PRESSURE OR INJECTION MOLDING TOOL

Abstract

A die-casting or injection molding tool with at least one tool insert (7) for conformal temperature control of a tool cavity (2), comprising a tool wall (3) forming the tool cavity (2), which is back-flowed by at least one first fluid (9) in a fluid line (4), wherein the at least one fluid line (4) extends to at least one continuous cavity (5) which conforms to an outer surface (6) of the tool wall (3) facing away from the tool cavity (2) and to which at least one electrical heating element is assigned, characterized in that the at least one cavity (5) is supported by means of fluid-flowed truss structures (8) which are assigned to the tool wall and / or the tool insert and the at least one electrical heating element is an induction coil (10) which is arranged adjacent to the cavity (5) in a coil receptacle (9).

Description

[0001] The present invention relates to a pressure die or injection molding tool with at least one tool insert for the conformal temperature control of a tool cavity, comprising a tool wall defining the tool cavity, behind which at least one first fluid flows in a fluid line, wherein the at least one fluid line widens to form at least one continuous cavity which flatly conforms to an outer side of the tool wall facing away from the tool cavity and at least one electrical heating element is assigned to the cavity.

[0002] Such a die-casting or injection-molding tool is already known from DE 10 2012 106 871 B4. Furthermore, with regard to the prior art, reference should be made to DE 10 2015 112 395 A1, US 2009 / 0 239 023 A1, and DE 199 03 436 C2.

[0003] Such tools are already generally known from the state of the art. Traditional cooling systems are implemented using plugged bore systems and are reaching their limits in terms of contour accuracy and tool weakening.

[0004] In the field of additively manufactured tool inserts, channel structures are currently typically incorporated into the tool and designed along the contour of the tool cavity or the tool itself. A medium, usually a fluid such as air, is passed through the channel structures to influence the tool temperature. Additive cooling channel approaches are usually slender, meandering tube channels with a limiting pressure drop and the well-known design limitations of additive manufacturing processes.

[0005] Heating power is traditionally provided by electric heating cartridges with high local heat flux densities. Parasitic temperature rises naturally arise at every mechanical transition, especially at air gaps or due to manufacturing tolerances. Thermal compensation of an air gap using thermal fillers limits the permissible application range and precise controllability due to hysteresis, aging, and filler shrinkage.

[0006] The primary goal of known solutions is cooling, i.e., dissipating heat from the mold or tool. Additive approaches have so far been limited to small tools with an expected low pressure drop in the cooling channel, where manual channel creation is still feasible in terms of time. The discretely modeled channel structures, individually engineered into the tool, are not suitable for standardized temperature control assemblies. Targeted control or even measurement of the quality and efficiency of temperature control in specific regions of the component is only possible to a limited extent. Furthermore, a variable concept is required that can be used both as a standardized component and individually adapted.

[0007] Contour-close temperature control of large, complex tools requires more efficient methods for creating flow zones and applying increased heat output in a short time. High heat outputs lead to local overtemperatures and parasitic temperature gradients in the tool with conventional heating cartridges.

[0008] These solutions envisage using the fluid as a medium for heating and cooling based on its temperature or state of aggregation. However, the limitations of these variants do have some weak points. Firstly, the structural design of the channel geometry is very complex. The design requires manual or at least semi-automatic channel generation. Furthermore, the ability to dissipate heat from the component is limited by the low flow rate caused by the thin channels. The channel diameter is the limiting factor here, and can be increased during production up to a maximum diameter of around 8 mm. It should be noted that a large diameter increasingly worsens the conformal connection because only one point is at the shortest distance to the temperature-controlled area. For all diameters of a circular geometry, only one point of a cross-section is directly adjacent to the contour.However, the size of the channel also affects stability. The load-bearing capacity of the channel and the stability of the tool decrease with larger channel diameters. A compromise is therefore necessary between conformal temperature control and the responsiveness of a possible temperature control system, as well as tool stability.

[0009] Furthermore, free-flowing channel geometries can only be produced through additive manufacturing processes. A complicated channel design impairs the powder removal process required for specific manufacturing after the laser melting process. There is a risk that powder will remain in the component, impairing its function or even making it impossible to use.

[0010] Finally, heating with hot fluids poses the risk of steam injuries, high pressures, fire, and explosions. Mineral oils, in particular, pose a risk in this regard for casting tools.

[0011] Against this background, the present invention is based on the task of designing a bidirectional temperature control system for the mold wall for any mold geometry that is close to the contour, flow-optimized, and optimized for production. In addition, undesirable temperature gradients and hysteresis effects during mold use are to be avoided.

[0012] This object is achieved by a pressure or injection molding tool according to the features of independent claim 1. Useful embodiments of such a pressure or injection molding tool can be found in the subsequent dependent claims.

[0013] According to the invention, a pressure die or injection molding tool is provided with at least one tool insert for the near-contour tempering of a tool cavity, comprising a tool wall defining the tool cavity, behind which at least one first fluid flows in a fluid line, wherein the at least one fluid line widens to form at least one continuous cavity which flatly conforms to an outer side of the tool wall facing away from the tool cavity and at least one electrical heating element is assigned to the cavity.

[0014] The invention combines heating and cooling in a single component in the form of contoured tool inserts. Both an electric heating means and a fluid cooling means are provided in the tool insert, which allows local heat input and output. The solution according to the invention can be integrated as a mold insert into the pressure or injection molding tool, or attached to the contour from the outside as an external tile. In particular, it is also possible to separate the tool insert from the surface element of the tool contour and connect it to another tool contour, so that the tool insert can be reused even when the tool is changed. A tool insert can largely fill the tool or be attached locally as a bell-shaped attachment. In this way, the arrangement of several local tool inserts on a tool contour is also possible.

[0015] Such a tool can preferably provide that the tool wall is sealingly connected to the tool insert on its outer side, wherein the tool insert has the fluid line and at least one peripheral fluid cavity into which the fluid line opens at least on one side and which, together with the tool wall, forms the at least one hollow space. As a result, the form-fitting integration is largely independent of the degree of complexity of the tool cavity and can be integrated in a largely standardized manner. In particular, the invention allows for almost unrestricted, contour-hugging backflows of complex geometries. Since the shape of the hollow space is jointly predetermined by the tool wall and the tool insert, and identical tool inserts with different tool cavities - and vice versa - can be used, this facilitates not only standardized production but also flexible use and simple adaptation of a tool.

[0016] Specifically, the at least one cavity can be supported by means of lattice structures with fluid flow around them, which are assigned to the mold wall and / or the mold insert. Since a cooling fluid is used for cooling, a space must be provided in which the cooling fluid can act. In this case, additively manufactured lattice structures can preferably be provided in the cooling channel, filling the cavity. These lattice structures delimit a space on the one hand, but also keep it open for flow on the other, enabling larger flow rates and increased heat transfer with a low pressure drop compared to classic, meandering cooling channels. The lattice structures can be located both in the mold insert and in the mold wall. Flow-optimized and simultaneously production-optimized additive structures play a key role here.

[0017] Specifically, the truss structures can have a plurality of spatially arranged struts, each arranged at angles of 45°, 60°, 90°, 120°, and / or 180° to adjacent struts. This does not preclude the possibility of other angles between the struts, nor does it preclude the possibility of rounding the angles to facilitate construction. While angles of 45° and 90° are classically suitable for truss structures, the use of the well-known tetrahedral angle of 120° represents another preferred embodiment. Honeycomb structures operating at angles of 60° and multiples thereof are also particularly preferred, as are minimal surfaces such as gyroids.

[0018] Furthermore, the at least one electrical heating element can be an induction coil, which is arranged adjacent to the cavity in a coil receptacle. Such a configuration offers particular advantages. The power of the coil, and thus also the heating power, is digitally adjustable and can be precisely timed. The use of an induction coil allows for agile yet tool-friendly heating. The inductor generates heat directly at the desired tool regions without itself creating a hotspot. The digital control of a network of distributed heating and cooling power allows for extensive stabilization of process parameters and thus sustainably increases product quality.

[0019] In a specific embodiment, the induction coil can be assigned a coil core, which either extends into the cavity and is surrounded by the first fluid contained therein, or contacts an outer wall of the cavity. The large-area cooling and non-contact heating allow very large amounts of heat to be introduced and extracted in a short time. The coil core amplifies the generated coil field and ensures more efficient energy transfer to the fluid or the tool wall.

[0020] In a further development, the at least one induction coil can be designed as a hollow coil in which a second fluid is conveyed. The induction coil can be cooled from the inside via an internal cooling circuit in which a second fluid is conveyed, in order to limit the temperature here as well.

[0021] Preferably, a tool comprises several interacting tool cavities and several tool inserts, with one or more electrical heating elements and / or one or more fluid lines being assigned to each tool insert, and the flow through each heating element and / or each fluid line being regulated by a control unit. There are applications in which different temperature profiles must be achieved at different points. For example, it may be useful to change the temperatures more slowly in a more massive area of ​​a workpiece than is necessary in a more delicate area. In combination with an inductive, digitally controlled heater, combined areas of a tool can be temperature-controlled in a concerted manner, thus achieving the required temperature curve for each individual area.

[0022] Specifically, the first fluid and / or the second fluid may be a gas or a liquid, in particular an oil, and the first fluid and / or the second fluid may preferably be circulated.

[0023] The invention described here is explained in more detail below using exemplary embodiments.

[0024] It shows Fig. 1 a tool according to the invention with an inductive heating element in a schematic cross-sectional view from the side, as well as Fig. 2 a variant of the tool according to Fig. 1 with an inductive heating element.

[0025] Fig. 1 shows a pressure die or injection molding tool 1 with a tool insert 7 for the conformal temperature control of a tool cavity 2 in the vertical gate. Associated with the tool insert 7, which conforms to a tool wall 3 at least in its edge regions, are a fluid line 4 and an inductive heating element 10, which extends into a cavity 5 maintained free between the tool insert 7 and the tool wall 3 and is held insulated within the tool insert 7. The fluid line 4 forms an inlet and an outlet of the cavity 5, which as such represents part of a fluid circuit in which a first fluid circulates to maintain temperature control on the surface of the tool wall 3 together with the electrical heating element.

[0026] The mold cavity 2 is completed by at least one further, comparable part of a mold wall to form a closed cavity, so that a workpiece can be injected into the then closed mold cavity 2. Several mold parts are temperature-controlled in a coordinated manner via a common control unit, so that the specific characteristics of each workpiece section can be addressed in detail to avoid shrinkage cavities, porosity, distortion, or stress cracks.

[0027] In this context, the described design is intended to ensure that the control can be operated as reactively and effectively as possible for the most precise temperature control, whether in terms of setting the correct temperatures or maintaining a time profile. Instead of constructing meandering cooling channels additively beneath the tool wall 3 as in the prior art, the invention provides for the tool insert 7 to be placed on the tool wall 3 or fitted into it, so that a cavity 5 is kept free between the tool wall 3 and the tool insert 7. The first fluid supplied by the fluid line 4 can now flow through such a cavity 5. The open cavity 5 allows both a large quantity of first fluid to come into direct contact with the tool wall 3 and that the contact is very close to the contour, thus avoiding hot spots caused by channeling.

[0028] As soon as the tool body 7 is in liquid-tight contact with an outer side 6 of the tool wall 3, which lies on the side of the tool wall 3 facing away from the tool cavity 2, the aforementioned closed cavity 5 is formed and the fluid circuit is closed. The first fluid, already pre-tempered, can be introduced into this cavity 5 and the tool wall 3 can cool down. Heating, however, occurs via the inductive heating element 10, which is in intimate contact with the fluid. The resulting temperature is coupled into a workpiece via the outer side 6 of the tool wall 3 and its temperature is adjusted accordingly. In this configuration, the heating power of the inductive heating element 10 can be transferred to the tool wall 3 via the first tempered fluid 9, which acts as a medium for the inductive heating element 10.

[0029] If more spontaneous temperature changes are necessary, the inductive heating element 10 can be additively manufactured as a hollow coil (not shown here), allowing a second fluid to be passed through this hollow coil. Both the first and second temperature-controlled fluids can be cooled along the line outside the tool 1, for example, by a heat exchanger.

[0030] Fig. Figure 2 shows an alternative embodiment of such a pressure or injection molding tool 1 with formed framework structures 8, which are introduced into the cavity 5, and with an inductive heating element, i.e., an induction coil 10. This offers several advantages. Firstly, the framework structures 8 allow the cavity 5 in which they are formed to continue to be flowed through in all directions over a large area. The framework structures 8 can also be expanded in all directions, so that complex conduit routing can be omitted. Furthermore, the framework structures 8 are intimately surrounded by the first fluid, which is supplied via the fluid line 4 and enters the framework structures 8 in the same way as in the embodiment according to Fig. 1 into the cavity 5. However, the fluid comes into intimate contact with the framework structures 8, so that a further significantly improved heat exchange can take place.

[0031] Additionally, an induction coil 10 is provided as an electrical heating element, which makes it possible to inductively couple its heating power into the framework structures 8, so that the induction coil 10 as such is not a hotspot, but only the framework structures 8 and the outer side 6 of the tool wall 3, which is also in intimate contact with them, are heated due to the heating power of the induction coil 10. The induction coil 10 is arranged in a coil receptacle 9, which is essentially a cavity in the tool insert 7. If necessary, a coil core can be added, which also finds space in the coil receptacle but is not shown in the drawing. Contacting such a coil core made of a metallic material can contact the framework structures 8 as needed to improve the transmission of the heating power.

[0032] When constructing the framework structures 8, which can be connected to both the mold wall 3 and the mold insert 7, the struts can be arranged at different angles to one another, for example, to create a honeycomb structure, a lattice, or other permeable structure. The struts of such a framework structure 8 can be incorporated additively. Due to the necessarily modular design, any complex geometry of the mold wall 3 can be efficiently flowed behind. Since the cavity 5 is internally flanked in this embodiment of the mold 1, the cavity can be constructed in previously inaccessible dimensions.

[0033] Such a design can be particularly efficient where spatially focused heating of the mold wall 3 is necessary. Through induction, possibly through several locally applied and aligned induction coils 10, the heat can be introduced into the desired areas of the framework structures 8 in the shortest possible time. This variant of the mold 1 offers not only bidirectional temperature control but also high spatial resolution for the temperature control of the mold 1.

[0034] The above-described tool allows for the temperature control of the mold wall for any desired mold geometry, close to the contour, optimized for flow, and optimized for production. In addition, both cooling and heating are possible with the simultaneous use of a fluid and an electric heating element within a fluid line. Heating is digitally controlled and the temperature is precisely timed to the desired range, thus avoiding undesirable temperature gradients during production. LIST OF REFERENCE SYMBOLS 1 tool 2 tool cavity 3 Tool wall 4 Fluid line 5 Cavity 6 Outside 7 Tool use 8 truss structures 9 spool holder 10 Induction coil

Claims

[1] Pressure or injection molding tool with at least one tool insert (7) for the near-contour tempering of a tool cavity (2), comprising a tool wall (3) defining the tool cavity (2) and behind which at least one first fluid (9) flows in a fluid line (4), wherein the at least one fluid line (4) widens to form at least one continuous cavity (5) which flatly conforms to an outer side (6) of the tool wall (3) facing away from the tool cavity (2), and at least one electrical heating element is assigned to the cavity (5), characterized by in that the at least one cavity (5) is supported by means of lattice structures (8) around which fluid flows, which are assigned to the tool wall and / or the tool insert, and the at least one electrical heating element is an induction coil (10) which is arranged adjacent to the cavity (5) in a coil receptacle (9). [2] Tool according to claim 1, characterized bythat the tool wall (3) is sealingly connected on its outer side (6) to the tool insert, wherein the tool insert (7) has the fluid line (4) and at least one marginal fluid cavity into which the fluid line (4) opens at least on one side and which forms the at least one cavity (5) with the tool wall (3). [3] Tool according to at least one of the preceding claims, characterized by that the truss structures (8) have a plurality of spatially arranged struts, which are each arranged at angles of 45°, 60°, 90°, 120° and / or 180° to adjacent struts. [4] Tool according to at least one of the preceding claims, characterized by that the induction coil (10) is assigned a coil core which either projects into the cavity (5) and is surrounded by the first fluid guided therein or contacts an outer wall of the cavity (5). [5] Tool according to at least one of the preceding claims, characterized by that the induction coil (10) is designed as a hollow coil in which a second fluid is guided. [6] Tool according to at least one of the preceding claims, comprising a plurality of cooperating tool cavities (2) and a plurality of tool inserts (7), wherein each tool insert (7) is assigned one or more electrical heating elements and / or one or more fluid lines (4) and the flow through each heating element and / or each fluid line (4) is controlled by means of a control unit. [7] Tool according to at least one of the preceding claims, characterized by that the first fluid and / or the second fluid is a gas or a liquid, in particular an oil, and that the first fluid and / or the second fluid is preferably circulated.

Images