Advanced Thermoforming, 2nd Edition

Chapter 6Fuel Tank Production on Sheet Machines

Written in cooperation with Manfred Geiss, Geiss AG, Sesslach, Germany

By law, fuel tanks are required to have certain internal components. The twin sheet procedure is suitable for the production of a closed tank with all the parts integrated in one production step.

Producing high‐quality twin sheet parts such as fuel tanks calls for adequate heater control, sheet support during heating, and independent prestretching of the sheets. The machine described in this application has four independent heater fields. Each single element is infinitely adjustable. Individual override of each field is possible. The temperature of each field is controlled by a pyrometer. There is a function control to each element.

The closed chamber machine types such as those from Geiss AG allow pressurization. Sheet temperature adjustment is independent of sagging effect. Any material can be chosen. Special extrusion methods are not necessary to make the semifinished product thermoformable. To obtain better material distribution, the lower sheet can be prestreched upward or downward. The same is possible for the upper sheet and independent of the lower sheet.

Both sheets are loaded automatically and simultaneously, and all four sides are clamped on top of a closed chamber. Then both sheets are simultaneously heated and automatically supported. After the heating process both sheets are prestretched simultaneously. The lower mold and the upper mold move into ...