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Rapid tooling has numerous advantages when prototyping injection molded components, but the effects of the tooling on the resulting part properties are often overlooked. The purpose of this paper is to consider the effect of tooling on the final part properties and morphology.

Digital polyacrylonitrile-butadiene-styrene (ABS) tooling and aluminum tooling were used to mold test specimens from isotatic polypropylene (iPP). Tensile behavior, impact strength, shrinkage, surface roughness and porosity were evaluated for both sets of samples. Additionally, differential scanning calorimeter (DSC) and wide-angle X-ray scattering (WAXS) were used to assess the crystallinity of the samples.

Characterization of the molded parts showed that slower cooling rates in the Digital ABS inserts promoted the formation of ß-PP, while this crystal structure was not found in the parts molded using aluminum tooling. Additionally, parts molded on the digital ABS inserts exhibited higher mold shrinkage and SEM images identified microscopic shrinkage voids within the material. The change in morphology and the presence of voids significantly affected the tensile behavior with the parts molded in Digital ABS, which broke with little cold drawing and exhibited higher tensile moduli and higher yield strengths.

The results show that the choice of rapid tooling technique plays an important role on determining the properties of the final parts.

Previous studies have not characterized the effect of rapid tooling on the morphology of the molded articles fully or over a variety of processing conditions. This study builds on prior work by using both WAXS and DSC to characterize morphological changes over a wide range of processing conditions and comparing results to mechanical property and shrinkage data.

This study aims to evaluate the performance of injection molding inserts produced via rapid and conventional manufacturing techniques considering the mechanical and thermal performance of the tools as well as the resulting molded part quality.

Three insert materials and manufacturing techniques were evaluated, jetted photopolymer (PolyJet) 3D printing using digital ABS, direct metal laser sintering (DMLS) using bronze and machining using stainless steel. Molding trials were performed, and the insert surface temperature, longevity and part properties were evaluated. Complementary information was acquired using computer simulation.

Similar behavior and part quality were observed in machined and DMLS inserts. The latter were used for 500 cycles without any signs of failure. PolyJet inserts had increased cycle time and slower rate of cooling which increased shrinkage and crystallinity in the molded parts. PolyJet inserts could be produced quickly at a lower cost than machined or DMLS inserts.

Cooling within the insert was not studied; inserts were cooled indirectly by the mold plates behind them. Subsequent studies will incorporate cooling lines directly into the inserts.

Little research has been done to understand the thermal behavior of inserts manufactured via rapid tooling techniques. This study provides a direct comparison between rapid tooling techniques, which is supported by simulation results and analysis of the actual molding properties.