When manufacturing fuel tanks for the automotive industry, the multi-layer or co-extrusion process “Coex” is used. However, the process step was very cost-intensive and time-consuming. “Cooling the plastic product represents both one of the most critical and most lengthy sub-processes in the extrusion blow moulding process,” explains Aaron Farrag, deputy CEO of Farragtech GmbH. “Especially during production of multi-layer products such as modern fuel tanks, a lot of time can be saved and the Evoh-layer protected against damages from heat exposure.” During the process, difficulties can occur due to the temperature drop between the exterior, which is cooled by means of cold water, and the still warm interior of the product. These temperature differences often led to significant material stress – above all, because the large-scale tanks are complexly shaped, featuring wall thicknesses ranging between 1.35 mm and 3.80 mm. Until recently, this was counteracted by means of interval blowing. As a rule, the results were unsteady product quality as well as a failure to pass the subsequently carried out tightness tests, load tests as well as drop tests. Because of the relatively high scra...