Multi-stage Fully Automatic Processing of PA and TPE Tubing

A globally active automotive supplier, which manufactures or processes brake and oil tubing, among other things, wanted to streamline its production in this area, but at the same time increase the number of units and product quality. To achieve these goals, the company replaced several manual workstations, where previously processing steps such as cutting to length, phasing, blowing out and printing of the material were carried out, with a customer-specific production line from Metzner Maschinenbau.

The machinery consists of the following components: two unwinders for tube reels, one unwinder for tube bundles, feeding device, two contact-free loop controls with additional material storage, reel straightening station, tool changer with cutting module for cutting to length, stripping, chamfering the cutting edges and blowing out the PA tubes, printer and stacker. There is a suitable tool set for each tube diameter, consisting among other things of sockets, guides and gripper jaws, which must be installed in the machine before production.

The operator can either process material that is on a reel or that is in the form of a tube bundle. Depending on the type of material, he loads the appropriate unwinder. Since only one unwinder model is used at a time, material can be changed between different types of tubing during production, which means a significant time saving. From the unwinder, the material runs through the first contact-free loop control with light barrier, which ensures that the tube from the reel unwinder always remains tensioned. The material is then transported by a feeder to a second contact-free loop control with additional storage. This has special guides so that tubes which have a relatively large intrinsic twist cannot twist in themselves, which would make feeding more difficult.

After the material has been mechanically straightened by means of two straighteners the actual processing takes place: a tool changer in combination with the cutting module can slit the tube, strip it at any point (even with a window), bevel its cutting edges and blow out and cut the material to length (accuracy: 0.1-0.2% of the cut length). Since several tools are arranged vertically one above the other, the individual processing steps can be carried out in any order. Multi-stage processing is thus possible in one process. For material 1, for example, the outer layer of a thermoplastic vulcanisate is slit and stripped. For material 2, the processing steps are cutting to length, chamfering the cutting edges and blowing out. The printer then marks the tubes at both ends with various information such as article number and insertion markings (+/- 1 mm accuracy). Finally, the processed material is removed by a gripper system and, depending on the length, is then placed in either a larger or smaller rollable collection container.

Because the brake and oil tubes are now machined, there is no longer any accidental damage to the inside of the tube during stripping, which was often the case when the process was carried out manually and resulted in a certain amount of waste. Because the material leaves the machine with bevelled cutting edges, it is perfectly prepared for the subsequent connector assembly. Another advantage of the machinery: It can automatically process both batch sizes and parts lists, which gives the operator flexibility.