Device and method for controlling temperature of mold of injection molding machine

Abstract

The invention relates to a device and a method for controlling the temperature of a mold of an injection molding machine, comprising at least one Peltier element (5) which can be placed between a mold holder (10) and a mold insert (1) and at least one first temperature sensor (12) which is arranged on the mold insert (1) side in the region of a cavity (2), the first sensor is connected by an actual value generator to an electronic control unit (13) for temperature control, which controls the temperature of the mold to a predetermined setpoint value or setpoint value range (Tmin-Tmax) and for this purpose in order to compensate for control deviations, the first sensor being connected by the actual value generator to the electronic control unit (13), which controls the temperature of the mold to a predetermined setpoint value or setpoint value range (Tmin-Tmax) if the temperature of the mold needs to be increased. If the mold temperature is required to be reduced, the at least one Peltier element (5) is charged with a direct current to heat the mold insert (1), or if the mold temperature is required to be reduced, the at least one Peltier element (5) is charged with a direct current having a polarity opposite to that of the at least one Peltier element (5) to cool the mold insert (1).

Description

Technical Field

[0001] The present invention relates to a device and method for temperature control of molds in an injection molding machine, and an injection molding machine equipped with such a device for manufacturing plastic parts.

[0002] The application of this invention extends to injection molding machine technology. Particularly relevant is the use of injection molding machines for thermoplastic injection molding, typically implemented as screw-plastic type injection molding machines and consisting of an injection unit for plasticizing, preparing, and dispensing plastic material, and a so-called clamping unit that closes, holds, and reopens the mold. The clamping unit comprises the mold itself, which is divided into two halves. These two halves are detachably mounted on the mold receiving section of the machine.

[0003] The cavity formed by filling plastic to create the plastic component is typically formed on the sides of both halves of the mold. The mold temperature must be adjusted according to the plastic material, component shape, and process parameters to provide the most uniform possible mold temperature at different stages of the injection molding process. Background Technology

[0004] According to well-known existing technologies, heating elements or similar devices are typically used to heat the plasticizing barrel to assist in the melting of thermoplastic materials. For cross-linked plastics, cryogenic liquids are used for temperature control. The mold needs to be heated to an optimal operating temperature related to the plastic material to ensure cross-linking. This yields the optimal operating temperature range for the mold, which is defined by the lowest temperature T. min and the highest temperature T max This is limited and ensured by adjusting the temperature of the mold.

[0005] Recently, there has been an increasing use of so-called conformal mold temperature control (konturnaheWerkzeugtemperierung) to temperature control the plastic component to be manufactured as close as possible to the object during injection molding. This allows for relatively shorter cycle times while achieving higher quality. Until now, this conformal mold temperature control has been achieved through a channel system introduced conformally into the mold, through which cold or hot water flows for temperature regulation. Summary of the Invention

[0006] The objective of this invention is to provide an apparatus and method for conformal temperature control of injection molding machine molds, which ensures optimal high operating temperature in the cavity region during plastic injection and also ensures rapid heat conduction for solidification.

[0007] This task is solved in terms of apparatus by claim 1. Claim 9 provides an injection molding machine having an apparatus for temperature control of a mold according to the invention. This task is solved in terms of method by claim 10. The dependent claims are intended to achieve advantageous extensions of the invention.

[0008] This invention includes the following technical teaching: a device for temperature control of a mold in an injection molding machine has at least one Peltier element that can be placed between a mold receiving member and a mold insert, and at least one first temperature sensor arranged in a region of the cavity on the mold insert side. This first sensor is connected by a real-value transmitter to an electronic control unit for temperature regulation, which adjusts the mold temperature to a pre-given rated value or range of rated values ​​(T). min -T max ), and this is used to compensate for adjustment bias. - If it is necessary to increase the mold temperature, apply direct current to at least one Peltier element to heat the mold insert, or - If it is necessary to reduce the mold temperature, at least one Peltier element is loaded with direct current of opposite polarity to cool the mold insert.

[0009] Furthermore, to improve temperature regulation, at least one second temperature sensor can be installed on the mold receiving side, i.e., the heat dissipation side, to incorporate the temperature difference into the actual value calculation in conjunction with the first temperature sensor. This allows for the reduction of the time required to compensate for regulation deviations by correspondingly driving at least one Peltier element, thus improving the regulator's dynamics. PID control is preferred.

[0010] According to the invention, a manufacturing method is performed using the apparatus according to the invention, in which a mold insert is brought into or maintained within a pre-given operating temperature range for the current process conditions by means of at least one Peltier element integrated therein, through heating or cooling.

[0011] The solution according to the invention is based on the understanding that Peltier elements are suitable for both heating and cooling of metal bodies arranged adjacent to selected action surfaces during polarity reversal operation, thus allowing for flexible temperature control of the metal body. Therefore, Peltier elements can function as small heat pumps because heat is transferred from one action surface to the opposite action surface according to the applied DC voltage, where the direction of action reverses after polarity reversal. Unlike typically coolant-based temperature control solutions for molds of interest, Peltier elements eliminate leakage and the cumbersome process of creating coolant circuits. Energy consumption is reduced by approximately five times to achieve the same temperature control effect. Furthermore, Peltier elements ensure more efficient heat removal from particularly hot areas of the mold cavity, whereas conventional liquid cooling tends to act on an area-specific basis and is rather slow. Cooling complex, small, thin geometries in mold cavities is much easier to implement using Peltier elements than using conventional water cooling channels. Cooling using water cooling channels is often difficult due to limited space. There, Peltier elements can be set in combination with thermally conductive inserts.

[0012] According to another measure to improve localized heat conduction, at least one metal heat-conducting insert is disposed in a corresponding groove of the mold insert, the metal heat-conducting insert extending from the region of the associated Peltier element toward the cavity therein into the mold insert. Here, the mold insert is made of a material with a thermal conductivity much higher than that of the mold material, thereby enabling rapid and concentrated localized thermal bridging.

[0013] To provide additional heat flow compensation, a heat-conducting plate can be arranged on the bottom side of the mold insert between the heat-conducting insert and at least one Peltier element. This ensures that, in addition to localized heat supply, surface temperature control of the mold can also be achieved from the entire bottom. Therefore, the combination of the mold insert and the heat-conducting plate achieves the requirements for efficient and uniform temperature control with a simple technical means.

[0014] According to a preferred embodiment, the metal heat-conducting insert and / or heat-conducting plate is made of copper or a copper alloy, while the mold insert having a cavity constructed therein opposite to the bottom surface is made of steel, as is common practice.

[0015] As an additional thermal technology measure, a heat insulation plate made of insulating material is preferably disposed between the heat-conducting plate on the bottom side and the mold receiving component, wherein at least one Peltier element is inserted into and positioned in its respective corresponding notch in the heat insulation plate. This arrangement of the Peltier element ensures direct contact between it and the surface of the mold receiving component, so as to ensure heat pump function despite the presence of the heat insulation plate. The heat insulation plate primarily ensures that the heat generated by the Peltier element and transferred to the heat-conducting plate is mainly conducted to the mold and not reversed back to the mold receiving component and thus lost.

[0016] The mold receiving element preferably functions as a coolant and has at least one cooling channel for guiding coolant through at varying flow rates. Therefore, the mold receiving element complements the heat flow chain in that, if the Peltier element is operating in cooling mode, the heat pumped by the Peltier element is dissipated through the metal mold receiving element and the coolant. Alternatively, the mold receiving element can be considered as a preheating stage in heating mode, where hot liquid flows through the cooling channel, allowing the Peltier element to heat more rapidly due to the smaller temperature difference. However, this system exhibits rather slow switching between heating and cooling.

[0017] According to a preferred structural configuration, the components—Peltier element, thermally conductive insert, thermally conductive plate, and thermal insulation plate—are integral parts of the mold insert as structural units. Electrical wiring and sensor connections are also preferably integrated into this structural unit. Therefore, compared to a fixed mold receiving unit with the same structure, the injection molding machine can be quickly and easily retrofitted by replacing this pre-equipped mold.

[0018] It should be noted that it is preferable to provide multiple Peltier elements and thermally conductive inserts associated with these Peltier elements, which are arranged on or inside the mold insert opposite to the cavity of the mold insert, so as to provide localized temperature control of the cavity. This ensures optimal temperature control along with the cavity. Attached Figure Description

[0019] Further measures to improve the present invention are described in detail below with reference to the accompanying drawings and the description of preferred embodiments thereof.

[0020] The attached diagram shows: Figure 1 Top view of the mold inserts in an injection molding machine mold. Figure 2 :according to Figure 1 The longitudinal section view of the mold insert along section BB. Figure 3 A three-dimensional view of the mold of an injection molding machine, consisting of mold inserts and mold receiving parts. Figure 4 : Figure 3 A perspective view of the mold insert from below. Figure 5 : A schematic diagram of the heat flow used to cool the mold inserts, and Figure 6 : Schematic diagram of the heat flow used to heat the mold insert. Detailed Implementation

[0021] according to Figure 1The upper side of the mold insert 1 of the injection molding machine (not shown further here) has a cavity 2 for injection molding a plastic component. The cavity 2 has a sprue 3 through which liquid plastic material under high pressure is injected into the cavity 2 in a manner known per se. In addition, the mold insert 1 is surrounded by heat insulation plates 4 on the sides for heat insulation.

[0022] according to Figure 2 On the underside of the mold insert 1, a plurality of Peltier elements 5 (exemplary) are arranged in corresponding notches in the heat insulation plate 6. On the mold side, the Peltier elements 5 abut against the heat-conducting plate 7, which extends over the entire bottom side of the mold insert 1. A cylindrical heat-conducting insert 8 is adjacent to the bottom heat-conducting plate 7, arranged in a corresponding groove in the mold insert 1 and extending from the area of ​​the Peltier elements 5 through the heat-conducting plate 7 toward the cavity 2. In this embodiment, both the heat-conducting insert 8 and the heat-conducting plate 7 are made of copper, while the mold insert 1 is made of steel in a conventional manner.

[0023] according to Figure 3 The mold insert 1 described above is inserted into a mating mold receiver 10 for use in an injection molding machine. Exemplary Peltier elements 5 (of which multiples are present) are arranged between the mold insert 1 and the mold receiver 10 within the scope of the heat insulation plate 6 adjacent to the heat-conducting plate 7 on the mold side, as described above.

[0024] Regarding the electrical operating devices, a temperature sensor 11 is arranged on the mold receiving side 10, and another temperature sensor 12 is arranged in the vicinity of the cavity 2 on the mold insert side. The two temperature sensors 11 and 12 are connected to an electronic control unit 13 for measuring the temperature difference. This control unit is configured for temperature regulation: if a higher mold temperature is required during the injection molding process, direct current is applied to at least one Peltier element 5 to heat the mold insert. However, if a lower mold temperature is required during the injection molding process, direct current of opposite polarity can also be applied to at least one Peltier element 5 to cool the mold insert 1.

[0025] When heated, the mold receiving part 10 serves as a cooling body and is provided with a cooling channel 14 for guiding water as a coolant through it.

[0026] according to Figure 4 In this embodiment, the mold insert 1, as a structural unit, has a total of five Peltier elements 5 (exemplary), which are embedded and wired in the corresponding notches of the heat insulation plate 6 on the bottom side.

[0027] Figure 5 The explanation illustrates the cooling mode of the device according to the invention, in which the cooling temperature is reduced from a maximum temperature T exceeding 80°C. maxExcess heat is pumped out by Peltier element 5 through heat-conducting insert 8 and heat-conducting plate 7 and transferred to mold receiving part 10, which acts as a cooling radiator.

[0028] about Figure 6 Then, proceeding in the opposite direction, in order to heat the mold receiving part 10 closer to the cavity, from a minimum temperature T of 50°C. min Heat is supplied to the heat-conducting insert 8 via the Peltier element 5 and the heat-conducting plate 7.

[0029] This invention is not limited to the preferred embodiments described above. Instead, variations are conceivable, and these variations are also included within the scope of the following claims. It should be noted that the temperature control device according to the invention is applied to both mold sides of an injection molding machine, which together form a cavity for a plastic component to be manufactured using injection molding technology. Furthermore, it should be reiterated that the number of Peltier elements and thermally conductive inserts used varies and depends on the configuration of the cavity in the mold inserts and the plastic material to be injected.

Claims

1. A device for temperature control of a mold in an injection molding machine, comprising: At least one Peltier element (5) is available for placement between the mold receiving member (10) and the mold insert (1), and At least one first temperature sensor (12) is disposed in the region of the cavity (2) on the side of the mold insert (1). The first temperature sensor is connected by an actual value generator to an electronic control unit (13) for temperature regulation, which adjusts the temperature of the mold to a pre-given rated value or rated range (T). min -T max ), and this is used to compensate for adjustment bias. - If it is necessary to increase the mold temperature, apply direct current to at least one Peltier element (5) to heat the mold insert (1), or - If it is necessary to reduce the mold temperature, apply a direct current of opposite polarity to at least one Peltier element (5) to cool the mold insert (1).

2. The apparatus according to claim 1, Its features are, At least one second temperature sensor (11) is provided on the mold receiving part (10) side so as to perform temperature difference measurement for actual value determination in conjunction with the first temperature sensor (12).

3. The apparatus according to claim 1, Its features are, For the improved local heat conduction of the temperature regulation, at least one metal heat-conducting insert (8) is disposed in the corresponding groove of the mold insert (1), the heat-conducting insert extending from the area of ​​the associated Peltier element (5) toward the cavity (2) into the mold insert (1).

4. The apparatus according to claim 3, Its features are, A heat-conducting plate (7) for heat flow compensation is arranged on the bottom side of the mold insert (1) between the heat-conducting insert (8) and the at least one Peltier element (5).

5. The apparatus according to claim 3 or 4, Its features are, The heat-conducting insert (8) and / or the heat-conducting plate (7) of the metal are made of copper or copper alloy, while the mold insert (1) having a cavity (2) formed therein is made of steel.

6. The apparatus according to claim 4, Its features are, A heat insulation plate (6) made of heat insulation material is arranged between the heat-conducting plate (7) on the bottom side and the mold receiving member (10), wherein at least one Peltier element (5) is inserted into each of the corresponding notches of the heat insulation plate (6).

7. The apparatus according to claim 6, Its features are, The following components: Peltier element (5), thermal insert (8), thermal plate (7) and heat insulation plate (6) are components of the mold insert (1).

8. The apparatus according to claim 3, Its features are, Multiple Peltier elements (5) and thermally conductive inserts (8) associated with these Peltier elements are provided, which are arranged on or within the mold insert (1) opposite to the cavity (2) of the mold insert, in order to locally regulate the temperature of the injection material therein.

9. The apparatus according to claim 1, Its features are, The mold receiving component (10) is provided with at least one cooling channel (14) as a cooling body for guiding coolant through at varying flow rates.

10. An injection molding machine having a mold, the mold being equipped with a device for temperature control according to any one of the preceding claims.

11. A method for temperature control of a mold in an injection molding machine using the apparatus according to any one of claims 1 to 8, wherein, The mold insert (1) is brought into or maintained within a pre-given operating temperature range by means of at least one Peltier element (5) integrated therein, through heating or cooling.

12. The method according to claim 11, Its features are, From reaching the lowest temperature (T) min From this point on, the heat required for heating is supplied to the region of the cavity (2) of the mold insert (1) through the at least one Peltier element (5).

13. The method according to claim 11, Its features are, From reaching the highest temperature (T) max In order to cool down, excess heat is discharged from the region of the cavity (2) of the mold insert (1) to the cooled mold receiver (10) through the at least one Peltier element (5).

14. The method according to claim 10, Its features are, The mold insert (1) is preheated before the injection molding process begins.

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