Extrusion International 1-2025

48 Extrusion International 1/2025 the productivity. This due to the fact that it cuts the cycle time when avoiding thick wall regions in the part. As a consequence more articles can be produced per unit of time. Every existing head can be easily retro tted with a solid GWDS-die and a solid GWDS-mandrel by only ex- changing the existing conventional die and mandrel. So it is very inexpensive to retro t an existing head. As a consequence extreme short times can be reached until the investment is paid back and signi cant improve - ments of the rate of return can be reached. Picture 4 compares the wall thickness distributions, the weight and the cycle times achieved when producing four dif- ferent articles with a conventional conical die and alter- natively with a predominantly cylindrical GWDS-die. For over a decade in Europe nobody dares to replace a head that was equipped with a PWDS-system by a GWDS-die. Now an Asian blow molding machines pro- ducer of all companies dared to substitute his Asian copy of a PWDS-system by a GWDS-die. The company was forced to do that as the customer did not accept to pay for the ordered machine as they claimed that the weight of the 20 liter cans which were produced were too high. That is why the company decided to dismantle the Asian copy of a PWDS-system and to attach a solid GWDS-die and a solid mandrel (Picture 5). The company managed it to further reduce the weight of the cans by 5 %. In Eu- rope some few producers of blow molded articles have already successfully replaced their conventional conical dies by GWDS-dies in order to further improve the quality of their parts. The quality was improved and the weight of the articles and the cycle time were reduced. But for what reason ever still no Europeanmachine producer has decided yet to design and to offer predominantly cylin- drical GWDS-dies to their potential customers. Dr.-Ing Heinz Groß Dr.-Ing. Heinz Groß Kunststoff-Verfahrenstechnik Ringstr. 137, 64380 Roßdorf, Germany www.gross-k.de BLOWMOLDING – FROM THE RESEARCH 4b: Using the following QR-codes short video can be seen which show the discharge of the parison for the part on top (left) and for the part shown on the bottom (right) Picture 4: Articles that have been produced with a conventional conical die and with a predominantly cylindrical GWDS-die Picture 5: Components of the Asian copy of a PWDS-system that has been dismantled from the head (left side) and GWDS-die and GWDS-mandrel that have been attached to the head instead (right side)