Slip rings made by LTN for plastic injection moulding machines

Plastic injection moulding machine

Plastic injection moulding machine

In plastic injection moulding, various plastics are injected into the mould from different directions. The mould must therefore be turnable. Slip rings connect the signal lines and cables used to monitor the temperature in the mould.

Detailed application description

Description of problem:

Injection moulding predominates in plastics manufacturing. Large plastic injection moulding machines are customised, so that slip ring configurations differ as regards installation space and transmission requirements. In this example, a slip ring with a cyclic motion profile of 4 or 5 cycles per minute, comparable to a rotary table, had to be adapted to the existing interface due to limited space inside the machine. It is vertically mounted at the base of the machine and therefore difficult to access for maintenance. A service life of 5 to 10 years was specified. The customer guided the rotor-end cables through a media duct, which can get extremely hot, so thermal decoupling had to be integrated at the mechanical interface. High demands were also placed on the slip ring’s tightness because the housing comes into contact with various liquids.

Description of solution:

Owing to the limited height available inside the injection moulding machine, a combination of a disc slip ring with concentrically arranged sliding tracks and a type SC012 signal slip ring was selected for data transmission. A thermal insulation plate was installed to protect the lines at the rotor end from the heat of the special media ducts. This plate provides thermal decoupling of the slip ring body. All cables are made of silicone, which affords high flexibility over a wide temperature range. Silicone cables remain adaptable even when exposed to very high temperatures.

To protect the slip ring from impinging fluids in the environment, drainage channels were integrated in the slip ring rotor. In addition, the flange surface at the top of the slip ring housing was given a slightly conical shape to prevent the accumulation of fluids which might otherwise penetrate inside the slip ring over prolonged periods.

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