Blow Molders & Thermoformers Try Plastic Rapid Tooling

Tag : Solvent Resistant

In blow molding, there is significant interest in developing moldsfor prototype PET bottles for water and carbonated soft drinks(CSD), according to Fred Fischer, Stratsys product marketingmanager. With FDM tooling, the lead time for prototype parts isreduced from weeks to less than five days, says Fischer. Inaddition, the cost is reportedly one-third to half that of aprototype aluminum tool. Stratasys usually recommends its PCmaterial for blow molding tools. It can withstand short-runproduction of hundreds to thousands of HDPE, PET, PVC, PS, or PCparts, according to Fischer.
With the exception of venting and shut-offs, the FDM tool’sdesign is similar to a machined version. Since the FDM cavity has asmall amount of porosity, air trapped between the molded plasticand tool surface is vented through the body of the tool. Tominimize flash, a sloped, raised rib is added around the contour ofthe cavity. Cooling channels can be built into the tool, butStratasys says it’s simpler and faster to use a standardmounting plate with cooling lines. Since the PC tool retains someheat, more cooling is required.
One container manufacturer used FDM to build a PC mold for6-in.-tall, 3-in.-diam. HDPE bottles in two days. The customermolded near-production-quality bottles in less than five days fromthe start of the FDM build. Another manufacturer blow molded 800PET bottles with no wear, distortion, or dimensional change to theFDM tool. The company concluded that the tool could producethousands of parts, if necessary.
For thermoform tooling, all of Stratasys’ materials arepotential candidates. In demanding applications, PPSF and PC offera higher Tg than ABS. Depending on the tool and part material, FDMtool life can range from 100 to 1000 parts. With the exception ofventing through the porosity of the tool (as in blow molding) andthe addition of a perimeter rib, the tool is designed like anytypical machined mold. Cooling channels may be constructed in theFDM tool, but it is believed to be simpler and faster to use astandard mounting plate with cooling lines.
One aerospace supplier uses FDM to make thermoform molds for airducts, engine cowlings, and antenna covers. FDM tooling reportedlycosts less and has shorter lead time than composite molds made byhand lay-up of carbon-fiber prepreg.