1.9 Test Rig for Welding Plastic Samples

Infrared welding is an established method for joining plastic pipes. The pipes are heated at their end faces by infrared heating until the plastic melts. Then the tubes are pressed together with a defined force and cooled down. Due to the contactless heating of the tubes, the weld seams are of high purity. For this reason, this process is used for example for the production of pipelines in clean rooms in the semiconductor industry. Different heating system solutions are to be evaluated on a test rig on the basis of simple plastic samples with regard to optimum weld seam quality.

Contributors: Partner(s): Funding: Duration: N. Jenal, M. Gorbar, S. Spirig, T. Hocker, C. Brändli ZHAW IMPE Teams C. Brändli und D. Penner, Georg Fischer Piping Systems Innosuisse 2018–2021

In cooperation with Georg Fischer Piping Systems, a test rig was developed to join cuboid-shaped plastic samples with the infrared welding process. Different heating system concepts can be tested on the test rig with regard to optimum weld seam quality, see figure 1. Figure 1: Test rig for welding plastic samples. A welding process consists of three steps. First, the end faces of the samples are heated until the plastic melts. Second, the samples are pressed together. Afterwards the cooling takes place until the weld seam solidifies. The faces of the samples are not in contact with the heating system during heating. For this reason, the ends are heated primarily by thermal radiation. A new type of heating system should provide a melt front that is as uniform as possible. The melt front describes the transition between the liquid and solid plastic after the heating pro-

cess, see figure 2.

Figure 2: Contactless heating of cuboid-shaped plastic samples.

Microtome section are taken from the welded samples to examine the shape of the melt front under a light microscope, see figure 3. These images are used to evaluate the best heating system and to validate the CFD models. The simulations are used to reproduce the entire welding process.

Figure 3: Microtome section under microscope.