PETpla.net Insider 03 / 2017

The LayerWatcher at the K Show: inspecting preforms precisely and non- destructively all around The preform layers are measured all around by coherent infrared light within 25 seconds INSPECTION 16 PET planet Insider Vol. 18 No. 03/17 www.petpla.net Inspecting barrier layers in transparent and coloured translucent preforms Non-destructive measurement Gabriele Kosmehl: Dr Fuhrmann, your new development, the Layer- Watcher, is a system for the inspec- tion of multilayer preforms. Can you please explain to us how the system works? Gerd Fuhrmann: The technology behind the LayerWatcher is based on the same principles as known from ultrasonic examinations. A pulse is sent into the material and the echo is analysed. But as we all know from our physics lessons at school, the lateral resolution is a function of the frequency of the probing wave; the higher the fre- quency the better the resolution. This is the reason for us to use infrared light. Gabriele Kosmehl: Other systems work with terahertz measuring. What are the differences to your system? Gerd Fuhrmann: Both systems are based on the same principle. However, terahertz radiation has a much longer wavelength than infrared light. While this affects the penetration characteristics, it also leads to signifi- cantly longer measurement times and a reduced resolution, for the reason mentioned above. A user will first recognise that the LayerWatcher system will give him a high resolution image like he would see it with a microscope when he cuts a preform wall. He will be able to see clearly even the smallest turbulences of the different materials which form the diverse layers. Terahertz systems measure layer thicknesses at just one point to finally spitting out some num- bers. It stays obscure what a terahertz based system will measure in the presence of irregularities, for instance if the flow front of a barrier divides into two flows or shows turbulences. This is especially true as you have to tell a terahertz system for how many layers you are looking before you start. So the method thus involves a kind of guessing about the result before the measurement at all starts. Terahertz systems measure thick Dr Gerd Fuhrmann, managing director of Intravis GmbH The LayerWatcher by the German company Intravis GmbH is able to visualise the structure of layers in preforms, using measurements with infrared light. The non-destructive imaging device delivers an accurate picture of a virtual cut through the preform wall. Intravis pre- sented the LayerWatcher at the K show at the booth of Husky Injection Molding Systems S.A.- a good opportunity for PETplanet to speak to the managing director of Intravis, Dr Gerd Fuhrmann. INSPECTION S P E C I A L