Choosing Materials for Injection Molding: a Case Study

3D printers are capable of printing a wide variety of essential objects, products, and part components for an array of industries and applications.

One company, Grundfos, decided to test various 3D printing technologies when it came time to use injection molding to create a new mold for a series of essential parts to their products, circulator and centrifugal pumps used in everything from water supply to heating and air conditioning.

Grundfos, based out of Denmark, worked with Stratasys, our main supplier of Stratasys 3D printers. The entire case study can be found here.

The Challenge

Grundfos wanted to prototype parts for its pumps, to ensure that they can withstand a battery of tests that replicate a high-temperature, fluid-rich environment. Not just any material would do; the material chosen would have to pass geometry, functionality, hydraulic, electric, and burning testing. Resiliency was the key.

The Testing

Working with Stratasys 3D printers, Grundfos created two tests. The first involved injection molding a relatively simple part; the second involved a more complex part that required a nine-step process.

Two 3D printing technologies were used in the trials: PolyJet™ and SLS. Both methods were used in conjunction with different mold polymers, ranging from Transparent and Digital ABS (with PolyJet™) and PA2200 and PA3200 (with SLS). Each mold was then used with a wide range of materials, including:

  • POM
  • Noryl with 20 percent glass fiber component
  • Polycarbonate with 10 percent glass
  • PPS that is 40 percent glass-filled
  • PA66 30GF that is 30-percent glass-filled

Testing found that for surface smoothness, the two SLS mold types were unsatisfactory. Only that created with the PolyJet™ process were satisfactory, so the company decided to go exclusively with PolyJet™ for the remainder of the tests.

As a result, Transparent and Digital ABS molds passed the test.

Once the company decided on the PolyJet™ mold materials, it decided to test a more cmplex part that required a nine-part injection mold.

During this run, the company used 30 percent glass-filled Noryl (PPE-PS-GF30%). Grundfos quickly found that the Transparent mold developed cracks and tears, that only increased with each shot. After the seventh shot, the company decided to stop using Transparent.

Digital ABS, however, did not tear or crack like Transparent. The company found that surface quality was good with Digital ABS.

The Results

The company estimated that by using PolyJet, they could save 50 percent in costs and 70 percent in lead time compared to traditional molds made in aluminum. They were also able to produce a prototype in just 10 days, from start to finish; the time pales in comparison to the five weeks it would’ve taken for a cast prototype.

Furthermore, Digital ABS was determined to be ideal for their prototyping needs, allowing Grundfos to create accurate injected parts with a high level of detail for complicated components.

Using Stratasys 3D printers and a rigorous testing process can allow a company like Grundfos to find the ideal material mix for its parts, whether it’s injection molding or traditional printing. Request a quote for a Stratasys 3D printer and begin your testing and prototyping processes today.