WO1994021440A1 - Procede de moulage de pieces structurales en plastique - Google Patents

Procede de moulage de pieces structurales en plastique Download PDF

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Publication number
WO1994021440A1
WO1994021440A1 PCT/US1993/002550 US9302550W WO9421440A1 WO 1994021440 A1 WO1994021440 A1 WO 1994021440A1 US 9302550 W US9302550 W US 9302550W WO 9421440 A1 WO9421440 A1 WO 9421440A1
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WO
WIPO (PCT)
Prior art keywords
cavity
insert
mold
mold cavity
plastic part
Prior art date
Application number
PCT/US1993/002550
Other languages
English (en)
Inventor
Charles W. Bailey
Original Assignee
Signet Industries
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Signet Industries filed Critical Signet Industries
Priority to AU39261/93A priority Critical patent/AU3926193A/en
Priority to PCT/US1993/002550 priority patent/WO1994021440A1/fr
Publication of WO1994021440A1 publication Critical patent/WO1994021440A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
    • B29C45/56—Means for plasticising or homogenising the moulding material or forcing it into the mould using mould parts movable during or after injection, e.g. injection-compression moulding
    • B29C45/5675—Means for plasticising or homogenising the moulding material or forcing it into the mould using mould parts movable during or after injection, e.g. injection-compression moulding for making orifices in or through the moulded article
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/22—Hinges, pivots

Definitions

  • the present invention relates to processes for converting plastics into products, and more particularly to improvements in injection molding processes.
  • the present invention also relates to improved apparatus for use with the improved processes.
  • Injection molding is used for making plastic parts in highly automated processes that require little finishing of the parts made.
  • An injection molding process analogous to metal die casting, involves heating a granular plastic material, forcing it through a heated cylinder where it is plasticized, and injecting the material through a nozzle into a mold cavity shaped to the specification of the finished plastic part.
  • the basic steps of such a process include closing the mold containing the cavity and forcing the mold against the nozzle.
  • the plastic material is fed into the cylinder from a hopper.
  • a screw, plunger, or combination of screw and plunger forces the material within the heated cylinder toward the nozzle, plasticizing the material and forcing the material through the nozzle and into the mold cavity.
  • the screw or plunger or both maintain pressure through the nozzle until the plastic material is cooled and/or set.
  • the screw or nozzle or both then reverse to relieve pressure.
  • the mold opens so that the plastic molded part can be removed.
  • injection molding processes have many advantages.
  • An injection molding process is capable of high output rates of producing parts that need very little finishing. This is because of the high automation of injection molding processes.
  • material waste may be avoided in many instances by collecting material including material cut or machined from parts during finishing, again plasticizing the waste material, and injecting the plasticized material into the mold cavity to produce another plastic part.
  • injection molding processes are not without shortcomings.
  • High equipment costs are associated with injection molding processes, including the costs of making and purchasing molds.
  • a plastic part that is solid in a finished state has been affected by the flow patterns of the molten polymer or plasticized material in a molten state during the injection molding process. An the finished plastic parts are not well served by uneven finishing techniques and workmanship, regardless of how little finishing is needed.
  • Prior Art Figs. 3A and 3B it is known to form a hole in an injection molded plastic part by injecting molten, plasticized material 10A (for example, a polymer) around a pin 64 spanning the cross-section of the mold cavity 32 forming the cross-section of the plastic part.
  • molten, plasticized material 10A for example, a polymer
  • the flow pattern of the molten material 10A is along flow lines 10B which pattern stress lines that develop in the finished plastic part. Because the pin 64 restricts the flow of the molten material 10A, flow marks, weld lines, and possible cracking develop because of the molten stress.
  • the mechanical properties of the finished plastic part vary according to the stress patterns.
  • the above-mentioned conditions are particularly pronounced for composite materials, such as fifty percent (50%) long glass fiber filed nylon used for high strength characteristics and used for parts that are subjected to high stress conditions.
  • the glass fibers follow the flow lines and cause bunching or disorientation in front of the pin 64 opposite the gate through which the material flows.
  • a weld line is formed. This weld line represents a line for potential cracking of the plastic part.
  • sink marks are irregularities in the wall thickness of molded plastic parts. They are unsightly and may create internal stresses.
  • the sink marks result from not having enough of the molten material in the mold to completely fill the cavity during the cooling process, during which there is some shrinkage of the material as it solidifies.
  • This condition is pronounced when the molten material moves from a thin cross-section of the mold cavity into a thicker cross-section as when a wall section, for example wall 22 of Fig. 7, has a boss, for example screw boss 12 of Fig. 7, formed in it.
  • the thick cross-section across the boss cools more slowly than the thin wall section and the density of the molten material as it expands, with less pressure, into the cavity forming the boss, contribute to the creation of the sink marks and the differential shrinking in the plastic material.
  • a limitation of the use of injection molding processes in forming certain parts is associated with molten material flowing from thick into thin cross-sections of a mold cavity and the differential cooling that causes thinner cross-sections of the material to set, solidify, or "freeze” during the injection molding process. Disadvantageous "freezing” occurring when the material cools and sets up in the mold cavity before completely filling it.
  • certain cross-sections cannot be successfully molded by injection molding, particularly thin transparent cross-sections of parts disposed between upstream and downstream thick cross-sections. It is for this reason that plastic tail lights are formed in various subparts that are assembled in subsequent manufacturing processes.
  • the gate is the point of entry of the molten material into a mold cavity. Gates may be of any size and shape. The smaller the size of the gate, the easier it is to cut from a finished part and leave a less perceptible blemish, requiring less machining to finish the part. But smaller gates require greater pressure and, hence, energy to force the molten into the mold cavity. Thus, bigger gates requiring less pressure require less energy to manufacture parts, but require more expense to machine and finish the parts.
  • Yet still another advantage of the present invention is to provide an improved injection molding process for manufacturing living hinges attached to thick walled portions of a plastic part.
  • Still yet another advantage of the present invention is to provide an injection molding process allowing for degating without blemishes and without regard to the size of the gates involved.
  • an object of the present invention to provide apparatus for carrying out an injection molding process that accomplishes the above objections.
  • the present invention is an injection molding that improves upon existing processes of injection molding.
  • the process includes steps of injecting a molten plastic material into a mold cavity and moving an insert into the mold cavity to produce a predetermined structure of the part being molded.
  • the improved process of the present invention may be used to displace the molten material such as would be used in forming holes in a part to be molded, to compress portions of a part to thin out thickened walls before the material has had a chance to "freeze", and to densify the plastic material in a manner that is not unlike forging steel.
  • the method accomplishes hole punching by injecting the molten material into the cavity of the mold, which is unobstructed by inserts so as not to affect the flow of the molten material in the cavity. While the material is still plasticized, the insert advances through the cavity and through the material therein, punching a hole having the shape and dimension of the transverse cross-section of the insert (the cross-section transverse to the axis of the insert). When the plastic part is ejected from the mold, no machining would be required for the formed hole. Accordingly, the automated process of making the part with the hole would not require additional labor or manufacture.
  • a movable insert and a movable support are disposed in neutral positions bounding the cavity at either end of a hole to be formed through the part to be molded.
  • the molten material is injected into the cavity without encountering the insert as an obstruction to the flow of the molten material.
  • simultaneous movement of the insert into and through the cavity and the support away from the boundary of the cavity will capture the material between the insert and the support—the material plugging the hole—and displace the material so captured out of the cavity and away from the part to be molded, thereby forming a hole in the part.
  • this displaced material will not clog up the mold cavity, or other part of the mold, it is preferable that after the hole is formed or "punched," the displaced material is placed back to plug the hole by returning the insert and the support to their neutral positions bounding the cavity.
  • the timing of this sequence would be such that the hole is punched through the plasticized material and the material freezes enough for the plug to make tacky contact with the part when the plug of material is placed back in the hole. The plug would thereby be captured by the part, and when the part is ejected, the plug may be punched out by hand, by anyone associated with either the manufacturer or the end user.
  • the method may be used with an intermediate step to densify the material surrounding the hole. If the hole is to be used in joining a structural component, obvious stresses will be placed on the material surrounding the hole when the part is in use. Thus, if the material around the hole can be made more dense to withstand greater stress, the part will be stronger as it is used. The method can be used to accomplish this end.
  • the insert may be moved without the movable support being moved.
  • the material captured between the moving insert and the movable support is squeezed and some of the material captured between the moving insert is displaced thereby into the volume of molten material surrounding the hole, causing the material surrounding the hole to be more dense and thereby strengthened.
  • the support may move with insert to displace the material remaining between them from the cavity altogether. Thereafter, the insert and support together may be moved back to replace the plug of material.
  • the part ejected from the mold will have an easily identifiable plug which may be punched out by hand.
  • the volume surrounding the hole will be more dense having accepted some of the displaced material from the hole.
  • burn-off tests tests performed by burning off the matrix material of a finished part to leave the fibers oriented as they were in the part—show that the fibers in the volume surrounding the hole become cross-liked or interlaced during displacement of the material into the volume surrounding the hole.
  • the cross-linked or interlaced fibers strengthen the material in the volume surrounding the hole. Accordingly, the steps are used to first densify and/or cross-link fibers in the material, and then, displace the material.
  • This process of densification may be advantageously used to eliminate sink marks behind thickened cross-sections of a part, particularly behind a screw boss.
  • the material is injected into the mold cavity, creating the boss without the hole for the screw.
  • the moving insert in this case a core pin, may be used to move into the plasticized material along the axis of the screw hole. This creates compression and densifies the material surrounding the screw hole of the boss, particularly at the base of the screw hole. The more dense material at the base of the screw hole, which is at the base of the boss, will not shrink more than the cross-section of the plastic wall and the sink mark will not result during cooling.
  • this process avoids the short-coming already discussed in connection with the coventional forming of a hole, whereby material injected around an insert already in place in the cavity before the material is injected into the cavity causes a weld line to develop opposite the gate through which the material is injected into the cavity.
  • This process may also be used for a boss having no screw hole by simply replacing the core pin with a compression pin which presses against the boss, rather than into the boss.
  • a compression pin or bar having a V-formed edge is inserted into the mold cavity to compress (and densify) the plasticized material to form a living hinge.
  • the method has the steps of holding the compression pin in a retracted position, injecting the plasticized material into the cavity of the mold, advancing the compression pin at a predetermined time to compress the material in the hinge area as required, and retracting the compression pin to open the mold and eject the formed part having the living hinge.
  • a punch pin and support pin are in a neutral position allowing the molten material to enter through a gate to form a part in the mold cavity attached to a sprue in the channel leading to the cavity.
  • the punch pin is advanced and the support pin is retracted to remove the gate connecting the part and the runner.
  • the punch pin in its advanced position acts as a check or shut-off valve holding the cabin pressure and eliminating the need for injection hold time—the time necessary for continuing pressure until the molten material solidifies—and thereby reducing the injection molding cycle time.
  • the punch and support pins are thereafter returned to their respective neutral positions, so that the gate is placed back in position where it is ejected with the part from the mold.
  • Fig. 1 is perspective view of a plastic part, which is a base for an automobile seat assembly, showing a sprue, runner, and gate attached thereto.
  • Fig. 2 is a cross-section of an injection mold containing the plastic part therein.
  • Fig. 3A is a diagramatic plan view of the flow pattern in a mold cavity in accordance with the prior art.
  • Fig. 3B is a partial sectional view taken in the direction of arrows 3B—3B in Figure 3A.
  • Fig. 4A is a plan diagrammatical view in a cavity without a pin therein.
  • Fig. 4B is a partial sectional view taken in the direction of arrows 4B-— B in Figure 4A.
  • Fig. 4C is a cross-sectional view as shown in Figure 4B, but with an insertion pin or punch pin inserted into the mold cavity.
  • Fig. 4D is a cross-sectional view as shown in Figure 4C, but with a support pin being moved away from bordering the mold cavity and the punch pin moved through the cavity.
  • Fig. 5 is the cross-sectional view of Figures 4B, C and D, but with the insertion pin moved into the mold cavity and the support pin moving away from the cavity without the material therebetween being compressed.
  • Fig. 6A is a cross-sectional view of a mold cavity with an insert or compression part aligned with one wall of the mold cavity.
  • Fig. 6B is a cross-sectional view as shown in Figure 6A, but with the compression part moved into the mold cavity so as to compress the plasticized material therein into a thinner cross-section.
  • Fig. 7 is a cross-sectional view of a screw boss formed out of one wall of a molded part showing a sink mark formed therein, in accordance with the prior art.
  • Fig. 8A is a cross-sectional view of a boss formed out of one wall of a screw boss within the mold cavity showing a sink mark therein.
  • Fig. 8B is a cross-sectional view of a mold cavity with a screw boss formed out of a wall of the part to be molded, showing an insert within the mold cavity.
  • Fig. 9A is a partial diagrammatical, partial cross-sectional view of a polymer flowing into a mold cavity through a gate bounded by inserts.
  • Fig. 9B shows an insert inserted through the mold cavity and trapping material between the insert and support.
  • Fig. 10A shows a cross-sectional view of plasticized material within the mold cavity and representing a hinge forming insert or hinge compression pin moving to compress the material.
  • Fig. 10B shows a partial perspective view of a living hinge formed by the process of Figure 10A.
  • Fig. 1 shows a plastic part 10 (a base for a seat assembly) manufac ⁇ tured by an injection molding process.
  • the plastic part 10 is an inte ⁇ gral unit, that is, plastic part 10 is not assembled by joining or machining subparts to attain its structure; the subparts are molded integrally into plastic part 10. Accordingly, the subparts include a screw boss 12, holes 14, a plug 16, openings 18, a boss 20, and walls 22. Attached to the plastic part 10 during the injection molding process is a sprue 24, runners 26, and gates 28.
  • the sprue 24, runners 26, and gates 28 are by-products of the injection molding process that produces plastic part 10.
  • plastic part 10 As is known by those of ordinary skill in the injection molding art, when molten plastic material is forced through a nozzle into a mold, the molten plastic material flows through channels to get to the mold's cavity, which is shaped to yield the plastic part when the molten plastic material becomes solid in the finished state. In the molding of plastic part 10, the material that is left in these channels when the plastic is solid in a finished state is formed as the sprue 24, runners 26, and gates 28.
  • An injection molding process not using the teachings of the present invention would require that the sprue 24, runners 26, and gates 28 be machined or cut from plastic part 10.
  • FIG. 2 A design of a two-piece, one cavity injection mold 30 is shown in Fig. 2.
  • the cross-section of what will be the plastic part 10 in the finished state is shown within a mold cavity 32 that is in the cavity half 34 of an injection mold 30. Integral subparts of the plastic part 10, including walls 22, an opening 18, and a boss 20 can be seen. Runner 26, in cross-section, also can be seen.
  • a backup plate 36 is supported by means known to those of ordinary skill in the art.
  • a punch pin carrier plate 38 Between the backup plate 36 and the cavity half 34 of mold 30 is a punch pin carrier plate 38. Depending from the punch pin carrier plate 38, through the cavity half 34 of mold 30, is a punch pin 40.
  • the punch pin carrier plate 38 is supported in the apparatus of Fig. 2 by hydraulic cylinders 42, which are shown to either side of the apparatus of Fig. 2.
  • the hydraulic cylinders 42 carry pistons and piston rods that, when extended, move punch pin carrier plate 38 upwardly (in the orientation shown in Fig. 2) and, when retracted, downwardly. Movement of the punch pin carrier plate 38 will cause the punch pin 40 depending therefrom to move accordingly.
  • the bottom half 44 of injection mold 30, as shown in Fig. 2, has a support pin 46 extending through it.
  • Support pin 46 is supported by a support pin carrier plate 48.
  • Support pin carrier plate 48 is supported on guide column 50 and on locking wedges 52.
  • Support pin carrier plate 48 has cam following surfaces 54 which compliments camming surfaces 56 of locking wedges 52.
  • Locking wedges 52 are attached to piston rods of hydraulic cylinders 58, in a manner known to those of ordinary skill in the art, so that when the piston rods are extended by hydraulic cylinders 58, locking wedges 52 cam support pin carrier plate 48 upwardly, and when hydraulic cylinders 58 retract piston rods attached to locking wedges 52, locking wedges 52 allow support pin carrier plate 48 to drop downwardly as came following surfaces 54 and camming surfaces 56 stay in camming contact.
  • core pin 60 Supported by a core pin carrier plate 49 is a core pin 60.
  • core pin 60 Adjacent mold cavity 32, core pin 60 has an end portion that is shaped as a conventional core pin for a screw hole.
  • core pin carrier plate 49 moves upwardly, by the same camming mechanism for moving support pin carrier plate 48 (although those skilled in the art will recognized that a separate actuating mechanism may be construct for moving core pin carrier plate 49, with its own hydraulic cylinders, locking wedges, and camming surfaces), core pin 60 invades mold cavity 32 and into plastic part 10 when in a plasticized or molten state. As will be later explained, this action by core pin 60 is advantageous to the forming of a screw boss in plastic part 10.
  • ejector pin 62 Indicated in phantom in Fig. 2 is an ejector pin 62, which those of ordinary skill in the art will understand is to be used to eject the finished plastic part 10 from the mold after it reaches a solid state. Ejector pin 62 is supported by an ejector pin carrier plate 64, only a portion of which is being shown in the drawings. It is to be appreciated that other parts of the injection mold press machinery will be understood by those of ordinary skill in the art. It is only necessary here to explain the mechanisms that actuate dynamic inserts that invade the mold cavity 32 or that actuate support mechanism that cooperate with the inserts to displace material. Those of ordinary skill in the art will know that other actuating devices may be used instead of the hydraulic cylinders and locking wedges disclosed. It is the purpose of disclosing the examples of actuating mechanisms shown in Fig. 2 to teach those of , ordinary skill in the art how these dynamic parts will work to accomplish the processes now to be explained.
  • the invention contemplates a process by which a molten plastic material is injected into a mold cavity, for example the mold cavity 32 of Fig. 2, and by which an insert, for example punch pin 40 or compression core pin 60 of Fig. 2, is moved into the mold cavity after the molten material has filled the mold cavity 32 before it has become solid in the finished state.
  • the insert affects the plasticized material to produce a structural configuration in addition to the configuration it obtains from the structure of the cavity 32.
  • compression core pin 60 affects the plasticized material to produce a screw hole in boss 20 of Fig. 2.
  • punch pin 40 produces a hole in plastic part 10 while in a plasticized state, when punch pin 40 is inserted into and beyond cavity 32 and support pin 46 is retracted to allow the displaced material to be taken out of plastic part 10, which the material is in a plasticized state.
  • punch pin 40 is withdrawn from the mold cavity 32 when the molten material 10A is injected into the mold cavity 32. In the withdrawn position, punch pin 40 forms a part of the boundary of cavity 32. Preferably, a seal is formed between the punch pin 40 and the cavity half of the mold 34 so that the molten material does not escape from the cavity 32 around punch pin 40.
  • punch pin 40 may be advanced (inserted) into the cavity in accordance with the dynamics explained with regard to Fig. 2, while support pin 46 is moved to allow a plug of the material 10A to be removed from the mold cavity 32. As shown in the figure, support pin 46 moves downwardly away from cavity 32 at the same speed that punch pin 40 moves away from cavity 32. Thus, a hole 14 (Fig. 1) is produced in plastic part 10 as a plug 66 of the material 10A is removed from what will be the plastic part when the material 10A solidifies.
  • Fig. 4C shows a different application to that shown in Fig. 5 whereby additional advantages occur out of the process of the present invention.
  • punch pin 40 enters cavity 32 and into molten material 10A before support pin 46 is withdrawn from the wall of cavity 32.
  • material is squeezed into the volume of cavity 32 surrounding punch pin 40.
  • This process which is not unlike forging steel, is called by the inventor "densification", whereby the material is made more dense or is “densified” by the compression caused by punch pin 40 entering cavity 32.
  • Timing in accordance with emperical results and/or/temperature and/or/pressure determinates will be used to judge when support pin 46 is retracted to allow a thinner, more dense plug 66A to be displaced from cavity 32 as shown in Fig. 4D. Again, the material is allowed to set up and solidify to a state where at it is tacky and the plug 66A is returned to hole 14 to be later punched out by the manufacturer or end user.
  • this application uses the process of first positioning punch pin 40 and support pin 46 in neutral positions, whereat they present no obstruction to the plastic flow in cavity 32 of injection mold 30. Molten material is then injected into cavity 32, filing the mold cavity 32. At a pre-determined time, punch pin 40 is advanced into mold cavity and support pin 46 retracts to cause the required hole or shape to be incorporated into the plastic part 10 being molded. As a final step, upon completion of the punching operation, punch pin 40 and support pin 42 are reset into their neutral positions and a plug 66 or 66A is captured in the punched hole. Plastic part 10 is then ejected from the mold with the plug 66 or 66A still captured in the hole 14.
  • Punch part 68 operates as punch pin 40 to enter the mold cavity 32 when the molten material 10A has filled mold cavity 32.
  • Punch part 68 may be shaped with a punch face 70 that is circular, rectangular, or any other desired shape. As punch part 68 moves downwardly into molten material 10A within cavity 32, the material is pressed out from or squeezed from under punch face 70 into the area surrounding punch part 68, thereby densifying that material. Perhaps of more importance to this application, however, is that the material beneath punch face 70 is thinned to a pre-determined specification.
  • plastic part 10 may have certain portions of such thin cross-section . that they may be transparent. Of course, if this is the desired structure, clear plastics without reinforcement would be used.
  • punch part 68 may be duplicated in the bottom half of mold 30 so that the thinned area may be situated along the cross-sectional axis of the wall 22, as one punch part moves upwardly while the other moves downwardly.
  • the method just described may be modified and used in a timing sequence in which the punch part 68 is positioned so that the material may be squeezed through a thin cross-section extending into the cavity bounded by punch part 68. As the material flows beneath the punch part 68, it may be retracted to draw the material into a thickened part with the temperature and pressure remaining constant.
  • molten material 10A is injected into the mold cavity 32 and a boss 20 is formed in the mold cavity 32.
  • Compression core pin 60 is in a neutral position out of cavity 32.
  • core pin 60 is inserted into the molten material 10A within the cavity 32, squeezing the material surrounding the core pin 60 and between the core pin 60 and the wall of mold 30.
  • the process just described involves first placing the core pin 60 in a neutral, that is, a retracted position.
  • the plastic material 10A is injected into the mold cavity 32.
  • the compression core pin is advanced to compress material 10A in the location of boss 20.
  • the core pin is retracted, again at a pre-determined time, the mold opens and plastic part 10 with a screw boss 12 is rejected from the mold 30.
  • a gate punch pin 40A is used in combination with a support pin.
  • the pins form a gate through which the molten material or polymer flows along the channel that forms a runner, for example runner 26 of Fig. 1, through the gate that forms a gate, for example gate 28 of Fig. 1, and into the mold cavity 32 forming a plastic part, for example, plastic part 10 of Fig. 1.
  • gate punch pin 40A moves with support pin 46 (or if densification is needed in the area immediately adjacent the gate, gate punch pin 40 may compress material into the surrounding area before support pin 46 is retracted) to punch out a portion of runner 26 at gate 28. At a pre-determined time, this portion is replaced and provides a tack hold between the runner and plastic part 10.
  • the gate 28, runner 26, and sprue 24 are ejected also, but now the end user or the manufacturer may snap the by-products from the finished plastic part without need of cutters or machining.
  • the operation of degating involves first placing the gate punch pin 40A and the support pin 46 in neutral positions.
  • Plastic molten material 10A is injected into the mold cavity 32.
  • the gate punch pin is advanced and the support pin is retracted, removing the gate connecting the plastic part 10 and the runner 26.
  • the punch pin 40A and the support pin 46 are returned to neutral positions, the mold is opened, and the part is ejected.
  • the gate 28, the runner 26, and the sprue 24, can be broken off the finished plastic part by hand, leaving a finished plastic part 10 without a need for machining.
  • a final application of the invention to be disclosed herein involves creating a living hinge by operation of the dynamic inserts.
  • Figs. 10A and 10B Molten material 10A is injected into a mold cavity and forms a hinge "boss" in the area in which a living hinge is desired.
  • the hinge boss is formed by a hinge compression pin 76 in a neutral position.
  • the hinge compression pin is advanced into the molten material 10A within cavity 32, the material is squeezed into the area surrounding the hinge area, thereby densifying the material.
  • the hinge punch pin 76, with its wedge face, 78 stops short of the opposite wall of cavity 32, forming the living hinge.
  • hinge pin 76 is retracted and the plastic part is ejected from the mold.
  • the living hinge 80 is formed within the plastic part 10.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Abstract

Procédé et appareil qui permettent d'améliorer le moulage par injection d'une pièce. Ledit procédé consite à injecter un matériau plastique moulable (10A) dans un moule (30) doté d'une cavité (32) et à introduire un élément (40) dans la cavité (32) constituée de moitiés de moule (34 et 44) pour modifier la structure de la pièce. La structure peut être modifiée en y formant des trous, en densifiant le matériau autour des trous, en densifiant le matériau sur une zone particulière, en amincissant des zones de la pièce à mouler, en formant des protubérances sur les parois de la pièce à mouler sans provoquer des dépressions en surface et en formant des charnières mobiles qui joignent des zones de plus forte épaisseur d'une pièce en plastique fabriquée d'un seul tenant. Un appareil utilise une broche d'introduction (40) et une broche de soutien (46) actionnées par des surfaces à cames et des pistons pour appliquer ledit procédé amélioré.
PCT/US1993/002550 1993-03-16 1993-03-16 Procede de moulage de pieces structurales en plastique WO1994021440A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU39261/93A AU3926193A (en) 1993-03-16 1993-03-16 Method of molding plastic structural parts
PCT/US1993/002550 WO1994021440A1 (fr) 1993-03-16 1993-03-16 Procede de moulage de pieces structurales en plastique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1993/002550 WO1994021440A1 (fr) 1993-03-16 1993-03-16 Procede de moulage de pieces structurales en plastique

Publications (1)

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WO1994021440A1 true WO1994021440A1 (fr) 1994-09-29

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PCT/US1993/002550 WO1994021440A1 (fr) 1993-03-16 1993-03-16 Procede de moulage de pieces structurales en plastique

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WO (1) WO1994021440A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19541394A1 (de) * 1995-11-07 1997-05-15 Menzolit Fibron Gmbh Verfahren zur Herstellung von Werkstücken aus einem Kunststoff insbesondere mit fester Fasereinlage und mit einer glatten Werkstückoberfläche
DE19727774A1 (de) * 1997-06-30 1999-01-07 Klein Schanzlin & Becker Ag Verfahren zur Herstellung eines kunststoffummantelten Bauteils
FR2770801A1 (fr) * 1997-11-12 1999-05-14 Legrand Sa Procede de fabrication d'une piece moulee comportant une zone formant charniere et moule pour la mise en oeuvre de ce procede
US6161450A (en) * 1995-03-03 2000-12-19 Hasse & Wrede Gmbh Viscosity-type torsional-vibration damper
WO2004000528A2 (fr) * 2002-06-21 2003-12-31 N-Fold Limited Articles en plastique moules par injection
GB2404895A (en) * 2003-08-13 2005-02-16 Lear Corp Multi-shot moulding method and assembly
JP2018047608A (ja) * 2016-09-21 2018-03-29 マツダ株式会社 可動構造体を内部に備えた金型および当該金型を用いた成形品の製造方法
WO2021079721A1 (fr) * 2019-10-25 2021-04-29 株式会社デンソー Corps moulé en résine

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US5093049A (en) * 1988-07-18 1992-03-03 Aida Engineering Ltd. Injection molding method with stamping compression
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US3825637A (en) * 1967-07-26 1974-07-23 Ici Ltd Injection molding of foam cored sandwich structures
US3632729A (en) * 1968-08-21 1972-01-04 Eckert & Ziegler Gmbh Method of injection molding with thermosetting resins
US3937779A (en) * 1972-05-03 1976-02-10 Emi Limited Moulding of gramophone records
US3996329A (en) * 1975-01-20 1976-12-07 Misto & Gen Equipment Co. Two-step injection molding
US4097571A (en) * 1976-02-05 1978-06-27 Cox Bernard K Method for producing a foldable plastic strip
JPS608026B2 (ja) * 1977-07-27 1985-02-28 三菱化学株式会社 複素環系染料の製造法
JPS59185636A (ja) * 1983-04-08 1984-10-22 Ricoh Co Ltd 射出圧縮成形法
US4729863A (en) * 1984-05-26 1988-03-08 Bayer Aktiengesellschaft Process and molding tool for the manufacture of molded parts having areas in the form of grids, grills or gratings, such as motor vehicle soft-faces, spoilers, bumpers from a fluid mass
JPH01316234A (ja) * 1988-06-15 1989-12-21 Mitsubishi Motors Corp 複合材成形方法
US5093049A (en) * 1988-07-18 1992-03-03 Aida Engineering Ltd. Injection molding method with stamping compression
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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6161450A (en) * 1995-03-03 2000-12-19 Hasse & Wrede Gmbh Viscosity-type torsional-vibration damper
DE19541394B4 (de) * 1995-11-07 2009-05-14 Menzolit-Fibron Gmbh Verfahren zur Herstellung von Werkstücken aus einem Kunststoff insbesondere mit fester Fasereinlage und mit einer glatten Werkstückoberfläche
DE19541394A1 (de) * 1995-11-07 1997-05-15 Menzolit Fibron Gmbh Verfahren zur Herstellung von Werkstücken aus einem Kunststoff insbesondere mit fester Fasereinlage und mit einer glatten Werkstückoberfläche
DE19727774A1 (de) * 1997-06-30 1999-01-07 Klein Schanzlin & Becker Ag Verfahren zur Herstellung eines kunststoffummantelten Bauteils
FR2770801A1 (fr) * 1997-11-12 1999-05-14 Legrand Sa Procede de fabrication d'une piece moulee comportant une zone formant charniere et moule pour la mise en oeuvre de ce procede
WO2004000528A2 (fr) * 2002-06-21 2003-12-31 N-Fold Limited Articles en plastique moules par injection
WO2004000528A3 (fr) * 2002-06-21 2004-03-11 Fold Ltd N Articles en plastique moules par injection
GB2404895A (en) * 2003-08-13 2005-02-16 Lear Corp Multi-shot moulding method and assembly
GB2404895B (en) * 2003-08-13 2005-12-14 Lear Corp Multi-shot molding method and assembly
US7108825B2 (en) 2003-08-13 2006-09-19 Lear Corporation Multi-shot molding method and assembly
JP2018047608A (ja) * 2016-09-21 2018-03-29 マツダ株式会社 可動構造体を内部に備えた金型および当該金型を用いた成形品の製造方法
WO2021079721A1 (fr) * 2019-10-25 2021-04-29 株式会社デンソー Corps moulé en résine
JP2021066127A (ja) * 2019-10-25 2021-04-30 株式会社デンソー 樹脂成形体

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