pps proceeding - Abstract Preview
pps proceeding
Symposium: S04 - Injection Molding and Molds
Oral Presentation
 
 

Influence of Mold Surface Temperature on Polymer Part Warpage in Rapid Heat Cycle Molding

Berger Gerald Roman (1)*, Pacher Gernot A. (2), Gruber Dieter P. (2), Pichler Astrid (2), Friesenbichler Walter (1)

(1) Dpt. Polymer Engineering and Science, Chair of Injection Molding of Polymers, MU Leoben - Leoben - Austria, (2) Polymer Competence Center Leoben GmbH - Leoben - Austria

Dynamic mold surface temperature control continuously gains importance in achieving high grade polymer surface finishes. To examine its influence on the polymer part warpage, a test mold was developed, using two different dynamic mold temperature technologies. The specimens are complex plate-shaped parts having different ribs, varying thin-wall regions, and both, circular and rectangular cut-outs. The features are repeated along the flow direction. The mold’s nozzle side is equipped with the areal heating and cooling technology BFMOLD®, which tempers a chamber below the cavity by using hot and cold water sequentially. Two local electrical ceramic heating elements are installed into the ejection side of the mold. This combination of heating systems enables dynamic mold surface temperature control on both, the top and bottom surfaces of the specimens. Based on full-factorial designs of experiments, varying nozzle temperature, maximum mold surface temperature as well as holding pressure, specimens of POM were manufactured systematically. The transient process parameters melt temperature, mold surface temperature and cavity pressure were acquired by triple-combined FOS MTPS408 sensors in the cavity directly. The resulting warpage was evaluated by 10 surface line scans at each part using the non-contact confocal microscopy system FRT MicroProf®. Both, conventional processing and dynamic mold surface temperature control were analyzed for their influence on the part shape. Finally, mathematical models were determined to describe the warpage as a function of the process parameters. Selected results were checked by injection molding simulation.