Injection molding process with an ejector device in a compensation position for the production of a textured plastic component and injection molding device for carrying out the injection molding process.

Abstract

An injection molding process (500) for producing a textured plastic component (30) for a motor vehicle in an injection molding device (10) is described, wherein the injection molding device (10) comprises: a first mold half (12), a second mold half (14), and at least one ejector device (16) movable relative to the second mold half (14), wherein the process (500) in particular comprises the following step: moving (S502) the ejector device (16) relative to the second mold half (14) into a compensating position and holding the ejector device (16) in the compensating position during the subsequent steps. Furthermore, an injection molding device (10) with a control unit (50) for carrying out the injection molding process (500) is described.

Description

[0001] The invention relates to an injection molding process for producing a textured plastic component for a motor vehicle in an injection molding device, wherein the injection molding device comprises: a first mold half, a second mold half, and at least one ejector device movable relative to the second mold half. The invention further relates to an injection molding device configured to carry out the injection molding process.

[0002] Such a procedure is known, for example, from DE 11 2021 002 642 T5.

[0003] Plastic components manufactured using standard injection molding processes, for example from polycarbonate and acrylonitrile styrene acrylate (PC-ASA) or polycarbonate and acrylonitrile butadiene styrene (PC-ABS), and featuring a fine grain, exhibit specific surface defects. These defects cannot be classified as typical surface defects found in injection-molded parts. They occur only on injection-molded parts with a fine grain and are only visible under a strong light source (greater than 5000 lux) and at the correct viewing angle. These surface defects are therefore also referred to as defect holograms. Such defect holograms can also be observed by motorists, for example, under appropriate sunlight.Microscopic examination of affected areas on a plastic component revealed differences in the appearance of the fine grain compared to the surrounding areas. The defect holograms are particularly noticeable on and around the ejector pin areas.

[0004] The object underlying the invention is seen as being to specify an injection molding process and an injection molding device with which the occurrence of defect holograms can be avoided.

[0005] This problem is solved by an injection molding process and an injection molding device with the features of the respective independent patent claim. Advantageous embodiments with expedient further developments are specified in the dependent patent claims.

[0006] A proposed injection molding process for manufacturing a textured plastic component for a motor vehicle in an injection molding device is thus presented, wherein the injection molding device comprises: a first mold half, a second mold half and at least one ejector device movable relative to the second mold half, wherein the process comprises the steps: a) Closing the two mold halves and building up a desired closing force, in particular about 600t; b) Injecting a plastic compound; c) Pressing down the plastic mass; d) Reducing the closing force; e) Opening the two halves of the mold; f) Moving the ejector device relative to the second mold half into an ejection position; g) Removal of the plastic component; h) Moving the ejector device relative to the second mold half into a rest position.

[0007] The procedure stipulates that the following step is performed before or during step b) or step c): a1) Moving the ejector device relative to the second mold half into a compensating position and holding the ejector device in the compensating position during steps b) and / or c).

[0008] By such a step a1), the at least one ejector device, which can also be referred to as an ejector pin or ejector element, projects to a small extent into a mold cavity formed by the closed mold halves. In other words, the at least one ejector device is positioned so that any compression of the ejector device, and in particular of an associated ejector plate, that typically occurs during injection and compression molding is compensated for.

[0009] In the injection molding process, the ejector device can be moved into the compensation position by approximately 0.01mm to 0.5mm, in particular 0.1mm to 0.2mm, in step a1).

[0010] In the injection molding process, the following step can be performed before step d): c1) During a final phase of step c), in particular during the last 0.5 to 10 s of step c) or at the start of cooling and after a delay time of 0.1 s to 5 s since the start of cooling: moving the ejector device, in particular by 0.05 mm to 0.5 mm, preferably 0.1 mm to 0.2 mm, from the compensation position to the rest position and holding the ejector device in the rest position.

[0011] In a final stage of the compression process or during the cooling phase and shrinkage of the plastic, the at least one ejector device is moved away from the mold cavity, in particular so that the at least one ejector device is flush with an inner surface of the second mold half. This prevents the ejector devices (which are compressed in known methods) from transferring pressure back to the component, which would otherwise create the defect holograms in the textured surface.

[0012] In other words, at least one ejector device is moved into the mold cavity under a kind of preload during injection and compression to counteract compression that would otherwise occur. When the at least one ejector device is released or moved back to its rest position, pressure equalization takes place in the area of ​​the ejector device, with the pressure decreasing locally compared to a conventional method. In the conventional method, the ejector device is initially compressed during injection and compression, and then, during cooling, it exerts increased local pressure on the plastic component (countermovement to the previous compression), which causes the undesirable defect holograms.

[0013] In the injection molding process, step d) may include a reduction of the clamping force to a lower value, in particular 100t or less, and further cooling of the plastic component may take place at this lower clamping force.

[0014] The lower closing force can be reduced once cooling is complete and before step e) is carried out.

[0015] In the injection molding process, the plastic component can be manufactured from a mixture of polycarbonate and acrylonitrile styrene acrylate (PC / ASA) or from a mixture of polycarbonate and acrylonitrile butadiene styrene (PC / ABS). Of course, other plastics or plastic mixtures can also be processed using the described method.

[0016] In the injection molding process, a fine texture can be created on the plastic component using the first half of the mold. In other words, the first half of the mold has a textured cavity or mold cavity.

[0017] A further proposal is an injection molding device comprising a first mold half; a second mold half; wherein the first mold half and the second mold half are movable relative to each other between an open position and a closed position; at least one ejector device connected to an ejector plate, wherein the ejector device is movable relative to the second mold half between a rest position and an ejection position; and at least one return-push device connected to the ejector plate and configured to move the ejector device to its rest position by means of the first mold half. The injection molding device is provided to include a control unit configured to carry out the injection molding process described above.

[0018] In the injection molding device, a contact surface of the push-back device that can be brought into contact with the first mold half can be located behind the inside of the second mold half in a rest position of the ejector device with respect to an inside.

[0019] The distance between the inside of the second mold half and the contact surface of the push-back device can be 0.05mm to 5mm, in particular 0.1 to 0.2mm.

[0020] In other words, the push-back device is designed to be somewhat shorter in terms of its longitudinal extent, so that when the at least one ejector device is moved from the rest position to the compensation position by means of the ejector plate, it can be moved along with it without its contact surface coming into contact with the opposite second mold half too early.

[0021] In the injection molding process described above, or using the injection molding device described above, a reduction or prevention of defective holograms is achieved by relaxing the ejector mechanism during the cooling phase. This can also be supported by lowering the holding pressure at the end of the holding pressure phase.

[0022] Further advantages and details of the invention will become apparent from the following description of embodiments with reference to the figures. These show: Fig. 1. A simplified and schematic sectional view of an injection molding device at the beginning of an injection molding process; Fig. 2 in a simplified and schematic sectional view of the injection molding device during the injection molding process; Fig. 3. A simplified and schematic sectional view of the injection molding device during the injection molding process; Fig. 4 in a simplified and schematic sectional view of the injection molding device during the injection molding process; Fig. 5 in a simplified and schematic sectional view of the injection molding device during the injection molding process; Fig. 6 in a simplified and schematic sectional view the injection molding device at the end of the injection molding process;

[0023] In Fig. Figure 1 is a simplified and schematic example of an injection molding device 10 shown as a sectional view. The injection molding device 10 comprises a first mold half 12 and a second mold half 14, wherein the first mold half 12 and the second mold half 14 are separated relative to each other by a Fig. 1 shown opening position and one in Fig. The two parts shown in Figure 2 are movable in the closed position. In the example shown of the injection molding device 10, it is assumed that the second mold half 14 is stationary, while the first mold half 12 is movable, as illustrated by the white contour arrow OS.

[0024] Each mold half 12, 14 has a respective mold cavity 12k, 14k. In the closed position of the injection molding device 10 ( Fig. 2) The two mold cavities 12k, 14k together form the mold in which the plastic component to be manufactured can be formed.

[0025] The injection molding device 10 further comprises at least one ejector device 16 connected to an ejector plate 18. For illustrative purposes, two ejector devices 16 are shown in the example of the injection molding device 10. It should be noted that the injection molding device 10 can also have more than two ejector devices 16. In particular, the number of ejector devices 16, which can also be referred to as ejector pins or ejector elements, depends on the size, shape, and complexity of the plastic component to be produced using the injection molding device 10.

[0026] The ejector device 16 is positioned relative to the second mold half 14 between a rest position shown in the Fig. and a position shown in Fig. The ejection position shown in section 6 is movable.

[0027] The injection molding device 10 further comprises at least one push-back device 20, which is connected to the ejector plate 18. The push-back device 20 is configured to move the ejector device 16 into the rest position by means of the first mold half 12. The push-back device 20 serves in particular to move the ejector devices 16 away from the first mold half 12 during a closing movement, so that the ejector devices 16 do not penetrate the mold cavity 12k or damage it. In other words, the push-back device 20 constitutes a safety device in case a normally hydraulic movement of the ejector devices 16 from the ejection position ( Fig. 6) into the resting position ( Fig. 1) cannot be carried out.

[0028] The ejector device 16, the ejector plate 18 and the push-back device 20 are movable relative to a simplified representation of the base 22.

[0029] The injection molding device 10 also has a control unit 50 which is configured to control the injection molding device 10 or its components in order to carry out an injection molding process.

[0030] In particular, the control unit 50 is configured to carry out an injection molding process 500, which is described in more detail below. This process focuses on the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. 6 Reference is made to the figures in which the corresponding reference symbols of the process steps are shown to the right of the injection molding device.

[0031] The injection molding process 500 is used to produce a textured plastic component for a motor vehicle in the injection molding device 10. Starting from an open injection molding device 10, which is in Fig. As shown in Figure 1, the procedure 500 can be described as follows.

[0032] According to step S501, the two mold halves 12, 14 are closed and a desired clamping force is applied. The clamping force can be, for example, approximately 600t.

[0033] According to step S502, the ejector device 16 is moved, in particular by about 0.01 mm to 0.5 mm, preferably 0.1 mm to 0.2 mm, relative to the second mold half 14 into a compensating position and held in the compensating position. This is described in the Fig. Figure 3 illustrates the direction of movement of the ejector device 16. This direction is indicated by a double-pointed arrow.

[0034] In the compensation position, the ejector devices 16 protrude slightly into the mold cavity 14k. In particular, each end face 16s of the ejector device 16 lies a few tenths of a millimeter in front of an inner surface 14s of the mold cavity 14k.

[0035] In the compensatory position ( Fig. 3) The ejector plate 18 with the ejector devices 16 attached to it is arranged and held at a corresponding distance AB from the base 22.

[0036] It is further noted that a contact surface 20f of the push-back device 20, which can be brought into contact with the first mold half 12, lies behind the inner surface 14i of the second mold half 14 in a rest position of the ejector device 16 with respect to an inner surface 14i. This is particularly evident from the Fig. 1 and Fig. 2 is evident.

[0037] A distance AB between the inside 14i of the second mold half 14 and the contact surface 20f of the push-back device 20 is 0.05mm to 5mm, in particular 0.1 to 0.2mm.

[0038] In the compensation position according to Fig. 3 The ejector plate 18, together with the ejector device 16 and the push-back device 18, is moved by the distance AB in the direction of the first mold half 12. Accordingly, the contact surface 20f rests against the first mold 12 and the ejector devices 16 protrude into the mold cavity 14k by essentially the same distance AB.

[0039] In the process, according to step S503, a plastic mass is injected, which in Fig. 4 is illustrated by the dotted pattern in the mold cavity 12k, 14k. In step S504, the plastic compound is pressed in.

[0040] During steps S503 and S504, the ejector devices 16 are held in the compensation position, which also results from the Fig. 4 is evident.

[0041] Step S505 marks the start of the cooling process. According to step S506, after a delay of 0.1 s to 5 s since the start of the cooling process (S505), the ejector device 16 is moved, in particular by 0.05 mm to 0.5 mm, preferably 0.1 mm to 0.2 mm, from the compensation position to the rest position and held in the rest position. This is particularly relevant in the Fig. Figure 5 illustrates the direction of movement of the ejector device 16. The direction of movement is indicated by a double-headed arrow. It should be noted that step S506 can also be performed during the final phase of step S504, in particular during the last 0.5 to 10 s of step S504.

[0042] In step S506, the ejector device 16, in particular together with the ejector plate 18 and the push-back device 20, is moved by the distance AB (see Fig. 3 and Fig. 4) moved back to the base 22. Accordingly, the ejector devices 16 are moved out of the mold cavity 12k, 14k. In particular, the ejector devices 16 or their end faces 16s are essentially flush with the inside 14s of the cavity 14k of the second mold half 14 at the end of step S506.

[0043] The process 500 is then completed by the following steps: In step S507, the clamping force is reduced. This takes place in the still closed position of the injection molding device, as described in Fig. 5 is shown.

[0044] According to step S508, the two mold halves 12 and 14 are opened. Finally, in step S509, the ejector device 16 is moved relative to the second mold half 14 into an ejection position. The direction of movement of the ejector device 16 is Fig. Figure 6 is illustrated by the arrow with a concave arrowhead. Thus, the finished plastic component 30 can be ejected or removed from the injection molding device in one step S510. This is simplified in the Fig. 6 shown.

[0045] According to step S511, the ejector device 16 is moved relative to the second mold half 14 into the rest position, i.e. opposite to the position shown in Fig. 6. The direction of movement shown (arrow with a concave arrowhead) so that the situation corresponds again to the representation in the Fig. 1 has been reached.

[0046] Method 500 can optionally include, in step S507 (reducing the clamping force), a reduction of the clamping force to a lower value, in particular 100 t, whereby further cooling of the plastic component takes place at this lower clamping force. In other words, the lower clamping force is maintained for a certain period of time. The lower clamping force is then reduced once cooling is complete and before step S508 (opening the mold halves 12, 14) is performed.

[0047] In injection molding process 500, the plastic component 30 can be produced from a mixture of polycarbonate and acrylonitrile styrene acrylate (PC / ASA) or from a mixture of polycarbonate and acrylonitrile butadiene styrene (PC / ABS). However, other plastics or plastic mixtures can also be processed using the described process 500.

[0048] In the injection molding process 500, a fine texture is produced on the plastic component 30 by means of the first mold half 12, in particular by means of the mold cavity 12k.

[0049] The injection molding process 500 presented here prevents the ejector devices 16 (which are compressed in known processes) from releasing pressure back onto the component during cooling. Accordingly, the formation of defect holograms in the textured surface of the plastic component can be reduced or avoided. In other words, the at least one ejector device 16 is moved into the mold cavity 12k, 14k under a kind of preload during injection and compression to counteract any compression that may occur. When the at least one ejector device 16 is released or moved back to its rest position, pressure equalization takes place in the area of ​​the ejector device 16, particularly at its end face 16s, with the pressure decreasing locally compared to a conventional process. Thus, the formation of defect holograms on the plastic component 30 can be reduced or avoided. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 11 2021 002 642 T5

[0002]

Claims

[1] Injection molding method (500) for producing a textured plastic component (30) for a motor vehicle in an injection molding device (10), wherein the injection molding device (10) comprises: a first mold half (12), a second mold half (14) and at least one ejector device (16) movable relative to the second mold half (14), wherein the method (500) comprises the steps: a) Closing (S501) the two mold halves (12, 14) and building up a desired closing force, in particular about 600t; b) Injection (S503) of a plastic compound; c) Pressing down (S504) the plastic compound; d) Reducing (S507) the closing force; e) Opening (S508) the two mold halves (12, 14); f) Moving (S509) the ejector device (16) relative to the second mold half (14) into an ejection position; g) Removal (S510) of the plastic component (30); h) Moving (S511) the ejector device (16) relative to the second mold half (14) into a rest position; characterized by , that in the procedure (500) the following step is performed before or during step b) or step c): a1) Moving (S502) the ejector device (16) relative to the second mold half (14) into a compensating position and holding the ejector device (16) in the compensating position during steps b) and / or c). [2] Injection molding process (500) according to claim 1, characterized by , that the ejector device (16) is moved in step a1) by about 0.01mm to 0.5mm, in particular 0.1mm to 0.2mm, into the compensation position (S502). [3] Injection molding process (500) according to claim 1 or 2, characterized by , that in procedure (500) the following step is performed before step d): c1) During a final phase of step c), in particular during the last 0.5 to 10 s of step c), or at the start (S505) of cooling and after a delay time of 0.1 s to 5 s since the start of cooling: Moving (S506) the ejector device (16), in particular by 0.05 mm to 0.5 mm, preferably 0.1 mm to 0.2 mm, from the compensation position to the rest position and holding the ejector device (16) in the rest position. [4] Injection molding process (500) according to any one of the preceding claims, characterized by , that in the process step d) includes a reduction of the clamping force to a lower value, in particular 100t or less, and further cooling of the plastic component takes place at this lower clamping force [5] Injection molding process according to claim 4, characterized by , that the lower closing force is reduced once cooling is complete and before step e) is carried out. [6] Injection molding process according to any one of the preceding claims, characterized by that the plastic component is made from a mixture of polycarbonate and acrylonitrile styrene acrylate (PC / ASA) or from a mixture of polycarbonate and acrylonitrile butadiene styrene (PC / ABS). [7] Injection molding process according to any one of the preceding claims, characterized by that a fine texture is produced on the plastic component using the first half of the mold. [8] Injection molding device with of a first mold half; a second mold half; wherein the first mold half and the second mold half are movable relative to each other between an open position and a closed position; at least one ejector device connected to an ejector plate, wherein the ejector device is movable relative to the second mold half between a rest position and an ejection position, at least one push-back device connected to the ejector plate and configured to move the ejector device into the rest position by means of the first mold half, a control unit configured to carry out the method according to one of the preceding claims. [9] Injection molding device according to claim 8, characterized by , that a contact surface of the push-back device which can be brought into contact with the first mold half lies behind the inside in a rest position of the ejector device with respect to an inside of the second mold half. [10] Injection molding device according to claim 9, characterized by, that the distance between the inside of the second mold half and the contact surface of the push-back device is 0.05mm to 5mm, in particular 0.1 to 0.2mm.

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