Tool insert with layer heating, mold plate with such a tool insert and method for operating such a tool insert

Abstract

Tool insert (1) for at least partially delimiting a mold cavity (102) which is formed in a mold plate (101) of an injection mold (100) for producing components (P) from a flowable material (M), with a base body (10) which has a shaping front (S1) for the mold cavity (102) and a rear (S2) opposite the shaping front (S1), wherein the base body (10) carries a layer heating element (20) on its shaping front surface (S1), and wherein the layer heating element (20) is covered in the direction of the front surface (81) by a final contour layer (26) which forms the shaping front surface (81), characterized in that - that the layer heating (20) has a heating conductor track (21) manufactured using thick-film technology, and - that the layer heater (20) has a first electrical insulating layer (22) manufactured using thick-film technology and covering the heating conductor track (21) in the direction of the front (S1), wherein the first electrical insulation layer (22) is configured to compensate for micro-ripples caused by the heating conductor track (21), wherein the first electrical insulation layer (22) is between 10 and 50 micrometers thick, and the contour layer (26) is between 50 and 500 micrometers thick.

Description

[0001] The invention relates to a tool insert, a mold plate with such a tool insert and a method for operating such a tool insert according to the appended patent claims.

[0002] Injection molds typically comprise a mold plate with a mold cavity into which a heated, flowable material, particularly plastic, is introduced through at least one sprue opening. The flowable material hardens within the mold cavity, forming a component. This component is then demolded.

[0003] In the simplest case, the mold plate is constructed in two parts, and the mold halves are separated for demolding. However, designs with a larger number of mold plate fragments or so-called movable slides are known to enable demolding of complex structures with undercuts.

[0004] The temperature distribution during the introduction of the flowable material into the mold cavity and during curing is problematic. Common defects resulting from this include shrinkage cavities, incompletely filled cavities, shear lines (also known as tiger lines), weld lines, and incomplete graining. These defects are not only aesthetically pleasing, but also pose a risk to safety-critical components. The production of components with a high aspect ratio is particularly problematic. This is determined by the ratio of the cavity depth, starting from the sprue opening, to the smallest lateral dimension of the cavity, as well as by the overall size of the component. The smaller the component, the higher the aspect ratio.During the filling process of a mold cavity with a high aspect ratio, the flowable material cools down while still in motion to such an extent that it stagnates - shear lines are formed and the mold cavity may not be completely filled - the grain structure is not completely filled - incomplete grain characteristics are formed - and a hardened film is formed at the material front, so that a weld line is formed when two partial flows meet.

[0005] Given the demands placed on today's components, these problems can no longer be resolved by high injection pressures alone. Therefore, heating devices on the injection molding nozzle and mold plate sides, as well as cooling devices on the mold plate side, are known to influence the temperature distribution. This should help prevent the resulting defects.

[0006] The most common methods for tempering the mold plate include channel structures for the passage of tempered fluids, internal and external induction heaters, infrared radiation when the mold is open, and resistance heating elements.

[0007] Temperature control using water or oil as a heat transfer medium is well established, but suffers from poor efficiency. This is due to high losses in the supply line and the sluggish dynamics of temperature changes. The latter is necessary to heat the mold plate before and during the introduction of the flowable material into the mold cavity and to subsequently cure the flowable material by cooling. Furthermore, temperature control is limited to approximately 160 °C to 200 °C.

[0008] While higher performance can be achieved with induction heating, integration into the injection mold is very complex and expensive. Furthermore, it also heats relatively large, mass-bearing components whose temperature changes are slow. This slows down production cycles.

[0009] Heating with infrared radiation uses the principle of thermal radiation. Here, the mold cavity surface is heated from the outside using thermal radiation. However, due to the usually very finely machined surfaces of the mold cavities, the emission factor is high and the heating efficiency is low. Furthermore, the achievable temperatures are limited by the size and power distribution of the emitters. Finally, the irradiation takes place with the mold open, which significantly extends production cycles.

[0010] In the article "Functional Surfaces Dynamically Tempered" by Ingo Brexeler and Nico Küls (BREXLER et al.), published in wt Werkstatttechnik online, Volume 99 (200), Issue 11 / 12, pp. 830-836, a highly dynamic mold temperature control system is described. This involves mold inserts integrated into the mold with a high-performance ceramic (CPH) and near-cavity cooling.

[0011] A disadvantage, however, is that the heating elements, according to Brexler et al., comprise a relatively large heated mass. This leads to slow cooling of the mold cavity, resulting in long cycle times. This can only be partially remedied by the proposed cooling method by passing a cooling medium through fluid channels.

[0012] The documents DE 10 2009 053 517 A1, EP 0 335 100 A2, DE 199 29 731 A1, DE 90 12 186 U1, US 2007 / 0 092 595 A1, US 8 052 415 B2, DE 10 2008 022 075 A1, DE 10 2010 003 033 A1, JP 2000 000 823 A and DE 10 2010 018 590 A1 describe relevant prior art in the field of injection molding technology.

[0013] The object of the invention is therefore to eliminate the disadvantages of the prior art and to create a device that enables the fastest possible cycle times in the production of components from a flowable material, in particular plastic, while maintaining high component quality. In particular, the device should enable highly dynamic temperature control of the mold cavity, which can be variably adapted to the required temperatures, is easy to install, reliable in operation, cost-effective, and highly efficient.

[0014] In a tool insert for at least partially delimiting a mold cavity, which is formed in a mold plate of an injection molding tool for producing components from a flowable material, with a base body which has a shaping front side for the mold cavity and a rear side opposite the shaping front side, the invention provides that the base body carries a layer heater on its shaping front side.

[0015] With such a tool insert, very fast cycle times are now possible when manufacturing components from a flowable material, as the layer heating is directed toward the mold cavity. Thus, thorough heating of the base body is unnecessary. The layer heating thus heats the molding surface of the tool insert extremely quickly. When the layer heating is deactivated, the small amount of thermal energy in this thin layer is dissipated very quickly, primarily into the base body and from there into the mold plate of a tool.

[0016] Due to the short heating and cooling times due to the minimally heated mass of the layer heater, very fast cyclic temperature profiles are achieved. Since the heating takes place directly at the surface, it is harmless to continuously cool the mold plate behind the tool insert and / or the base body of the tool insert to a low temperature. The curing rate of the flowable material can also be controlled by regulating the layer heater. By using different cross-sections of the heating conductors, targeted distribution of the heating conductors, and / or separate heating conductors, temperature control can even be adjusted locally without any significant thermal influences on the adjacent surface areas. This enables highly dynamic temperature control of the mold cavity with high temperature gradients across the surface and high efficiency.

[0017] Using the tool insert according to the invention, components made of flowable material, particularly plastic, can be manufactured that exhibit very high component quality. Among other things, the flow of the flowable material is not impeded by a rapidly cooling melt front. Accordingly, lower injection pressures are sufficient to fill the mold cavity. This allows clamping units with lower clamping forces to be realized, which leads to lower unit costs per component. Furthermore, improved molding of surface structures / grains, easier mold filling of thin-walled parts, and a reduction in weld lines, shear lines, and flow lines are achieved. For this purpose, it is possible, for example, to raise the surface of the mold cavity to its glass or melting temperature shortly before injecting the flowable material and to cool it to demolding temperature after the filling process, if necessary assisted by a heat transfer medium flowing in cooling channels.

[0018] Furthermore, the installation of tool inserts has been tested many times in practice, which means that a tool insert according to the invention with layer heating can also be easily installed.

[0019] The layer heater should generally be between 10 and 500 micrometers thick. However, local peak thicknesses of up to 2 mm can also be provided, especially if the surface contour of the mold cavity requires it. Thin- and thick-film technologies are particularly suitable for producing the layer heater.

[0020] In a further development of the invention, the layer heater comprises a heating conductor track manufactured using thick-film technology. This allows a preferred thickness of the heating conductor track of 1 to 50 micrometers to be achieved. As can be seen, this results in a very small mass to be heated, which enables very dynamic temperature control. Particularly suitable materials for manufacturing the heating conductor track are silver (Ag), palladium (Pd), platinum (Pt), ruthenium (Ru), and gold (Au), or mixtures of these materials. To create the surface contour, manufacturing the heating conductor track using a 3D printing process is recommended, particularly using inkjet processes, aerosol processes, dispensing, or microdispensing. Pad printing or screen printing can also be effective.

[0021] According to a more detailed embodiment of the layer heater according to the invention, it has a first electrical insulation layer manufactured using thick-film technology and covering the heating conductor track towards the front. This protects persons handling the tool from electric shocks. In addition, damage to the heating conductor track caused by short circuits, e.g., due to mechanical bridging, and mechanical damage is prevented. Finally, the insulation layer can compensate for micro-ripples caused by the heating conductor track. To fulfill this function, the first electrical insulation layer is between 10 and 50 micrometers thick; however, local peak thicknesses of up to 2 mm may be necessary to replicate the surface geometry of the mold cavity. With this material thickness, the mass to be heated remains small and highly dynamic temperature control is possible.Glass, glass ceramic, or enamel are particularly suitable materials for the production of the first insulation layer. Optimization of these materials with regard to high thermal conductivity should be sought. The production itself is preferably carried out using a 3D coating process to reproduce the surface geometry of the mold cavity. Inkjet processes, aerosol processes, dispensing or microdispensing, pad printing, and screen printing are particularly suitable for this purpose, as are electrophoresis, spraying, or dipping processes, as well as other processes commonly used in enamel technology.

[0022] According to one variant of the invention, the layer heater has a second electrical insulation layer produced using thick-film technology between the heating conductor track and the base body. This is particularly necessary when the base body is electrically conductive. Although the base body can also be made of a non-conductive material, embedding a tool insert in a mold cavity is usually easier when using tool steel, in particular the same as the material of the mold plate. In this case, the base body has the same thermal properties, in particular the same thermal expansion, as the mold plate. The second electrical insulation layer should have a thickness of between 10 and 50 micrometers. This makes it possible to achieve a continuously electrically insulating layer that also has a low mass.Glass, glass ceramic, or enamel are particularly suitable materials for the second electrical insulation layer. Optimizing these materials for high thermal conductivity should be strived for. The second electrical insulation layer is preferably produced using a 3D coating process to replicate the surface contour of the mold cavity. Suitable methods include inkjet processes, aerosol processes, dispensing or microdispensing, pad printing, and screen printing, as well as electrophoresis, spraying, or dipping, and other processes commonly used in enamel technology.

[0023] According to a more detailed embodiment of the heating conductor track according to the invention, it is provided with connection contacts arranged on a tongue of the base body, wherein the tongue can be positioned outside the mold cavity and on which a sealing surface is formed towards the front, which sealing surface delimits the shaping region of the front. Thus, the tongue and thus the connection contacts can be positioned outside the mold cavity and are not exposed to the high injection pressures. In addition, a more flexible design of the connection contacts outside the mold cavity is possible, since no defined surface geometry needs to be formed. Furthermore, operation of the layer heater with an external power source and / or control unit is possible. The sealing surface can correspond to an opposite sealing surface of a mold plate or another tool insert. Accordingly, the mold cavity is securely closed except for desired openings.

[0024] In a further embodiment of the invention, the heating conductor track is provided with connection contacts that extend through the base body toward the rear. This allows the sealing surface to be formed entirely through the mold plates, thus avoiding fitting difficulties. At the same time, the electrical connections can be easily routed out of the mold cavity below the tool insert.

[0025] To ensure secure contact between the connection contacts and the heating conductor, a further development is advantageous in which the connection contacts are subjected to a force in the direction of the connection surfaces of the heating conductor. Alternatively or additionally, the connection contacts can be firmly bonded to the connection surfaces of the heating conductor.

[0026] If the connection contacts extend through the base body toward the rear, a variant of the invention is advantageous in which an insulating body with one or more connection contacts is extended through the base body. The insulating body is flush with the base body on the side of the layer heater, and the connection contacts form contact surfaces on this side. The second electrical insulation layer should have at least one recess in the area of ​​the contact surfaces of the connection contacts. Preferably, the heating conductor track is subsequently applied with its connection areas to the contact surfaces of the connection contacts using thick-film technology.

[0027] An important development of the invention provides that the layer heater is covered toward the front side by a final contour layer, which forms the shaping front side. Typically, the surfaces and material properties of mold cavities and layer heaters differ. This makes matching the surfaces to achieve a uniform component surface difficult. The contour layer according to the invention can easily overcome this problem.

[0028] According to a design according to the invention, the contour layer is between 50 and 500 micrometers thick. This is sufficient to provide the quality of the surface contour and to cover the wave structure of a heating conductor track. In addition, the contour layer can be post-processed after application, for example, a common graining of the contour layer with the remaining contour surface of the mold cavity. By using materials with the same reaction for the contour layer and the mold plate, uniform chemical graining can also be achieved across the parting lines. The contour layer is particularly preferably essentially between 70 and 150 micrometers thick, although material thicknesses of up to 2 mm can be provided in local peak areas. This also keeps the mass of the contour layer low and only slightly influences the highly dynamic temperature control by the layer heating.

[0029] In one variant of the invention, the contour layer is produced by detonation coating or microforging. Detonation coating allows for the creation of particularly fine microstructures with residual porosities below 0.25%. Furthermore, the bond strength exceeds 70 MPa, and the contour layer has a long service life, even after numerous injection processes. In a microforging process, metal powder is compacted under high pressure. For this purpose, the metal powder is compacted using water, electricity, and compressed air. This creates very fine structures that can also be very complex.

[0030] In another manufacturing variant, the contour layer is created using electroplating or a chemical coating process. For example, using electroplating nickel, nickel layers can be deposited in very short times and with very thick layers by regulating the current flow. In contrast, chemical nickel is deposited without the application of an external electric current. The electrons required to deposit the nickel ions are generated by a chemical oxidation reaction in the bath itself. This results in coatings with particularly precise contours. The chemical nickel process is particularly well-suited for layers up to 50 micrometers thick, since mechanical stresses occur in the layer with greater layer thicknesses, making deposition significantly more time-consuming than with the electroplating nickel process.

[0031] The electroplating nickel process requires a conductive substrate or intermediate layer. The electroless nickel process requires at least nucleation on a non-conductive substrate, as deposition begins on bare metal surfaces. The production of a conductive intermediate layer can be achieved using one of the previously mentioned coating processes.

[0032] Before applying the contour layer using a galvanic or chemical process, a chemically aggressive cleaning process should be performed to ensure the layer's adhesion. When using a first electrical insulation layer that is not resistant to the cleaning agents, a variant of the invention provides for a chemically resistant intermediate layer to be arranged beneath the contour layer. This layer thus has the properties of both a protective layer and an adhesive layer. This ensures particularly good durability of the tool insert. The intermediate layer can also be applied using one of the previously described 2D or 3D coating processes.

[0033] Furthermore, a more detailed embodiment of the invention provides for the contour layer to be made of a metal, in particular tool steel or nickel. These are particularly well suited both with regard to the coating process and the requirements for durability, adhesion, thermal conductivity, surface finish, and surface quality.

[0034] According to one embodiment of the invention, the base body is made of metal, in particular of a hard metal or a tool steel or an alloy comprising chromium, tungsten, nickel, molybdenum, and carbon or an alloy comprising chromium, manganese, phosphorus, silicon, sulfur, and carbon or an alloy comprising chromium, titanium, niobium, manganese, and carbon. These materials are particularly well adapted to a surrounding mold plate. Hard metals, in particular, are also well suited for coating with standard glass.

[0035] According to an alternative embodiment of the invention, the base body is made of a ceramic. This allows the base body to be directly coated with the heating conductor track. Furthermore, ceramics are well suited for coating with standard glasses.

[0036] A further development of the invention relates to a layered thermocouple which is carried by the base body towards the front. Due to its low mass and the possibility of direct integration into the layered heater, e.g. between the heating conductors or separated by a thin insulating layer directly above or below the heating conductor, such a device enables the temperature to be measured extremely quickly and in the correct position. The temperature can therefore be determined particularly accurately. Classic thermocouples with a sensor tip, on the other hand, would have to be positioned at a distance from the contour-defining front side. However, since only a very thin layer is heated by the layered heater, the temperature in the area of ​​the sensor tip could deviate considerably. This is avoided by the layered thermocouple according to the invention, which is particularly advantageous since it is precisely the highly dynamic thermal changes in the layered heater or the heating conductor that are most effectively measured.on the heater surface. This also enables direct, timely control of the layer heater and the injection mold, especially the injection cycles. The connections of the layer thermocouple can be designed in a similar way to the connections of the layer heater. Joint or separate devices can be provided.

[0037] The invention further relates to a mold plate for an injection mold for producing components from a flowable material, comprising a mold cavity surrounded by a molding surface, a sprue opening opening into the mold cavity, and a mold insert receptacle in which a mold insert according to one of the preceding claims is received. With such a mold plate, the temperature control of the surface within the mold cavity can be achieved particularly dynamically. The other previously described advantages of the mold insert can also be realized.

[0038] According to an inventive further development of the mold plate, the tool insert is embedded with its shaping front side flush with the shaping surface of the mold cavity. This allows the surface geometry to be formed over the tool insert without any noticeable transition.

[0039] A special variant of the invention also contributes to this, in which the front side of the tool insert and the shaping surface of the mold cavity are machined together by machining, grinding, and / or polishing when the tool insert is installed in the tool insert holder. Accordingly, this machining allows offsets between the front side of the tool insert and the surface of the mold cavity to be leveled. Fine structures can also be produced across the parting line.

[0040] Particularly preferably, machining and / or grinding and / or polishing takes place while the layer heater is heated. Minimal thermally induced contour fluctuations are thus taken into account during production. This allows the first insulation layer and the contour layer to be made particularly thin without the heating conductor track causing a wavy surface. However, the heating conductor tracks can also function as contour generators if this is desired for design reasons. Ideally, machining takes place at a temperature that corresponds to the later operating temperature during curing of the flowable material or the glass transition temperature of the flowable material. The surface contour of the tool insert can therefore only change when the layer heater cools down. However, the component is at least partially cured and retains its shape.

[0041] In another manufacturing variant, a grain pattern on the front side of the tool insert and the mold cavity's shaping surface is produced together when the tool insert is installed in the tool insert holder. This type of technical or chemical grain pattern can thus also be produced across the dividing line between the tool insert and the mold cavity's surface.

[0042] In an advantageous installation variant according to the invention, the mold insert is arranged in the area of ​​a weld line position of a component. The location of a weld line can be determined by an injection simulation before the injection mold is manufactured. Local heating in the area of ​​the weld line dissolves the frontal hardened film, and the material fronts fuse without material and / or optical defects.

[0043] To ensure uniform temperature control of the mold cavity and to dissipate the heat generated by the layered heating and the injected flowable material, a further development of the mold plate provides for fluid channels. A heat transfer medium can be passed through these channels during the process. This allows the mold plate, for example, to be continuously cooled. Cooling does not need to be interrupted during operation of the layered heating. Efficiency remains very high due to the low mass of the areas to be heated.

[0044] In a further development of the invention, the tool insert is fixed in the tool insert holder by means of a detachable fixing means. This allows the tool insert to be replaced, reworked and reconditioned separately from the mold plate. In the event of a defect, the injection mold is also quickly ready for use again. Preferably, the fixing means can be actuated through an opening in the mold plate located outside the mold cavity. This eliminates the need for handling inside the mold cavity, and damage to the mold cavity surface is avoided. Such a fixing means can be formed by a threaded hole or a hole with a bayonet contour in the base body, or by a hole that leads through the mold plate into the tool insert holder. A screw or bayonet can then be guided through the latter and secured in the hole in the base body.Alternatively, other clamping elements such as clamps could be used that engage with the mold plate and base body.

[0045] Floating the tool insert in the tool holder is also recommended. This reduces deformation of the tool insert due to uneven thermal and / or pressure-related stresses.

[0046] According to a further development of the invention, the base body is thermally coupled to the tool insert holder. This allows the thermal energy introduced by the layer heating and the injected flowable material to be dissipated from the mold cavity area as quickly and easily as possible. This is achieved by a (large) contact surface between the base body and the tool insert holder. A thermally conductive paste between the base body and the tool insert holder also provides helpful support.

[0047] The invention further relates to a method for operating a previously described tool insert in a mold cavity of a mold plate of an injection mold for producing components from a flowable material, in which the layer heater is first heated by applying a voltage, followed by starting a filling cycle in which flowable material is introduced into the mold cavity, and in which the voltage of the layer heater is reduced or removed before, during or after the filling cycle, before the mold cavity is opened after a cooling phase and the at least partially cured component is removed.

[0048] The tooling used according to the invention allows for particularly fast injection cycles. Nevertheless, the quality of the molded components is particularly high due to the highly dynamic temperature control using layer heating.

[0049] An additional optional step of the method according to the invention involves conducting the thermal energy of the flowable material and the layer heater through the base body into the mold plate during the cooling phase. In this way, the heat is dissipated from the area of ​​the mold cavity as quickly and as simply as possible. Shortly after the tension is removed, the layer heater and the immediate area around the mold cavity have cooled to the temperature of the mold plate, since only a very small mass was heated, which also has a large surface area for heat conduction relative to its volume.

[0050] A variant of the method according to the invention provides for the passage of a heat transfer medium through fluid channels within the mold plate during the cooling phase. This allows the heat to be continuously dissipated from the typically relatively voluminous and heavy mold plates, ensuring reliable dynamic temperature control even over a large number of injection cycles.

[0051] The layer heating according to the invention also allows a process variant in which a heat transfer medium is passed through fluid channels within the mold plate during heating of the layer heating and / or the filling cycle. The layer heating and the mold plate can thus be dual-temperature-controlled. It is conceivable that certain areas of the mold plate are heated using the heat transfer medium. Particularly advantageous, however, is the option that the mold plate can also be cooled when the layer heating is activated in order to keep the temperature at the lowest possible level. Accordingly, the temperature flow into the mold plate from the layer heating and out of the mold cavity when the layer heating is deactivated is as fast as possible.

[0052] Furthermore, a further development of the method provides for heating the layer heating to at least 150 °C before starting the filling cycle. At this temperature, a significant improvement in filling behavior is noticeable for most flowable materials compared to filling an unheated mold plate, and the components have a correspondingly high quality. A particular advantage of layer heating is the ability to complete heating within 20 seconds, and particularly preferably within 8 seconds. The injection cycles are correspondingly fast, and a large number of components can be manufactured per unit time, resulting in low unit costs.

[0053] A process addition that maintains the temperature of the base body at essentially the temperature of a tool insert holder that accommodates the tool insert, and essentially limits the heating to the layer heating area, also contributes to achieving highly dynamic temperature control. This temperature maintenance can also include the activation phases of the layer heating, so that the largest possible temperature gradient is achieved between the layer heating and the base body. The base body can also have fluid channels for this purpose, which are preferably coupled to cooling channels in the mold plate. This ensures particularly good temperature dissipation from the mold cavity area.

[0054] Further features, details, and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. They show: Fig. 1 an injection molding tool with a tool insert in exploded view; Fig. 2 a section through an injection molding tool with a tool insert; Fig. 3 a mold plate and a tool insert in exploded view; Fig. 4 a section of a detailed view through an injection molding tool with a tool insert in the area of ​​the electrical connection of a layer heater; Fig. 5 a section of a detailed view through a tool insert in the area of ​​the electrical connection of a layer heater; Fig. 6 a section of a detailed view through a mold plate with a tool insert in the area of ​​the electrical connection of a layer heater; and Fig. 7 a section of a detailed view through a tool insert with a layer heater in the area of ​​the electrical connection of the layer heater.

[0055] Fig. 1 shows an injection molding tool 100 for producing components P from a flowable material M with a tool insert 1 in an exploded view. In Fig. 2 shows a section through such an injection molding tool 100 with a tool insert 1. The injection molding tool 100 according to the Fig. 1 and Fig. 2 has a two-part mold plate 101. In the mold plate 101, in particular between its two halves, a mold cavity 102 with a shaping surface 103 is formed. The upper half of the mold plate 101 has a sprue opening 104 for filling the mold cavity with flowable material M. A nozzle insert 111 is inserted into the sprue opening 104, into which an injection molding nozzle 110 extends. The design of the injection molding nozzle 110 with its nozzle tip, the material tube, the housing, the material tube head, the heating devices, the thermal sensor, their electrical connections, and the connection of the injection molding nozzle 110 to a machine nozzle or a distributor will not be discussed in detail here.

[0056] To control the temperature of the mold plate 101, a fluid channel 107 is introduced into it, through which a heat transfer medium F can be conducted. In the lower half of the mold plate 101, a tool insert holder 105 is formed within the mold cavity 102, in which the tool insert 1 is received. In the embodiment shown here, the tool insert 1 is mounted floating in the tool insert holder 105. The tool insert 1 and the tool insert holder 105 are thermally coupled, in particular by a relatively large contact surface on the rear side S2 of the tool insert 1. To support the thermal contact, a thermally conductive paste can additionally be introduced between the tool insert 1 and the tool insert holder 105.

[0057] Furthermore, the tool insert 1 has a shaping front side S1 pointing in the direction of the mold cavity 102. The rear side S2 points, as described, in the direction of the mold plate 101. In the direction of the rear side S2, the tool insert 1 comprises a base body 10, which carries a layer heater 20 in the direction of the front side S1. The layer heater 20 is essentially between 10 and 500 micrometers thick. A detailed view of a layer heater 20 can be found in Fig. 7. It can also be seen that the layer heater 20 has a heating conductor track 21 manufactured using thick-film technology. This track is between 1 and 50 micrometers thick, and the conductor cross-section and thus the local electrical resistance are adapted to the local heat requirements. This is made possible by the production of the heating conductor track 21 using a 3D coating process. For flat surfaces, 2D processes such as screen printing can also be used.

[0058] The layer heater 20 also has a first electrical insulation layer 22 manufactured using thick-film technology and covering the heating conductor track 21 in the direction of the front side S1. This first electrical insulation layer 22 is between 10 and 50 micrometers thick. It can be made of glass, glass ceramic, or enamel. The first electrical insulation layer 22 is also produced using a 3D coating process. For flat surfaces, 2D processes such as screen printing can also be used. In addition, there is a second electrical insulation layer 23 arranged between the heating conductor track 21 and the base body 10 and manufactured using thick-film technology. The second electrical insulation layer 23 is between 10 and 50 micrometers thick. It can be made of glass, glass ceramic, or enamel. The second insulation layer 23 is necessary if the base body 10 is made of a metal, in particular of tool steel. This selected material is electrically conductive.

[0059] Furthermore, the layer heater 20 is coated toward the front side S1 by a final contour layer 26, which forms the shaping front side S1. The contour layer 26 is essentially between 50 and 500 micrometers thick, but has local peak thicknesses of up to 2 mm. The contour layer 26 can be produced by detonation coating or microforging. Alternatively, it can be produced by electroplating or a chemical coating process.

[0060] The contour layer 26 consists of a metal, in particular tool steel or nickel. If a non-electrically conductive material is selected for the contour layer 26, it can assume the function of the first electrical insulation layer 22, or the first electrical insulation layer 22 forms the contour layer 26.

[0061] The tool insert 1 also has a layered thermocouple 30. This is supported by the base body 10 toward the front side S1. In particular, it is integrated as a thermocouple track into the layered structure of the layered heater 20. Temperature measurement is based, in particular, on electrical voltages that correlate with temperature.

[0062] The heating conductor track 21 is provided with connection contacts 24, which are arranged on a tongue 11 of the base body 10. More detailed views of such connection contacts 24 can be found in the Fig. 2, Fig. 3, Fig. 4 and Fig. 5. The tongue 11 is positioned outside the mold cavity 102 and forms a sealing surface 12 toward the front side S1, which defines the forming area of ​​the front side S1. This sealing surface 12 corresponds to a sealing surface of the upper half of the mold plate 101. The electrical connections of the layered thermocouple 30 are similarly located in the area of ​​the tongue 11.

[0063] With such an injection molding tool 100, a method for operating the tool insert 1 can now be carried out, in which the layer heater 20 is first heated by applying a voltage. Subsequently, a filling cycle is started, during which flowable material M is introduced into the mold cavity 102. During or after the filling cycle, the voltage of the layer heater 20 is reduced or removed in order to dissipate the heat from the region of the mold cavity into the mold plate 101, in particular by conducting the thermal energy E of the flowable material M and the layer heater 20 through the base body 10 into the mold plate 101. The heat can be dissipated from the latter by temperature control by means of a flow of a heat transfer medium F through the fluid channels 107. After a cooling phase, the mold cavity 102 is opened and the at least partially cured component P is removed.The cooling of the mold plate 102 with the heat transfer medium F can also take place during the heating of the layer heater 20 and / or the filling cycle. Ideally, this keeps the temperature of the base body 10 essentially at the temperature of the tool insert holder 105 and limits the heating by the layer heater 20 to the area of ​​the layer heater 20, possibly including the contour layer 26. The heating of the layer heater 20 and thus the front side S1 of the tool insert 1 preferably takes place to at least 150 °C before the start of the filling cycle. Due to the low mass, this can be achieved in a very short time, e.g., within 8 seconds. Cooling after deactivation of the layer heater 20 can also take place very quickly. Alternatively, it can be specifically influenced by a temperature profile of the layer heater 20.

[0064] In Fig. 3 shows an exploded view of a mold plate 101, in particular one half thereof, and a tool insert 1. The mold plate 101 is designed for an injection molding tool for producing components from a flowable material. It has a mold cavity 102 in which a tool insert receptacle 105 is formed. The tool insert 1 is received in the latter. In particular, the tool insert 1 is fixed in the tool insert receptacle 105 by means of a releasable fixing means (not shown). The tool insert 1 is largely floatingly mounted in the tool insert receptacle 105. The base body 10 is thermally coupled to the tool insert receptacle 105, in particular by a relatively large contact surface. The circumferential groove in the tool insert 1 becomes a fluid channel 13 through installation in the tool insert receptacle 105, to which a heat transfer medium is supplied through a fluid channel 107 in the mold plate 101.This allows the heat transfer medium to be guided directly along the tool insert 1.

[0065] The tool insert 1 has a shaping front side S1 facing the mold cavity 102, which is clearly three-dimensional. A rear side S2 of the tool insert 1 faces the mold plate 101. In the direction of this rear side S2, the tool insert 1 has a base body 10, which carries a layer heater 20 and a layer thermocouple 30 in the direction of the front side S1. For a more detailed description of the structure, please refer to the description of the Fig. 1, Fig. 2 and Fig. 7. The layer heater 20 is further covered in the direction of the front side S1 by a final contour layer 26, which forms the shaping front side S1, which is also described in more detail in the explanations of the Fig. 1, Fig. 2 and Fig. 7 is described.

[0066] The layer heater 20 and the layer thermocouple 30 each have connecting contacts arranged on a tongue 11 of the base body 10, with the tongue 11 positioned outside the mold cavity 102. Toward the front side S1, the tongue 11 forms a sealing surface 12 that delimits the forming area of ​​the front side S1. As can be seen, the sealing surface 12 radially encompasses the entire forming front side S1. This ensures a continuous seal, and sealing problems at transitions are avoided.

[0067] The Fig. 4, Fig. 5 and Fig. 6 each show a section of a detailed view through a tool insert 1 in the area of ​​the electrical connection of a layer heater 20. In Fig. 4 shows two halves of a mold plate 101 in a closed position, whereas in the Fig. 5 and Fig. 6 only one half of the mold plate 101 is visible.

[0068] The mold plates 101 of the Fig. 4 to 6 each form a mold cavity 102 with a shaping surface 103. They also have a tool insert holder 105 in which the tool insert 1 is received.

[0069] The tool insert 1 has a shaping front side S1 pointing in the direction of the mold cavity 102 and a rear side S2 pointing in the direction of the mold plate 101. In the direction of the rear side S2, the tool insert 1 has a base body 10, which carries a layer heater 20 in the direction of the front side S1. In addition, it also carries a layer thermocouple 30. For the construction of the layer heater 20 with its heating conductor track 21 and the layer thermocouple 30, reference is made at this point to the explanations regarding the Fig. 1, Fig. 2 and Fig. 7. The heating conductor 21 is provided with connection contacts 24. The same applies to the layer thermocouple 30.

[0070] According to the Fig. 4 and Fig. 5, the connection contacts 24 are each arranged on a tongue 11 of the base body 10. The connection contacts 24 are located here on the front side S1, which is why the tongue 11 is positioned outside the mold cavity 102. A sealing surface 12 is formed on the tongue 11 in the direction of the front side S1, which sealing surface delimits the shaping region of the front side S1. As a result, the connection contacts 24 are located outside the shaping region of the front side S1. A connection surface 25 of the heating conductor track 21 is exposed on the tongue 11, in particular, the connection surface 25 is not covered by a first insulation layer 22 and / or a contour layer 26. Corresponding to the connection surface 25, the connection contact 24 is formed with a contact surface 241. According to Fig. 4, the connecting contact 24 is pressed with its contact surface 241 onto the connecting surface 25 by means of a force accumulator, in particular a spring element 41. In contrast, the contact surface 241 of the connecting contact 24 is according to Fig. 5 is firmly bonded to the connection surface 25, in particular by soldering or welding.

[0071] A special feature is Fig. 5, where a fluid channel 13 is formed in the base body 10 in order to be able to cool it particularly quickly.

[0072] According to Fig. 6, the heating conductor track 21 and the layer thermocouple 30 are provided with connection contacts 24, which are passed through the base body 10 in the direction of the rear side S2. For this purpose, an insulating body 40 with the connection contacts 24 is passed through the base body 10. The insulating body 40 and the connection contacts 24 are flush with the base body 10 on the side of the layer heater 20, and the connection contacts 24 form contact surfaces 241 here. In the area of ​​these contact surfaces 241, the second electrical insulation layer 23 has a recess 231. Furthermore, the connection contacts 24 are integrally connected to the connection surfaces 25 of the heating conductor track 21. In particular, the heating conductor track 21 with its connection contacts 24 is applied to the contact surfaces 241 of the connection contacts 24 using thick-film technology.

[0073] A detailed view of a connection according to Fig. 6 and the structure of the layer heater 20 and the layer thermocouple 30 can be found in Fig. 7. This shows a detailed view of a tool insert 1 in a mold cavity 102 in a mold plate 101 of an injection mold for producing components from a flowable material. A shaping front side S1 of the tool insert 1 points toward the mold cavity 102, and a rear side S2 points toward the mold plate 101. A base body 10 of the tool insert 1, pointing toward the rear side S2, carries a layer heater 20 toward the front side S1.

[0074] Formed in the mold plate 101, particularly in the region of the mold cavity 102, is a tool insert receptacle 105 in which the tool insert 1 is received. The tool insert 1 is fixed in the tool insert receptacle 105 by means of a releasable fixing means 108, particularly a screw. The fixing means 108 can be actuated through an opening 109 in the mold plate 101 located outside the mold cavity 102. As can be seen here, the screw engages in a threaded bore 14 on the rear side S2 of the base body 10. The base body 10 is made of a tool steel, or of an alloy comprising chromium, tungsten, nickel, molybdenum, and carbon, or of an alloy comprising chromium, manganese, phosphorus, silicon, sulfur, and carbon, or of an alloy comprising chromium, titanium, niobium, manganese, and carbon.

[0075] Through thermal contact between the base body 10 and the tool insert holder 105 or the mold plate 101, thermal energy E from the mold cavity 102 and the layer heater 20 can be conducted through the base body 10 into the mold plate 101. For rapid dissipation of the thermal energy E, a fluid channel 107 in the mold plate 101 and a fluid channel 13 in the base body 10 are also provided, through each of which a heat transfer medium F can be conducted.

[0076] The layer heater 20 has a heating conductor track 21 manufactured using thick-film technology, which is between 1 and 50 micrometers thick. It consists of Ag, Pd, Pt, Ru, Au, or mixtures thereof. It is manufactured using a 2D or 3D coating process, for which inkjet processes, aerosol processes, dispensing or microdispensing, pad printing processes, and screen printing processes are particularly suitable.

[0077] Furthermore, the layer heater 20 has a first electrical insulation layer 22 manufactured using thick-film technology and covering the heating conductor track 21 toward the front side S1. This layer is between 10 and 50 micrometers thick, consists of glass, glass ceramic, or enamel, and is produced using a 2D or 3D coating process. Inkjet processes, aerosol processes, dispensing or microdispensing, pad printing processes, and screen printing processes are also suitable for this purpose, as are electrophoresis, spraying or dipping processes, or other processes commonly used in enamel technology.

[0078] Between the heating conductor track 21 and the base body 10, the layer heater 20 comprises a second electrical insulation layer 23 manufactured using thick-film technology. This layer is between 10 and 50 micrometers thick, consists of glass, glass ceramic, or enamel, and is produced using a 2D or 3D coating process. Inkjet processes, aerosol processes, dispensing or microdispensing, pad printing processes, and screen printing processes are also suitable for this purpose, as are electrophoresis, spraying or dipping processes, or other processes commonly used in enamel technology.

[0079] The heating conductor track 21 is provided with connection contacts 24, which extend through the base body 10 toward the rear side S2. For this purpose, an insulating body 40 with the connection contacts 24 is extended through the base body 10. This insulating body is flush with the base body 10 on the side of the layer heater 20, and the connection contacts 24 form contact surfaces 241 on this side. The second electrical insulating layer 23 has a recess 231 in the region of the contact surfaces 241. Because the heating conductor track 21 with its connection areas is applied using thick-film technology to the contact surfaces 241 of the connection contacts 24, a materially bonded connection exists between the connection contacts 24 and the connection surfaces 25 of the heating conductor track 21.

[0080] Embedded between the first electrical insulation layer 22 and the second electrical insulation layer 23, the base body 10 also carries a layered thermocouple 30 in the direction of the front side S1. Not visible are its electrical connection contacts, which can be designed analogously to those of the layered heater 20.

[0081] The layer heater 20 is covered toward the front side S1 by a final contour layer 26, which forms the shaping front side S1. The contour layer 26 is essentially between 50 and 500 micrometers thick. Only in small local peak areas is a material thickness of up to 2 mm provided. Furthermore, the contour layer consists of a metal, in particular of tool steel or nickel. It is manufactured by a detonation coating process or by microforging. Alternatively, production by electroplating or a chemical coating process is possible. To achieve a highly durable fixation of the contour layer 26, a chemically resistant intermediate layer 27 is arranged beneath it. This protects the first electrical insulation layer 22 during surface preparation using aggressive cleaning agents.The intermediate layer 27 then forms an adhesive layer for the contour layer 20.

[0082] As can be seen, the front side S1 of the tool insert 1 is embedded flush with the shaping surface 103 of the mold cavity 102. For this purpose, the front side S1 of the tool insert 1 and the shaping surface 103 of the mold cavity 102 are machined together by machining, grinding, and polishing in the illustrated installation situation of the tool insert 1 in the tool insert holder 105. This machining was carried out, in particular, with the layer heater 20 heated. In addition, a grain was produced on the front side S1 and the shaping surface 103 of the mold cavity 102 together in the installation situation of the tool insert 1 in the tool insert holder 105.

[0083] The invention is not limited to one of the previously described embodiments, but can be modified in a variety of ways. In particular, depending on the material selected, the layer heater 20 can have only one insulation layer or no insulation layer at all, or the first insulation layer 22 and the contour layer 26 can be formed from a single layer.

[0084] Combinations of the various electrical connections are also possible, as are different numbers of layered thermocouples 30 and heating conductor tracks 20 in a common layered structure. The peripheral boundaries of the tool insert 1 located within the mold cavity 101 can be specifically positioned in visible edges or design beads of the component. Finally, it is also fundamentally possible to apply the contour layer 26 beyond the peripheral boundary of the tool insert 1 during installation in the tool insert holder 105, thus creating a smooth transition between the tool insert 1 and the shaping surface 103 of the mold cavity 102. The arrangement of several tool inserts 1 in a single mold cavity 102 is also conceivable. List of reference symbols 1 tool insert 10 basic bodies 11 Tongue 12 Sealing surface 13 Fluid channel 14 threaded hole 20 layer heating 21 Heating conductor track 22 first electrical insulation layer 23 second electrical insulation layer 231 Recess (second electrical insulation layer) 24 connection contact 241 Contact surface (of the connection contact) 25 connection surface 26 Contour layer 27 Intermediate layer 30 layer thermocouples 40 insulation bodies 41 spring element 100 injection molds 101 mold plate 102 mold cavity 103 forming surface (mold cavity) 104 sprue opening 105 Tool insert holder 107 Fluid channel 108 Fixatives 109 Opening 110 injection molding nozzle 111 Nozzle insert E thermal energy F Heat transfer medium M Material P component S1 front S2 back

Claims

[1] Tool insert (1) for at least partially defining a mold cavity (102) which is formed in a mold plate (101) of an injection molding tool (100) for producing components (P) from a flowable material (M), with a base body (10) which has a shaping front side (S1) for the mold cavity (102) and a rear side (S2) opposite the shaping front side (S1), wherein the base body (10) carries a layer heater (20) on its shaping front side (S1), and wherein the layer heater (20) is covered in the direction of the front side (81) by a final contour layer (26) which forms the shaping front side (81), characterized by , - that the layer heater (20) has a heating conductor track (21) manufactured using thick-film technology, and - that the layer heater (20) has a first electrical insulation layer (22) produced using thick-film technology and covering the heating conductor track (21) in the direction of the front side (S1), wherein the first electrical insulation layer (22) is configured to compensate for a micro-ripple caused by the heating conductor track (21), the first electrical insulation layer (22) being between 10 and 50 micrometers thick for this purpose, and the contour layer (26) is between 50 and 500 micrometers thick. [2] Tool insert (1) according to claim 1, characterized by that the heating conductor track (21) has a thickness of 1 to 50 micrometers. [3] Tool insert (1) according to one of claims 1 or 2, characterized by that the heating conductor track (21) is made of the materials silver (Ag), palladium (Pd), platinum (Pt), ruthenium (Ru) and gold (Au) or a mixture of these materials. [4] Tool insert (1) according to one of the preceding claims, characterized by that the heating conductor track (21) is produced by a pad printing process, a screen printing process, a 3D printing process, an inkjet process, an aerosol process, dispensing or micro-dispensing. [5] Tool insert (1) according to one of the preceding claims, characterized by that the first electrical insulation layer (22) is produced in a 3D coating process, an inkjet process, an aerosol process, dispensing, micro-dispensing, a pad printing process, a screen printing process, electrophoresis or a spraying or dipping process. [6] Tool insert (1) according to one of the preceding claims, characterized by that the layer heater (20) has a second electrical insulation layer (23) produced using thick-film technology between the heating conductor track (21) and the base body (10). [7] Tool insert (1) according to one of the preceding claims, characterized by in that the heating conductor track (21) is provided with connection contacts (24) which are arranged on a tongue (11) of the base body (10), wherein the tongue (11) can be positioned outside the mold cavity (102) and a sealing surface (12) is formed on the tongue (11) in the direction of the front side (S1), which sealing surface delimits the shaping region of the front side (S1). [8] Tool insert (1) according to one of the preceding claims, characterized by that the heating conductor track (21) is provided with connection contacts (24) which are guided through the base body (10) in the direction of the rear side (S2). [9] Tool insert (1) according to one of the preceding claims, characterized by that the contour layer (26) is produced by detonation coating or by microforging. [10] Tool insert (1) according to one of the preceding claims, characterized bythat the contour layer (26) is produced by electroplating or by a chemical coating process. [11] Tool insert (1) according to one of the preceding claims, characterized by that the contour layer (26) consists of a metal, in particular of a tool steel or of nickel. [12] Tool insert (1) according to one of the preceding claims, characterized by that a chemically resistant intermediate layer (27) is arranged under the contour layer (26). [13] Tool insert (1) according to one of the preceding claims, characterized by that the base body (10) is made of hard metal or tool steel or an alloy comprising chromium, tungsten, nickel, molybdenum and carbon or an alloy comprising chromium, manganese, phosphorus, silicon, sulfur and carbon or an alloy comprising chromium, titanium, niobium, manganese and carbon. [14] Tool insert (1) according to one of claims 1 to 12, characterized by that the base body (10) is made of a ceramic. [15] Tool insert (1) according to one of the preceding claims, characterized by that the base body (10) carries a layer thermocouple (30) in the direction of the front side (S1). [16] Mold plate (101) for an injection molding tool (100) for producing components (P) from a flowable material (M), comprising a mold cavity (102) enclosed by a shaping surface (103), a sprue opening (104) opening into the mold cavity (102) and a tool insert holder (105) in which a tool insert (1) according to one of the preceding claims is received. [17] Mold plate (101) according to claim 16, characterized by that the tool insert (1) is embedded with the shaping front side (S1) flush into the shaping surface (103) of the mold cavity (102). [18] Mold plate (101) according to one of claims 16 or 17, characterized bythat the front side (S1) of the tool insert (1) and the shaping surface (103) of the mold cavity (102) are machined together by machining and / or grinding and / or polishing in the installation situation of the tool insert (1) in the tool insert holder (105). [19] Mold plate (101) according to one of claims 16 to 18, characterized by that fluid channels (107) are formed therein. [20] Mold plate (101) according to one of claims 16 to 19, characterized by that the tool insert (1) is fixed in the tool insert holder (105) by means of a releasable fixing means (108). [21] Mold plate (101) according to one of claims 16 to 20, characterized by that the base body (10) is thermally coupled to the tool insert holder (105). [22] Method for operating a tool insert (1) according to one of claims 1 to 15 in a mold cavity (102) of a mold plate (101) of an injection molding tool (100) for producing components (P) from a flowable material (M), characterized by following steps: • Heating the layer heater (20) with the heating conductor track (21) produced using thick-film technology by applying a voltage; • Subsequently starting a filling cycle in which flowable material (M) is introduced into the mold cavity (102); • Reducing or removing the voltage of the layer heater (20) before, during or after the filling cycle; • Opening the mold cavity (102) after a cooling phase and removing the at least partially cured component (P). [23] Method according to claim 22, characterized by following step: • Conducting the thermal energy (E) of the flowable material (M) and the layer heating (20) through the base body (10) into the mold plate (101) during the cooling phase. [24] Method according to one of claims 22 or 23, characterized by following step: • Passing a heat transfer medium (F) through fluid channels (107) within the mold plate (101) during the cooling phase. [25] Method according to one of claims 22 to 24, characterized by following step: • Passing a heat transfer medium (F) through fluid channels (107) within the mold plate (101) during heating of the layer heater (20) and / or the filling cycle. [26] Method according to one of claims 22 to 25, characterized by following step: • Heat the layer heater (20) to at least 150 °C before starting the filling cycle. [27] Method according to one of claims 22 to 26, characterized by following step: • Maintaining the temperature of the base body (10) at substantially the temperature of a tool insert holder (105) receiving the tool insert (1), and • Limiting the heating essentially to the area of the layer heating (20).

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