Method and injection-moulding device for injection moulding of plastics parts

Abstract

The invention relates to an improvement in the field of injection-moulding technology. An improvement proposed includes a method for injection moulding of plastics parts (2), wherein, in order to produce a plastics part (2), liquefied plastics material is injected into a mould cavity (4), which is equipped with a core (5), of an injection mould (3). The method is characterized in that the core (5) is inductively heated before the plastics material is injected.

Description

[0001] Method and injection molding device for injection molding plastic parts

[0002] The invention relates to a method and an injection molding device for injection molding plastic parts, in particular medical products. To produce a plastic part, liquefied plastic material is injected into a mold cavity of an injection molding tool equipped with a core.

[0003] By using a core as part of the forming injection mold, it is possible to produce plastic parts that have cavities.

[0004] The object of the invention is to provide a method and an injection molding device for injection molding injection-molded plastic parts, which are particularly suitable for the production of plastic parts with a relatively large ratio of surface area to material volume.

[0005] To solve the problem, a method for injection molding plastic parts is first proposed, which has the means and features of the independent claim directed to such a method.

[0006] To achieve this objective, a method for injection molding plastic parts, in particular medical products, is proposed, wherein, to produce a plastic part, liquefied plastic material is injected into a mold 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 the injection of the plastic material.

[0007] The invention is based on the finding that difficulties can arise during injection molding due to the cores in the production of plastic parts which have a comparatively large surface area in relation to their material volume. These difficulties are caused by the cores drawing heat away from the plastic material injected into the mold cavity to produce the plastic parts, which can impair the quality of the plastic parts produced by the injection molding process. It is particularly problematic when the cores have a particularly large volume of material in relation to the volume of the mold cavity which is filled with the plastic material to produce the plastic parts. The cores can then act like heat sinks, drawing heat away from the injected plastic material relatively quickly.

[0008] The inductive heating of the core prior to injection of the plastic material, as provided for in the invention, makes it possible to reduce or even completely eliminate heat extraction from the plastic material injected into the mold cavity during the production of the plastic part. Inductive heating of the core has the particular advantage of being particularly fast, energy-efficient, and thus cost-effective for the manufacturing process.

[0009] In one embodiment of the method, it is provided that the core, in particular at least one shaping surface of the core, is heated to a temperature between 50°C and 100°C, in particular to a temperature between 60°C and 80°C. Heating the core, in particular at least its shaping surface, to such a temperature can promote particularly efficient implementation of the method and the production of plastic parts of the desired quality.

[0010] In one embodiment of the method, at least one shaping surface of the core is heated during inductive heating of the core. This ensures that at least the shaping surface of the core that comes into contact with the molten plastic material is heated before the plastic material is injected. The injected plastic material then contacts the inductively heated surface of the core within the mold cavity. This prevents heat from being extracted from the plastic material too quickly by the core.

[0011] In one embodiment of the method, the core is inductively heated within the injection mold, in particular within the mold cavity, preferably with the injection mold open.

[0012] In another embodiment of the method, the core is inductively heated outside the injection mold and thus outside the mold cavity and is then inserted into the mold cavity of the injection mold.

[0013] In this embodiment of the process, the core is first inductively heated outside the injection mold and, after inductive heating, inserted into the injection mold and its mold cavity. The injection mold and thus the mold cavity can then be closed. This variant of the process is advantageous because it allows for comparatively short cycle times.

[0014] The inductive heating of a core can take place outside the injection mold, while another, already inductively heated core can be arranged within the mold cavity to carry out the process. The injection mold can thus be used to produce plastic parts independently of the inductive heating of a core. In this way, downtime during which the injection mold and its at least one mold cavity cannot be used to produce plastic parts can be reduced or even completely eliminated.

[0015] The core can be heated with an inductive heating coil of an inductive heating device. The core can be arranged within the inductive heating coil for inductive heating. The use of an inductive heating coil enables external and thus superficial heating of the core. This can, as explained in more detail below, promote comparatively rapid cooling of the plastic parts on the core.

[0016] In order to arrange the core within the inductive heating coil, it may be provided to place the inductive heating coil over the core or to insert the core into the inductive heating coil.

[0017] It is advantageous if the inductive heating coil has a receiving space for the core with an inner contour adapted to an outer contour of the core, preferably an inner contour adapted to a shaping surface of the core, and / or at least inductively heats the shaping surface of the core.

[0018] The inner contour of the receiving space for the heating coil can correspond to the outer contour of the core, in particular its shaping surface. This allows for uniform heating of the surface of the core, which at least partially defines the mold cavity, when the core is inserted into the mold cavity.

[0019] The core can be heated superficially by inductive heating. The core can preferably consist of a solid material and / or be at least substantially void-free. Thus, it is possible for a temperature gradient to arise during the inductive heating of the core, in particular of at least one shaping surface of the core, between the heated surface of the core and a less heated or unheated interior region of the core. Because 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.

[0020] However, if the core is not heated through, but preferably only its shaping surface is heated, this has advantages during the subsequent cooling of the injection-molded plastic parts. Due to the aforementioned temperature gradient, the core material can absorb the heat from the injection-molded plastic part from the plastic material and dissipate it from the plastic part. This enables rapid cooling of the injection-molded plastic part at the core, despite the inductive heating of the core, and thus also the shortest possible cycle times during the process.

[0021] The inductive heating of the core can be monitored using a temperature sensor. Furthermore, it is possible to regulate the inductive heating of the core using a control unit. The inductive heating of the core can be regulated by the control unit depending on the temperature of the core to be inductively heated, as determined by the temperature sensor.

[0022] It is advantageous if the inductive heating of the core takes place immediately before the plastic material is injected into the mold cavity. This promotes an energy-efficient implementation of the process, as the time in which the core can cool before the plastic material is injected is reduced, and the core only needs to be heated to a temperature that is only slightly higher than the temperature the core should have when the plastic material is injected into the mold cavity.

[0023] In one embodiment of the method, at least one insert, for example a pin, a medical piercing device and / or an RFID chip, is inserted into the mold cavity and at least partially over-molded with the plastic material. In this way, it is possible to produce a plastic part which has an at least partially over-molded insert. The method can be carried out particularly efficiently if the at least one insert is arranged on the core and / or is inserted into the mold cavity with the core. The core can thus be used not only as the shaping part of the injection mold, but also as a holder and / or transport means for the at least one insert.

[0024] If the insert has an electrical and / or electronic function, for example, because it is designed as an RFID chip, it may be advantageous to equip the core with the insert only after inductive heating. This prevents damage and / or functional impairment of the insert due to inductive heating of the core. If the insert is not affected by inductive heating, the core can also be equipped with the insert before inductive heating.

[0025] After its production, the plastic part can initially remain on the core and be held by it. It is also possible to remove the plastic part together with the core from the mold cavity and / or the injection mold and leave it on the core to cool.

[0026] For inductive heating of the core, the core and the heating coil can be arranged relative to one another at a distance of 1-5 mm, in particular 0.5-2 mm, particularly preferably 0.2-1 mm. This can be achieved using a positioning device. The positioning device can be configured to move the core into the heating coil and / or to place the heating coil over the core.

[0027] In one embodiment of the method, the mold cavity and the core are configured such that a plastic part in the form of a plastic spring is produced during the method. The core can also be used as a transport means for removing the plastic part from the mold cavity of the injection mold and / or from the injection mold. Furthermore, it is possible for the plastic part to remain on the core after injection molding and cool there.

[0028] A plastic spring, in particular a coiled plastic spring, can be manufactured as a plastic part. The plastic spring can, for example, have a ratio of coil length to coil width of between 20:1 and 100:1, in particular 50:1, and / or, for example, a ratio of coil thickness measured transversely to the longitudinal axis of the plastic spring to coil width measured in the direction of the longitudinal axis of the plastic spring of between 1:2 and 1:10, in particular 1:5.

[0029] To achieve the object, an injection molding device for injection molding plastic parts, in particular medical products, is also proposed, which has the means and features of the independent claim directed to such an injection molding device. To achieve the object, an injection molding device is therefore proposed in particular which is designed for injection molding plastic parts, wherein the injection molding device has at least one injection molding tool with at least one mold cavity, at least one core which is arranged in the mold cavity for injection molding a plastic part, and an inductive heating device which is designed for inductively heating the at least one core, in particular at least one shaping surface of the at least one core, before the injection molding of the plastic part.

[0030] The inductive heating device of the injection molding device can be configured, in particular, to heat the at least one core, in particular at least one shaping surface of the at least one core, to a temperature between 50 ° C and 100 ° C, preferably to a temperature between 60 ° C and 80 ° C. The inductive heating of the at least one core, in particular at least its shaping surface, to a temperature within these temperature ranges can be particularly advantageous for producing plastic parts of the desired quality.

[0031] The injection molding device can be designed to carry out the method already explained above and thus to carry out the method according to one of the claims directed to such a method.

[0032] The injection molding device may have a control unit and / or at least one temperature sensor. The control unit may be configured to regulate the inductive heating device as a function of a temperature of the core to be inductively heated, as determined by the at least one temperature sensor.

[0033] The inductive heating device can have at least one inductive heating coil, by means of which the inductive heating device is configured for inductively heating the at least one core, in particular at least its shaping surface. For this purpose, the heating coil can have a receiving space for receiving a core to be heated. Particularly efficient inductive heating is promoted if the shape or inner contour of the receiving space is adapted to the shape or outer contour of the core to be heated.

[0034] If the injection mold has multiple cavities, it is advantageous if the inductive heating device has a number of inductive heating coils that corresponds to the number of cavities in the injection mold. In this way, all cavities can be simultaneously filled with an inductively heated core.

[0035] It is particularly advantageous if the injection molding device comprises a plurality of groups of cores, each group of cores having a number of cores which corresponds to the number of mold cavities in the injection mold. In this way it is possible to inductively heat one group of cores outside the mold cavities, while another group of cores is arranged in the mold cavities for injection molding plastic parts. A further group of cores, with plastic parts attached to them, can remain in a position outside the injection mold and its mold cavities for cooling the plastic parts. A further group of cores can be arranged in a loading position, for example for loading inserts.

[0036] In one embodiment of the injection molding apparatus, the at least one mold cavity and the core associated with the mold cavity are configured such that, when the mold cavity is filled with plastic material, a plastic part in the form of a plastic spring, in particular a coiled plastic spring, is produced. The plastic spring can, for example, have a ratio of coil length to coil width of between 20:1 and 100:1, for example a ratio of 50:1, and / or a ratio of coil thickness measurable transversely to the longitudinal axis of the plastic spring to coil width measurable in the direction of the longitudinal axis of the plastic spring of between 1:2 and 1:10, in particular 1:5.

[0037] The injection molding device, in particular its inductive heating device, can have a positioning device. The positioning device makes it possible to move the at least one heating coil into a heating position on the at least one core or to move the at least one core into a heating position on the at least one heating coil.

[0038] The at least one inductive heating coil and the at least one core can be arranged in the heating position during inductive heating of the core at a distance of 1-5 mm, preferably 0.5-2 mm, and particularly preferably 0.2-1 mm from each other. This promotes energy-efficient and fastest possible inductive heating of the core, in particular its shaping surface.

[0039] The inductive heating device can be configured for inductive heating of the at least one core inside and / or outside the injection mold, in particular the mold cavity.

[0040] The injection molding apparatus may comprise a transport device. The transport device may be configured, for example, as a rotary indexing table. The transport device may be configured to transport the at least one core from a heating position into the injection molding tool and, in particular, into the mold cavity. The core may be transported by the transport device from a heating position located outside the mold cavity on the inductive heating device into the injection molding tool and, preferably, thus, into the mold cavity.

[0041] The transport direction can further be configured to transport the at least one core, in particular with a plastic part arranged thereon, from the mold cavity into a removal position outside the mold cavity. In the removal position, the plastic part can then initially cool on the core and subsequently be removed from the core. In this way, the core functions not only as a shaping part of the injection mold, but also as a transport means with which the injection-molded plastic parts can be removed from the mold cavity of the injection mold.

[0042] The injection molding apparatus may comprise a removal device with which a plastic part, particularly after cooling, can be removed from the at least one core. For this purpose, the removal device may comprise at least one removal gripper. It is advantageous if the removal device comprises a number of removal grippers that corresponds to the number of mold cavities in the injection mold. In this way, it is possible to remove all plastic parts produced in one injection molding step in one removal process.

[0043] The injection molding apparatus can be configured to at least partially overmold inserts, in particular pins and / or medical piercing devices and / or RFID chips. In this context, it can be advantageous if the at least one core is configured to hold at least one insert to be at least partially overmolded. The core can, for example, be equipped with an insert outside the mold cavity of the injection mold and then inserted into the mold cavity together with the insert. This preferably takes place after the inductive heating of the core. The core can be equipped with the insert before or after the heating of the core.

[0044] The injection molding device may comprise an insertion device with which inserts can be arranged on the at least one core. For this purpose, the insertion device may comprise at least one insertion gripper.

[0045] The injection molding device may comprise an injection molding machine with which plastic material can be injected into the at least one mold cavity of the injection mold of the injection molding device.

[0046] The injection molding tool can have a nozzle-side mold half and an ejector-side mold half, between which the at least one mold cavity is formed.

[0047] The control unit can be configured to control functional units of the injection molding device, in particular to control the injection mold, in particular its opening and closing movement, and / or the inductive heating device and / or the positioning device for moving the at least one inductive heating coil between a starting position and a heating position and / or the transport device and / or the removal device with its removal gripper and / or the loading device with its loading gripper and / or the injection molding machine. The aforementioned control unit of the injection molding device can have a data interface with which the control unit can be connected at least temporarily to a data storage device, for example to a cloud-based data storage device.

[0048] A computer program can be stored in the data memory, which includes instructions which cause the injection molding device according to the invention to carry out the steps of the method according to the invention.

[0049] To achieve this objective, a computer program is also proposed, which includes instructions causing the claimed injection molding device to carry out the steps of the claimed method. The computer program can, for example, be executed on the aforementioned control unit of the injection molding device. The control unit can convert the instructions of the computer program into control commands in order to appropriately control the aforementioned functional units of the injection molding device, which are respectively used to carry out the steps of the method. The control unit can function as a control computer configured to execute the computer program.

[0050] To achieve this object, a computer-readable medium is also proposed on which the computer program according to the invention is stored. A computer-readable data storage device, in particular a cloud-based data storage device, can serve as the computer-readable medium. The computer-readable medium can in particular be the aforementioned cloud-based data storage device, to which the injection molding device can be connected at least temporarily via the data interface of its control unit. The invention is described in more detail below using an exemplary embodiment, but is not limited to this exemplary embodiment. Further exemplary embodiments arise from combining the features of one or more claims with one another and / or from combining one or more features of the exemplary embodiment. The figures show:

[0051] Figure 1 is a perspective view of an injection molding device with an injection molding tool having a nozzle-side and an ejector-side mold half, which form a total of four mold cavities between them, with a total of four groups of cores movable along a closed movement path of a transport device between individual stations of the injection molding device, and with an inductive heating device having four inductive heating coils for inductively heating the cores,

[0052] Figure 2 is a perspective view of the injection molding device shown in Figure 1 with a closed injection mold, wherein the four inductive heating coils of the inductive heating device are arranged in a heating position on four cores located on the inductive heating device in the heating position,

[0053] Figure 3 shows the injection molding device shown in Figures 1 and 2 with the injection molding tool open, whereby four injection-molded plastic parts in the form of plastic springs can be seen on the four cores arranged on the injection molding tool,

[0054] Figure 4 is an exploded overview view with a core, a plastic part, an insert which is at least partially overmolded with plastic material during the production of the plastic part, as well as a nozzle-side mold half and an ejector-side mold half of the injection molding tool of the injection molding device shown in Figures 1-3,

[0055] Figure 5 is a partially sectioned view of a core equipped with an insert in its heating position within an inductive heating coil of the inductive heating device shown in Figures 1-3,

[0056] Figure 6 is a sectional view of the plastic part shown in Figure 4 and

[0057] Figure 7 is a perspective view of the plastic part shown in Figure 6 with a partially overmolded insert at its tip, the plastic part being a coiled plastic spring.

[0058] Figures 1-3 show an injection molding device, designated overall by 1. The injection molding device 1 is designed to produce injection-molded plastic parts 2, namely coiled plastic springs, which can be used, for example, as a component of a medical injection device or a medical blood collection device.

[0059] The injection molding device 1 comprises an injection mold 3 with a total of four mold cavities 4 .

[0060] Furthermore, the injection molding device 1 has a total of four groups of four cores 5 each, which can be arranged in the mold cavities 4 of the injection mold 3 for injection molding plastic parts 2. The injection molding device 1 also has an inductive heating device 6, which is arranged upstream of the injection mold 3 and is designed to inductively heat the cores 4 before the injection molding of the plastic parts 2. The inductive heating device 6 of the injection molding device 1 is designed to heat the cores 5, namely at least their shaping surfaces 23, to a temperature between 50°C and 100°C, preferably to a temperature between 60°C and 80°C.

[0061] The injection molding device 1 comprises a control unit 7 and a total of four temperature sensors 8. The control unit 7 is configured to regulate the inductive heating device 6 depending on the temperatures of the cores 5 to be heated, as determined by the temperature sensors 8. The inductive heating device 6 has a total of four inductive heating coils 9. The inductive heating coils 9 enable the inductive heating device 6 to inductively heat four cores 5 of one of the four individual groups of cores 5 simultaneously. When the cores 5 are heated, primarily the shaping surfaces 23 of the cores 5 are heated, with which plastic material comes into contact during injection molding of the plastic parts 2 in the mold cavities 4.

[0062] The inductive heating device 6 thus has a number of inductive heating coils 9 which corresponds to the number of mold cavities 4 of the injection mold 3.

[0063] The mold cavities 4 and the cores 5 assigned to the mold cavities 4 are designed such that when the respective mold cavity 4 is filled with plastic material, plastic parts 2 in the form of coiled plastic springs are produced.

[0064] In particular, the overview representation in Figure 4 illustrates the shape of the cores 5, their shaping surfaces 23 which grip the spiral shape of the plastic parts 2, as well as the shape of the mold cavities 4 predetermined by the two mold halves 10 and 11 and also the shape of the plastic parts 2 which can be produced in the injection mold 3.

[0065] The plastic springs which can be produced as plastic parts 2 using the injection moulding device 1 can, for example, have a ratio between coil length and coil width B of between 20 to 1 and 100 to 1, for example a ratio of 50 to 1. The plastic springs can furthermore, for example, have a ratio of coil thickness D measurable transversely to the longitudinal axis of the plastic springs to coil width B measurable in the direction of the longitudinal axis of the plastic springs of between 1 to 2 and 1 to 10, particularly preferably a ratio of approximately 1 to 5.

[0066] The inductive heating device 6 has a positioning device 12. The positioning device 12 serves to move the four inductive heating coils 9 from their initial position shown in Figure 1 to their heating position on the cores 5 shown in Figure 2. In their heating position, the heating coils 9 are placed over the cores 5 to be heated.

[0067] In the heating position, the cores 5 are arranged within the heating coils 9. The heating coils 9 have a shape adapted to the shaping surfaces 23 and the outer contour of the cores 5. In the heating position, the inductive heating coils 9 and the cores 5 arranged in the heating coils 9 are arranged at a distance of 1-5 mm, preferably 0.5-2 mm, particularly preferably 0.2-1 mm, from each other.

[0068] The inductive heating device 6 is designed for inductive heating of the cores 5 outside the injection mold 3 and outside its mold cavities 4.

[0069] In an injection molding device not shown in the figures, the cores 5 can also be heated in their position within the injection mold 3 or within the mold cavities 4 using a correspondingly designed heating device 6. This preferably takes place with the injection mold 3 open.

[0070] The injection molding device 1 has a transport device 13. The transport device 13 is designed as a rotary indexing table and is configured to transport the four groups of four cores 5 from their heating position on the heating device 6 into the mold cavities 4 of the injection mold 2. The cores 5 move from the heating position on the inductive heating device 6, located outside the injection mold 3 and the mold cavities 4, into the injection mold 3 and ultimately into the mold cavities 4 of the injection mold 3.

[0071] The inductive heating device 6 and the injection molding tool 3 are arranged adjacent to each other at an angular distance of 90° on the outer circumference of the transport device 13. In this way, the cores 5 can be moved directly into the injection molding tool 3 and its mold cavities 4 after inductive heating.

[0072] Figure 1 shows a group of already heated inductive cores 5 in a position between two mold halves 10 and 11 of the opened injection mold 3. In Figure 2, the injection mold 3 is then shown closed, and plastic material is injected into the mold cavities 4, which are delimited by the mold halves 10 and 11, to produce the plastic parts 2. Figure 3 shows the plastic parts 2 immediately after the injection mold 3 has been opened.

[0073] From this position, the plastic parts 2 can be moved by means of the transport device 13 together with the cores 5 from the injection molding tool 3 into a downstream cooling position, which at the same time also serves as a removal position for the injection molded parts 2.

[0074] At the removal position, the injection molding device 1 has a removal device 14. The removal device 14 comprises a removal gripper 15, with which the plastic parts 2 can be removed from the cores 5 and deposited after cooling.

[0075] The injection molding device 1 is designed for at least partially overmolding insert parts 16, for example, pins, medical piercing devices, and / or RFID chips. The insert parts 16 are shown in Figures 1-3 and in particular also in Figures 4, 5, and 7.

[0076] In particular, when inserts 16 are used which have an electronic function, for example RFID chips, it may be advantageous to arrange the inserts 16 on the cores 5 only after the cores 5 have been heated.

[0077] In the embodiment of the injection molding device 1 shown in the figures, the cores 5 are each configured to hold an insert 16 to be overmolded. For this purpose, the cores 5 each have a receptacle 17 at their upper ends in the figures, into which the inserts 16 can be inserted. In order to equip the cores 5 with the inserts 16, the injection molding device has a loading device 18. The loading device 18 has a loading gripper 19 with which the inserts 16 can be arranged on the cores 5.

[0078] Adjacent to its injection molding tool 2, the injection molding device 1 has an injection molding machine 20. With the aid of the injection molding machine 20, plastic material can be injected into the mold cavities 4 of the injection molding tool 3 of the injection molding device 1.

[0079] The control unit 7 has a data interface 21, with which it can at least temporarily establish a data connection to a computer-readable medium 22, namely a cloud-based data storage device. A computer program is stored in the cloud-based data storage device, which includes commands that cause the injection-molding device 1 to carry out the method for injection-molding plastic parts 2, described in detail below.

[0080] According to the computer program, the control unit 7 then controls the functional units of the injection molding device 1, namely the injection mold 3, the inductive heating device 6, the positioning device 12 for moving the inductive heating coils 9, the transport device 13, the removal device 14 with the removal gripper 15, the loading device 18 with the loading gripper 19 and also the injection molding machine 20, in order to carry out the method and to produce the plastic parts 2.

[0081] In this case, it is provided that liquefied plastic material is injected into the mold cavities 4 of the injection mold 3, which are equipped with cores 5, to produce plastic parts 2. Before the plastic material is injected into the mold cavities 4, the cores 5 are inductively heated, at least their shaping surfaces 23 being heated. In the exemplary embodiment of the injection molding device 1 shown in the figures, it is provided that the cores 5 are inductively heated outside the injection mold 3 and its mold cavities 4. The cores 5 are inductively heated on the inductive heating device 6 of the injection molding device 1 and thus outside the mold cavities 4 and are then inserted directly into the injection mold 3 and into the mold cavities 4. The injection molding tool 3 is then closed by bringing the ejector-side mold half 11 closer to the nozzle-side mold half 10.

[0082] The cores 5 are heated with the inductive heating coils 9 of the inductive heating device 6. This occurs when the cores 5 are arranged inside the heating coils 9. In the embodiment of the injection molding device 1 shown in the figures, the inductive heating coils 9 are pulled over the cores 5 for this purpose. Once this has been done, the inductive heating device 6 is activated in order to heat the cores 5 with the aid of the inductive heating coils 9. The figures show that the heating coils 9 are adapted in terms of their shape to the shape of the cores 5 to be heated. For this purpose, the heating coils 9 have receiving spaces 25 for receiving the cores 5 to be heated, the shape of which is adapted to the shape of the cores 5 to be heated.

[0083] By inductive heating of the cores 5, the cores 5 are heated superficially in the region of their respective shaping surface 23. According to Figure 5, the cores 5 consist of a solid material and are at least predominantly void-free. The inductive heating creates a temperature gradient between the heated, shaping surface 23 of the respective core 5 and a less or unheated inner region 24 of the respective core 5. This temperature gradient promotes rapid cooling of the plastic part 2 injected around the core 5. The inductive heating device 6 of the injection molding device 1 is designed to heat the cores 5, in particular at least their shaping surfaces 23, to a temperature between 50 ° C and 100 ° C, preferably to a temperature between 60 ° C and 80 ° C.

[0084] The inductive heating of the cores 5 is monitored by means of the previously mentioned temperature sensors 8. The inductive heating of the cores 5 is regulated by the control unit 7 of the injection molding device 1. As soon as the temperature sensors 8 determine that the desired target temperature of the cores 5 has been reached, for example when at least the shaping surfaces 23 of the cores 5 have reached a temperature between 60°C and 80°C, the inductive heating device 6 can be deactivated by means of the control unit 7 and the heating of the cores 5 can be terminated.

[0085] Before the cores 5 are inductively heated by the heating device 6, they are fitted with the inserts 16. The cores 5 can also be fitted with inserts 16 after inductive heating. This prevents damage to the inserts 16 caused by the inductive heating device 6. This procedure is particularly preferable for inserts 16 with electrical or electronic functions.

[0086] In the injection molding device 1 shown in the figures, the cores 5 serve not only as shaping parts, but also as holders for the inserts 16 and as a means of transport for inserting the inserts 16 into the mold cavities 4 of the injection molding tool 3. Within the mold cavities 4, the inserts 16 arranged on the cores 5 are then at least partially overmolded with plastic material. For inductive heating of the cores 5, the cores 5 and the heating coils 9 are arranged relative to one another at a distance of 1-5 mm, in particular of 0.5-2 mm and particularly preferably at a distance of 0.2 mm to 1 mm. This is done with the aid of the previously mentioned positioning device 12 of the injection molding device 1. Figure 5 illustrates the distance between the inductive heating coil 9 and a core 5 in heating position within the heating coil 9.

[0087] The plastic parts 2 that can be produced by the process on the injection molding device 1 are coiled plastic springs. The plastic springs can, for example, have a ratio of coil length to coil width B of between 20:1 and 100:1, in particular of 50:1. The plastic springs can, for example, have a ratio of coil thickness D measurable transversely to the longitudinal axis of the plastic spring to coil width B measurable in the direction of the longitudinal axis of the plastic spring of between 1:2 and 1:10, in particular of approximately 1:5.

[0088] The cores 5 are also used as a means of transport for removing the plastic parts 2 from the injection mold 3. After injection molding, the plastic parts 2 initially remain on the cores 5 and cool there.

[0089] When the plastic parts 2 are cooled on the cores 5, the cores 5 act as heat sinks, since the inductive heating of the cores 5 primarily leads to an inductive heating of the shaping surface 23 of the cores 5, while an inner region 24 of the cores 5 remains comparatively cold.

[0090] A temperature gradient that occurs between the shaping surface 23 and the inner region 24 of the respective core 5 promotes cooling of the plastic parts 2 on the cores 5 after injection molding.

[0091] The invention relates to improvements in the field of injection molding technology. Among other things, a method for injection molding plastic parts 2 is proposed as an improvement. To produce a plastic part 2, liquefied plastic material is injected into a mold cavity 4 of an injection molding tool 3, which mold cavity is provided with a core 5. The method is characterized in that the core 5 is inductively heated before the plastic material is injected.

[0092] / List of reference symbols

[0093] List of reference symbols

[0094] 1 injection molding device

[0095] 2 plastic part

[0096] 3 injection mold

[0097] 4 mold cavity

[0098] 5 core

[0099] 6 inductive heating device

[0100] 7 Control unit

[0101] 8 Temperature sensor

[0102] 9 inductive heating coil

[0103] 10 nozzle-side mold halves

[0104] 11 ejector-side mold half

[0105] 12 Positioning device

[0106] 13 Transport device

[0107] 14 Removal device

[0108] 15 removal grippers

[0109] 16 Insert

[0110] 17 shot on 5 for 16

[0111] 18 Assembly device

[0112] 19 assembly grippers

[0113] 20 injection molding machines

[0114] 21 Data interface

[0115] 22 computer-readable medium

[0116] 23 forming surface of 5

[0117] 24 interior of 5

[0118] 25 Recording Room 25 out of 9 for 5

[0119] / Claims

Claims

Claims Method for injection molding plastic parts (2), in particular medical products, wherein, to produce a plastic part (2), liquefied plastic material is injected into a mold cavity (4) of an injection mold (3) equipped with a core (5), characterized in that the core (5) is inductively heated before the injection of the plastic material. Method according to claim 1, wherein the core (5), in particular at least one shaping surface (23) of the core (5), is heated to a temperature between 50°C and 100°C, in particular to a temperature between 60°C and 80°C.Method according to claim 1 or 2, wherein at least one shaping surface (23) of the core (5) is inductively heated, and / or wherein the core (5) is inductively heated within the injection molding tool (3), in particular within the mold cavity (4), preferably with the injection molding tool (3) open, or wherein the core (5) is inductively heated outside the mold cavity (4), in particular outside the injection molding tool (3). Method according to one of the preceding claims, wherein the core (5) is inductively heated outside the mold cavity (4), in particular outside the injection molding tool (3), and is inserted into the mold cavity (4) after the inductive heating, in particular after the injection molding tool (3) is closed. Method according to one of the preceding claims, wherein the core (5) is heated with an inductive heating coil (9) of an inductive heating device (6), in particular wherein the core (5) is arranged within the inductive heating coil (9) for inductive heating. Method according to the preceding claim, wherein the inductive heating coil (9) is placed over the core (5) or the core (5) is inserted into the inductive heating coil (9). Method according to one of the preceding claims, wherein the core (5) is heated superficially by the inductive heating, and / or wherein the core (5) consists of a solid material and / or is at least substantially void-free, and / or that during the inductive heating a temperature gradient is established between the heated surface (23) of the core (5) and a less heated or unheated inner region (24) of the core (5).Method according to one of the preceding claims, wherein the inductive heating of the core (5) is monitored by means of a temperature sensor (8) and / or wherein the inductive heating of the core (5) is regulated by a control unit (7). Method according to one of the preceding claims, wherein at least one insert part (16), for example a pin and / or a medical piercing device and / or an RFID chip, is inserted into the mold cavity (4) and at least partially over-molded with the plastic material, in particular wherein the at least one insert part (16) is arranged on the core (5) and / or inserted with the core (5) into the mold cavity (4). Method according to one of the preceding claims, wherein the core (5) and an inductive heating coil (9) of the heating device (6) for inductively heating the core (5) are arranged relative to one another at a distance (A) of 1-5 mm, in particular 0.5-2 mm, particularly preferably 0.2 mm to 1 mm, in particular with a positioning device (12). Method according to one of the preceding claims, wherein a plastic spring is produced as the plastic part (2), in particular one which has a ratio of coil length and coil width (B) of between 20:1 and 100:1, in particular 50:1, and / or in particular one which has a ratio of coil thickness (D) measurable transversely to the longitudinal axis of the plastic spring to coil width (B) measurable in the direction of the longitudinal axis of the plastic spring of between 1:2 and 1:10, in particular 1:5.Method according to one of the preceding claims, wherein the core (5) is used as a transport means for removing the plastic part (2) from the injection mold (3), and / or wherein the plastic part (2) is cooled on the core (5) after injection molding. Injection molding device (1) for injection molding plastic parts (2), wherein the injection molding device (1) has at least one injection mold (3) with at least one mold cavity (4), at least one core (5) which is arranged in the mold cavity (4) for injection molding a plastic part (2), and an inductive heating device (6) which is designed to inductively heat the at least one core (5) before injection molding the plastic part (2). Injection molding device (1) according to the preceding claim, wherein the injection molding device (1) is configured to carry out the method according to one of claims 1 to 12, and / or wherein the inductive heating device (6) is configured to heat the at least one core (5), in particular at least one shaping surface (23) of the at least one core (5), to a temperature between 50°C and 100°C, in particular to a temperature between 60°C and 80°C. Injection molding device (1) according to one of the two preceding 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 configured to regulate the inductive heating device (6) as a function of a temperature of the core (5) to be heated, determined by the at least one temperature sensor (8).Injection molding device (1) according to one of the preceding claims, wherein the inductive heating device (6) has at least one inductive heating coil (9), by means of which the inductive heating device (6) is configured to inductively heat the at least one core (5), preferably wherein the inductive heating device (6) has a number of inductive heating coils (9) that corresponds to the number of mold cavities (4) of the injection mold (3). Injection molding device (1) according to 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 such that when the mold cavity (4) is filled with plastic material, a plastic part (2) in the form of a plastic spring is produced, which has a ratio. between coil length and coil width of between 20 to 1 and 100 to 1, for example a ratio of 50 to 1, and / or which has a ratio of coil thickness (D) measurable transversely to the longitudinal axis of the plastic spring to coil width (B) measurable in the direction of the longitudinal axis of the plastic spring of between 1 to 2 and 1 to 10, in particular of 1 to 5.Injection molding device (1) according to one of the preceding claims, wherein the injection molding device (1), in particular the inductive heating device (6), has a positioning device (12) with which the at least one inductive heating coil (9) can be arranged in 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 inductive heating coil (9), and / or wherein the at least one inductive heating coil (9) and the at least one core (5) are arranged in the heating position during inductive heating of the core (5) at a distance of 1-5 mm, preferably 0.5-2 mm, and particularly preferably 0.2-1 mm from one another. Injection molding device (1) according to one of the preceding claims, wherein the inductive heating device (6) is designed for inductive heating of the at least one core (5) inside and / or outside the injection mold, in particular inside the mold cavity (4).Injection molding device (1) according to one of the preceding claims, wherein the injection molding device (1) has a transport device (13), in particular a rotary indexing table, which is designed to transport the at least one core (5) from a 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 on the inductive heating device (6) located outside the mold cavity (4).

21. Injection molding device (1) according to the preceding claim, wherein the transport device (13) is designed to transport the at least one core (5), in particular with a plastic part (2) arranged thereon, from the injection molding tool (3) into a removal position outside the mold cavity (4), in particular outside the injection molding tool (3).

22. Injection molding device (1) according to one of the preceding claims, wherein the injection molding device (1) has a removal device (14), in particular with at least one removal gripper (15), with which a plastic part (2), in particular after cooling, can be removed from the at least one core (5).

23. Injection molding device (1) according to one of the preceding claims, wherein the injection molding device (1) is configured for at least partially encapsulating insert parts (16), in particular pins and / or medical piercing devices and / or RFID chips.

24. Injection molding device (1) according to the preceding claim, wherein the at least one core (5) is designed to hold at least one insert part (16) to be at least partially overmolded.

25. Injection molding device (1) according to one of the two preceding claims, wherein the injection molding device (1) has a loading device (18), in particular with at least one loading gripper (19), with the inserts (16) can be arranged on the at least one core (5). Injection molding device (1) according to one of the preceding claims, wherein the injection molding device (1) comprises an injection molding machine (20) with 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). Computer program comprising instructions which cause the injection molding device (1) to Claims which carries out the steps of the method according to one of claims 1 to 12. Computer-readable medium (22) with a computer program according to the preceding claim. / Summary

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