The invention relates to a heating device according to the introductory clause of Claim 1, an injection moulding system equipped with such a heating device, and a method for producing plastic moulded parts from a semi-finished product which is overmoulded with a plastic material.
A generic heating device is known from DE102014010173A1. This heating device is usually used in injection moulding systems in order to produce plastic moulded parts which consist of a semi-finished product which is overmoulded with plastic material. The heating device known from DE102014010173A1 has a carriage system by which a frame can be moved through a heating region formed by radiant heaters.
According to a first embodiment (DE102014010173A1, FIG. 4), a clamping frame is provided with several spring-loaded holding devices formed as clamps. The semi-finished product is held in its position by means of the clamps. The clamps are spring-loaded, in order to compensate for thermal deformations of the semi-finished product and the thermal expansion of the clamping frame. According to a second embodiment (DE102014010173A1, FIG. 5) a wire support formed from several wires is clamped into the frame, wherein the wires are spring-loaded for the compensation of thermal deformations. In this case, the semi-finished product is only deposited on the wire support.
Basically, it is regarded as advantageous if during the movement of the wire support a slipping of the semi-finished product can be prevented. In the example embodiment according to FIG. 5 of DE102014010173A1, in which the semi-finished product only rests on the wire support, therefore only small speeds of travel can be set. The situation is different in the example embodiment of FIG. 4 in DE102014010173A1, where spring-loaded clamps are used as positioning aid and for holding the semi-finished product. With this embodiment, higher speeds of travel can also be provided. A disadvantage herein, however, is that these positioning aids must be adapted respectively individually for differently configured semi-finished products. When such positioning aids consist of a metallic material, these heat up, which involves some disadvantages. On the one hand, changes in the position of the semi-finished product can occur in the oven, and on the other hand the heating-up behaviour of the semi-finished product can be negatively influenced through the thermal capacity of the positioning aid.
Proceeding herefrom, the invention is based on the problem of indicating a heating device which is able to be used for differentially shaped semi-finished products, without adaptations to the wire support having to be carried out.
The solution to this problem takes place through a heating device having the features of Claim 1. Advantageous configurations and further developments are to be found in the dependent claims.
Through the fact that the wires of the wire support are electrically conductive and that selected wires are acted upon with a voltage and can thereby be heated, wherein the voltage is able to be set and/or able to be regulated in such a way that the wires can assume a predefinable temperature, the surface of the semi-finished product can be heated above the melting temperature of the matrix of the semi-finished product. This leads to a bonding of the semi-finished product with the wire support, whereby a positioning aid is superfluous. The position, once adopted, is not left any more on depositing of the semi-finished product on the wire base. Also in the case of comparatively high speeds of travel, the semi-finished product remains lying securely in its position on the wire support.
A further advantage lies in that one and the same wire support is able to be used for differently shaped semi-finished products, as long as the semi-finished product is smaller than the available support area of the wire support. Thereby, one and the same wire support can be used for differently contoured semi-finished products. In the case of a change of the semi-finished product, in contrast to the prior art, no adaptations to the wire support are to be carried out. As no positioning aids are present, the disadvantages connected with these, as have been mentioned above, are also eliminated.
According to a first embodiment, the wire support can be formed from several wires lying parallel to one another. Furthermore, it is possible that the wire support is formed from several wires crossing each other, wherein the wires preferably cross each other at an angle of 90°. A suitable insulation can be provided at the crossing points.
Preferably, a temperature sensor is provided at one or more of the wires, in order to measure the temperature of this wire and to be able to set a suitable temperature for the semi-finished product.
In further development of the invention, a carriage can be provided for moving the wire support, which carriage can be moved on a rail system into the oven and out from the latter. The oven and the carriage system can be configured here in the manner as is the case in DE102014010173A1, i.e. the rail system extends through the oven in such a way that a carriage with a wire support on the one side can be moved into the oven and on the opposite side can be moved out from the oven. The oven and the carriage system can, however, also be configured in such a manner that the carriage with the wire support can be moved on one and the same side of the oven into the latter and out therefrom again.
Furthermore, a control device can be provided, by which the voltage is adjustable and/or controllable in such a way that the wires can maintain a predefinable temperature. Thereby, external influences which could lead to temperature fluctuations can be compensated.
A preferred field of application of the heating device according to the invention is a system for the production of plastic moulded parts from a semi-finished product, which is overmoulded with a plastic material. The system comprises an injection moulding machine, known per se, with a clamping unit and with an injection unit, a robot and a heating device according to the invention.
The invention relates in addition to a method for the production of plastic moulded parts from a semi-finished product, which is overmoulded with a plastic material, wherein the semi-finished product is heated by means of a heating device according to the invention, wherein the voltage of the wires is set to a value at which the wires assume a temperature which bring about a melting of the semi-finished product, wherein the heated semi-finished product is removed from the wire support after moving of the wire support out from the oven, and is overmoulded with a plastic material in an injection moulding machine. Robots, known per se, can be used for handling the semi-finished product.
Preferably, steps can be taken in order to set the temperature of the wires in a suitable manner, namely:
In accordance with the present invention, in particular so-called organic sheets or fibre-plastic composite inserts are to be regarded as semi-finished product. Furthermore, the following products can be regarded as semi-finished products in accordance with the present invention:
natural fibre semi-finished products
non-woven materials
all flat semi-finished products consisting of fibres and of thermoplastic or thermosetting matrix.
Typical fibre-matrix combinations are:
The invention is to be described further below with the aid of example embodiments and with reference to the figures. There are shown:
In
In
Between the heating device 20 and the injection moulding machine 1, a robot 40 is arranged which is configured for the handling of the organic sheets 9 and in particular has a suitable gripping device 41. By means of the robot 40, an organic sheet 9 which is to be heated can be removed from a storage stack—not illustrated here—and placed onto an empty wire support 30. After the organic sheet 9 has been heated and moved out from the oven 20 again, the heated organic sheet 9 can be brought by means of the same robot 40 into the space between the open mould halves 7 and 8 and fixed there in its position for an injection moulding process. Of course, several robots, also several different robots, can be provided in order to accomplish the handling of the stored organic sheets, of the heated organic sheets and of the finished plastic moulded parts.
Steps can be taken in order to set the temperature of the wires 32 in a suitable manner, namely:
This form fit leads to a reliable fixing of the organic sheet on the wire support and enables a quick movement of travel of the wire support without displacement of the organic sheet on the oven grid.
The wire support 30 according to the invention is used in a method for the production of plastic moulded parts from an organic sheet 9 or from another semi-finished product, which is overmoulded, or respectively is to be overmoulded, with a plastic material. Here, an organic sheet 9 or respectively the semi-finished product is heated by means of a heating device of the type previously described. The voltage of the wires 32 or 32a/32b is set to a value at which the wires adopt a temperature which brings about a fusing of the organic sheet 9. The carriage 25 can therefore be moved at a comparatively high speed of travel into the oven 20 and, after heating of the organic sheet 9, can be moved out therefrom again. After the moving of the wire support 30 or respectively 32a/32b out from the oven 20, the organic sheet 9 is removed from the wire support and is overmoulded with a plastic material in the injection moulding machine 1.
1 injection moulding machine
2 machine bed
3 fixed platen
4 movable platen
5 horizontal columns
6 linear guides
7 first injection mould half
8 second injection mould half
9 organic sheet
20 heating device
21 oven
22 carriage system
23 rail
24 rail
25 carriage
30 wire support
31 frame
32 wires
32
a wires
32
b wires
33 connecting cable
34 connecting cable
35 voltage source
36 temperature sensor
37 controller
40 robot
41 gripping device
Number | Date | Country | Kind |
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10 2018 109 945.2 | Apr 2018 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2019/059263 | 4/11/2019 | WO | 00 |