PATENT DOCUMENT

Publication Number: US-9085107-B2
Application Number: US-201313895954-A
Country: US
Kind Code: B2

Title: Tooling concepts for reducing sink and improving as-molded cosmetics and drawings

Abstract:
The described embodiments relate generally to improvements to injection molding equipment. More specifically, concepts for reducing sink and improving cosmetics of portions of injection molded parts in close proximity to gate areas of an injection mold are disclosed. A cold runner system is described in which molding material disposed in a mold cavity is separated from excess molding material in the runner system shortly after the mold is filled at a predetermined packing pressure.

Claims:
What is claimed is: 
     
       1. An injection mold for forming a molded structure, comprising:
 a runner configured to guide a flow of molding material into a cavity at a gate area in accordance with a forward pressure exerted on the molding material; and 
 a flow controller passing through the gate area of the runner proximate the cavity and configured to transition between an open position in which the molding material can pass into the cavity and a closed position in which the molding material cannot pass into the cavity in accordance with a pressure differential between the forward pressure exerted on the molding material and a back pressure generated by an amount of molding material in the cavity, the flow controller comprising:
 a slider defining an opening aligned with the gate area of the runner when the slider is in the open position, the slider comprising a distal end configured to receive a force generated by pressurized air exiting the cavity by way of a number of pressure vents, 
 
 wherein once the back pressure within the cavity reaches a predetermined threshold the force acting upon the distal end of the slider shifts the slider in a direction substantially perpendicular to the flow of molding material to reach a closed position in which the opening is no longer aligned with the gate area. 
 
     
     
       2. The injection mold as recited in  claim 1 , wherein the slider defines a number of openings that control the flow of molding material into the cavity through a number of runners. 
     
     
       3. The injection mold as recited in  claim 1 , wherein the predetermined threshold of the back pressure corresponds to a packing pressure of the molding material within the cavity being reached, the packing pressure being a pressure at which the injection mold is designed to operate. 
     
     
       4. The injection mold as recited in  claim 1 , wherein a spring is configured to bias the slider of the flow controller towards the open position until the force supplied by the pressurized air overcomes the biasing exerted by the spring. 
     
     
       5. An injection molding apparatus, comprising:
 a runner configured to guide a flow of pressurized molten molding material into a cavity, the runner comprising a gate area disposed at an end of the runner that intersects the cavity; and 
 a pressure actuated flow controller, comprising:
 a slider that passes through the gate area of the runner and defines an opening through which the flow of pressurized molten material passes into the cavity when the slider is in an open position, the slider comprising a first end configured to receive a pneumatic force from pressurized air vented out of the cavity as the pressurized molten molding material fills the cavity; 
 
 wherein when a predetermined pressure is reached within the cavity, the pneumatic force transitions the slider to a closed position, causing the opening to shift away from the gate area so that a connection between the molten molding material in the runner and the molten molding material in the cavity is severed. 
 
     
     
       6. The injection molding apparatus as recited in  claim 5 , wherein when the flow controller transitions to the closed position, a cavity-facing surface of the slider leaves only a minimal amount of material extending outside the cavity and into the gate area, insufficient to generate a sink condition on an opposing surface of a molded structure formed within the cavity. 
     
     
       7. The injection molding apparatus as recited in  claim 5 , wherein the molten molding material is thermoplastic material. 
     
     
       8. The injection molding apparatus as recited in  claim 7 , wherein the flow controller is mechanically constrained by a spring that biases the flow controller towards the open position. 
     
     
       9. The injection molding apparatus as recited in  claim 5 , wherein the slider transitions between the open and closed positions in a direction substantially perpendicular to the flow of pressurized molten molding material in the runner. 
     
     
       10. A method for forming an injection molded part, the method comprising:
 injecting pressurized molten molding material into a cavity of an injection mold through a runner until a predetermined pressure is reached in the cavity; and 
 closing a path between the runner and the cavity with a slider by shifting an opening defined by the slider away from a gate area of the runner leading into the cavity once the predetermined pressure is established in the cavity, 
 wherein the predetermined pressure within the cavity pressurizes air exiting the cavity, the pressurized air being directed towards one end of the slider to exert a force upon the slider that moves the slider from an open position to a closed position, and 
 wherein in the open position the opening defined by the slider in cooperation with the runner defines a path along which the molten molding material flows into the cavity. 
 
     
     
       11. The method as recited in  claim 10 , wherein in the closed position the slider completely cuts off the flow of pressurized molten molding material into the cavity. 
     
     
       12. The method as recited in  claim 11 , wherein a spring coupled directly to the slider biases the slider towards the open position. 
     
     
       13. The method as recited in  claim 10 , further comprising:
 allowing both the molten molding material disposed within the cavity and the molten molding material within the runner to cool after the path is closed.

Description:
BACKGROUND 
     1. Technical Field 
     The described embodiments relate generally to improvements to injection molding equipment. More specifically, tooling concepts for reducing sink and improving cosmetics of injection molded parts are disclosed. 
     2. Related Art 
     Injection molded materials have a tendency to contract during solidification after an injection molding process. Contraction can generally be accommodated for by making a cavity of the injection mold correspondingly larger; however, asymmetric contraction can be much harder to accommodate. Accommodations for asymmetric contraction can include additional time consuming finishing operations to produce a cosmetically acceptable part. Asymmetric contraction can be caused by contraction of the plastic material into portions of the mold called gates and/or runners. Contraction of the plastic into the gates can cause sink on portions of the injection molded part opposite the gates. 
     Therefore, what is desired is a way to reduce or eliminate asymmetric sink near gate and runner portions of an injection molded part. 
     SUMMARY 
     This paper describes various embodiments that relate to tooling concepts for reducing sink and improving cosmetics of injection molded parts. 
     An injection mold for forming a molded structure is disclosed. The injection mold includes at least the following: a runner configured to guide a flow of molding material into a cavity at a gate area in accordance with a forward pressure exerted on the molding material; and a flow controller. The flow controller is disposed within the runner and configured to control the flow of the molding material into the cavity in accordance with a pressure differential between the forward pressure exerted on the molding material and a back pressure generated by an amount of molding material in the cavity. The flow controller includes at least the following: a body portion having a size and shape that cooperates with the runner to form a channel through which the molding material flows in response to the pressure differential; and a flow control portion integrally formed with the body portion, having a size and shape that cooperates with the runner to form a flow control region for separating the channel and the cavity. The pressure differential acting on the flow control portion regulates the flow of molding material into the cavity to prevent the formation of a sink formation in the molded structure. 
     In another embodiment an injection molding apparatus is disclosed. The injection mold includes at least the following: a runner configured to guide a flow of pressurized molten molding material into a cavity, the runner having a gate area disposed at an intersection of the runner and the cavity; and a pressure actuated flow controller. The pressure actuated flow controller includes a body portion disposed within the runner, and a flow control portion integrally formed with the body portion. The flow control portion is disposed substantially within the gate area of the runner. When a predetermined pressure is reached within the cavity, the pressurized molten material in the cavity exerts a force on the flow control portion of the flow controller that overcomes a force exerted by a supply pressure of the molten molding material in the runner. When the force exerted by the molten molding material within the cavity pushes the flow controller into a closed position against a sidewall of the gate area, the flow controller severs a connection between the molten molding material in the runner and the molten molding material in the cavity. 
     In yet another embodiment a method for forming an injection molded part is disclosed. The method includes at least the following steps: injecting pressurized molten molding material into a cavity of an injection mold through a runner until a predetermined pressure is reached in the cavity; and closing a path between the runner and the cavity. The path is closed with a flow controller disposed within the runner once the predetermined pressure is established in the cavity. The predetermined pressure within the cavity exerts a force on the flow controller that overcomes a force provided by pressurized molten molding material in the runner to move the flow controller axially within the runner from an open position to a closed position. In the open position the flow controller in cooperation with the runner defines a path between the flow controller and sidewalls of the runner along which the molten molding material flows into the cavity. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The described embodiments may be better understood by reference to the following description and the accompanying drawings. Additionally, advantages of the described embodiments may be better understood by reference to the following description and accompanying drawings in which: 
         FIG. 1  shows cross-sectional view of an injection mold with a close up view of a cosmetic imperfection; 
         FIGS. 2A-2B  show cross-sectional views of a valve pin disposed in a runner and gate area of an injection mold; 
         FIGS. 3A-3B  show cross-sectional views of a reverse valve pin disposed in a runner and gate area of an injection mold; 
         FIG. 3C  shows how supply pressure is balanced against packing pressure with a reverse valve pin configuration; 
         FIGS. 4A-4B  show an injection mold having a slider configured to sever a connection between molten molding material disposed in a mold cavity and molten molding material disposed in a runner; 
         FIG. 4C  shows one way the slider depicted in  FIGS. 4A and 4B  can be configured to be actuated by pressure supplied by molten molding material within a mold cavity; 
         FIG. 5A  shows a mold having a runner structure connected to a mold cavity by a conduit configured with a piston; 
         FIG. 5B  shows how molten molding material can be injected in the conduit of the mold depicted in  FIG. 5A ; 
         FIG. 5C  shows how the piston of the mold depicted in  FIGS. 5A and 5B  can be used to push the molten molding material out of the conduit and into the mold cavity; 
         FIG. 5D  shows how a front face portion of the piston of the mold depicted in  FIGS. 5A-5C  can push the molten molding material into the mold cavity until the front face reaches the mold cavity; and 
         FIG. 6  shows a flow chart describing a method for controlling the flow of molten molding material into a mold cavity. 
     
    
    
     DETAILED DESCRIPTION OF SELECTED EMBODIMENTS 
     Representative applications of methods and apparatus according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
     In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. 
     Injection molding processes typically involves two steps: melting an appropriate amount of molding material, and then injecting the melted material into a mold cavity having a shape in accordance with a finished part. The molding material can be made up of any number of polymers, including thermoplastics, thermosets and elastomers. For exemplary purposes only the molding material will be exemplified by plastic resin without implying any loss of generality. The melted plastic resin can be delivered from the heater to the mold cavity using multiple conduits that are disposed throughout the mold, to deliver plastic resin to various portions of the mold cavity. These conduits are typically referred to as runners in the injection molding industry. The opening leading from each runner to the mold cavity is referred to as a gate or gate area. Once the mold cavity has been filled, extra molten plastic material is typically trapped inside the runners and gate areas of the mold. In a cold runner system (one in which material within the runners are not kept at molten temperatures), as the mold cools and the part solidifies, so does the plastic material trapped in the runners and gates. When plastic resin cools a certain amount of contraction takes place. Given a sealed mold cavity having a substantially uniform cross-section, shrinkage of the plastic material tends to be substantially uniform across the part; however, because the material trapped in the runners and gate areas remains attached to the plastic part during cooling the uniformity of the part becomes variable, causing a certain amount of asymmetric shrinkage to occur in portions of the part in close proximity to the gates. This asymmetric shrinkage is commonly referred to as sink. Sink is quite common in portions of the part opposite gate areas, as the plastic that should be present along the surface tends to be pulled into nearby gate and runner structures during the plastic contraction. Since contraction of the plastic is typically centered about a center point of the plastic part, longer gate and runner structures tend to cause more severe cases of sink, as a center point of the plastic part tends to be displaced farther from the actual part. 
     One solution to the sink phenomenon is to separate the resin in the cavity from the resin in the gate area and runner structure shortly after completing the injection of the melted plastic resin into each cavity. In this way, plastic resin from the cavity is separated from the gate structure early enough that it is not pulled into the gate and runner structures during cooling and sink can be avoided. When the resin is separated along a surface of the plastic part, variations in cosmetic surfaces near the gates can also be avoided, as portions of the part in close proximity to gate regions can have a similar appearance as the rest of the part. Separation of resin in the cavity from resin in the runners and gate regions can be accomplished in a number of ways. 
     In one embodiment a valve pin can be situated within the runner, close to the gate structure. The valve pin can have a first position that allows molten plastic resin to flow past it and a second position in which the liquefied plastic resin in the runner and gate areas is physically separated from the plastic resin injected into the cavity. In this way, the valve pin operates as a flow controller for the molten molding material entering the cavity. The valve pin can be configured with various geometries that are suited for separating the cavity from the gate and runner structures. In some implementation the valve pin can be mechanically, electrically or pneumatically actuated between positions by a discrete actuation system. This implementation allows for shutoff of resin supply to the cavity at any time. In another implementation, the valve pin can be actuated when a pressure of the plastic resin within the mold cavity reaches a predefined pressure, often referred to as a packing pressure. The pressurized molten plastic within the cavity can be configured to exert pressure on the valve pin, causing the valve pin to press against a portion of the sidewalls defining the gate area into the second position. In this way, a design of the mold can be simplified, as the valve pin doesn&#39;t require an actuator for modulating a position of the valve pin. Furthermore, another advantage of such a configuration is that it allows the mold cavity to be consistently pressurized at the packing pressure before the valve pin prevents passage of the molten plastic. 
     In another embodiment an intervening slider can be configured to cleave all but a small vestige from the cooling plastic part situated in the cavity of the mold. The slider can be situated within the mold and be configured to sever molten plastic within the runner at a position that is close to the plastic resin cooling in the mold cavity. By minimizing the amount of material left attached to the plastic material in the cavity, sink can be substantially eliminated. When there are a number of closely spaced gates a single slider can be configured to concurrently sever a number of runners. In this way a number of gate and runner structures can be severed from the cavity by adding a single structure to the mold. In some configurations, a pressure within the mold cavity can be used to actuate the slider. 
     These and other embodiments are discussed below with reference to  FIGS. 1-6 ; however, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
       FIG. 1  shows one configuration of an injection mold  100 . Injection mold  100  includes two sides: a cavity side  102  and a core side  104 . The injection molding process includes melting and compressing plastic pellets with ram  106 . In addition to melting and compressing the plastic pellets, ram  106  is also operable to drive the molten plastic forward into the mold, thereby keeping it flowing through cavity side  102 . Once the molten plastic passes ram  106 , it is pushed farther into the mold by pressurized molten plastic behind it. The path the plastic takes through the injection mold is commonly referred to in the industry as a sprue. The sprue can be divided into a number of runners at position  108 , including runner  110 , that distribute the molten plastic to various positions in mold cavity  112  from position  108  of the sprue. The runner structure can allow the molten plastic to evenly fill injection mold cavity  112 . In some embodiments a series of runners can be configured to distribute plastic to each of a number of cavities, within the injection mold. Once cavity  112  is filled with molten plastic at a predefined pressure, commonly referred to as a packing pressure, the plastic is allowed to cool and at least partially solidify. Close-up view  114  shows gate structure  116  of the injection mold. Gate structure  116  is where the molten plastic is introduced into the mold cavity. A phenomenon known as sink can occur as a result of material in mold cavity  112  being sucked up into runner  110  through gate structure  116  during solidification of the molten plastic. As a result of a portion of the plastic being sucked into runner  110 , shrinkage of the plastic during cooling is asymmetric, causing sink portion  118  to form along a surface of the part. Such an imperfection can cause serious cosmetic imperfections in a finished part, thereby requiring finishing operations on the injection molded part to smooth out the imperfections. 
       FIG. 2A  shows one solution to asymmetric shrinkage in which valve pin  206  is positioned in close proximity to a gate structure of injection mold  200 . A valve pin can have a geometry corresponding to a cone or frustum of a cone with a wider base of the cone disposed away from cavity  208  of injection mold  200 . Valve pin  206  is depicted in  FIG. 2A  and has at least two positions: an open position, and a closed position. In the open position, as depicted in close up view  209 , molten plastic can move past either side of valve pin  206 . When cavity  208  is filled to a packing pressure, valve pin  206  can assume the closed position. In its closed position, valve pin  206  can sever the cooling molten plastic in cavity  208  from any plastic within the gate structure. In some embodiments valve pin  206  can be formed so that in a closed position, valve pin face  210  can be substantially flush with cavity face  212  of cavity  208 . Such a configuration can prevent any vestige from being formed on the finished part near the gate structure. Valve pin  202  can be actuated between the closed and open positions in a number of ways. 
       FIG. 2B  shows one way in which valve pin  206  can be actuated. The depiction in  FIG. 2B  shows how a portion of valve pin  206  can be coupled to an actuating element  214 . Actuating element  214  can be attached to valve pin  206  anywhere along a length of valve pin  206 . When actuating element  214  is disposed near a rear portion of valve pin  206 , actuating element  214  can be positioned near an exterior portion of cavity side  202 , thereby simplifying a design of actuating element  214 . Actuating element  214  can be implemented in a number of different configurations and powered electrically, hydraulic and/or pneumatically. In one embodiment, actuating element  214  can be an arm extending through a sidewall of the runner that is mechanically coupled to valve pin  206  and around which molten plastic can flow. In a first position molten plastic can flow easily around valve pin  206  and in a second position valve pin  202  can be pushed up against surface  216  of cavity side  202 , effectively severing a connection between molten plastic in the cavity and molten plastic trapped in the runner system. In addition to providing a means for transitioning valve pin  202  between positions, actuating element  214  can also be configured to constrain valve pin  202  within the runner, thereby helping to properly position it throughout an injection molding process. 
       FIGS. 3A-3B  illustrate injection mold  300  having a reverse valve pin configuration. In the reverse valve pin configuration a supply pressure or forward pressure of molten plastic keeps reverse valve pin  301  in an open configuration during an injection molding operation. Reverse valve pin  301  includes a flow control portion  302  and a body portion  303 . Flow control portion  302  can have a cone shaped geometry and body portion  303  can have a cylindrical geometry. A broad end of flow control portion  302  can be disposed towards cavity  304  and a narrow end of cone shaped flow control portion  302  can be integrally formed with body portion  303 .  FIG. 3A  depicts molten plastic passing along either side of reverse valve pin  301 . Due to the shape of flow control portion  302  incoming molten plastic is driven at an angle with respect to its original direction of travel in the runner. Such a change in direction can advantageously reduce blushing on the finished part as the incoming molten plastic hits an opposing side of cavity  304  at a relatively lower speed. As mold cavity  304  fills with molten plastic, an amount of back pressure builds up within cavity  304 . The amount of built up back pressure corresponds to the amount of molten plastic that has been injected into cavity  304 . 
     Injection mold  300  can have a packing pressure  306  at which injection mold  300  is configured to most successfully operate. By carefully designing the geometry of reverse valve pin  302 , packing pressure  306  within cavity  304  can create a negative pressure differential between the plastic in the cavity and the plastic in the runner just great enough to push reverse valve pin  302  into a closed position by overcoming supply pressure  308 , as depicted in  FIG. 3B . In some configurations a cavity facing surface of flow control portion  302  can be substantially coplanar with a wall defining cavity  304  when reverse valve pin  301  is in a closed position. In this way reverse valve pin  301  can be operative as a molten plastic flow controller for injection mold  300 . Such a configuration leaves minimal traces on a cosmetic surface of the finished part corresponding to the intersection of the runner with cavity  304 . In an alternative embodiment, suction can be used to substantially reduce pressure in the runner system of mold  300  once a predetermined amount of molten plastic has been introduced into the system. In some embodiments the suction can be great enough to substantially clear molten plastic remaining outside of the mold cavity  304 . In this way, reverse valve pin  302  is sucked into a closed position and the runner system is substantially cleared of molten plastic between injection molding operations. It should be noted that the packing pressure can be an ideal pressure for the molten plastic within cavity  304  to be at just prior to cooling of the plastic within cavity  304 . Cooling can be accomplished passively or actively. In some embodiments mold  300  can be water cooled, to allow the molten plastic within mold  300  to quickly solidify. 
       FIG. 3C  shows more precisely how a supply pressure  308  of incoming molten plastic balances against packing pressure  306  being provided by the molten plastic within cavity  304 . This balance can be adjusted by changing geometry of various portions of reverse valve pin  302 . For example, a diameter  310  of reverse valve pin  302  can be increase, thereby reducing the area across which supply pressure  308  can act. A slope of surfaces  312  can also be adjusted to change the amount of force supply pressure  308  can exert upon surfaces  312 . These types of adjustments can be utilized to fine tune the actuation of reverse valve pin  302  to coincide with an ideal packing pressure  306  for any given part. In some embodiments, reverse valve pin  302  can be configured to be biased towards a closed position by a spring. In such an embodiment, reverse valve pin  302  can be configured to be closed by the spring both before and after molten molding material is provided at a supply pressure great enough to overcome the force provided by the spring. Consequently, this allows for a lower pressure within the mold cavity to actuate reverse valve pin  302  to a closed position, since the spring can assist the mold cavity pressure in pushing reverse valve pin  302  against sidewalls in the gate region. It should be noted that in other embodiments the spring can be configured to be biased towards an open position by the spring. 
       FIG. 4A  shows an illustration of a slider configured to terminate a connection between molten plastic in a mold cavity and excess plastic left within the runner system. Slider  402  can sever a connection between sprue  404  and molten plastic disposed within mold cavity  406 . Actuator  408  can actuate slider  402 . Actuator  408  interacts with slider  402  to move slider  402  to the left as illustrated in  FIG. 4B . Mold thickness  410  between slider  402  and cavity  406  can be minimized, thereby leaving a small portion of excess material attached to the molten plastic in cavity  406 . By minimizing excess material left about the gate region a likelihood of causing sink in an opposing side of the finished part can be greatly reduced.  FIG. 4C  shows an alternative way of actuating slider  402 . Pressure from the molten plastic can be used to push against slider  402 . For example, cavity  406  can include pressure vents for allowing air to escape from cavity  406  as cavity  406  is filled with molten plastic. At least some of the air vented from the cavity can be directed into pathway  412 , which can be configured to actuate slider  402 . When pressure provided by the molten plastic displacing air in the cavity exceeds a spring based or supply pressure based force  414  acting on an opposite side of slider  402 , slider  402  closes and terminates a connection between sprue  404  and molten plastic within cavity  406 . 
       FIGS. 5A-5D  show a series of illustrations showing another configuration for injecting molten plastic into a mold cavity.  FIG. 5A  shows mold  500  having a runner  502  for supplying molten plastic to cavity  504 . Runner  502  can be configured to deposit the molten plastic into conduit  506 . In  FIG. 5B , once a predetermined amount of molten plastic  508  is delivered by runner  502  into conduit  506 , piston  510  can push molten plastic  508  into cavity  504 . As piston  510  passes runner  502 , molten plastic in runner  502  is severed from molten plastic  508 . In  FIG. 5C  piston  510  is shown partially depressed as it pushes molten plastic  508  into cavity  504 . As molten plastic  508  is pushed into cavity  504 , air trapped within cavity  504  can escape cavity  504  via small vent holes etched along parting lines  512 .  FIG. 5D  shows how once piston  510  has pushed molten plastic  508  fully into cavity  504  it is positioned along a wall of cavity  504 . A front portion of piston  510  can be shaped to match a surface defining cavity  504 . In this way, the finished part can have little or no tool marks along the portion of the finished part that is in contact with piston  510  during the cooling process. It should be noted that another advantage of such a configuration is that because the piston leaves little or no marks or sink on an opposing portion of the finished part, a size of the conduit can be larger than a typical runner would be. A larger gate area can reduce problems with blushing on the finished part, as narrow gate areas can lead to early solidification of the molten plastic. Early solidification of the molten plastic prevents the plastic from fully conforming to the mold cavity, thereby causing blushing/defects on various portions of the finished part. 
       FIG. 6  shows a flow chart  600  describing a method for controlling the flow of molten molding material into a mold cavity. In a first step  602  a shot of molten molding material is injected into a runner. The shot of molten molding material can be sufficient to fill both a mold cavity and the runner. The runner defines a path along which the molten molding material travels to the cavity. The shot of molten molding material can be provided at a supply pressure sufficient to push the material into the cavity at a packing pressure. In step  604  a flow controller can be configured to sever a connection between the molding material in the mold cavity and the molding material in the runner, prior to the molding material solidifying. In some embodiments the flow controller can be configured to sever the connection along an interface between the runner and the mold cavity. In such an embodiment the finished part can have a blemish free surface at the portion where the material is severed. At step  606  the molding material within the mold cavity is cooled enough so that a resulting part is at least partially solidified. At step  608 , the resulting part can be ejected from the mold cavity. Since the part is already separated from the solidified molding material within the runner, the resulting part can be ejected separately or concurrently with solidified material disposed in the runner. 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a computer readable medium for controlling manufacturing operations or as computer readable code on a computer readable medium for controlling a manufacturing line. The computer readable medium is any data storage device that can store data, which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20130516
Publication Date: 20150721
Grant Date: 20150721
Priority Date: 20130516
Inventors: WITTENBERG MICHAEL B.
CHRISTOPHY MIGUEL C.
JARVIS DANIEL W.
MALEK SHAYAN
Assignee: APPLE INC
CPC Classifications: [{"code": "B29C45/2806", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C45/0025", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/7613", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C2045/306", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/2806", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C45/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C45/2806", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C45/7613", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C45/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C2045/306", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/0025", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 51895162