Utilizing PolyJet Technology for Injection Molding
Injection molded impeller created from a 3D printed mold.
Three-piece mold made with PolyJet Digital ABS material.
High-resolution PolyJet molds produce fine features in injection molded parts.
3D printing is commonly used to build prototype parts to highlight design issues related to form, fit, and function. However, 3D printed prototypes cannot provide a complete assessment of an injection molded part’s functional performance, as 3D material properties are different than those actually used in injection molding. Until recently, the only option for manufacturers to conduct design and functional testing of injection molded parts was to machine an aluminum (soft) tool for part creation. While these molds are far less expensive than their steel (hard) counterparts, costs and lead times are still significant.
Today, PolyJet 3D printed injection molds are a better option for evaluating part design and performance. Using data from computer-aided design (CAD) files along with its inkjet-like process, PolyJet 3D printing can deliver high resolution and smooth surfaces that are ideal for building injection molds capable of producing prototype parts in end-use thermoplastic. Plus, they can be constructed in one or two days as opposed to days and weeks for metal tools.
The objective of a PolyJet mold is not to replace short-run tooling options. Instead, it is a solution that fills the gap between production level, machined molds and less expensive silicone rubber molds that can only simulate injection molded parts. Typically costing 50% to 70% less than an aluminum tool, PolyJet molds offer the advantages of silicone rubber molds — fast production of complex parts and the ability to make frequent revisions. Furthermore, molds produced with PolyJet technology have the ability to be used with production-grade thermoplastics, therefore allowing the creation of a prototype that completely simulates both the fit and function of the production part.
Many thermoplastic resins can be injected into a PolyJet mold. Commonly used resins, such as polypropylene, polyethylene, acrylonitrile butadiene styrene (ABS), polyamide, thermoplastic elastomers, and glass-filled polyamide and polypropylene resins are good candidates for molds with challenging features.
Cavity side of 3D printed injection mold.
Seuffer’s polyethylene housing createdwith a PolyJet tool.
PolyJet molds require a few adjustments in the tool design and injection molding process to compensate for their mechanical and thermal properties. For example:
• PolyJet molds use larger draft angles and gates as opposed to metal tools.
• Injection molding temperatures and pressures are decreased to avoid damage to the PolyJet mold and extend its life.
• Cycle times are increased to allow the plastic to solidify and keep the PolyJet mold at an ideal operating temperature.
Robert Seuffer GmbH & Co., based in Germany, manufactures sensors, electronics and controls for use on finished products in numerous industries. During its quality control process, Seuffer conducts testing to validate the fit and functionality of any potential new part by creating prototypes with metal molds. However, the company’s management was interested in exploring alternatives that would allow them to accelerate the process, and reduce the number of design iterations, before allocating valued resources.
Their solution was to use a PolyJet 3D Printer as a mold-making machine. To test the approach, Seuffer selected a part that was geometrically complex; its design included shut-off surfaces, thin walls, and tall core pins which would normally require multiple inserts and many labour hours to fit into a normal metal mold base. By using a PolyJet 3D Printer, a prototype mold was built in one day and required only three hours of component fitting and assembly. What’s more, the PolyJet mold cost less than $1,400 to produce.
54 days (96%)
Now, with the help of PolyJet 3D printed molds, Seuffer can:
• Quickly and cost-effectively produce new molds following each round of design modification.
• Reduce and / or eliminate rework on final production molds.
• Create prototypes from final production material with complex geometries, thin walls, and fine details.
• Gather true-to-life performance data much earlier in the process than ever possible before.
“In the past, we could not conduct performance tests until we had built a steel or aluminum tool and used it to create injection molded prototypes on actual production machines. Now we have the ability to perform functional tests and modify designs faster and at much lower costs.”
- Wilfred Zachman, Sueffer R&D Manager
To view the technical application guide for creating injection molds with PolyJet technology, click here. For additional case studies, news, and more, visit us at www.cimetrixsolutions.com
- Cimetrix Staff