Printing Success

Printing Success

PMT Successfully Processes Prototypes from 3-D Printed Mold Cavity Inserts 
A set of plastic mold cavity inserts designed by PMT's engineering team and 3-D printed by Stratasys.

A set of plastic mold cavity inserts designed by PMT’s engineering team and 3-D printed by Stratasys.

Picture this: prototype tool fabrication, taking place in a foundry-esque workshop. Ambience: heavy equipment, clanking tools and grinding metal with hours stacked upon hours of highly skilled labor.

Now picture this: the same tool fabrication, taking place in a lab. Ambience: muted whirring sounds, one piece of high-tech equipment and about 12 hours of plastic layered upon plastic with minimal human labor.

The second picture is now reality at PMT, and 3-D printing now presents new options for prototype development. PMT just completed Phase 1 of a three-part project, with a goal of accelerating mold cavity time-to-first-shots using 3-D printing technology.

The company successfully processed plastic prototype parts from 3-D printed mold cavity insert samples on August 9. The insert samples were made possible by a partnership with the University of Texas at El Paso’s W.M. Keck Center for 3-D Innovation and with Stratasys.

The team used the initial phase of the project to document and collect data, finding and recording answers to questions about the processing capability of 3-D printed mold cavity inserts. PMT’s engineers were able to experiment with the new technology, testing options and solutions for successful prototype part processing.


Preparing the custom mold frame that will hold the printed cavity inserts.

PMT’s been using transformative 3-D printing technology since 2014, when the company installed its first desktop printer to create custom ABS fixtures for the factory’s Secondary Operations & Assembly area. Building on this success, PMT decided to explore more substantial and customer-centric prototyping ideas.

“We saw and understood the importance of 3-D printing when it appeared in our industry a few years ago,” said PMT CEO Charles A. Sholtis. “It’s not just cool—we see that it could also represent actual, significant cost and time savings for our customers’ rapid product development and prototyping timeframes.”

Many industries are pursuing 3-D printing and additive manufacturing in a big way, from BMW’s in-house rapid prototyping to General Electric’s recent push to purchase two European additive manufacturing suppliers.

Accompanying the quick progression of technology development in 3-D printing is the recent evolution in filament materials. With a wide variety of materials now available, custom molders can print plastic insert cavities that can withstand the rigors of processing production-grade plastic resin.

PMT used Stratasys’ GreenFire PolyJet material, also known as Digital ABS, for the first set of inserts. PolyJet has a fast build process, is good for complex features and has a higher Heat Distortion Temperature (HDT) and elongation-to-break ratio. According to Stratasys, the material is a good fit to confirm part design and functionality, as well as to conduct UL compliance testing.

The material is suitable to run in injection molding machines up to 80 tons, and inserts made of the material can process a variety of resins. For the first phase of the project, PMT ran the inserts in a 45-ton electric Toshiba press, and performed resin tests with PP, ABS and Nylon.


PMT ran the 3-D printed cavity inserts in a 45-ton injection molding machine.

To run the printed cavity inserts in the press, PMT designed a customized mold frame purchased from DME. Preparing the customized frame took the longest time in the project—56 hours total to mill and carve out both cavities and the ejector plate. Once placed in an steel mud base, the printed cavities can be easily switched out of the mold frame.

After troubleshooting the insert design at PMT, the team at Stratasys printed the insert sets. One set with top and bottom plates took a total of 12 hours to print—about 1/3 of the time compared to aluminum tool fabrication.

A more complex mold design would further increase the time and costs savings, according to Andrew Rodriguez, PMT’s engineering manager. The results of the experiment provided valuable information as PMT moves into Phase 2 of the project at the end of September.

“We had good success on our first trial run of the inserts,” Rodriguez said. “Future phases of prototype testing will allow for a true evaluation of part design, performance and tolerances.”

The team concluded that the mud base with printed changeable inserts can become a more affordable and efficient option compared to traditional prototype tooling.

PMT’s engineering-focused environment fostered interest in the project, which required collaboration between the company’s tool room, engineering and processing departments. In Phase 2 of the project, the team will continue to document and collect data to further improve and optimize the process. Ultimately, the company’s goal is to print prototype cavity inserts in-house to expand the range of full-service options offered to customers.