Method for injection moulding plastic parts and injection moulding device
By induction heating of the forming surface of the core before injection molding, the problem of rapid heat absorption of the core is solved, and high-quality plastic parts are efficiently produced, especially parts with large surface area to material volume ratios.
Patent Information
- Application Number
- CN202380081262.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-11-24
- Filing Date
- 2023-09-27
- Publication Date
- 2025-07-04
AI Technical Summary
During injection molding, the relatively large surface area of the core leads to rapid absorption of heat, affecting the production quality of plastic parts, especially in the case of large material volumes.
Before injection of plastic material, heat the forming surface of the core by induction, especially heating to a temperature between 50°C and 100°C, reducing or avoiding heat absorption.
It improves the production efficiency and quality of plastic parts, reduces cycle time, is energy-saving and economical, and is suitable for the production of plastic parts with a large surface area to material volume ratio.
Smart Images
Figure CN120265449A_ABST
Abstract
Description
Field of the Invention
[0001] The present invention relates to a method and an injection molding device for injection molding plastic parts, in particular medical products. To produce plastic parts, liquefied plastic material is injected into a cavity of an injection molding tool equipped with a core. Background Art
[0002] By using a core as part of a forming injection molding tool, plastic parts with cavities can be produced. Summary of the Invention
[0003] The object of the present invention is to provide a method and an injection molding device for injection molding plastic parts, which are particularly suitable for producing plastic parts with a relatively large surface area to material volume ratio.
[0004] To achieve this object, a method for injection molding plastic parts is first proposed, which method has the means and features of the independent claims related to this type of method.
[0005] To achieve this object, a method for injection molding plastic parts, in particular medical products, is proposed, wherein, to produce plastic parts, liquefied plastic material is injected into a cavity of an injection molding tool equipped with a core. According to the invention, the method is characterized in that the core is inductively heated before injecting the plastic material.
[0006] The present invention is based on the finding that due to the cores in the production of plastic parts, difficulties occur during injection molding, which cores have a relatively large surface area relative to their material volume. These difficulties are caused by the fact that the cores remove heat from the plastic material injected into the cavity to produce the plastic parts, which can adversely affect the quality of the plastic parts produced in the injection molding method. This is particularly problematic if the core has a particularly large material volume relative to the volume of the cavity filled with the plastic material for producing the plastic parts. Then, the core can act like a radiator, which relatively quickly absorbs heat from the injected plastic material.
[0007] The inductive heating of the core provided according to the invention before injecting the plastic material enables the reduction or even complete avoidance of the heat absorption from the plastic material injected into the cavity caused by the core during the production of plastic parts. The inductive heating of the core has the particular advantage that it can be carried out particularly quickly, energy-efficiently and thus economically for the manufacturing process.
[0008] In one embodiment of the method, it is provided that the core, in particular at least one forming surface of the core, is heated to a temperature between 50 °C and 100 °C, in particular between 60 °C and 80 °C. Heating the core, in particular at least its forming surface, to a temperature of this type can promote a particularly efficient implementation of the method and the production of plastic parts of the desired quality.
[0009] In one embodiment of the method, it is provided that during the induction heating of the core, at least one forming surface of the core is heated. This ensures that, before injecting the plastic material, the forming surface of the core that is at least in contact with the molten plastic material is heated. Then, the injected plastic material strikes the inductively heated surface of the core inside the mold cavity. This prevents the core from drawing heat from the plastic material too quickly.
[0010] In one embodiment of the method, preferably when the injection molding tool is open, the core is inductively heated inside the injection molding tool, in particular inside the mold cavity.
[0011] In another embodiment of the method, it is provided that the core is inductively heated outside the injection molding tool and thus outside the mold cavity and is then inserted into the mold cavity of the injection molding tool.
[0012] In this embodiment of the method, the core is first inductively heated outside the injection molding tool and, after the induction heating, the core is inserted into the injection molding tool and its mold cavity. Then, the injection molding tool and thus the mold cavity can be closed. This variant of the method is advantageous because a relatively short cycle time can be achieved when carrying out the method.
[0013] The inductive heating of the core can be carried out outside the injection molding tool, while another already inductively heated core can be arranged inside the mold cavity to carry out the method. Thus, the injection molding tool can be used for the production of plastic parts independently of the inductive heating of the core. In this way, the downtime during which the injection molding tool and at least one of its mold cavities cannot be used for the production of plastic parts can be reduced or even completely avoided.
[0014] The core can be heated with the inductive heating coil of an induction heating device. In this case, the core for inductive heating can be arranged inside the inductive heating coil. The use of the inductive heating coil allows the core to be heated on the outside and thus on the surface. As will be explained in more detail below, this can promote the relatively rapid cooling of the plastic part on the core.
[0015] In order to arrange the core inside the inductive heating coil, it can be provided that the inductive heating coil is slipped over the core or the core is inserted into the inductive heating coil.
[0016] Advantageously, the induction heating coil has a receiving space for the core, the receiving space having an inner contour adapted to the outer contour of the core, preferably an inner contour adapted to the shaping surface of the core, and / or inductively heats at least the shaping surface of the core.
[0017] The inner contour of the receiving space of the heating coil can correspond to the outer contour of the core, in particular its shaping surface. In this way, when the core is inserted into the mold cavity, at least the core surface delimiting the mold cavity can be uniformly heated.
[0018] The core can be surface-heated by induction heating. The core can preferably consist of a solid material and / or be designed to be at least substantially cavity-free. Thus, for the induction heating of the core, in particular for the induction heating of at least one shaping surface of the core, a temperature gradient can be generated between the heated surface of the core and the inner region of the core that is less heated or not heated at all. Due to the fact that the surface, in particular the shaping surface of the core, is heated, premature heat extraction from the plastic material injected into the mold cavity can be avoided.
[0019] However, if the core is not heated thoroughly, but preferably only its shaping surface is heated, this has advantages during the subsequent cooling of the injection-molded plastic part. Due to the aforementioned temperature gradient, the core material in the inner region of the core can absorb the heat of the injection-molded plastic part from the plastic material and dissipate this heat from the plastic part. Despite the induction heating of the core, this allows the injection-molded plastic part on the core to cool quickly and thus also allows for as short a cycle time as possible when carrying out the method.
[0020] A temperature sensor can be used to monitor the induction heating of the core. The induction heating of the core can also be adjusted with a control unit. In this case, the induction heating of the core can be adjusted by the control unit depending on the temperature of the core to be inductively heated, which is determined using the temperature sensor.
[0021] Advantageously, the induction heating of the core takes place immediately before the plastic material is injected into the mold cavity. This promotes an energy-efficient execution of the method, since in this way the time during which the core can cool before the injection of the plastic material is reduced, and thus the core only needs to be heated to a temperature that is only slightly higher than the temperature that the core should have when the plastic material is injected into the mold cavity.
[0022] In one embodiment of the method, at least one insert (such as a pin, a medical puncturing device, and / or an RFID chip) is inserted into the mold cavity and at least partially overmolded with a plastic material. In this way, a plastic part with at least partially overmolded inserts can be produced. If at least one insert is arranged on a core and / or inserted into the mold cavity together with the core, the method can be carried out particularly efficiently. Thus, the core can not only serve as a forming part of an injection molding tool, but also as a holder and / or transport device for the at least one insert.
[0023] If the insert has an electrical and / or electronic function, for example because it is designed in the form of an RFID chip, it would be advantageous to equip the core with the insert only after induction heating. In this way, damage and / or functional impairment of the insert caused by induction heating of the core are avoided. If the insert is not affected by induction heating, then the core can be equipped with the insert before induction heating.
[0024] After production, the plastic part can initially remain on and be held by the core. It is also possible to remove the plastic part together with the core from the mold cavity and / or the injection molding tool and leave it on the core to cool.
[0025] For induction heating of the core, the core and the heating coil can be arranged at a distance of 1 - 5 mm, in particular 0.5 - 2 mm, particularly preferably 0.2 - 1 mm relative to each other. This can be carried out using a positioning device. The positioning device can be set to move the core into the heating coil and / or to slip the heating coil over the core.
[0026] In one embodiment of the method, the mold cavity and the core are designed in such a way that as part of the method, a plastic part in the form of a plastic spring is produced. The core can also serve as a transport device for removing the plastic part from the mold cavity and / or the injection molding tool. It is also possible that the plastic part remains on the core after injection molding and cools there.
[0027] A plastic spring, in particular a helical plastic spring, can be produced as the plastic part. The plastic spring can have, for example, a ratio of coil length to coil width between 20∶1 and 100∶1, in particular 50∶1, and / or, for example, a ratio of coil thickness to coil width between 1∶2 and 1∶10, in particular 1∶5. The coil thickness can be measured transversely to the longitudinal axis of the plastic spring, and the coil width can be measured in the direction of the longitudinal axis of the plastic spring.
[0028] To achieve this purpose, an injection molding device for injection molding plastic parts, especially medical products, is also proposed, which has the devices and features of the independent claims related to this type of injection molding device. To achieve this purpose, an injection molding device is particularly proposed, which is arranged for injection molding plastic parts. The injection molding device includes at least one injection molding tool, which has at least one mold cavity, at least one core arranged in the mold cavity for injection molding plastic parts, and an induction heating device, which is arranged for inductively heating the at least one core, especially at least one forming surface of the at least one core, before injection molding of the plastic part.
[0029] The induction heating device of the injection molding device can be arranged to particularly heat the at least one core, especially at least one forming surface of the at least one core, to a temperature between 50°C and 100°C, preferably between 60°C and 80°C. Inductively heating the at least one core, especially at least its forming surface, to a temperature within these temperature ranges can be particularly advantageous for producing plastic parts of the desired quality.
[0030] The injection molding device can be arranged to perform the method already explained above and thus perform the method according to any claim related to this method.
[0031] The injection molding device can have a control unit and / or at least one temperature sensor. The control unit can be arranged to adjust the induction heating device depending on the temperature of the core to be inductively heated, which is determined using the at least one temperature sensor.
[0032] The induction heating device can have at least one induction heating coil by means of which the induction heating device is arranged for inductively heating the at least one core, especially at least its forming surface. For this purpose, the heating coil can have a receiving space for receiving the core to be heated. When the shape or inner contour of the receiving space adapts to the shape or outer contour of the core to be heated, particularly efficient induction heating is promoted.
[0033] If the injection molding tool has a plurality of mold cavities, it is advantageous for the induction heating device to have a number of induction heating coils corresponding to the number of mold cavities in the injection molding tool. In this way, all the mold cavities can each be equipped with an inductively heated core simultaneously.
[0034] Particularly advantageously, the injection molding device comprises a plurality of groups of cores, each group of cores having a number of cores corresponding to the number of cavities in the injection molding tool. In this way, a group of cores outside the cavity can be inductively heated while another group of cores is arranged in the cavity for injection molding a plastic part. The other group of cores on which the plastic part lies can be kept in a position outside the injection molding tool and its cavity for cooling the plastic part. Another group of cores can be arranged, for example, in a fitting position for fitting inserts.
[0035] In one embodiment of the injection molding device, the at least one cavity and the core assigned to the cavity are designed such that when the cavity is filled with plastic material, a plastic part in the form of a plastic spring, in particular a helical plastic spring, is produced. The plastic spring can, for example, have a ratio of coil length to coil width between 20:1 and 100:1, for example a ratio of 50:1, and / or a ratio of coil thickness to coil width between 1:2 and 1:10, in particular 1:5. The coil thickness can be measured transversely to the longitudinal axis of the plastic spring, and the coil width can be measured in the direction of the longitudinal axis of the plastic spring.
[0036] The injection molding device, in particular its inductive heating device, can have a positioning device. With the positioning device, the at least one heating coil can be brought into a heating position on the at least one core, or the at least one core can be brought into a heating position on the at least one heating coil.
[0037] During the inductive heating of the core, the at least one inductive heating coil and the at least one core can be arranged in the heating position at a distance of 1 - 5 mm, preferably 0.5 - 2 mm, particularly preferably 0.2 - 1 mm from each other. In this way, energy-saving and as fast as possible inductive heating of the core, in particular its forming surface, is promoted.
[0038] The inductive heating device can be arranged to inductively heat the at least one core inside and / or outside the injection molding tool, in particular the cavity.
[0039] The injection molding device can have a transport device. The transport device can be designed, for example, as a rotary indexing table. The transport device can be arranged to transport the at least one core from the heating position into the injection molding tool and in particular into the cavity. The core can be transported from the heating position outside the cavity, which is located on the inductive heating device, into the injection molding tool and preferably thus into the cavity with the transport device.
[0040] The transport direction can also be set to transport the at least one core, in particular the core on which the plastic part is arranged, from the mold cavity to a removal position outside the mold cavity. In the removal position, the plastic part can then initially be cooled on the core and then removed from the core. In this way, the core not only functions as a forming part of the injection molding tool but also as a transport device by means of which the injection-molded plastic part can be removed from the mold cavity of the injection molding tool.
[0041] The injection molding device can have a removal device by means of which the plastic part can be removed from the at least one core, in particular after its cooling. For this purpose, the removal device can have at least one removal clamp. Advantageously, the removal device has several removal clamps corresponding to the number of mold cavities in the injection molding tool. In this way, all the plastic parts produced in the injection molding step can be removed in one removal process.
[0042] The injection molding device can be set up for at least partial overmolding of inserts, in particular pins and / or medical puncture devices and / or RFID chips.
[0043] In this case, it can be advantageous if the at least one core is set up to hold at least one insert to be at least partially overmolded. For example, the core can be equipped with the insert outside the mold cavity of the injection molding tool and then inserted into the mold cavity together with it. This is preferably done after the core has been inductively heated. The equipment of the core can be carried out before or after heating the core.
[0044] The injection molding device can have an insertion device by means of which the insert can be arranged on the at least one core. For this purpose, the insertion device can have at least one insertion clamp.
[0045] The injection molding device can include an injection molding machine by means of which plastic material can be injected into the at least one mold cavity of the injection molding tool of the injection molding device.
[0046] The injection molding tool can have a nozzle-side half-mold and an ejector-side half-mold between which the at least one mold cavity is designed.
[0047] The control unit can be set up to control the functional units of the injection molding device, in particular to control the injection molding tool, in particular its opening and closing movements, and / or the inductive heating device and / or the positioning device for moving the at least one inductive heating coil between an initial position and a heating position, and / or the transport device and / or the removal device with its removal clamps and / or the equipment device with its equipment clamps and / or the injection molding machine.
[0048] The aforementioned control unit of the injection molding device may have a data interface through which the control unit can be at least temporarily connected to a data memory, such as a cloud-based data memory.
[0049] A computer program may be stored in the data memory, which includes commands for causing the injection molding device according to the invention to perform the steps of the method according to the invention.
[0050] To achieve this purpose, a computer program is therefore also proposed, which includes commands for causing the claimed injection molding device to perform the steps of the claimed method. The computer program may be executed, for example, on the aforementioned control unit of the injection molding device. In this case, the control unit may convert the commands of the computer program into control commands in order to correspondingly control the aforementioned functional units of the injection molding device, which are respectively used to perform the steps of the method. The control unit may act as a control computer configured to run the computer program.
[0051] To achieve this purpose, a computer-readable medium is also proposed, on which a computer program according to the invention is stored. For example, a computer-readable data memory, especially a cloud-based data memory, may be used as the computer-readable medium. The computer-readable medium may in particular be the aforementioned cloud-based data memory to which the injection molding device can be at least temporarily connected via the data interface of its control unit. Description of the Drawings
[0052] The present invention will be described in more detail below using embodiments, but the present invention is not limited to these embodiments. Further embodiments are obtained by combining the features of a single or multiple claims with each other and / or by combining the features of a single or multiple embodiments. In the drawings:
[0053] Figure 1 A perspective view of an injection molding device having an injection molding tool is shown, the injection molding tool having a nozzle-side half mold and an ejector-side half mold, between which a total of four mold cavities are formed, which have a total of four sets of cores that can be moved between the respective stations of the injection molding device along a closed movement path of a transport device, and having an induction heating device having four induction heating coils for inductively heating the cores.
[0054] Figure 2 Shows Figure 1 A perspective view of the injection molding device shown in, in which the injection molding tool is closed, and in the heating position, the four induction heating coils of the induction heating device are arranged in the heating position on four cores located on the induction heating device.
[0055] Figure 3 Shows Figure 1 AndFigure 2 The injection molding device shown, in which the injection molding tool is open, and on four cores arranged on the injection molding tool, four injection molded plastic parts in the form of plastic springs can be seen,
[0056] Figure 4 shows Figures 1-3 An exploded general view of the core, plastic part, insert part, nozzle-side half mold and ejector-side half mold of the injection molding tool of the injection molding device shown, the insert part being at least partially overmolded with plastic material during the production of the plastic part,
[0057] Figure 5 shows a partial cross-sectional view of the core equipped with the insert, the core being in its heating position inside the induction heating coil of the induction heating device shown in Figures 1-3
[0058] Figure 6 shows Figure 4 a cross-sectional view of the plastic part shown in
[0059] Figure 7 shows Figure 6 a perspective view of the plastic part shown in DETAILED DESCRIPTION
[0060] Figures 1-3 shows an injection molding device generally designated 1. The injection device 1 is arranged for the production of injection molded plastic parts 2, namely plastic helical springs, which can be used as part of, for example, a medical injection device or a medical blood collection device.
[0061] The injection molding device 1 includes an injection molding tool 3 which has a total of four cavities 4.
[0062] Furthermore, the injection molding device 1 has a total of four sets of four cores 5 each, which can be arranged in the cavities 4 of the injection molding tool 3 for injection molding the plastic parts 2.
[0063] The injection molding device 1 also has an induction heating device 6 which is located upstream of the injection molding tool 3 and is arranged for inductively heating the cores 4 before the plastic parts 2 are injection molded. The induction heating device 6 of the injection molding device 1 is arranged to heat the cores 5 (i.e. at least their forming surfaces 23) to a temperature between 50 °C and 100 °C, preferably to a temperature between 60 °C and 80 °C.
[0064] The injection molding device 1 includes a control unit 7 and a total of four temperature sensors 8. The control unit 7 is configured to adjust the induction heating device 6 depending on the temperature of the core 5 to be heated, which temperature is determined using the temperature sensors 8. The induction heating device 6 has a total of four induction heating coils 9. The induction heating device 6 is arranged by means of the induction heating coils 9 to simultaneously inductively heat four cores 5 of one of four individually grouped cores 5. When heating the core 5, first the forming surface 23 of the core 5 is heated, and during the injection molding of the plastic part 2 in the mold cavity 4, the plastic material comes into contact with the forming surface 23.
[0065] The induction heating device 6 thus has a number of induction heating coils 9 corresponding to the number of mold cavities 4 of the injection molding tool 3.
[0066] The mold cavity 4 and the core 5 assigned to the mold cavity 4 are designed in such a way that when the corresponding mold cavity 4 is filled with plastic material, a plastic part 2 in the form of a helical plastic spring is produced.
[0067] In particular, the overview from Figure 4 illustrates the shape of the cores 5, their forming surfaces 23 (which assume the helical shape of the plastic part 2), as well as the shape of the mold cavity 4 defined by the two half - molds 10 and 11 and also the shape of the plastic part 2 that can be produced in the injection molding tool 3.
[0068] The plastic spring that can be produced as the plastic part 2 with the injection molding device 1 can have a ratio of coil length to coil width B between 20:1 and 100:1, for example a ratio of 50:1. The plastic spring can also have, for example, a ratio of coil thickness D to coil width B between 1:2 and 1:10, particularly preferably a ratio of approximately 1:5. The coil thickness D can be measured transversely to the longitudinal axis of the plastic spring, and the coil width B can be measured in the direction of the longitudinal axis of the plastic spring.
[0069] The induction heating device 6 has a positioning device 12. The positioning device 12 is used to move the four induction heating coils 9 from their initial position shown in Figure 1 to their heating position on the core 5 shown in Figure 2 . In their heating position, the heating coils 9 are slipped over the core 5 to be heated.
[0070] In the heating position, the core 5 is arranged inside the heating coil 9. The heating coil 9 has a shape adapted to the forming surface 23 and the outer contour of the core 5. In the heating position, the induction heating coil 9 and the core 5 arranged in the heating coil 9 are arranged at a distance of 1 - 5 mm, preferably 0.5 - 2 mm, particularly preferably 0.2 - 1 mm from each other.
[0071] The induction heating device 6 is arranged to inductively heat the cores 5 outside the injection molding tool 3 and outside its mold cavity 4.
[0072] In the case of an injection molding device (not shown in the figures), the cores 5 can also be heated in their positions inside the injection molding tool 3 or inside the mold cavity 4 using a correspondingly designed heating device 6. This is preferably done when the injection molding tool 3 is open.
[0073] The injection molding device 1 has a transport device 13. The transport device 13 is designed as a rotary indexing table and is arranged to transport each of four groups of four cores 5 from their heating positions on the heating device 6 into the mold cavity 4 of the injection molding tool 2. The cores 5 are moved from the heating positions outside the injection molding tool 3 and the mold cavity 4 on the induction heating device 6 into the injection molding tool 3 and finally into the mold cavity 4 of the injection molding tool 3.
[0074] The induction heating device 6 and the injection molding tool 3 are arranged adjacent to each other on the outer circumference of the transport device 13 at an angular distance of 90°. In this way, after induction heating, the cores 5 can be directly moved into the injection molding tool 3 and its mold cavity 4.
[0075] Figure 1 A group of heated induction cores 5 is shown in the position between the two mold halves 10 and 11 of the open injection molding tool 3.
[0076] In Figure 2 the injection molding tool 3 is then shown as closed, and plastic material is injected into the mold cavity 4 defined by the mold halves 10 and 11 for the production of the plastic part 2. Figure 3 The plastic part 2 is shown immediately after opening the injection molding tool 3.
[0077] From this position, the plastic part 2 can be moved together with the cores 5 from the injection molding tool 3 to a downstream cooling position using the transport device 13, which also serves as a removal position for the injection molded part 2.
[0078] The injection molding device 1 has a removal device 14 at the removal position. The removal device 14 includes a removal clamp 15 by means of which the plastic part 2 can be removed from the cores 5 and stored after they have cooled.
[0079] The injection molding device 1 is arranged for at least partial overmolding of inserts 16, such as pins, medical piercing devices and / or RFID chips. The inserts 16 are shown in Figures 1-3 and in particular also in Figure 4 and 5 and 7.
[0080] In particular, when using an insert 16 with electronic functionality, such as an RFID chip, it can be advantageous to arrange the insert 16 on the core 5 only after heating the core 5.
[0081] In the illustrated embodiment of the injection molding device 1, each core 5 is provided to hold an insert 16 to be overmolded. For this purpose, in the figure, each core 5 has a receptacle 17 at its upper end into which the insert 16 can be inserted. To equip the cores 5 with the inserts 16, the injection molding device has an equipping device 18. The equipping device 18 has an equipping clamp 19 by means of which the insert 16 can be arranged on the core 5.
[0082] The injection molding device 1 has an injection molding machine 20 adjacent to its injection molding tool 2. The injection molding machine 20 can be used to inject plastic material into the cavity 4 of the injection molding tool 3 of the injection molding device 1.
[0083] The control unit 7 has a data interface 21 by means of which the control unit 7 can at least temporarily record a data connection to a computer-readable medium 22, namely a cloud-based data memory. A computer program is stored in the cloud-based data memory, the computer program comprising commands that cause the injection molding device 1 to execute a method for injection molding a plastic part 2, which method will be described in detail below.
[0084] According to the computer program, the control unit 7 then controls the functional units of the injection molding device 1, namely the injection molding tool 3, the inductive heating device 6, the positioning device 12 for moving the inductive heating coil 9, the transport device 13, the removal device 14 with the removal clamp 15, the equipping device 18 with the equipping clamp 19, and the injection molding machine 20, to execute the method and produce the plastic part 2.
[0085] It is provided that liquefied plastic material for producing the plastic part 2 is injected into the cavity 4 of the injection molding tool 3 equipped with the cores 5. Before the injection of the plastic material into the cavity 4 takes place, the cores 5 are inductively heated, at least their forming surfaces 23 are heated.
[0086] In the illustrated embodiment of the injection molding device 1, it is provided that the cores 5 are inductively heated outside the injection molding tool 3 and its cavity 4. The cores 5 are inductively heated on the inductive heating device 6 of the injection molding device 1 and are thus inductively heated outside the cavity 4 and are then directly inserted into the injection molding tool 3 and the cavity 4. The injection molding tool 3 is then closed by bringing the ejector-side half mold 11 close to the nozzle-side half mold 10.
[0087] The core 5 is heated by the induction heating coil 9 of the induction heating device 6. This occurs when the core 5 is arranged inside the heating coil 9. For this purpose, in the embodiment of the injection molding device 1 shown in the figures, the induction heating coil 9 is slipped over the core 5. Once this occurs, the induction heating device 6 is activated in order to heat the core 5 using the induction heating coil 9. The figures show that the shape of the heating coil 9 is adapted to the shape of the core 5 to be heated. For this purpose, the heating coil 9 has a receiving space 25 for receiving the core 5 to be heated, the shape of which is adapted to the shape of the core 5 to be heated.
[0088] Due to the induction heating of the core 5, the core 5 is surface-heated in the region of its corresponding forming surface 23. According to Figure 5 , the core 5 consists of a solid material and is designed to be at least mainly cavity-free. The induction heating produces a temperature gradient between the heated forming surface 23 of the corresponding core 5 and the inner region 24 of the corresponding core 5, which inner region 24 is less heated or not heated at all. This temperature gradient promotes the rapid cooling of the plastic part 2 injected around the core 5.
[0089] The induction heating device 6 of the injection molding device 1 is set to heat the cores 5, in particular at least their forming surfaces 23, to a temperature between 50 °C and 100 °C, preferably to a temperature between 60 °C and 80 °C.
[0090] The induction heating of the core 5 is monitored using the temperature sensor 8 already mentioned. In this case, the induction heating of the core 5 is regulated by the control unit 7 of the injection molding device 1. Once the temperature sensor 8 has determined that the desired setpoint temperature of the core 5 has been reached, for example when at least the forming surface 23 of the core 5 has reached a temperature between 60 °C and 80 °C, the induction heating device 6 can be deactivated using the control unit 7 and the heating of the core 5 can be stopped.
[0091] Before the cores 5 are inductively heated on the heating device 6, they are equipped with inserts 16. The cores 5 can also be equipped with inserts 16 only after the induction heating. In this way, damage to the inserts 16 due to the influence of the induction heating device 6 can be avoided. This process is preferred especially in cases where the inserts 16 have electrical or electronic functions.
[0092] In the injection molding device 1 shown in the figures, the cores 5 not only serve as forming parts, but also as holders for the inserts 16 and as transport devices for inserting the inserts 16 into the mold cavity 4 of the injection molding tool 3. Inside the mold cavity 4, the inserts 16 arranged on the cores 5 are then at least partially overmolded with plastic material.
[0093] In order to inductively heat the core 5, the core 5 and the heating coil 9 are arranged at a distance of 1 - 5 mm, in particular 0.5 - 2 mm, and particularly preferably 0.2 mm to 1 mm relative to one another.
[0094] This is accomplished by using the positioning device 12 of the injection molding device 1 already mentioned. Figure 5 The figure shows the distance between the inductive heating coil 9 and the core 5 in the heating position inside the heating coil 9.
[0095] The plastic part 2 that can be produced on the injection molding device 1 according to this method is a helical plastic spring. The plastic spring can have, for example, a ratio of coil length to coil width B between 20:1 and 100:1, in particular 50:1. The plastic spring can have, for example, a ratio of coil thickness D to coil width B between 1:2 and 1:10, in particular approximately 1:5. The coil thickness D can be measured transversely to the longitudinal axis of the plastic spring, and the coil width B can be measured in the direction of the longitudinal axis of the plastic spring.
[0096] The core 5 also serves as a transport device for removing the plastic part 2 from the injection molding tool 3.
[0097] The plastic part 2 initially remains on the core 5 after injection molding and cools there.
[0098] When the plastic part 2 on the core 5 cools, the core 5 acts as a heat sink because the inductive heating of the core 5 mainly causes the inductive heating of the forming surface 23 of the core 5, but the internal region 24 of the core 5 remains relatively cold.
[0099] The cooling of the plastic part 2 on the core 5 after injection molding is promoted by the temperature gradient that occurs between the forming surface 23 and the internal region 24 of the corresponding core 5.
[0100] The present invention relates to an improvement in the field of injection molding technology. Furthermore, an improved method for injection molding a plastic part 2 is proposed, in which liquefied plastic material is injected into the cavity 4 of the injection molding tool 3 equipped with the core 5 to produce the plastic part 2. The method is characterized in that the core 5 is inductively heated before injecting the plastic material.
[0101] List of reference numerals
[0102] 1 Injection molding device
[0103] 2 Plastic part
[0104] 3 Injection molding tool
[0105] 4 Cavity
[0106] 5 Core
[0107] 6 Induction heating device
[0108] 7 Control unit
[0109] 8 Temperature sensor
[0110] 9 Induction heating coil
[0111] 10 Nozzle side half mold
[0112] 11 Ejector side half mold
[0113] 12 Positioning device
[0114] 13 Transport device
[0115] 14 Removal device
[0116] 15 Removal fixture
[0117] 16 Insert
[0118] 17 Seat for 16 at 5
[0119] 18 Equipment device
[0120] 19 Equipment fixture
[0121] 20 Injection molding machine
[0122] 21 Data interface
[0123] 22 Computer-readable medium
[0124] 23 Forming surface area of 5
[0125] 24 Internal area of 5
[0126] 25 Receiving space of 9 for 5
Claims
1. A method for injection molding plastic parts (2), in particular medical products, wherein, The liquefied plastic material is injected into the cavity (4) equipped with the core (5) of the injection molding tool (3) to produce a plastic part (2), characterized in that the core (5) is inductively heated before injecting the plastic material.
2. The method according to claim 1, wherein, The core (5), in particular at least one forming surface (23) of the core (5), is heated to a temperature between 50 °C and 100 °C, in particular between 60 °C and 80 °C.
3. The method according to claim 1 or claim 2, wherein At least one forming surface (23) of the core (5) is inductively heated, and / or wherein the core (5) inside the injection molding tool (3), in particular the core (5) inside the cavity (4), is preferably inductively heated when the injection molding tool (3) is open, or wherein the core (5) outside the cavity (4), in particular the core (5) outside the injection molding tool (3), is inductively heated.
4. The method according to any one of the preceding claims, wherein, The core (5) is inductively heated outside the cavity (4), in particular outside the injection molding tool (3), and is inserted into the cavity (4) after inductive heating, in particular after the injection molding tool (3) is closed.
5. The method according to any one of the preceding claims, wherein, The core (5) is heated by the induction heating coil (9) of the induction heating device (6), in particular wherein the core (5) for inductive heating is arranged inside the induction heating coil (9).
6. The method according to the preceding claim, wherein, The induction heating coil (9) is slipped over the core (5), or the core (5) is inserted into the induction heating coil (9).
7. The method according to any one of the preceding claims, wherein, The core (5) is surface-heated by induction heating, and / or wherein the core (5) is made of solid material and / or is designed to be at least substantially cavity-free, and / or wherein a temperature gradient is provided between the heated surface (23) of the core (5) and the inner region (24) of the core (5) that is less heated or not heated at all during induction heating.
8. The method according to any one of the preceding claims, wherein, A temperature sensor (8) is used to monitor the inductive heating of the core (5), and / or wherein the inductive heating of the core (5) is regulated by a control unit (7).
9. The method according to any one of the preceding claims, wherein, At least one insert (16) is inserted into the cavity (4) and is at least partially overmolded with the plastic material, in particular wherein the at least one insert (16) is arranged on the core (5) and / or is inserted into the cavity (4) together with the core (5), and the insert is, for example, a pin and / or a medical puncture device and / or an RFID chip.
10. The method according to any one of the preceding claims, wherein, The core (5) and the induction heating coil (9) of the heating device (6) are arranged relative to each other at a distance (A) of 1 - 5 mm, in particular 0.5 - 2 mm, particularly preferably 0.2 mm to 1 mm, for inductively heating the core (5), in particular by means of a positioning device (12).
11. The method according to any one of the preceding claims, wherein, A plastic spring is produced as a plastic part (2), the plastic spring in particular having a ratio of coil length to coil width (B) between 20:1 and 100:1, in particular 50:1, and / or the plastic spring in particular having a ratio of coil thickness (D) to coil width (B) between 1:2 and 1:10, in particular 1:5, the coil thickness (D) being measurable transversely to the longitudinal axis of the plastic spring and the coil width (B) being measurable in the direction of the longitudinal axis of the plastic spring.
12. The method according to any one of the preceding claims, wherein, The core (5) is used as a transport device for removing the plastic part (2) from the injection molding tool (3), and / or wherein the plastic part (2) cools on the core (5) after injection molding.
13. An injection molding device (1) for injection molding a plastic part (2), the injection molding device (1) comprising at least one injection molding tool (3) having at least one mold cavity (4), at least one core (5) arranged in the mold cavity (4) for injection molding the plastic part (2), and having an induction heating device (6) which is arranged to inductively heat the at least one core (5) before injection molding of the plastic part (2).
14. The injection molding device (1) according to the previous claim, wherein, The injection molding device (1) is arranged to carry out the method according to any one of claims 1 to 12, and / or wherein the induction heating device (6) is arranged to heat the at least one core (5), in particular at least one forming surface (23) of the at least one core (5), to a temperature between 50 °C and 100 °C, in particular between 60 °C and 80 °C.
15. The injection molding device (1) according to any one of the preceding two claims, wherein, The injection molding device (1) has a control unit (7) and / or at least one temperature sensor (8), in particular wherein the control unit (7) is arranged to adjust the induction heating device (6) depending on the temperature of the core (5) to be heated, the temperature being determined using the at least one temperature sensor (8).
16. The injection molding device (1) according to any one of the preceding claims, wherein, The induction heating device (6) has at least one induction heating coil (9) by means of which the induction heating device (6) is arranged to inductively heat the at least one core (5), preferably wherein the induction heating device (6) has a plurality of induction heating coils (9) corresponding to the number of mold cavities (4) of the injection molding tool (3).
17. The injection molding device (1) according to any one of the preceding claims, wherein, The at least one mold cavity (4) and the core (5) assigned to the mold cavity (4) are designed in such a way that when the mold cavity (4) is filled with plastic material, a plastic part (2) in the form of a plastic spring is produced, the plastic spring having a ratio of coil length to coil width between 20:1 and 100:1, for example a ratio of 50:1, and / or the plastic spring having a ratio of coil thickness (D) to coil width (B) between 1:2 and 1:10, in particular 1:5, the coil thickness (D) being measurable transversely to the longitudinal axis of the plastic spring and the coil width (B) being measurable in the direction of the longitudinal axis of the plastic spring.
18. The injection molding device (1) according to any one of the preceding claims, wherein, The injection molding device (1), in particular the induction heating device (6), has a positioning device (12) by means of which the at least one induction heating coil (9) is moved into a heating position on the at least one core (5), or the at least one core (5) can be arranged in a heating position on the at least one induction heating coil (9), and / or in which the at least one induction heating coil (9) and the at least one core (5) are arranged at a distance of 1 - 5 mm, preferably 0.5 - 2 mm, and particularly preferably 0.2 - 1 mm from one another in the heating position during the induction heating of the core (5).
19. The injection molding device (1) according to any one of the preceding claims, wherein, The induction heating device (6) is provided for inductively heating the at least one core (5) inside and / or outside the injection molding tool, in particular inside the mold cavity (4).
20. The injection molding device (1) according to any one of the preceding claims, wherein, The injection molding device (1) has a transport device (13), in particular a rotary indexing table, which is set up to move the at least one core (5) from the heating position into the injection molding tool (2), in particular into the mold cavity (4) of the injection molding tool (2), preferably from a heating position outside the mold cavity (4) onto the induction heating device (6).
21. The injection molding device (1) according to the previous claim, wherein, The transport device (13) is set up to transport the at least one core (5), in particular on which a plastic part (2) is arranged, from the injection molding tool (3) to a removal position outside the mold cavity (4), in particular outside the injection molding tool (3).
22. The injection molding device (1) according to any one of the preceding claims, wherein, The injection molding device (1) has a removal device (14) which, in particular, has at least one removal clamp (15) by means of which the plastic part (2) can be removed from the at least one core (5), in particular after cooling.
23. The injection molding device (1) according to any one of the preceding claims, wherein, The injection molding device (1) is provided for at least partial overmolding of an insert (16), in particular a pin and / or a medical puncture device and / or an RFID chip.
24. The injection molding device (1) according to the previous claim, wherein, The at least one core (5) is set up to hold at least one insert (16) to be at least partially overmolded.
25. The injection molding device (1) according to any one of the preceding two claims, wherein, The injection molding device (1) has a loading device (18) which, in particular, has at least one loading clamp (19) by means of which the insert (16) can be arranged on the at least one core (5).
26. The injection molding device (1) according to any one of the preceding claims, wherein, The injection molding device (1) includes an injection molding machine (20) by means of which plastic material can be injected into the at least one mold cavity (4) of the injection molding tool (3) of the injection molding device (1).
27. A computer program comprising instructions which cause an injection molding device (1) according to any one of the preceding claims to carry out the steps of a method according to any one of claims 1 to 12.
28. A computer-readable medium (22) having a computer program according to the preceding claim.