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PolyJet 3D Printing For Injection Molding

By <a href="" target="_self">Rod Mackay</a>

By Rod Mackay

Posted on August 23, 2022

3D printing for injection molding is commonly used by manufacturers to create prototype parts for the detection of issues in a part’s form, fit or function.

Injection molding is one of the most popular manufacturing processes. It is best used to mass-produce highly accurate, and often complex, three dimensional (3D) end-use parts. With cycle times ranging from a few seconds to a few minutes, injection molding is ideal for high-volume manufacturing applications.

Injection Mold

3D Printed Injection Mold

Until recently, the only option to create injection molded parts for testing by manufacturers and molders was to machine an aluminum (soft) tool with little or no action, such as cams, lifters or slides for side pulls. While these molds are far less expensive than their steel (hard) counterparts, costs and lead times are still significant. For example, the price to create a small, straight-pull mold ranges from $2,500 to $15,000 with delivery taking 10 days to 4 weeks. This is an investment that is hard for most companies to justify for a few dozen test parts. However, without proper testing, these investments may be diminished if further revisions to the part’s design are required.

Evaluating part design and performance

The objective of a PolyJet mold isn’t to replace short-run tooling options. Instead, it is a solution that fills the gap between 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 — with the ability to use production-grade thermoplastics.

PolyJet™ 3D printed injection molds are a good option for evaluating part design and performance. Capable of producing 5 to 100 parts in the same thermoplastic that will be used in production, they can be constructed in one or two days for a fraction of the cost of soft metal or steel tooling. By using PolyJet molds manufacturers can rapidly and cost-effectively assess a part’s form, fit and true function.

  1. Mold Design
  2. 3D Print the Mold in Less than 1 Day
  3. Finish and Mount the Mold
  4. Injection Trial
  5. Test the Injected 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.

3D Printing For Injection Molding application

  • Goal:
    • Confirm design / functionality
    • Conduct product compliance testing (e.g., UL or CE).
  • Thermoplastics:
    • Molding temperatures <300°C (570°F)
    • Good flowability
    • Candidates–PE, PP, PS, ABS, TPE, PA, POM, PC-ABS and glass-filled resins
  • Quantity:
    • Small volume (5 – 100 molded parts)
  • Size:
    • Less than 165 cm3 (10 in3)
    • Best suited for a 50- to 80-ton injection molding machine.
  • Design:
    • Straight-pull molds

Learn more about the process

Download the technical guide to learn more about the process of designing and 3D printing for injection molding, including:

  • Using PolyJet molds for pilot runs or low-volume manufacturing
  • Use in product development phase to produce functional prototypes.
  • Molding complex parts with creatively designed 3D printed mold inserts that compensate for features that normally require complex sliders, and manually eject the mold inserts after injection. These inserts aid the creation of complex designs with challenging features like negative draft angles and snap fits.
Article by <a href="" target="_self">Rod Mackay</a>

Article by Rod Mackay

Rod has been using 3D CAD software for over 25 years and has trained thousands of designers to use their CAD systems more effectively.