Device and method for controlling the temperature of a molding tool of an injection molding machine
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2024-07-22
- Publication Date
- 2026-06-10
AI Technical Summary
Existing injection molding machines face challenges in maintaining optimal temperature control within the molding tool cavities during the injection molding process, particularly in achieving uniform temperature distribution and efficient heat removal, which affects cycle times and product quality.
The implementation of a facility and procedure utilizing Peltier elements connected to an electronic control unit with temperature sensors to dynamically control the tool temperature, combined with metallic heat control inserts and thermal conductors, allows for precise temperature management, eliminating coolant leaks and energy inefficiencies, and enabling faster heating and cooling.
This solution ensures optimal temperature control within the tool cavities, reducing cycle times and improving product quality by providing efficient and uniform heating and cooling, while avoiding the limitations of conventional coolant-based systems.
Smart Images
Figure EP2024070702_06022025_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title:
[0003] Device and method for tempering a mold of an injection molding machine
[0004] The present invention relates to a device and a method for tempering a mold of an injection molding machine and to an injection molding machine equipped with such a device for producing plastic parts.
[0005] The field of application of the invention extends to injection molding machine technology. Injection molding machines are used, particularly for the thermoplastic injection molding process of interest here. These machines are usually designed as screw-piston injection molding machines and consist of an injection unit for plasticizing, preparing, and metering plastic material, and a so-called clamping unit, which closes, holds, and reopens a mold. The clamping unit consists of the mold itself, which is divided into halves. The halves are detachably mounted on the machine's tool holders.
[0006] The cavities, which form the plastic component to be produced by filling it with plastic, are usually formed on both sides of the halves of the mold.
[0007] The mold must be tempered according to the plastic material, the component shape and the process parameters in order to provide the most uniform mold temperature possible in the various phases of an injection molding process.
[0008] State of the Art According to the generally known state of the art, the plasticizing cylinder is usually heated with heating bands or the like to assist in melting the thermoplastic material. Low-temperature liquid temperature control is used for cross-linked plastics. It is necessary to heat the mold to an optimal operating temperature, which depends on the plastic material, to ensure cross-linking of the plastic material. This results in an optimal operating temperature range for the mold, which ranges from a minimum temperature T min and a maximum temperature T maxis limited and must be ensured by tempering the mold.
[0009] Recently, so-called conformal mold temperature control has been increasingly used to control the temperature of the plastic component being manufactured during injection molding as close as possible to the object. This allows for relatively shorter cycle times while simultaneously achieving higher quality. Such conformal mold temperature control has previously been implemented using channel systems integrated into the molds, which are then flowed with appropriately cold or warm water for variothermal temperature control.
[0010] It is the object of the present invention to provide a device and a method for contour-following tempering of a mold of an injection molding machine, which ensures an optimally high operating temperature in the area of the cavities during injection of the plastic and also ensures rapid heat dissipation for solidification.
[0011] Disclosure of the invention
[0012] The object is achieved in terms of device technology by claim 1. Claim 9 specifies an injection molding machine with a device according to the invention for tempering the mold. The object is achieved in terms of process technology by claim 10. The respective dependent claims are directed to advantageous developments of the invention. The invention includes the technical teaching that for tempering a mold of an injection molding machine, with at least one Peltier element that can be placed between a tool receiving part and a tool insert part and at least one first temperature sensor arranged on the part of the tool insert part in the region of a cavity, which first temperature sensor is connected as an actual value transmitter to an electronic control unit for temperature control, which controls the mold to a predetermined setpoint or setpoint range (T min -T max) and, to compensate for a control deviation, the at least one Peltier element is supplied with a direct current to heat the tool insert if an increase in the tool temperature is required, or the at least one Peltier element is supplied with a direct current with the opposite polarity to cool the tool insert if a reduction in the tool temperature is required.
[0013] Additionally, to improve temperature control on the part of the tool holder—that is, on the part of the temperature sink—at least a second temperature sensor can be provided to incorporate the temperature difference into the actual value determination in conjunction with the first temperature sensor. This allows the time required to compensate for a control deviation to be shortened by appropriately controlling the at least one Peltier element, which improves the controller dynamics. PID control is preferably used.
[0014] According to the invention, a manufacturing method is carried out with the device according to the invention, with which the tool insert part with the at least one Peltier element integrated therein is brought or maintained by heating or cooling into an operating temperature range predetermined for the current process situation.
[0015] The inventive solution is based on the finding that a Peltier element is suitable for both heating and, in non-polarized operation, cooling a metallic body arranged adjacent to the selected active side, and can thus be used for flexible temperature control. A Peltier element can thus perform the function of a small heat pump, since, depending on the applied DC voltage, heat is transported from one active side to the opposite active side, with the direction of action reversing after polarity reversal. In contrast to otherwise conventional coolant-based temperature control solutions for the molds of interest here, the use of Peltier elements prevents leaks and eliminates the effort required to create a coolant circuit. The energy consumption is comparatively five times lower to generate the same temperature control effect.In addition, Peltier elements ensure more efficient heat dissipation from particularly hot areas of the mold cavity, whereas conventional liquid cooling tends to be flat and rather sluggish. Cooling complex, small, and thin geometries in mold cavities is easier with Peltier elements than with conventional water cooling channels. Often, cooling with water cooling channels is not feasible due to limited space. In these cases, Peltier elements can be combined with heat-conducting inserts.
[0016] According to a further measure to improve local heat dissipation, it is proposed to provide at least one metallic heat-conducting insert in a corresponding recess of the mold insert, which extends from the area of an associated Peltier element into the mold insert toward the cavity there. This tool insert is made of a material with a much higher thermal conductivity than the material of the mold, so that a rapid and concentrated local thermal bridge can be created.
[0017] For additional heat flow compensation, a heat-conducting plate can also be arranged on the bottom side of the mold insert between the heat-conducting insert and the at least one Peltier element. This ensures that, in addition to local heat supply, a surface-wide temperature control of the mold from the entire bottom is also possible. The combination of the mold insert and the heat-conducting plate thus meets the requirements for efficient, uniform temperature control using simple technical means. According to a preferred embodiment, the metallic heat-conducting insert and / or the heat-conducting plate are made of copper or a copper alloy, whereas the mold insert with the cavity formed therein opposite the bottom surface is made of a steel material, as is usual.
[0018] As a further thermal measure, an insulating plate made of a heat-insulating material is preferably provided between the bottom-side heat-conducting plate and the tool holder, with at least one Peltier element being inserted into a respective opening in the insulating plate and thus being positioned. This arrangement of the Peltier element ensures direct contact with the surface of the tool holder, thus ensuring the heat pump function despite the insulating plate. The insulating plate primarily ensures that the heat generated by the Peltier element and transferred to the heat-conducting plate is primarily passed on to the molding tool and does not flow backward into the tool holder and thus be lost.
[0019] The tool holder preferably functions as a heat sink and has at least one cooling channel for conducting a cooling fluid with a variable flow rate. Thus, the tool holder complements the heat flow chain by dissipating the heat pumped out by the Peltier element through the metallic tool holder and the cooling fluid to the outside when the Peltier element is operated in cooling mode. It is also conceivable to operate the tool holder as a preheating stage in the Peltier element's warm-up mode, with hot fluid flowing through the cooling channels, allowing the Peltier element to heat up more quickly due to the smaller temperature difference. However, such a system behaves quite sluggishly when alternating between heating and cooling.
[0020] According to a preferred design, the components Peltier element, heat-conducting insert, heat-conducting plate, and insulating plate are part of the mold insert as a structural unit. The electrical wiring and sensor connections are also preferably integrated into this structural unit. Thus, an injection molding machine can be quickly and easily converted by replacing molds pre-equipped in this way with a stationary tool holder of the same construction. It should be noted that preferably several Peltier elements and associated heat-conducting inserts are provided, which are arranged on or in the mold insert opposite its cavities in order to locally control their temperature. This ensures optimal cavity-following temperature control.
[0021] Detailed description based on drawing
[0022] Further measures improving the invention are presented in more detail below together with the description of a preferred embodiment of the invention with reference to the figures.
[0023] It shows:
[0024] Fig. 1 is a plan view of a tool insert part of a mold of an injection molding machine,
[0025] Fig. 2 shows a longitudinal section through the tool insert part according to Fig. 1 in section BB,
[0026] Fig. 3 is a perspective view of a mold of an injection molding machine composed of a tool insert and a tool holder,
[0027] Fig. 4 is a perspective view from below of the tool insert part of Fig. 3,
[0028] Fig. 5 is a schematic representation of the heat flow for cooling the tool insert, and
[0029] Fig. 6 is a schematic representation of the heat flow for heating the tool insert.
[0030] According to Fig. 1, the upper side of a tool insert 1 of a mold (not shown here) of an injection molding machine has a cavity 2 for injection molding a plastic component. The cavity 2 has a sprue 3 through which the liquid plastic material is injected under high pressure into the cavity 2 in a conventional manner. Furthermore, the tool insert 1 is surrounded by lateral insulation plates 4 for thermal insulation. According to Fig.2, on the underside of the tool insert part 1, a plurality of Peltier elements 5 are arranged (by way of example) in corresponding openings in an insulating plate 6. On the tool side, the Peltier elements 5 come into contact with a heat-conducting plate 7 which extends over the entire bottom side of the tool insert part 1. Adjacent to the bottom-side heat-conducting plate 7 is a cylindrical heat-conducting insert 8 which is arranged in a corresponding recess in the tool insert part 1 and extends from the area of the Peltier element 5 over the heat-conducting plate 7 in the direction of the cavity 2. In this exemplary embodiment, both the heat-conducting insert 8 and the heat-conducting plate 7 are made of copper, whereas the tool insert part 8 is made in the conventional manner from a steel material.
[0031] According to Fig. 3, the tool insert 1 described above is inserted into a matching tool holder 10 for use in an injection molding machine. The exemplary Peltier element 5, of which several are present here, is arranged between the tool insert 1 and the tool holder 10 - as described above - within an insulating plate 6 adjacent to a tool-side heat-conducting plate 7.
[0032] With regard to the electrical equipment, a temperature sensor 11 is arranged on the side of the tool holder part 10 and a further temperature sensor 12 is arranged on the side of the tool insert part in the vicinity of the cavity 2. Both temperature sensors 11 and 12 are connected to an electronic control unit 13 for differential temperature measurement, which is configured for temperature control by applying a direct current to the at least one Peltier element 5 to heat the tool insert part if an elevated tool temperature is required during an injection molding process. However, the at least one Peltier element 5 can also be applied with a direct current with reversed polarity to cool the tool insert part 1 if a reduced tool temperature is required during the injection molding process.During heating, the tool holder part 10 serves as a heat sink and is provided with a cooling channel 14 for the passage of water as a cooling liquid.
[0033] According to Fig. 4, the tool insert part 1 in this embodiment comprises a total of five Peltier elements 5 (exemplary) as a structural unit, which are embedded and wired in associated openings in the base-side insulating plate 6.
[0034] Fig. 5 illustrates the cooling mode of the device according to the invention, in which, upon reaching a maximum temperature T max of over 80°C, excess heat is pumped away from the Peltier element 5 via the heat conducting insert 8 and the heat conducting plate 7 and transferred into the tool holder part 10 serving as a cold sink.
[0035] With regard to Fig. 6, in the opposite direction to the cavity-near heating of the tool insert part 1 from a minimum temperature T minof 50 °C, heat is supplied through the Peltier element 5 via the heat conducting plate 7 to the heat conducting insert 8.
[0036] The invention is not limited to the preferred embodiment described above. Rather, modifications thereof are also conceivable, which are also encompassed by the scope of the following claims. It should be noted that the device according to the invention is intended to be used for temperature control on the part of both molds of an injection molding machine, which, in conjunction, form a cavity for a plastic component to be produced by injection molding. Furthermore, it should be noted again that the number of Peltier elements and heat-conducting inserts used is variable and depends on the shape of the cavity of the mold insert and the plastic material to be injected.
Claims
Claims 1 . Device for tempering a mold of an injection molding machine, with at least one Peltier element (5) that can be placed between a tool receiving part (10) and a tool insert part (1) and at least one first temperature sensor (12) arranged on the side of the tool insert part (1) in the region of a cavity (2), which first temperature sensor (12) is connected from an actual value transmitter to an electronic control unit (13) for temperature control, which controls the mold to a predetermined setpoint or setpoint range (T min -T max ) and to compensate for a control deviation - the at least one Peltier element (5) is supplied with a direct current to heat the tool insert part (1) if an increase in the tool temperature is required, or - the at least one Peltier element (5) is supplied with a direct current with reversed polarity to cool the tool insert part (1) if a reduction in the tool temperature is required.
2. Device according to claim 1, characterized in that at least one second temperature sensor (11) is provided on the part of the tool holder part (10) in order to carry out a differential temperature measurement for determining the actual value in cooperation with the first temperature sensor (12).
3. Device according to claim 1, characterized in that for improved local heat conduction of the temperature control at least one metallic heat conducting insert (8) is provided in a corresponding recess of the tool insert part (1), which extends from the area of an associated Peltier element (5) into the tool insert part (1) in the direction of the cavity (2).
4. Device according to claim 3, characterized in that a heat conducting plate (7) for heat flow compensation is arranged on the bottom side of the tool insert part (1) between the heat conducting insert (8) and the at least one Peltier element (5).
5. Device according to claim 3 or 4, characterized in that the metallic heat-conducting insert (8) and / or the heat-conducting plate (7) consists of copper or a copper alloy, whereas the tool insert part (1) with the cavity (2) formed therein consists of a steel material 6. Device according to claim 4, characterized in that an insulating plate (6) made of a heat-insulating material is arranged between the bottom-side heat-conducting plate (7) and the tool holder part (10), wherein the at least one Peltier element (5) is inserted in a respective associated opening in the insulating plate (6).
7. Device according to claim 6, characterized in that the components Peltier element (5), heat-conducting insert (8), heat-conducting plate (7) and insulating plate (6) are components of the tool insert part (1).
8. Device according to claim 3, characterized in that several Peltier elements (5) and heat-conducting inserts (8) associated therewith are provided, which are arranged on or in the tool insert part (1) opposite its cavities (2) in order to locally temper the injection molding material there.
9. Device according to claim 1, characterized in that the tool holder part (10) serving as a cooling body is provided with at least one cooling channel (14) for the passage of a cooling liquid with a variable flow rate.
10. Injection molding machine with a mold equipped with a tempering device according to one of the preceding claims.
11. Method for tempering a mold of an injection molding machine with a device according to one of the preceding claims 1 to 8, in which the tool insert part (1) with the at least one Peltier element (5) integrated therein is brought or maintained in a predetermined operating temperature range by heating or cooling.
12. Method according to claim 11, characterized in that upon reaching a minimum temperature (T min ) the heat required for heating is supplied by the at least one Peltier element (5) into the region of the cavity (2) of the tool insert part (1).
13. Method according to claim 11, characterized in that upon reaching a maximum temperature (T max ) for cooling, excess heat is dissipated by the at least one Peltier element (5) from the region of the cavity (2) of the tool insert part (1) into the cooled tool holder part (10).
14. Method according to claim 10, characterized in that the tool insert part (1) is preheated before the start of the injection molding process.