 . For example, the first mold cavity  103 - 1  would be reduced if the removable plate is inserted into the first mold cavity  103 - 1  and disposed between the first upper mold  101  and the lower mold  102 . In some embodiments, the removable plate is disposed between the protrusion  101   a  and the lower mold  102 . As such, the volume of the first mold cavity  103 - 1  can be adjusted by insertion of the removable plate between the first upper mold  101  and the lower mold  102  when the first molding device  100  is closed. 
     Referring back to  FIG. 2 , at the beginning of the injection molding method M 10 , the first molding device  100  is in the open configuration. The first molding device  100  is then changed to the closed configuration as shown in  FIG. 3 . In some embodiments, the first molding device  100  is closed by applying a first clamping force (not shown) over or around the first molding device  100 . In some embodiments, the first clamping force is continuously applied over the first molding device  100  during formation of the article or for a predetermined period of time. In some embodiments, the first upper mold  101  is tightly engaged with the lower mold  102  when the first molding device  100  is closed. 
     After the closing of the first molding device  100 , the first mold cavity  103 - 1  is formed as shown in  FIG. 3 . The first mold cavity  103 - 1  is configured to hold material and form the article within the recess  102   a . The first mold cavity  103 - 1  is communicable with the first passage  101   b . In some embodiments, the first mold cavity  103 - 1  is sealed when the first molding device  100  is closed. 
       FIGS. 6 to 9  are schematic cross-sectional views illustrating the first molding device  100  of the operations O 102  and O 103  of the method M 10  in accordance with some embodiments of the present disclosure. In some embodiments, the method M 10  of injection molding method includes step O 102 , which includes injecting a first material into the first mold cavity. In some embodiments, the method M 10  of injection molding method includes step O 103 , which includes forming a non-foamed layer from the first material. 
     When the first molding device  100  is closed, a first material  301  is injected into the first mold cavity  103 - 1  through the first passage  101   b  as shown in  FIG. 6 . In some embodiments, the first material  301  is injected into the first mold cavity  103 - 1  from a first injector  201  via a first outlet  201   a  of the first injector  201 . The first material  301  is flowed from the first outlet  201   a  into the first mold cavity  103 - 1  along the first passage  101   b . In some embodiments, the first outlet  201   a  is engaged with the first passage  101   b  upon injection of the first material  301 . In some embodiments, the first outlet  201   a  of the first injector  201  is extendable towards or retractable from the first passage  101   b . In some embodiments, the first material  301  includes thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. In some embodiments, the first material  301  is foamable material or less foamable material. In some embodiments, the first material  301  is non-foamable material. 
     During or after injecting the first material  301  into the mold cavity  103 - 1 , in some embodiments, an external force (not shown) may be applied over the first upper mold  101  or the lower mold  102  to press the first material  301 . In some embodiments, the external force is substantially greater than or equal to 150 Newton (N). In some embodiments, the external force is substantially greater than or equal to 200N. In some embodiments, the external force is applied for a predetermined period of time such as several seconds. In some embodiments, the first molding device  100  is idle for a predetermined period of time such as several seconds for cooling of the first material  301 . As a result, a first layer  301 ′ including the first material  301  is formed within the mold cavity  103 - 1 , as shown in  FIG. 6 . In some embodiments, the first layer  301 ′ is a foamed layer or a less foamed layer. In some embodiments, the first layer  301 ′ is a non-foamed layer. 
     After the formation of the first layer  301 ′, the first injector  201  leaves the first molding device  100 , and the first upper mold  101  is disengaged and withdrawn from the lower mold  102 , as shown in  FIG. 7 . The first outlet  201   a  is also disengaged from the first passage  101   b . The first molding device  100  is changed from the closed configuration as illustrated in  FIG. 6  to the open configuration as illustrated in  FIG. 7 . Further, in some embodiments, the lower mold  102  is conveyed away from the first upper mold  101  as shown in  FIG. 8 . 
     In some embodiments, the lower mold  102  is conveyed in a suitable speed or by a suitable force, such that the vibration of the lower mold  102  during the conveying is minimized or even prevented. Reduction or prevention of the vibration of the lower mold  102  during the conveying allows the first layer  301 ′ stably disposed in the first mold cavity  103 - 1  and temporarily adhered to the lower mold  102 . In some embodiments, the first layer  301 ′ can be firmly attached to the lower mold  102  during the conveying by any suitable mechanism such as a sufficient friction between the first layer  301 ′ and the inner sidewall of the lower mold  102 , a tab (not shown) protruded from the lower mold  102  towards the recess  102   a , etc. Therefore, reliability and quality of the first layer  301 ′ can be improved or increased. 
     Optionally, the lower mold  102  is then conveyed to another station for further treatment. For example, a surface treatment is performed after the formation of the first layer  301 ′. A surface of the first layer  301 ′ would be polished or treated to increase smoothness, or the first layer  301 ′ would be heat treated for activation, or any other suitable treatments. 
     After the formation of the first layer  301 ′ or treatment of the first layer  301 ′, an adhesive  501  is applied on the surface of the first layer  301 ′ as shown in  FIG. 9 . In some embodiments, a second injector  401  is disposed over the lower mold  102 , and the adhesive  501  is dispensed from the second injector  401  through a second outlet  401   a  of the second injector  401  towards the first layer  301 ′. In some embodiments, the second outlet  401   a  of the second injector  401  is extendable towards or retractable away from the lower mold  102 . In some embodiments, the first layer  301 ′ is coated with the adhesive  501 . 
       FIGS. 10 and 11  are schematic cross-sectional views illustrating a second molding device  200  of the operation O 104  of the method M 10  in accordance with some embodiments of the present disclosure. In some embodiments, the injection molding method M 10  includes step O 104 , which includes replacing the second mold by a third mold. In some embodiments, the replacement of the second mold includes removing the second mold, disposing the third mold over the first mold and moving the first mold towards the third mold to form the second mold cavity. In some embodiments, the second mold is the first upper mold  101 , the first mold is the lower mold  102 , and the third mold is a second upper mold  601 . 
     After the formation of the first layer  301 ′ or the application of the adhesive  501 , the lower mold  102  is conveyed towards another station including a second upper mold  601  as shown in  FIGS. 10 and 11 . In some embodiments, the lower mold  102  at least including the first layer  301 ′ is conveyed towards the second upper mold  601 . The lower mold  102  is disposed under the second upper mold  601  as shown in  FIG. 10 . It can be understood that a second molding device  200  refers to the second upper mold  601  and the lower mold  102 . 
     In some embodiments, the second upper mold  601  corresponds to the lower mold  102  in some configurations such as dimension, shape or the like. The second upper mold  601  can be placed on and engaged with the lower mold  102 . In some embodiments, the provision of the second molding device  200  includes conveying the lower mold  102  towards the second upper mold  601 . As such, the lower mold  102  would be disposed under the second upper mold  601  for subsequent steps. In some embodiments, the second upper mold  601  is aligned with the lower mold  102 . In some embodiments as shown in  FIG. 10 , the second molding device  200  is in an open configuration. 
     In some embodiments, the second upper mold  601  includes a second passage  601   b  extending through the second upper mold  601 . In some embodiments, the second passage  601   b  is communicable with a second mold cavity  103 - 2  when the second molding device  200  is in the closed configuration as shown in  FIG. 11 . The second mold cavity  103 - 2  is accessible through the second passage  601   b . For simplicity and clarity, only one second passage  601   b  is illustrated, however, it can be understood that any suitable numbers of the second passage  601   b  can be configured at the second upper mold  601 . In some embodiments, the number of the second passage  601   b  is identical to the number of the recess  102   a . In some embodiments, the number of the recess  102   a  is more than the number of the second passage  601   b . In some embodiments, the number of the second passage  601   b  is more than the number of the recess  102   a . In some embodiments, the second passage  601   b  corresponds to the recess  102   a . In some embodiments, each second passage  601   b  corresponds to one or more of the recesses  102   a.    
     In some embodiments, instead of configuring the second passage  601   b  at the second upper mold  601 , the second passage  601   b  can be configured at the lower mold  102  for accessing the recess  102   a  or the second mold cavity  103 - 2 . In some embodiments, the second passage  601   b  can be configured at a sidewall of the lower mold  102  or any other suitable positions as long as the second passage  601   b  is communicable with the recess  102   a  or the second mold cavity  103 - 2 . 
     In some embodiments, the second molding device  200  is then changed from the open configuration as shown in  FIG. 10  to the closed configuration as shown in  FIG. 11 . In some embodiments, the second molding device  200  is closed by applying a second clamping force (not shown) over or around the second molding device  200 . In some embodiments, the second clamping force is continuously applied over the second molding device  200  during formation of the article or for a predetermined period of time. In some embodiments, the second upper mold  601  is tightly engaged with the lower mold  102  when the second molding device  200  is closed. In some embodiments, the second clamping force is substantially less than the first clamping force. 
     After the closing of the second molding device  200 , a second mold cavity  103 - 2  is formed as shown in  FIG. 11 . The second mold cavity  103 - 2  is configured to hold material and form the article within the recess  102   a . The second mold cavity  103 - 2  is communicable with the second passage  601   b . In some embodiments, the second mold cavity  103 - 2  is sealed when the second molding device  200  is closed. 
       FIGS. 12 and 13  are schematic cross-sectional views illustrating the second molding device  200  of the operations O 105  and O 106  of the method M 10  in accordance with some embodiments of the present disclosure. In some embodiments, the method M 10  of injection molding method includes step O 105 , which includes injecting a second material into a second mold cavity defined by the first mold and the third mold, the first material is different from the second material. In some embodiments, the method M 10  of injection molding method includes step O 106 , which includes forming a foamed layer from the second material disposed over the non-foamed layer. 
     When the second molding device  200  is closed, a second material  801  is injected into the second mold cavity  103 - 2  through the second passage  601   b  as shown in  FIG. 12 . In some embodiments, the second material  801  is injected into the second mold cavity  103 - 2  from a third injector  701  via a third outlet  701   a  of the third injector  701 . The second material  801  is flowed from the third outlet  701   a  into the second mold cavity  103 - 2  along the second passage  601   b . In some embodiments, the third outlet  701   a  is engaged with the second passage  601   b  upon injection of the second material  801 . 
     In some embodiments, the second material  801  includes expanded thermoplastic polyurethane (ETPU), thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. In some embodiments, the second material  801  is foamable material or highly foamable material. In some embodiments, the second material  801  includes a blowing agent prior to injection from the third injector  701 . In some embodiments, a polymeric material is mixed with the blowing agent to become the second material  801  prior to the injection from the third injector  701 . In some embodiments, the second material  801  is a mixture of the polymeric material and the blowing agent. In some embodiments, the blowing agent can be any type of physical blowing agent known to those of ordinary skill in the art, such as atmospheric gases (e.g., nitrogen, carbon dioxide), hydrocarbons, chlorofluorocarbons, noble gases, or mixtures thereof. The blowing agent may be supplied in any flowable physical state, for example, a gas, liquid, or supercritical fluid. In some embodiments, the blowing agent is in the supercritical fluid state. 
     After injecting the second material  801  into the second mold cavity  103 - 2 , the second molding device  200  is idle for a predetermined period of time such as several seconds for foaming and cooling of the second material  801 . As a result, a second layer  801 ′ including the second material  801  is formed within the second mold cavity  103 - 2 . In some embodiments, the second layer  801 ′ is a foamed layer. 
     In some embodiments, a density of the foamed layer is substantially less than a density of the non-foamed layer. In some embodiments, density of the second layer  801 ′ is substantially less than density of the first layer  301 ′. In some embodiments, an elasticity of the foamed layer is substantially greater than an elasticity of the non-foamed layer. In some embodiments, elasticity of the second layer  801 ′ is substantially greater than elasticity of the first layer  301 ′. In some embodiments, the first layer  301 ′ is harder than the second layer  801 ′. In some embodiments, the second layer  801 ′ has a greater abrasion resistance than the first layer  301 ′. 
     In some embodiments, after the formation of the second layer  801 ′, the third injector  701  leaves the second molding device  200 , and the second upper mold  601  is disengaged and withdrawn from the lower mold  102 , as shown in  FIG. 13 . The third outlet  701   a  is disengaged with the second passage  601   b . The second molding device  200  is changed from the closed configuration ( FIG. 12 ) to the open configuration ( FIG. 13 ). 
       FIGS. 14A to 14C  are schematic cross-sectional views illustrating articles manufactured by the method M 10  in accordance with some embodiments of the present disclosure. As shown in  FIG. 14A , an article  140  at least including the first layer  301 ′ and the second layer  801 ′ is formed. In some embodiments, the article  140  includes a foamed portion (the second layer  801 ′) and a non-foamed portion (the first layer  301 ′). In some embodiments, after the formation of the article  140 , the article  140  is then picked out from the lower mold  102 . In some embodiments, the article  140  is picked out manually by human, or automatically by robot, robotic arm, gripper or the like. In some embodiments, the article  140  is a part of a footwear or a semi-product of a footwear. In some embodiments, the first layer  301 ′ is an outsole of the footwear. In some embodiments, the second layer  801 ′ is a midsole of the footwear. 
     As discussed above, the lower mold  102  may include more than one recess  102   a , and therefore, more than one first mold cavities  103 - 1  are present when the first molding device  100  is closed. As such, more than one first layers  301 ′ can be formed as shown in  FIG. 14B , and the article  140  may include more than one first layers  301 ′. Several first layers  301 ′ are attached to the second layer  801 ′ by the adhesive  501 . 
     In some embodiments, the first material  301  may dispose on bottom and sidewalls of the recess  102   a . In some embodiments, the first injector  201  may inject the first material  301  on the bottom and the sidewalls of the recess  102   a . As a result, the first layer  301 ′ surrounding a portion of the second layer  801 ′ is formed as shown in  FIG. 14C . Therefore, the article  140  may have the second layer  801 ′ at least partially surrounded by the first layer  301 ′. 
     Since all layers (the first layer  301 ′, the second layer  801 ′, etc.) of the article  140  are fabricated by the same lower mold  102 , adhesion between the first layer  301 ′ and the second layer  801 ′ is more secure and improved. Therefore, reliability and quality of the article  140  produced by the above injection molding method M 10  is improved or increased. 
     In some embodiments, the injection molding method M 10  further includes disposing a component within an opening of the third mold prior to the injection of the second material, wherein the component is attached to and disposed over the foamed layer.  FIGS. 15 to 17  are schematic cross-sectional views illustrating a third molding device  300  of the operations O 104  to O 106  of the method M 10  in accordance with some embodiments of the present disclosure.  FIG. 18  is a schematic cross-sectional view illustrating an article  180  manufactured by the method M 10  in accordance with some embodiments of the present disclosure. 
     In some embodiments, the second upper mold  601  is in another configuration such that a component  1000  is attached to the article  180  upon formation of the second layer  801 ′, as shown in  FIGS. 15-18 . In some embodiments, the second upper mold  601  includes an opening  601   a  as shown in  FIG. 15 , and the component  1000  is receivable by the opening  601   a  as shown in  FIG. 16 . In some embodiments, the second passage  601   b  is configured at the lower mold  102  as shown in  FIGS. 15 and 16 , instead of the second upper mold  601 . As such, the second material  801  is injected into a third mold cavity  103 - 3  between the component  1000  and the first material  301  or between the component  1000  and the adhesive  501  as shown in  FIG. 17 , similar to the step as shown in  FIG. 12 . The component  1000  is in contact with the second material  801  during formation of the second layer  801 ′. As such, the component  1000  is attached to the second layer  801 ′ during and after the formation of the second layer  801 ′. As a result, a product or a semi-product including the component  1000  and the article  180  (including the first layer  301 ′ and the second layer  801 ′) is fabricated as shown in  FIG. 18 . In some embodiments, the component  1000  is an insole, a footwear upper or any other suitable component of the footwear. 
       FIGS. 19 to 22  are schematic cross-sectional views illustrating a fourth molding device  400  of the method M 10  in accordance with some embodiments of the present disclosure.  FIG. 23  is a schematic cross-sectional view illustrating an article  230  manufactured by the method M 10  in accordance with some embodiments of the present disclosure. In some embodiments, a fourth molding device  400  is in the closed configuration as shown in  FIG. 19 , a fourth mold cavity  103 - 4  is defined by the first upper mold  101  and the lower mold  102 . The fourth mold cavity  103 - 4  is configured to hold material and form the article within a recess  102   a . The fourth mold cavity  103 - 4  is communicable with the first passage  101   b . In some embodiments, the fourth mold cavity  103 - 4  is sealed when the fourth molding device  400  is closed. 
     In some embodiments, a third material  1101  is injected into the fourth mold cavity  103 - 4  through the first passage  101   b  as shown in  FIG. 20  when the fourth molding device  400  is closed. In some embodiments, the third material  1101  is injected into the fourth mold cavity  103 - 4  from a fourth injector  1100  via a fourth outlet  1100   a  of the fourth injector  1100 . The third layer  1101 ′ is subsequently formed as shown in  FIG. 21 . 
     In some embodiments, the third material  1101  includes thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. In some embodiments, the third material  1101  is foamable material or less foamable material. In some embodiments, the third material  1101  is non-foamable material. In some embodiments, the third material  1101  is similar to the first material  301 . 
     In some embodiments, regarding the operation O 103 , during or after the formation of the third layer  1101 ′, the fourth injector  1100  leaves the fourth molding device  400 . Subsequently, the first upper mold  101  is moved away from the lower mold  102  to form a fifth mold cavity  103 - 5  as shown in  FIG. 21 . In some embodiments, during or after the injection of the third material  1101  into the fourth mold cavity  103 - 4 , the fourth mold cavity  103 - 4  is expanded by moving the first upper mold  101  away from the lower mold  102  to form the fifth mold cavity  103 - 5 . In some embodiments, at least a portion of the protrusion  101   a  is disposed in the recess  102   a  when the fifth mold cavity  103 - 5  is formed. In some embodiments, at least a portion of the protrusion  101   a  is exposed from the lower mold  102  when the fifth mold cavity  103 - 5  is formed. 
     In some embodiments, the first upper mold  101  is movable, while the lower mold  102  is stationary. In some embodiments, the lower mold  102  is moved away from the first upper mold  101  to form the fifth mold cavity  103 - 5 . In some embodiments, the lower mold  102  is movable, while the upper mold  101  is stationary. The movement of the first upper mold  101  or the lower mold  102  can adjust a volume of the fifth mold cavity  103 - 5 . In other words, a thickness T of the third layer  1101 ′ subsequently formed is also adjustable. 
     In some embodiments, the first upper mold  101  is moved away from the lower mold  102  in a first distance D, or the lower mold  102  is moved away from the first upper mold  101  in the first distance D. In some embodiments, the first distance D is different from or same as a thickness T of the third layer  1101 ′. In some embodiments, the first distance D is substantially greater or less than the thickness T of the third layer  1101 ′. In some embodiments, a volume of a fifth mold cavity  103 - 5  is different from or same as a volume of the fourth mold cavity  103 - 4 . In some embodiments, the volume of the fifth mold cavity  103 - 5  is substantially greater or less than the volume of the fourth mold cavity  103 - 4 . In some embodiments, the volume of the fourth mold cavity  103 - 4  is different from or same as the volume of the third layer  1101 ′. In some embodiments, the volume of the fifth mold cavity  103 - 5  is substantially greater or less than the volume of the third layer  1101 ′. The fourth molding device  400  is still in the closed configuration. 
     After the formation of the fifth mold cavity  103 - 5 , a fourth material  1102  is injected into the fifth mold cavity  103 - 5  through the first passage  101   b  as shown in  FIG. 22 . In some embodiments, the fourth material  1102  is injected into the fifth mold cavity  103 - 5  from a fifth injector  1200  via a fifth outlet  1200   a . The fourth layer  1102 ′ is subsequently formed. In some embodiments, the third material  1101  is different from the fourth material  1102 . In some embodiments, the third material  1101  and the fourth material  1102  are different from each other in physical properties such as density, foamability, flexibility, hardness, colors, etc. 
     In some embodiments, the fourth material  1102  includes expanded thermoplastic polyurethane (ETPU), thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. In some embodiments, the fourth material  1102  is foamable material or highly foamable material. In some embodiments, the fourth material  1102  includes a blowing agent prior to injection from the fifth injector  1200 . In some embodiments, a polymeric material is mixed with the blowing agent to become the fourth material  1102  prior to the injection from the fifth injector  1200 . In some embodiments, the fourth material  1102  is a mixture of the polymeric material and the blowing agent. In some embodiments, the blowing agent can be any type of physical blowing agent known to those of ordinary skill in the art, such as atmospheric gases (e.g., nitrogen, carbon dioxide), hydrocarbons, chlorofluorocarbons, noble gases, or mixtures thereof. The blowing agent may be supplied in any flowable physical state, for example, a gas, liquid, or supercritical fluid. In some embodiments, the blowing agent is in the supercritical fluid state. 
     After the formation of the fourth layer  1102 ′, the fifth injector  1200  leaves the fourth molding device  400 , and the fourth molding device  400  is changed from the closed configuration to the open configuration. Finally, as shown in  FIG. 23 , an article  230  at least including the third layer  1101 ′ and the fourth layer  1102 ′ is formed. In some embodiments, after the formation of the article  230 , the article  230  is then picked out from the lower mold  102 . In some embodiments, the article  230  is picked out manually by human, or automatically by robot, robotic arm, gripper or the like. In some embodiments, the article  230  is a part of a footwear or a semi-product of a footwear. In some embodiments, the third layer  1101 ′ is an outsole of the footwear. In some embodiments, the fourth layer  1102 ′ is a midsole of the footwear. In some embodiments, a density of the third layer  1101 ′ is different from a density of the third layer  1102 ′. In some embodiments, the density of the third layer  1101 ′ is substantially higher than the density of the fourth layer  1102 ′. 
       FIGS. 24 to 28 and 30  are schematic cross-sectional views illustrating a fifth molding device  500  of the method M 10  in accordance with some embodiments of the present disclosure.  FIGS. 29 and 31  are schematic cross-sectional view illustrating articles manufactured by the method M 10  in accordance with some embodiments of the present disclosure. 
     In some embodiments as shown in  FIGS. 24-31 , instead of formation of layers stacking over each other as shown in  FIGS. 19-23 , several portions are formed. In some embodiments, the lower mold  102  includes a protrusion  102   b  as shown in  FIG. 24 , and therefore more than one fourth mold cavities  103 - 4  can be formed when the fifth molding device  500  is closed as shown in  FIG. 25 . As a result, the third layer  1101 ′ in more than one portions  1101 ′- 1  and  1101 ′- 2  are formed as shown in  FIG. 26 . In some embodiments, the protrusion  102   b  is insertable or removable, such that numbers and dimensions of the portions  1101 ′- 1  and  1101 ′- 2  are adjustable depending on numbers and dimensions of the protrusion  102   b  inserted into the lower mold  102 . In some embodiments, the portion  1101 ′- 1  and portion  1101 ′- 2  are in similar or different configurations from each other, such as different shapes, physical properties, colors, etc. In some embodiments, volumes of the fourth mold cavities  103 - 4  can be same or different from each other. 
     In some embodiments, the portion  1101 ′- 1  and portion  1101 ′- 2  are formed one by one or simultaneously. In some embodiments, the third material  1101  is injected into one side of the lower mold  102  (one of the fourth mold cavity  103 - 4 ), and then injected into the other side of the lower mold  102  (the other one of the fourth mold cavity  103 - 4 ). In some embodiments, the third material  1101  is injected into the fourth mold cavities  103 - 4 . 
     After the formation of the portions  1101 ′- 1  and  1101 ′- 2  as shown in  FIG. 26 , in some embodiments, the first upper mold  101  is moved away from the lower mold  102  to form the fifth mold cavity  103 - 5  as shown in  FIG. 27 , similar to the way described above or illustrated in  FIG. 21 . In some embodiments, the protrusion  102   b  is removed as shown in  FIG. 27 , so that the fifth mold cavity  103 - 5  extends between two portions  1101 ′- 1  and  1101 ′- 2 . The fifth molding device  500  is still in the closed configuration. 
     In some embodiments, after the formation of the fifth mold cavity  103 - 5 , the fourth material  1102  is injected into the fifth mold cavity  103 - 5  as shown in  FIG. 28 , similar to the way described above or illustrated in  FIG. 22 . In some embodiments, the fourth material  1102  is disposed between two portions  1101 ′- 1  and  1101 ′- 2  and forms the fourth layer  1102 ′. 
     After the formation of the fourth layer  1102 ′, the fifth molding device  500  is changed from the closed configuration to the open configuration. Finally, as shown in  FIG. 29 , an article  290  at least including portion  1101 ′- 1 , portion  1101 ′- 2  and the fourth layer  1102 ′ is formed. In some embodiments, the article  290  is a part of a footwear or a semi-product of a footwear. In some embodiments, the portion  1101 ′- 1  and portion  1101 ′- 2  belongs to an outsole of the footwear. In some embodiments, the fourth layer  1102 ′ is a midsole of the footwear. 
     In some embodiments, in operation O 102  and/or O 105 , the steps of injecting materials into the mold cavity described above or illustrated in  FIG. 21-22 or 26-27  can be repeated to continue stacking layers/portions as shown in  FIGS. 30-31 . In some embodiments as shown in  FIG. 30 , the first upper mold  101  is moved away from the lower mold  102  to form a sixth mold cavity  103 - 6 , and then a fifth material  1103  is injected to the sixth mold cavity  103 - 6 . Finally, a fifth layer  1103 ′ is formed and disposed over the fourth layer  1102 ′ and the portions  1101 ′- 1  and  1101 ′- 2  as shown in  FIG. 31 . In some embodiments, the fifth material  1103  is injected into the sixth mold cavity  103 - 6  from a sixth injector  1300  via a sixth outlet  1300   a . The fifth layer  1103 ′ is subsequently formed. It can be understood that the steps of injecting materials into the mold cavity can be repeated, so that stacked layers/portions can be formed. Numbers of layers/portions are not limited. 
       FIGS. 32 to 36  are schematic cross-sectional views illustrating a sixth molding device  600  of the method M 10  in accordance with some embodiments of the present disclosure.  FIGS. 37-38  are schematic cross-sectional views illustrating articles manufactured by the method M 10  in accordance with some embodiments of the present disclosure. 
     In some embodiments as shown in  FIGS. 32-38 , a component  1104  is initially formed or placed within the lower mold  102 , and then several layers or portions  1101 ′- 1 ,  1101 ′- 2 ,  1102 ′ and  1103 ′ are disposed over the component  1104 . In some embodiments, the component  1104  is initially formed or placed within the lower mold  102  before performing the operation O 102 . In some embodiments as shown in  FIG. 32 , the component  1104  is initially formed or placed. Subsequently, several layers or portions  1101 ′- 1 ,  1101 ′- 2 ,  1102 ′ and  1103 ′ are formed and stacked over the component  1104  as shown in  FIGS. 33-38 . In some embodiments, the component  1104  is an insole, a footwear upper or any other suitable components of the footwear. In some embodiments, the articles  370  and  380  including the component  1104  can be formed as shown in  FIGS. 37-38 . 
     In some embodiments, the molding device  600  is in the closed configuration as shown in  FIG. 33 , a seventh mold cavity  103 - 7  is defined by the first upper mold  101 , the component  1104  and the lower mold  102 . The seven mold cavity  103 - 7  is configured to hold material and form an article within the recess  102   a . The seventh mold cavity  103 - 7  is communicable with the first passage  101   b . In some embodiments, the seventh mold cavity  103 - 7  is sealed when the molding device  600  is closed. 
     In some embodiments, the third material  1101  is injected into the seventh mold cavity  103 - 7  through the first passage  101   b  as shown in  FIG. 34  when the molding device  600  is closed. In some embodiments, the third material  1101  is injected into the seventh mold cavity  103 - 7  from the fourth injector  1100  via the fourth outlet  1100   a  of the fourth injector  1100 . The third layer  1101 ′ is subsequently formed on the component  1104  as shown in  FIG. 35 . 
     In some embodiments, regarding the operation O 103 , during or after the formation of the third layer  1101 ′, the fourth injector  1100  leaves the molding device  600 . Subsequently, the first upper mold  101  is moved away from the lower mold  102  to form an eighth mold cavity  103 - 8  as shown in  FIG. 35 . In some embodiments, during or after the injection of the third material  1101  into the seventh mold cavity  103 - 7 , the seventh mold cavity  103 - 7  is expanded by moving the first upper mold  101  away from the lower mold  102  to form the eighth mold cavity  103 - 8 . In some embodiments, the lower mold  102  is moved away from the first upper mold  101  to form the eighth mold cavity  103 - 8 . The movement of the first upper mold  101  or the lower mold  102  can adjust a volume of the eighth mold cavity  103 - 8 . 
     In some embodiments, a volume of the eighth mold cavity  103 - 8  is different from or same as a volume of the seventh mold cavity  103 - 7 . In some embodiments, the volume of the eighth mold cavity  103 - 8  is substantially greater or less than the volume of the seventh mold cavity  103 - 7 . In some embodiments, the volume of the seventh mold cavity  103 - 7  is different from or same as the volume of the third layer  1101 ′. In some embodiments, the volume of the eighth mold cavity  103 - 8  is substantially greater or less than the volume of the third layer  1101 ′. The molding device  600  is still in the closed configuration. 
     After the formation of the eighth mold cavity  103 - 8 , the fourth material  1102  is injected into the eighth mold cavity  103 - 8  through the first passage  101   b  as shown in  FIG. 36 , and the second layer  1102 ′ is subsequently formed. After the formation of the fourth layer  1102 ′, the fifth injector  1200  leaves the molding device  600 , and the molding device  600  is changed from the closed configuration to the open configuration. 
     Finally, as shown in  FIG. 37 , in some embodiments, an article  370  at least including the component  1104 , the third layer  1101 ′ and the fourth layer  1102 ′ is formed. In some embodiments, after the formation of the article  370 , the article  370  is then picked out from the lower mold  102 . In some embodiments, the article  370  is a footwear or a semi-product of a footwear. 
     In some embodiments, as shown in  FIG. 38 , an article  380  at least including the component  1104 , the portions  1101 ′- 1 ,  1101 ′- 2 , the fourth layer  1102 ′ and the fifth layer  1103 ′ is formed. In some embodiments, the article  380  is a footwear or a semi-product of a footwear. 
       FIG. 39  is a flowchart showing a method M 20  of injection molding method in accordance with some embodiments of the present disclosure. The method M 20  includes several operations: (O 201 ) providing a first carrier and a second carrier disposed adjacent to the first carrier, a first upper mold held by the first carrier, and a second upper mold held by the second carrier; (O 202 ) disposing a first lower mold under the second upper mold; (O 203 ) conveying the first lower mold from the second carrier to the first carrier to dispose the first lower mold under the first upper mold; (O 205 ) forming a first layer from the first material; (O 206 ) conveying the first lower mold holding the first layer from the first carrier to the second carrier to dispose the first lower mold under the second upper mold; (O 207 ) injecting a second material into a second mold cavity defined by the first lower mold and the second upper mold; and (O 208 ) forming a second layer from the second material disposed over the first layer. 
     In order to illustrate concepts and the method M 20  of the present disclosure, various embodiments are provided below. However, the present disclosure is not intended to be limited to specific embodiments. In addition, elements, conditions or parameters illustrated in different embodiments can be combined or modified to form different combinations of embodiments as long as the elements, parameters or conditions used are not in conflict. For ease of illustration, reference numerals with similar or same functions and properties are repeated in different embodiments and figures. The various stages of the injection molding method can be in various configurations as shown in any of  FIGS. 40 to 52 . 
       FIGS. 40 to 49  are schematic top views illustrating an injection molding system  700 . In some embodiments, the injection molding method M 10  as described above or illustrated in  FIGS. 1-38  is implemented by the injection molding system  700 . In some embodiments, the injection molding method M 20  is implemented by the injection molding system  700 . 
       FIG. 40  is a schematic top view illustrating an injection molding system  700  of the operation O 201  of the method M 20  in accordance with some embodiments of the present disclosure. In some embodiments, the method M 20  of injection molding method includes step O 201 , which includes providing a first carrier  1001  and a second carrier  1002  disposed adjacent to the first carrier  1001 , a first upper mold  101 - 1  held by the first carrier  1001 , and a second upper mold  601 - 1  held by the second carrier  1002 . 
     In some embodiments, the injection molding system  700  includes the first carrier  1001  and the second carrier  1002  disposed adjacent to the first carrier  1001 . In some embodiments, the first carrier  1001  and the second carrier  1002  are rotatable about a center C 1  of the first carrier  1001  and a center C 2  of the second carrier  1002  respectively. In some embodiments, the first carrier  1001  and the second carrier  1002  are in an annular shape. In some embodiments, the first carrier  1001  and the second carrier  1002  are turntables. In some embodiments, the first carrier  1001  is rotatable in a direction same as the second carrier  1002 . For example, both the first carrier  1001  and the second carrier  1002  are rotatable in anti-clockwise direction. In some embodiments, the first carrier  1001  is rotatable in a direction opposite to the second carrier  1002 . For example, the first carrier  1001  is rotatable in anti-clockwise direction, while the second carrier  1002  is rotatable in clockwise direction, or vice versa. For simplicity and clarity,  FIGS. 40-49  show that the first carrier  1001  is operated anti-clockwisely, while the second carrier  1002  is operated clockwisely. However, it can be understood that the first carrier  1001  can be operated in a direction same as or opposite to the second carrier  1002 . 
     In some embodiments, the first carrier  1001  includes several first holders  1001   a  for holding a molding device or a part of the molding device. It is readily understood that the first carrier  1001  can include any suitable number of first holders  1001   a . In some embodiments, each of the first holders  1001   a  can hold the corresponding first upper mold  101 . For example as shown in  FIG. 40 , three first upper molds  101 - 1 ,  101 - 2  and  101 - 3  are held by three first holders  1001   a  respectively. In some embodiments, the number of the first holders  1001   a  is more than or equal to the number of the first upper molds  101 . In some embodiments, the first upper mold  101  is in configuration similar to the one described above or illustrated in  FIGS. 2-7 . 
     In some embodiments, the first injector  201  is disposed over the first carrier  1001 . In some embodiments, the first injector  201  is in configuration similar to the one described above or illustrated in  FIG. 6 . In some embodiments, the first holders  1001   a  pass under the first injector  201  one by one upon rotation of the first carrier  1001 . In some embodiments, the first injector  201  is fixedly installed over the first carrier  1001 . The first carrier  1001  is movable relative to the first injector  201 , and the first injector  201  is stationary relative to the first carrier  1001 . In some embodiments, the first injector  201  is configured to inject the first material  301  from the first outlet  201   a  towards the first upper mold  101 . 
     In some embodiments, the second carrier  1002  includes several second holders  1002   a  for holding a molding device or a part of the molding device. It is readily understood that the second carrier  1002  can include any suitable number of second holders  1002   a . In some embodiments, each of the second holders  1002   a  can hold the corresponding second upper mold  601  and the lower mold  102 . For example as shown in  FIG. 40 , three second upper molds  601 - 1 ,  601 - 2  and  601 - 3  and three lower molds  102 - 1 ,  102 - 2  and  102 - 3  are held by three second holders  1002   a  respectively. In some embodiments, the number of the second holders  1001   a  is more than or equal to the number of the second upper molds  101  and the number of the lower molds  102 . In some embodiments, the number of the second upper molds  601  is identical to the number of the lower molds  102 . In some embodiments, the second upper mold  601  is in configuration similar to the one described above or illustrated in  FIGS. 10-13 . 
     In some embodiments, the second injector  401  is disposed over the second carrier  1002 . In some embodiments, the second injector  401  is in configuration similar to the one described above or illustrated in  FIG. 9 . In some embodiments, the second holders  1002   a  pass under the second injector  401  one by one upon rotation of the second carrier  1002 . In some embodiments, the second injector  401  is fixedly installed over the second carrier  1002 . The second carrier  1002  is movable relative to the second injector  401 , and the second injector  401  is stationary relative to the second carrier  1002 . In some embodiments, the second injector  401  is configured to dispense the adhesive  501  from the second outlet  401   a  towards the lower mold  102 . 
     In some embodiments, the third injector  701  is disposed over the second carrier  1002 . In some embodiments, the third injector  701  is in configuration similar to the one described above or illustrated in  FIG. 12 . In some embodiments, the second holders  1002   a  pass under the third injector  701  one by one upon rotation of the second carrier  1002 . In some embodiments, the third injector  701  is fixedly installed over the second carrier  1002 . The second carrier  1002  is movable relative to the third injector  701 , and the third injector  701  is stationary relative to the second carrier  1002 . In some embodiments, the third injector  701  is configured to inject the second material  801  from the third outlet  701   a  towards the lower mold  102 . In some embodiments, the third outlet  701   a  of the third injector  701  is extendable towards or retractable away from the lower mold  102 . 
     Initially, as shown in  FIG. 40 , the method M 20  includes operation O 201 , which includes providing a first carrier  1001  and a second carrier  1002  disposed adjacent to the first carrier, a first upper mold  101 - 1  held by the first carrier  1001 , and a second upper mold  601 - 1  held by the second carrier  1002 . Further, the method M 20  includes operation O 202 , which includes disposing the first lower mold  102 - 1  under the second upper mold  601 . For simplicity and clarity, only three first upper molds  101 - 1 ,  101 - 2 ,  101 - 3  are held by the first holder  1001   a , and three second upper molds  601 - 1 ,  601 - 2 ,  601 - 3  and three lower molds  102 - 1 ,  102 - 2 ,  102 - 3  are held by the second holder  1002   a . In some embodiments, the lower molds  102 - 1 ,  102 - 2  and  102 - 3  are disposed under the second upper molds  601 - 1 ,  601 - 2  and  601 - 3  correspondingly. It can be understood that each first holder  1001   a  can hold one first upper mold  101 , and each second holder  1002   a  can hold one second upper mold  601  and one lower mold  102 . 
     Subsequently, as shown in  FIG. 41 , in some embodiments, the method M 20  includes operation O 203 , which includes conveying the first lower mold  102 - 1  from the second carrier  1002  to the first carrier  1001  to dispose the first lower mold  102 - 1  under the first upper mold  101 - 1 . In some embodiments, the lower mold  102 - 1  disposed opposite to the first injector  201  is conveyed to the first holder  1001   a  under the first injector  201 . In some embodiments, the lower mold  102 - 1  is conveyed from the second holder  1002   a  to the first holder  1001   a  disposed opposite to the second holder  1002   a  by a conveying mechanism such as rollers, conveying belts or the like. In some embodiments the second holder  1002   a  holding the lower mold  102 - 1  is aligned with the first holder  1001   a  holding the first upper mold  101 - 1  during the conveying of the lower mold  102 - 1 . 
     After the conveying of the lower mold  102 - 1  from the second holder  1002   a  to the first holder  1001   a , the first molding device  100  now refers to the first upper mold  101 - 1  and the first lower mold  102 - 1 . The first molding device  100  is in configuration as described above or illustrated in  FIG. 2-3 or 4-5 . After the conveying of the lower mold  102 - 1  from the second holder  1002   a  to the first holder  1001   a , the first upper mold  101 - 1  at the first holder  1001   a  is engaged with the lower mold  102 - 1 . As such, the first molding device  100  is changed from the open configuration to the closed configuration, similar to the way described above or illustrated in  FIG. 2-3 or 4-5 . 
     In some embodiments, the method M 20  includes operation O 204 , which includes injecting a first material  301  into a first mold cavity  103 - 1  defined by the first lower mold  102 - 1  and the first upper mold  101 - 1 . In some embodiments, during or after the closing of the first molding device  100 , the first material  301  is injected towards the lower mold  102 - 1  into the first mold cavity  103 - 1  from the first injector  201  via a first outlet  201   a  of the first injector  201 , similar to the way described above or illustrated in  FIG. 3 . In some embodiments, the first material  301  is non-foamable material. 
     The method M 20  includes operation O 205 , which includes forming a first layer from the first material  301 . During or after injecting the first material  301 , an external force is applied over the first upper mold  101 - 1  or the lower mold  102 - 1  to press the first material  301 . In some embodiments, a duration for formation of the first layer  301 ′ (total time of injecting the first material  301 , cooling of the first material  301 , forming of the first layer  301 ′) is less than or equal to 60 seconds. As a result, a first layer  301 ′ including the first material  301  is formed within the lower mold  102 - 1 , similar to the way described above or illustrated in  FIG. 6 . After the formation of the first layer  301 ′, the first injector  201  leaves the first molding device  100 , and the first upper mold  101 - 1  is disengaged and withdrawn from the lower mold  102 - 1 , similar to the way described above or illustrated in  FIG. 6 . The first molding device  100  is changed from the closed configuration ( FIG. 3 ) to the open configuration ( FIG. 6 ). 
     The method M 20  includes operation O 206 , which includes conveying the first lower mold  102 - 1  holding the first layer  301 ′ from the first carrier  1001  to the second carrier  1002  to dispose the first lower mold  102 - 1  under the second upper mold  601 - 1 . In some embodiments, the lower mold  102 - 1  is conveyed from the first carrier  1001  to the second carrier  1002  after the opening of the first molding device  100 , as shown in  FIG. 42 . The lower mold  102 - 1  is conveyed from the first holder  1001   a  back to the second holder  1002   a  of the second carrier  1002  opposite to the first holder  1001   a . In some embodiments, the lower mold  102 - 1  is returned to the second carrier  1002  by a conveying mechanism such as rollers, conveying belts or the like. In some embodiments, the lower mold  102  is conveyed in a suitable speed or by a suitable force, such that the vibration of the lower mold  102  during the conveying is minimized or even prevented. 
     After the conveying the lower mold  102 - 1  back to the second holder  1002   a , the first carrier  1001  and the second carrier  1002  are rotated as shown in  FIG. 43 . In some embodiments, the first carrier  1001  is rotated anti-clockwisely and the second carrier  1002  is rotated clockwisely. In some embodiments, the rotation of the first carrier  1001  results in the first upper mold  101 - 1  moving away from the first injector  201  and the first upper mold  101 - 2  moving towards the first injector  201 . The rotation of the second carrier  1002  results in the second upper mold  601 - 1  and the lower mold  102 - 1  moving towards the second injector  401  or the third injector  701 . After the rotation of the first carrier  1001  and the second carrier  1002 , the first upper mold  101 - 2  is disposed opposite to the second upper mold  601 - 2  and the second lower mold  102 - 2 . 
     In some embodiments, the first carrier  1001  is rotated in a predetermined interval, such as an angular distance between adjacent first holders  1001   a . In some embodiments, the second carrier  1002  is rotated in a predetermined interval, such as an angular distance between adjacent second holders  1002   a . In some embodiments, the first carrier  1001  and the second carrier  1002  are rotated simultaneously and in the same interval. In some embodiments, the first carrier  1001  and the second carrier  1002  are rotated in different speed. 
     After rotating the first carrier  1001  and the second carrier  1002  in the corresponding predetermined intervals, the second lower mold  102 - 2  is conveyed from the second holder  1002   a  to the first holder  1001   a  opposite to the second holder  1002   a , as shown in  FIG. 44 . The conveying of the second lower mold  102 - 2  is in a way similar to the steps described above or illustrated in  FIG. 41 . The second lower mold  102 - 2  is now disposed under the first injector  201 . Subsequently, the first material  301  is injected towards the second lower mold  102 - 2 , similar to the steps as described above or illustrated in  FIG. 6 . After the injection of the first material  301 , the first layer  301 ′ is formed, similar to the steps as described above or illustrated in  FIG. 7 . After the formation of the first layer  301 ′, the second lower mold  102 - 2  is conveyed back to the second holder  1002   a  as shown in  FIG. 45 , similar to the way described above or illustrated in  FIG. 42 . 
     During the conveying of the second lower mold  102 - 2  towards the first carrier  1001  ( FIG. 44 ), the injection of the first material  301  ( FIG. 44 ) from the first injector  201  towards the second lower mold  102 - 2 , the formation of the first layer  301 ′ in the second lower mold  102 - 2  and/or the conveying of the second lower mold  102 - 2  back to the second carrier  1002  ( FIG. 45 ), the first layer  301 ′ in the first lower mold  102 - 1  disposed under the second injector  401  undergoes treatment such as surface treatment or application of the adhesive  501  over the first layer  301 ′, similar to the way as described above or illustrated in  FIG. 9 . In some embodiments, the adhesive  501  is dispensed on the first layer  301 ′ in the first lower mold  102 - 1  during the conveying of the second lower mold  102 - 2  towards the first carrier  1001  ( FIG. 44 ), the injection of the first material  301  ( FIG. 44 ) towards the second lower mold  102 - 2 , the formation of the first layer  301 ′ in the second lower mold  102 - 2  and/or the conveying of the second lower mold  102 - 2  back to the second carrier  1002  ( FIG. 45 ). 
     After the second lower mold  102 - 2  is returned to the second carrier  1002  and the treatment for the first layer  301 ′ in the first lower mold  102 - 1  is accomplished, the first carrier  1001  and the second carrier  1002  are further rotated as shown in  FIG. 46 . 
     After the rotation of the second carrier  1002 , the first upper mold  101 - 3  is disposed opposite to the second upper mold  601 - 3  and the third lower mold  102 - 3 , as shown in  FIG. 46 . The conveying of the third lower mold  102 - 3  from the second carrier  1002  to the first carrier  1001  as shown in  FIG. 47 , the injection of the first material  301  towards the third lower mold  102 - 3  by the first injector  201  as shown in  FIG. 47 , the formation of the first layer  301 ′ in the third lower mold  102 - 3  and the conveying of the third lower mold  102 - 3  back to the second carrier  1002  as shown in  FIG. 48  are performed in the way similar to steps as described above or illustrated in  FIGS. 41 to 45 . 
     After the rotation of the second carrier  1002 , the second upper mold  601 - 2  is disposed above the lower mold  102 - 2  as shown in  FIG. 46 . During the conveying of the lower mold  102 - 3  towards the first carrier  1001  ( FIG. 47 ), the injection of the first material  301  ( FIG. 47 ) from the first injector  201  towards the third lower mold  102 - 3 , the formation of the first layer  301 ′ in the third lower mold  102 - 3  and/or the conveying of the third lower mold  102 - 3  back to the second carrier  1002  ( FIG. 48 ), the first layer  301 ′ in the second lower mold  102 - 2  disposed under the second injector  401  undergoes treatment such as surface treatment or application of the adhesive  501  over the first layer  301 ′, similar to the way as described above or illustrated in  FIG. 9  or  FIGS. 43-45 . In some embodiments, the adhesive  501  is dispensed on the first layer  301 ′ in the lower mold  102 - 2  during the conveying of the lower mold  102 - 3  towards the first carrier  1001  ( FIG. 47 ), the injection of the first material  301  ( FIG. 47 ) from the first injector  201  towards the lower mold  102 - 3 , the formation of the first layer  301 ′ in the lower mold  102 - 3  and/or the conveying of the lower mold  102 - 3  back to the second carrier  1002  ( FIG. 48 ). 
     Furthermore, after the rotation of the second carrier  1002 , the second upper mold  601 - 1  is disposed above the first lower mold  102 - 1  as shown in  FIG. 46 . After the disposing of the lower mold  102 - 1  under the second upper mold  601 - 1 , the second molding device  200  now refers to the second upper mold  601 - 1  and the lower mold  102 - 1 . The second molding device  200  is in configuration as described above or illustrated in  FIGS. 10-13 . The second upper mold  601 - 1  is engaged with the first lower mold  102 - 1 . As such, the second molding device  200  is changed from the open configuration to the closed configuration, similar to the way described above or illustrated in  FIGS. 9-11 . 
     During the conveying of the third lower mold  102 - 3  towards the first carrier  1001  ( FIG. 47 ), the injection of the first material  301  ( FIG. 47 ) from the first injector  201  towards the third lower mold  102 - 3 , the formation of the first layer  301 ′ in the third lower mold  102 - 3  and/or the conveying of the third lower mold  102 - 3  back to the second carrier  1002  ( FIG. 48 ), the second material  801  is injected from the third injector  701  towards the first layer  301 ′, similar to the way as described above or illustrated in  FIG. 12 . 
     The method M 20  includes operation O 207 , which includes injecting a second material  801  into a second mold cavity  103 - 2  defined by the first lower mold  102 - 1  and the second upper mold  601 - 1 . During or after the closing of the second molding device  200 , the second material  801  is injected towards the first layer  301 ′ into the second mold cavity  103 - 2  from the second injector  701  via a second outlet  701   a , similar to the way described above or illustrated in  FIG. 13 . In some embodiments, the second material  801  is foamable material. 
     The method M 20  includes operation O 208 , which includes forming a second layer  801 ′ from the second material  801  disposed over the first layer  301 ′. In some embodiments, a duration for formation of the second layer  801 ′ (total time of injecting the second material  801 , foaming and cooling of the second material  801 , formation of the second layer  801 ′) is more than 60 seconds or is about 100 seconds to 150 seconds. After the formation of the second layer  801 ′, the second injector  701  leaves the second molding device  200 , and the second upper mold  601 - 1  is disengaged and withdrawn from the lower mold  102 - 1 , similar to the way described above or illustrated in  FIG. 13 . The second molding device  200  is changed from the closed configuration ( FIG. 12 ) to the open configuration ( FIG. 13 ). 
     After the opening of the second molding device  200 , an article similar to or different from the article  140  including the first layer  301 ′ and the second layer  801 ′ is formed and can be picked out from the lower mold  102 - 1 , similar to the way described above or illustrated in  FIGS. 14A-14C . Since all layers (the first layer  301 ′, the second layer  801 ′, etc.) of the article  140  are fabricated using the lower molds  102 - 1 ,  102 - 2 ,  102 - 3 , adhesion between the first layer  301 ′ and the second layer  801 ′ is more secure and improved. Therefore, reliability and quality of the article  140  produced by the above injection molding system  700  is improved or increased. 
     Afterwards, the first carrier  1001  and the second carrier  1002  are further rotated as shown in  FIG. 49 , and similar steps as described above or illustrated in  FIGS. 40-48  are repeated. 
     In some embodiments, the injection molding method M 10  as described above or illustrated in  FIGS. 1-18  is implemented by an injection molding system  800  as shown in  FIG. 50 .  FIG. 50  is schematic top view of the injection molding system  800 . The injection molding system of  FIG. 50  is similar to the one as described above or illustrated in  FIGS. 40-49 . In some embodiments, the injection molding system  800  of  FIG. 50  is in full capacity, that all first holders  1001   a  are holding corresponding first upper molds  101 - 1 ,  101 - 2 ,  101 - 3 ,  101 - 4 ,  101 - 5 ,  101 - 6 ,  101 - 7 ,  101 - 8 ,  101 - 9  and  101 - 10 , and all second holders  1002   a  are holding corresponding second upper molds  601 - 1 ,  601 - 2 ,  601 - 3 ,  601 - 4 ,  601 - 5 ,  601 - 6 ,  601 - 7 ,  601 - 8 ,  601 - 9  and  601 - 10  and corresponding lower molds  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4 ,  102 - 5 ,  102 - 6 ,  102 - 7 ,  102 - 8 ,  102 - 9  and  102 - 10 . In some embodiments, after the formation of an article at the third injector  701 , the second upper mold  601  and the lower mold  102  including the article therein are rotated by the second carrier  1002 . The article including the first layer  301 ′ and the second layer  801 ′ is ready to be picked out from a port  901  when the second upper mold  101  and the lower mold  102  are rotated and arrived at the port  901 . 
     In some embodiments, the injection molding method M 10  as described above or illustrated in  FIGS. 1-18  is implemented by an injection molding system  900  as shown in  FIGS. 51 and 52 .  FIG. 51  is schematic top view of the injection molding system  900 . In some embodiments, the second carrier  1002  is configured as a turntable, as described above or illustrated in  FIGS. 40-50 .  FIG. 52  is schematic side view of the first carrier  1001  in  FIG. 51 . In some embodiments, the first holders  1001   a  stack over each other as shown in  FIG. 52 . In some embodiments, the upper molds  101 - 1 ,  101 - 2 ,  101 - 3 ,  101 - 4 ,  101 - 5 ,  101 - 6 ,  101 - 7 ,  101 - 8 ,  101 - 9  and  101 - 10  are stacked over each other, the second upper molds  601 - 1 ,  601 - 2 ,  601 - 3 ,  601 - 4 ,  601 - 5 ,  601 - 6 ,  601 - 7 ,  601 - 8 ,  601 - 9  and  601 - 10  are stacked over each other. In some embodiments, the first carrier  1001  is rotated along a direction (indicated by arrows in  FIG. 52 ) during the implementation of the injection molding method described above. 
       FIG. 53  is a flowchart showing a method M 11  of injection molding method in accordance with some embodiments of the present disclosure. The method M 11  includes several operations: (O 111 ) providing a molding device including a first mold, a second mold over the first mold and a first mold cavity defined by the first mold and the second mold; (O 112 ) injecting a first material into the first mold cavity; (O 113 ) forming a first layer from the first material; (O 114 ) replacing the second mold by a third mold; (O 115 ) injecting a second material into a second mold cavity defined by the first mold and the third mold; and (O 116 ) forming a second layer from the second material, wherein the second layer at least partially contacts the first layer, wherein the first material is same as the second material. 
     In order to illustrate concepts and the method M 11  of the present disclosure, various embodiments are provided below. However, the present disclosure is not intended to be limited to specific embodiments. In addition, elements, conditions or parameters illustrated in different embodiments can be combined or modified to form different combinations of embodiments as long as the elements, parameters or conditions used are not in conflict. For ease of illustration, reference numerals with similar or same functions and properties are repeated in different embodiments and figures. The various operations and the thus formed articles of the injection molding method can be in various configurations as shown in any of  FIGS. 54 to 65 . 
       FIGS. 54 to 57  are schematic cross-sectional views illustrating a first molding device  110  of the operation O 111  of the method M 11  in accordance with some embodiments of the present disclosure. In some embodiments, the method M 11  of injection molding method includes step O 111 , which includes providing a first molding device  110  including a first mold, a second mold over the first mold and a first mold cavity defined by the first mold and the second mold. In some embodiments, a first molding device  110  is provided or received as shown in  FIG. 54 or 55 . In some embodiments, the first molding device  110  is configured to forming an article. In some embodiments, the first mold is a lower mold  112 , and the second mold is a first upper mold  111 . 
     In some embodiments, the first molding device  110  includes the first upper mold  111  and the lower mold  112 . In some embodiments, the first upper mold  111  corresponds to the lower mold  112  in some configurations such as dimension, shape or the like. The first upper mold  111  can be placed on and engaged with the lower mold  112 . In some embodiments, the provision of the first molding device  110  includes conveying the lower mold  112  towards the first upper mold  111 . As such, the lower mold  112  would be disposed under the first upper mold  111  for subsequent steps. In some embodiments, the first upper mold  111  is aligned with the lower mold  112 . In some embodiments as shown in  FIG. 54 , the first molding device  110  is in an open configuration. 
     In some embodiments, the first upper mold  111  includes a protrusion  111   a  protruded from the first upper mold  111 . In some embodiments, the lower mold  112  includes a recess  112   a  indented into the lower mold  112 . The protrusion  111   a  is receivable by the recess  112   a . In some embodiments, the protrusion  111   a  and the recess  112   a  are configured complementary with each other, such that the first upper mold  111  is engageable with the lower mold  112  when the first molding device  110  is in a closed configuration as shown in  FIG. 55 . In some embodiments, a first mold cavity  113 - 1  is formed when the first molding device  110  is in the closed configuration as shown in  FIG. 55 . Although  FIGS. 54 and 55  illustrate only one recess  112   a  at the lower mold  112 , it can be understood that any suitable numbers of the recess  112   a  can be configured at the lower mold  112 . 
     In some embodiments, the first upper mold  111  includes a first passage  111   b  extending through the first upper mold  111 . In some embodiments, the first passage  111   b  is communicable with the first mold cavity  113 - 1  when the first molding device  110  is in the closed configuration as shown in  FIG. 55 . The first mold cavity  113 - 1  is accessible through the first passage  111   b . For simplicity and clarity, only one first passage  111   b  is illustrated, however, it can be understood that any suitable numbers of the first passage  111   b  can be configured at the first upper mold  111 . In some embodiments, the number of the first passage  111   b  is identical to the number of the recess  112   a . In some embodiments, the number of the recess  112   a  is more than the number of the first passages  111   b . In some embodiments, the number of the first passages  111   b  is more than the number of the recess  112   a . In some embodiments, the first passage  111   b  corresponds to the recess  112   a . In some embodiments, each of the first passages  111   b  corresponds to one or more of the recesses  112   a.    
     In some embodiments, instead of configuring the first passage  111   b  at the first upper mold  111 , the first passage  111   b  can be configured at the lower mold  112  for accessing the recess  112   a  or the first mold cavity  113 - 1 . In some embodiments, the first passage  111   b  can be configured at a sidewall of the lower mold  112  or any other suitable positions as long as the first passage  111   b  is communicable with the recess  112   a  or the first mold cavity  113 - 1 . 
     In some embodiments, the first upper mold  111  may not include any protrusion. In some embodiments as shown in  FIGS. 56 and 57 , the first upper mold  111  does not include the protrusion  111   a  as described above or illustrated in  FIGS. 54 and 55 . For simplicity and clarity, only the first molding device  110  having the protrusion  11   a  as shown in  FIGS. 54 and 55  is illustrated for describing the injection molding method below. However, it can be understood that the first molding device  110  without the protrusion  111   a  as shown in  FIGS. 56 and 57  can also be used for the injection molding method described below. 
     In some embodiments, instead of configuring the protrusion  111   a  integrally formed with the first upper mold  111 , a removable plate (not shown) can be used. In some embodiments, the removable plate can be placed between the first upper mold  111  and the lower mold  112  for adjusting a volume of the first mold cavity  113 - 1 . For example, the first mold cavity  113 - 1  would be reduced if the removable plate is inserted into the first mold cavity  113 - 1  and disposed between the first upper mold  111  and the lower mold  112 . In some embodiments, the removable plate is disposed between the protrusion  111   a  and the lower mold  112 . As such, the volume of the first mold cavity  113 - 1  can be adjusted by insertion of the removable plate between the first upper mold  111  and the lower mold  112  when the first molding device  110  is closed. In some embodiments, the removable plate may include a pattern on its surface. The pattern may include a plurality of openings, recessions, holes, protrusions. For example, each of the openings or protrusions may correspond to a shape a mushroom, a pin, a stud or a pillar. 
     Referring back to  FIG. 54 , at the beginning of the injection molding method M 11 , the first molding device  110  is in the open configuration. The first molding device  110  is then changed to the closed configuration as shown in  FIG. 55 . In some embodiments, the first molding device  110  is closed by applying a first clamping force (not shown) over or around the first molding device  110 . In some embodiments, the first clamping force is continuously applied over the first molding device  110  during formation of the article or for a predetermined period of time. In some embodiments, the first upper mold  111  is tightly engaged with the lower mold  112  when the first molding device  110  is closed. 
     After the closing of the first molding device  110 , the first mold cavity  113 - 1  is formed as shown in  FIG. 55 . The first mold cavity  113 - 1  is configured to hold material and form the article within the recess  112   a . The first mold cavity  113 - 1  is communicable with the first passage  111   b . In some embodiments, the first mold cavity  113 - 1  is sealed when the first molding device  110  is closed. 
       FIGS. 58 to 60  are schematic cross-sectional views illustrating the first molding device  110  of the operations O 112  and O 113  of the method MI  1  in accordance with some embodiments of the present disclosure. In some embodiments, the method M 11  of injection molding method includes step O 112 , which includes injecting a first material into the first mold cavity. In some embodiments, the method M 11  of injection molding method includes step O 113 , which includes forming a non-foamed layer from the first material. 
     When the first molding device  110  is closed, a first material  311  is injected into the first mold cavity  113 - 1  through the first passage  111   b  as shown in  FIG. 58 . In some embodiments, the first material  311  is injected into the first mold cavity  103 - 1  from a first injector  211  via a first outlet  211   a  of the first injector  211 . The first material  311  is flowed from the first outlet  211   a  into the first mold cavity  113 - 1  along the first passage  111   b . In some embodiments, the first outlet  211   a  is engaged with the first passage  111   b  upon injection of the first material  311 . In some embodiments, the first outlet  211   a  of the first injector  211  is extendable towards or retractable from the first passage  111   b . In some embodiments, the first material  311  includes thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. In some embodiments, the first material  311  is foamable material or less foamable material. In some embodiments, the first material  311  is non-foamable material. 
     During or after injecting the first material  311  into the mold cavity  113 - 1 , in some embodiments, an external force (not shown) may be applied over the first upper mold  111  or the lower mold  112  to press the first material  311 . In some embodiments, the external force is substantially greater than or equal to 150 Newton (N). In some embodiments, the external force is substantially greater than or equal to 200N. In some embodiments, the external force is applied for a predetermined period of time such as several seconds. In some embodiments, the first molding device  110  is idle for a predetermined period of time such as several seconds for cooling of the first material  311 . As a result, a first layer  311 ′ including the first material  311  is formed (e.g., cured or solidified or cooled) within the mold cavity  113 - 1 , as shown in  FIG. 58 . In some embodiments, the first layer  311 ′ is a foamed layer or a less foamed layer. In some embodiments, the first layer  311 ′ is a non-foamed layer. 
     After the formation of the first layer  311 ′, the first injector  211  leaves the first molding device  110 , and the first upper mold  111  is disengaged and withdrawn from the lower mold  112 , as shown in  FIG. 59 . The first outlet  211   a  is also disengaged from the first passage  111   b . The first molding device  110  is changed from the closed configuration as illustrated in  FIG. 58  to the open configuration as illustrated in  FIG. 59 . Further, in some embodiments, the lower mold  112  is conveyed away from the first upper mold  111  as shown in  FIG. 60 . 
     In some embodiments, the lower mold  112  is conveyed in a suitable speed or by a suitable force, such that the vibration of the lower mold  112  during the conveying is minimized or even prevented. Reduction or prevention of the vibration of the lower mold  112  during the conveying allows the first layer  311 ′ stably disposed in the first mold cavity  113 - 1  and temporarily adhered to the lower mold  112 . In some embodiments, the first layer  311 ′ can be firmly attached to the lower mold  112  during the conveying by any suitable mechanism such as a sufficient friction between the first layer  311 ′ and the inner sidewall of the lower mold  112 , a tab (not shown) protruded from the lower mold  112  towards the recess  112   a , etc. Therefore, reliability and quality of the first layer  311 ′ can be improved or increased. 
     Optionally, the lower mold  112  is then conveyed to another station for further treatment. For example, a surface treatment is performed after the formation of the first layer  311 ′. A surface of the first layer  311 ′ would be polished or treated to increase smoothness, or the first layer  311 ′ would be heat treated for activation, or any other suitable treatments. 
       FIGS. 61 and 62  are schematic cross-sectional views illustrating a second molding device  210  of the operation O 114  of the method M 11  in accordance with some embodiments of the present disclosure. In some embodiments, the injection molding method M 11  includes step O 114 , which includes replacing the second mold by a third mold. In some embodiments, the replacement of the second mold includes removing the second mold, disposing the third mold over the first mold and moving the first mold towards the third mold to form the second mold cavity. In some embodiments, the second mold is the first upper mold  111 , the first mold is the lower mold  112 , and the third mold is a second upper mold  611 . 
     After the formation of the first layer  311 ′, the lower mold  112  is conveyed towards another station including a second upper mold  611  as shown in  FIGS. 61 and 62 . In some embodiments, the lower mold  112  at least including the first layer  311 ′ is conveyed towards the second upper mold  611 . The lower mold  112  is disposed under the second upper mold  611  as shown in  FIG. 61 . It can be understood that a second molding device  210  refers to the second upper mold  611  and the lower mold  112 . 
     In some embodiments, the second upper mold  611  corresponds to the lower mold  112  in some configurations such as dimension, shape or the like. The second upper mold  611  can be placed on and engaged with the lower mold  112 . In some embodiments, the provision of the second molding device  210  includes conveying the lower mold  112  towards the second upper mold  611 . As such, the lower mold  112  would be disposed under the second upper mold  611  for subsequent steps. In some embodiments, the second upper mold  611  is aligned with the lower mold  112 . In some embodiments as shown in  FIG. 61 , the second molding device  210  is in an open configuration. 
     In some embodiments, the second upper mold  611  includes a second passage  611   b  extending through the second upper mold  611 . In some embodiments, the second passage  611   b  is communicable with a second mold cavity  113 - 2  when the second molding device  210  is in the closed configuration as shown in  FIG. 62 . The second mold cavity  113 - 2  is accessible through the second passage  611   b . For simplicity and clarity, only one second passage  611   b  is illustrated, however, it can be understood that any suitable numbers of the second passage  611   b  can be configured at the second upper mold  611 . In some embodiments, the number of the second passage  611   b  is identical to the number of the recess  112   a . In some embodiments, the number of the recess  112   a  is more than the number of the second passage  611   b . In some embodiments, the number of the second passage  611   b  is more than the number of the recess  112   a . In some embodiments, the second passage  611   b  corresponds to the recess  112   a . In some embodiments, each second passage  611   b  corresponds to one or more of the recesses  112   a.    
     In some embodiments, instead of configuring the second passage  611   b  at the second upper mold  611 , the second passage  611   b  can be configured at the lower mold  112  for accessing the recess  112   a  or the second mold cavity  113 - 2 . In some embodiments, the second passage  611   b  can be configured at a sidewall of the lower mold  112  or any other suitable positions as long as the second passage  611   b  is communicable with the recess  112   a  or the second mold cavity  113 - 2 . 
     In some embodiments, the second molding device  210  is then changed from the open configuration as shown in  FIG. 61  to the closed configuration as shown in  FIG. 62 . In some embodiments, the second molding device  210  is closed by applying a second clamping force (not shown) over or around the second molding device  210 . In some embodiments, the second clamping force is continuously applied over the second molding device  210  during formation of the article or for a predetermined period of time. In some embodiments, the second upper mold  611  is tightly engaged with the lower mold  112  when the second molding device  210  is closed. In some embodiments, the second clamping force is substantially less than the first clamping force. 
     After the closing of the second molding device  210 , a second mold cavity  113 - 2  is formed as shown in  FIG. 62 . The second mold cavity  113 - 2  is configured to hold material and form the article within the recess  112   a . The second mold cavity  113 - 2  is communicable with the second passage  611   b . In some embodiments, the second mold cavity  113 - 2  is sealed when the second molding device  210  is closed. 
       FIGS. 63 and 64  are schematic cross-sectional views illustrating the second molding device  210  of the operations O 115  and O 116  of the method M 11  in accordance with some embodiments of the present disclosure. In some embodiments, the method M 11  of injection molding method includes step O 115 , which includes injecting a second material into a second mold cavity defined by the first mold and the third mold, the first material is different from the second material. In some embodiments, the method M 11  of injection molding method includes step O 116 , which includes forming a foamed layer from the second material disposed over the non-foamed layer. 
     When the second molding device  210  is closed, a second material  811  is injected into the second mold cavity  113 - 2  through the second passage  611   b  as shown in  FIG. 63 . In some embodiments, the second material  811  is injected into the second mold cavity  113 - 2  from a third injector  711  via a third outlet  711   a  of the third injector  711 . The second material  811  is flowed from the third outlet  711   a  into the second mold cavity  113 - 2  along the second passage  611   b . In some embodiments, the third outlet  711   a  is engaged with the second passage  611   b  upon injection of the second material  811 . The second material  811  is adhered to the first layer  311 ′ directly due to the adhesion of the second material  811 . 
     In some embodiments, the second material  811  includes expanded thermoplastic polyurethane (ETPU), thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. In some embodiments, the second material  811  is foamable material or highly foamable material. In some embodiments, the second material  811  includes a blowing agent prior to injection from the third injector  711 . In some embodiments, a polymeric material is mixed with the blowing agent to become the second material  811  prior to the injection from the third injector  711 . In some embodiments, the second material  811  is a mixture of the polymeric material and the blowing agent. In some embodiments, the blowing agent can be any type of physical blowing agent known to those of ordinary skill in the art, such as atmospheric gases (e.g., nitrogen, carbon dioxide), hydrocarbons, chlorofluorocarbons, noble gases, or mixtures thereof. The blowing agent may be supplied in any flowable physical state, for example, a gas, liquid, or supercritical fluid. In some embodiments, the blowing agent is in the supercritical fluid state. In some embodiments, the second material  811  may contacts the first layer  311 ′. In some embodiments, the first material  311  is same as the second material  811 . For example, the first material  311  and the second material  811  may both be thermoplastic polyurethane (TPU). 
     After injecting the second material  811  into the second mold cavity  113 - 2 , the second molding device  210  is idle for a predetermined period of time such as several seconds for foaming and cooling of the second material  811 . As a result, a second layer  811 ′ including the second material  811  is formed (e.g., cured or solidified or cooled) within the second mold cavity  113 - 2 . In some embodiments, the second layer  811 ′ is a foamed layer. In some embodiments, the second layer  811 ′ at least partially contacts the first layer  311 ′ directly. The second layer  811 ′ is adhered to the first layer  311 ′ directly due to the adhesion of the second material  811 . Thus, there is only one interface or boundary between the second layer  811 ′ and the first layer  311 ′. There is no adhesive layer between the second layer  811 ′ and the first layer  311 ′. The adhesion between the second layer  811 ′ and the first layer  311 ′ is caused by the adhesive property of the second layer  811 ′ itself and/or the adhesive property of the first layer  311 ′ itself rather than by an additional adhesive layer. 
     In some embodiments, a density of the foamed layer is substantially less than a density of the non-foamed layer. In some embodiments, density of the second layer  811 ′ may be substantially less than or equal to density of the first layer  311 ′. In some embodiments, an elasticity of the foamed layer is substantially greater than an elasticity of the non-foamed layer. In some embodiments, elasticity of the second layer  811 ′ may be substantially greater than or equal to elasticity of the first layer  311 ′. In some embodiments, the first layer  311 ′ is harder than the second layer  811 ′. In some embodiments, the second layer  811 ′ has a greater abrasion resistance than the first layer  31 ′. 
     In some embodiments, after the formation of the second layer  811 ′, the third injector  711  leaves the second molding device  210 , and the second upper mold  611  is disengaged and withdrawn from the lower mold  112 , as shown in  FIG. 64 . The third outlet  711   a  is disengaged with the second passage  611   b . The second molding device  210  is changed from the closed configuration ( FIG. 63 ) to the open configuration ( FIG. 64 ). 
       FIG. 65  is a schematic cross-sectional view illustrating an article  150  manufactured by the method MI  1  in accordance with some embodiments of the present disclosure. As shown in  FIG. 65 , an article  150  at least including the first layer  311 ′ and the second layer  811 ′ is formed. In some embodiments, the article  150  includes a foamed portion (the second layer  811 ′) and a non-foamed portion (the first layer  311 ′). In some embodiments, after the formation of the article  150 , the article  150  is then picked out from the lower mold  112 . In some embodiments, the article  150  is picked out manually by human, or automatically by robot, robotic arm, gripper or the like. In some embodiments, the article  150  is a part of a footwear or a semi-product of a footwear. In some embodiments, the first layer  311 ′ is a vamp of the footwear. In some embodiments, the second layer  811 ′ is an outsole of the footwear. 
     Since all layers (the first layer  311 ′ and the second layer  811 ′) of the article  150  are fabricated by the same lower mold  112 , adhesion between the first layer  311 ′ and the second layer  811 ′ is more secure and improved. Therefore, reliability and quality of the article  150  produced by the above injection molding method M 11  is improved or increased. 
       FIG. 66  is a perspective view illustrating an assembly  160  of polymeric components according to one embodiment of the present disclosure.  FIG. 67  is a side view of the assembly  160  of  FIG. 66 . The assembly  160  of polymeric components includes a first polymeric component  321  and a second polymeric component  821 . In some embodiments, the assembly  160  may be a footwear, the first polymeric component  321  may be a vamp of the footwear, and the second polymeric component  821  may be an outsole of the footwear. A thickness of the first polymeric component  321  may be less than a thickness of the second polymeric component  821 . 
     In some embodiments, the assembly  160  may include the article  150  of  FIG. 65 , the first polymeric component  321  may include the first layer  311 ′ of  FIG. 65 , and the second polymeric component  821  may include the second layer  811 ′ of  FIG. 65 . That is, the article  150  of  FIG. 65  may be a part of the assembly  160 , the first layer  311 ′ of  FIG. 65  may be a part of the first polymeric component  321 , and the second layer  811 ′ of  FIG. 65  may be a part of the second polymeric component  821 . 
     The second polymeric component  821  is directly attached to the first polymeric component  321 . A material of the first polymeric component  321  may be same as a material of the second polymeric component  821 , e.g., both of which may be expanded thermoplastic polyurethane (ETPU), thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. 
     The first polymeric component  321  may include a main portion  3211  and an extending portion  3212 . In some embodiments, the main portion  3211  and the extending portion  3212  are formed concurrently or separately. In some embodiments, the main portion  3211  and the extending portion  3212  are integrally formed. The extending portion  3212  may be a strip disposed at a bottom rim of the main portion  3211 . The extending portion  3212  may be in a U shape from a top view or a bottom view. The extending portion  3212  may have a first surface  32121  adhered to or attached to a first surface  8211  of the second polymeric component  821  directly. Thus, there is only one boundary or interface between the first polymeric component  321  and the second polymeric component  821 . That is, there is no additional adhesive layer between the first polymeric component  321  and the second polymeric component  821 . In some embodiments, additional parts such as strap, buckle or the like can be attached to the first polymeric component  321  or the second polymeric component  821  by any suitable manner such as snap fit, interlocking, gluing or the like. 
       FIG. 68  through  FIG. 69  illustrates an injection molding method in accordance with some embodiments of the present disclosure. The illustrated method may be used to manufacture an assembly  160   a  shown in  FIG. 71 . The initial stages of the illustrated method are similar to the stages illustrated in  FIG. 54  to  FIG. 59  except that the molding device  110   a  defines a plurality of recess portions  115 . As shown in  FIG. 68 , the protrusion  111   a  of the first upper mold  111  defines a plurality of recess portions  115  recessed from a bottom surface of the protrusion  111   a  of the first upper mold  111 . The recess portions  115  are in communication with the first mold cavity  113 - 1 . In addition, a shape of the recess portions  115  may include a mushroom, a pin, a stud and a pillar. 
     Referring to  FIG. 68A , a first material is injected into the first mold cavity  113 - 1  through the first passage  111   b  from a first injector via a first outlet of the first injector. The first material is flowed from the first outlet into the first mold cavity  113 - 1  along the first passage  111   b . After the formation of the first layer  331 ′, the first injector leaves the first molding device  110   a , and the first upper mold  111  with the recess portions  115  is disengaged and withdrawn from the lower mold  112 . Thus, the first layer  311 ′ includes a plurality of first protrusions  312  (corresponding to the recess portions  115 ) protruding from a surface  313  thereof. The first layer  311 ′ and the first protrusions  312  may be formed concurrently and integrally. In addition, a shape of the first protrusion  312  may include a mushroom, a pin, a stud and a pillar. 
     Then, the following stages of the illustrated method may be similar to the stages illustrated in  FIG. 61  to  FIG. 63 .  FIG. 69  depicts a stage similar to the stage depicted in  FIG. 64 . As shown in  FIG. 69 , the second layer  811 ′ covers and contacts the surface  313  of the first layer  311 ′. Further, the second layer  811 ′ contacts and surrounds the lateral surfaces of the first protrusions  312  of the first layer  311 ′. Further, the second layer  811 ′ is adhered to the lateral surfaces of the first protrusions  312  of the first layer  311 ′. 
     As shown in  FIG. 70 , an article  150 ′ at least including the first layer  311 ′, the first protrusions  312  and the second layer  811 ′ is formed. 
       FIG. 71  is a side view illustrating an assembly  160   a  of polymeric components according to one embodiment of the present disclosure.  FIG. 72  is a perspective and exploded view of the assembly  160   a  of  FIG. 71 . The assembly  160   a  is similar to the assembly  160  shown in  FIG. 66  and  FIG. 67 , except that a plurality of first protrusions  312  are further formed. The assembly  160   a  includes a first polymeric component  321  and a second polymeric component  821 . 
     In some embodiments, the assembly  160   a  may include the article  150 ′ of  FIG. 70 , the first polymeric component  321  may include the first layer  311 ′ of  FIG. 70 , and the second polymeric component  821  may include the second layer  811 ′ of  FIG. 70 . That is, the article  150 ′ of  FIG. 70  may be a part of the assembly  160   a , the first layer  311 ′ of  FIG. 70  may be a part of the first polymeric component  321 , and the second layer  811 ′ of  FIG. 70  may be a part of the second polymeric component  821 . 
     The first polymeric component  321  includes a plurality of first protrusions  312  protruding from the surface  32121  thereof. The first protrusions  312  and the first polymeric component  321  are formed concurrently and integrally. The second polymeric component  821  covers the surface  32121  and surrounds the first protrusions  312  of the first polymeric component  321 . In addition, the second polymeric component  821  adheres and contacts a lateral surface of each of the first protrusions  312  of the first polymeric component  321  directly. The openings  8213  of the second polymeric component  821  are defined and determined by the first protrusions  312 . The design of the first protrusions  312  can increase the attachment or bonding between the first polymeric component  321  and the second polymeric component  821 . 
     In some embodiments, the first protrusions  312  of the first polymeric component  321  may extend through a portion of the second polymeric component  821 . In some embodiments, the first polymeric component  321  and the second polymeric component  821  may be individually manufactured in different molding devices or different sites, and the first protrusions  312  of the first polymeric component  321  may be inserted into the openings  8213  of the second polymeric component  821 . 
       FIG. 73  through  FIG. 78  illustrates an injection molding method in accordance with some embodiments of the present disclosure. The illustrated method may be used to manufacture an assembly  160   b  shown in  FIG. 79 . The initial stages of the illustrated method are similar to the stages illustrated in  FIG. 54  to  FIG. 55  except that the molding device  110 ′ further includes a plurality of protruding portions  114 . As shown in  FIG. 73 , the protruding portions  114  protrude from the protrusion  111   a  of the first upper mold  111  toward the first mold cavity  113 - 1 . In addition, a shape of the protruding portion  114  may include a mushroom, a pin, a stud and a pillar. 
     Referring to  FIG. 74 , a first material  331  is injected into the first mold cavity  113 - 1  through the first passage  111   b . In some embodiments, the first material  331  is injected into the first mold cavity  103 - 1  from a first injector  211  via a first outlet  211   a  of the first injector  211 . The first material  331  is flowed from the first outlet  211   a  into the first mold cavity  113 - 1  along the first passage  111   b . In some embodiments, the first material  331  includes thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. In some embodiments, the first material  331  is foamable material or less foamable material. In some embodiments, the first material  331  is non-foamable material. 
     Referring to  FIG. 75 , after the formation of the first layer  331 ′, the first injector  211  leaves the first molding device  110 ′, and the first upper mold  111  with the protruding portions  114  is disengaged and withdrawn from the lower mold  112 . Thus, the first layer  331 ′ defines a plurality of openings  332  corresponding to the protruding portions  114 . 
     Referring to  FIG. 76 , after the closing of the second molding device  210 , a second mold cavity  113 - 2  is formed. The second mold cavity  113 - 2  is configured to hold material and form the article within the recess  112   a . The second mold cavity  113 - 2  is communicable with the second passage  611   b . In some embodiments, the second mold cavity  113 - 2  is sealed when the second molding device  210  is closed. 
     Referring to  FIG. 77 , when the second molding device  210  is closed, a second material  831  is injected into the second mold cavity  113 - 2  through the second passage  611   b . In some embodiments, the second material  831  is injected into the second mold cavity  113 - 2  from a third injector  711  via a third outlet  711   a  of the third injector  711 . The second material  831  is flowed from the third outlet  711   a  into the second mold cavity  113 - 2  along the second passage  611   b . In some embodiments, the third outlet  711   a  is engaged with the second passage  611   b  upon injection of the second material  811 . As shown in  FIG. 77 , a plurality of portions of the second material  831  extend into the openings  332  of the first layer  331  respectively. 
     In some embodiments, the second material  831  includes expanded thermoplastic polyurethane (ETPU), thermoplastic polyurethane (TPU), polyurethane (PU), plastics or any other suitable materials. In some embodiments, the second material  831  is foamable material or less foamable material. In some embodiments, the second material  831  is non-foamable material. In some embodiments, the second material  831  may contacts the first layer  331 ′. In some embodiments, the first material  331  is same as the second material  831 . For example, the first material  331  and the second material  831  may both be thermoplastic polyurethane (TPU). 
     Referring to  FIG. 78 , after the formation of the second layer  831 ′, a plurality second protrusions  8311  may protrude from the second layer  831 ′. Then, the third injector  711  leaves the second molding device  210 , and the second upper mold  611  is disengaged and withdrawn from the lower mold  112 . The third outlet  711   a  is disengaged with the second passage  611   b . Thus, an article  150 ″ at least including the first layer  331 ′ and the second layer  831 ′ is formed. 
       FIG. 79  is a side view illustrating an assembly  160   b  of polymeric components according to one embodiment of the present disclosure. The assembly  160   b  is similar to the assembly  160   a  shown in  FIG. 71  and  FIG. 72 , except that a plurality of second protrusions  8311  are formed. The assembly  160   b  includes a first polymeric component  341  and a second polymeric component  841 . In some embodiments, the assembly  160   b  may be a footwear, the first polymeric component  341  may be an outsole of the footwear, and the second polymeric component  841  may be a vamp of the footwear. A thickness of the first polymeric component  341  may be greater than a thickness of the second polymeric component  841 . 
     In some embodiments, the assembly  160   b  may include the article  150 ″ of  FIG. 78 , the first polymeric component  341  may include the first layer  331 ′ of  FIG. 78 , and the second polymeric component  841  may include the second layer  831 ′ of  FIG. 78 . That is, the article  150 ″ of  FIG. 78  may be a part of the assembly  160   b , the first layer  331 ′ of  FIG. 78  may be a part of the first polymeric component  341 , and the second layer  831 ′ of  FIG. 78  may be a part of the second polymeric component  841 . 
     The first polymeric component  341  defines a plurality of openings  332 . The second polymeric component  841  includes a plurality of second protrusions  8311  disposed in the openings  332  of the first polymeric component  341 . The first polymeric component  341  covers and surrounds the second protrusions  8311  of the second polymeric component  841 . In addition, the first polymeric component  341  adheres and contacts a lateral surface of each of the second protrusions  8311  of the second polymeric component  841  directly. The second protrusions  8311  of the second polymeric component  841  are defined and determined by the openings  332  of the first polymeric component  341 . The design of the second protrusions  8311  can increase the attachment or bonding between the first polymeric component  341  and the second polymeric component  841 . 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 
     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein, may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods and steps.