Patent Publication Number: US-2020282610-A1

Title: Combined injection moulding and extrusion

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/814,084 having a filing date of Mar. 5, 2019, which is incorporated by reference as if fully set forth. 
    
    
     FIELD OF INVENTION 
     The present application relates generally to an injection molding process. More particularly, the invention relates to a process that combines injection molding with extrusion for producing longer and thinner parts. 
     BACKGROUND 
     A catheter is a thin, flexible tube that may be inserted through a narrow opening into a body cavity to remove fluid, or facilitate performing other medical procedures. Injection molding is a process for producing parts comprising injecting a hot plastic material into a mold. Typically, there is a natural maximum fill length that can be achieved with injection molding due pressure drop within the cavity. As such, long and thin plastic parts, such as catheters, generally cannot be manufactured by injection molding. However, injection molding is a fast and efficient way to consistently produce parts with detailed features. As such, it would be desirable to have an injection molding process for producing longer and thinner parts. 
     SUMMARY 
     A method in accordance with the present disclosure combines injection molding and extrusion. First, a molten material is injected into a mold via an injection gate, the mold comprising a first portion and a second portion. Next, additional molten material is injected via the injection gate and pushed through an extrusion die located in the first portion of the mold, and the second portion is separated from the first portion. In embodiments, the second portion is separated from the first portion before the additional material is injected. In other embodiments, the second portion is separated from the first portion simultaneously with the additional material being injected. The method may be used to efficiently produce longer and thinner parts with detailed features, such as catheters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flowchart illustrating an injection molding process in accordance with the present disclosure; 
         FIG. 2  is an illustration of a mold assembly at method step  101  of  FIG. 1 ; 
         FIG. 3  is an illustration of the mold assembly at method step  102  of  FIG. 1 ; 
         FIG. 4  is an illustration of the mold assembly at method step  103  of  FIG. 1 ; and 
         FIG. 5  is an illustration of the mold assembly at method step  104  of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Examples of manufacturing methods for longer and thinner parts, such as catheters, will be described more fully herein with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example can be combined with features found in one or more other examples to achieve additional implementations. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only and they are not intended to limit the disclosure in any way. Like numbers refer to like elements throughout. 
     Injection molding is a process for manufacturing parts comprising injecting a molten material into a mold. In general, a material such as plastic is fed into a heated barrel, liquefied, mixed and forced into a mold cavity where it is cooled and hardened. Injection molding is a fast and efficient way to make parts with detailed features and complex geometry. 
     Extrusion is a process used to create objects of a fixed cross-sectional profile. Typically, a material is pushed through an extrusion die of a desired cross-section. Hot extrusion is a process in which the extrusion is performed above the material&#39;s recrystallization temperature to keep the material from hardening and to make it easier to push the material through the die. Advantages of extrusion include the ability to create complex cross-sections and to work with materials that are brittle, since the material encounters only compressive and shear stresses. Further, parts made via extrusion have relatively good surface finish. 
       FIG. 1  is a flowchart illustrating a method  100  for manufacturing a part via injection molding and extrusion in accordance with the present disclosure. The method may be used to manufacture longer and thinner parts such as catheters. At step  101 , a shorter version of the part is produced via injection molding. At step  102 , the shorter version of the part is extruded to a longer length. At step  103 , the part is cooled and the mold is opened. At step  104 , the part is demolded. Steps  101 - 104  will be explained in more detail below. 
       FIG. 2  is an illustration of the mold assembly  200  at method step  101 , the injection molding step. The mold assembly  200  comprises an inner core  201  and a mold  210 . A mold cavity  205  is defined by the mold  210  and the inner core  201 . 
     The mold  210  may be configured to produce detailed features of the part. For example, the mold assembly  200  illustrated in  FIGS. 2-5  comprises structures  204  configured to create two holes at one end of the part. 
     During step  101 , a material is injected into the mold cavity  205  of the mold  210  via injection gate  213 . The mold cavity  205  is sized to produce a “shorter” version of the part. In essence, this is a part having a length at the beginning of the process, that is shorter than the same part at the end of the process. When the material is injected into the mold cavity  205 , the material is in a molten state. In embodiments, the material used is plastic, but this is for illustrative purposes and the same process may be utilized with other materials in accordance with the teachings herein. 
     The mold  210  may be comprised of a plurality of distinctive components configured to be coupled together to ultimately for a part having a desired configuration. In the drawings, the mold  210  comprises components  210 A- 210 G. The number and configuration of the components shown in  FIGS. 2-5  are an example, and many different numbers and configurations of components are possible. In embodiments, one of the components comprises the injection gate  213  for injecting the molten material. For example, in the drawings, component  210 A comprises injection gate  213 . 
     In embodiments, the component comprising the injection gate  213  and one or more components adjacent to the injection gate  213  are maintained at a high temperature during injection molding and extrusion. The components may be maintained at a high temperature through various mechanisms, such as a heater. For example, in the embodiment illustrated in  FIG. 2 , component  210 A, which comprises the injection gate  213 , and component  210 B, which is adjacent to the injection gate  213 , are maintained at a high temperature. The temperature at which the components are maintained may depend on the material used. 
       FIG. 3  is an illustration of the mold assembly  200  at method step  102 , the extrusion step. The mold  210  comprises an extrusion die  214  with a desired cross-section. The extrusion die  214  may be formed by one or more of the components of the mold  210 . The cross-section of the extrusion die  214  may be circular, oval, rectangular, or any shape compatible with the exterior and interior geometry of the mold  210 . 
     At step  102 , additional material is injected via injection gate  213  and is pushed through the extrusion die  214 . Also during step  102 , a first portion  211  of the mold  210  stays in place and a second portion  212  of the mold  210  moves away from the first portion  211 . In embodiments, the second portion  212  separates from the first portion  211  prior to the additional material being injected. In other embodiments, the second portion  212  separates from the first portion  211  while the additional material is being injected. 
     In embodiments, the first portion  211  of the mold  210  comprises the injection gate  213 . In alternate embodiments, the second portion  212  comprises the injection gate  213 . In the embodiment illustrated in  FIG. 3 , components  210 A- 210 D comprise the first portion  211  of the mold  210  and components  210 E- 210 G comprise the second portion  212  of the mold  210 . 
     In embodiments, the first portion  211  and the second portion  212  are aligned vertically and the second portion  212  moves along a vertical plane during step  102 . In alternate embodiments, the first portion  211  and the second portion  212  are aligned horizontally and the second portion  212  moves along a horizontal plane during step  102 . In further embodiments, one or more supports are provided to support the extruded part as it cools. 
     In embodiments, the inner core  201  moves with the second portion  212  during method step  102 . In other embodiments, one end of the inner core  201  is aligned with the extrusion die  214  before method step  102 . In yet other embodiments, one end of the inner core  201  is positioned between the extrusion die  214  and the position of the inner core  201  during injection molding before method step  102 . In yet other embodiments, the inner core  201  stays in place during method step  102 , as illustrated in  FIG. 3 . 
       FIG. 4  is an illustration of the mold assembly  200  at method step  103  of  FIG. 1 . At step  103 , the components that were maintained at a high temperature during method steps  101  and  102  are cooled. In the embodiment illustrated in the drawings, components  210 A and  210 B are maintained at a high temperature during method steps  101  and  102 , and are subsequently cooled down during method step  103 . Once the mold  210  has cooled and the part is solid, the part is removed from the mold  210  by disassembling the mold  210 . 
       FIG. 5  is an illustration of the mold assembly  200  at method step  104  of  FIG. 1 . During method step  104 , the inner core  201  is removed from the solid p art. 
     Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements.