Prototyping Options for Injection Molding

There are many reasons why a medical device company may consider prototyping before launching a tool build for production parts. Often, rapid prototyping is used to validate a design and test the product form and fit to better understand device assembly and interoperability modifications that may be required. Other times, prototyping is a bridge to production when you need real molded parts immediately while you are waiting weeks – or sometimes months – for high cavitation tooling to be completed.

Forum Plastics offers multiple options, leveraging various technologies, to help you get parts faster and cost-effectively, as well as accelerate the product time to market.

Available Prototyping Options

Forum Plastics has invested in Stereo-Lithography (SLA) technology that uses an advanced 3D printer and UV laser which photo-cures epoxy-based material to form your parts. Once the parts are built, they are post-cured in a chamber. A benefit of using SLAs is that they can mimic engineering-grade plastics.

We also leverage 3D printing to build cavities or inserts for low volume tooling which can be utilized in MUD frames or Forum-designed modular tools. 3D printed cavities can produce up to 100 shots and is ideal for form, fit and function evaluation.

Forum builds tools in-house and typically produces SPI Class 101, 102 and 103 molds which are made from P20 hardened steel. For prototype tooling, Forum can offer both hard and soft steel inserts for use in their modular frames. When a hardened steel isn’t necessary due to a short product life cycle or lower demand, S50C or other soft steel inserts are an option. For example, soft steel is ideal for up to 1,000 shots or pieces, but if the volumes are in excess of 100,000 pieces, Forum would recommend a hardened steel insert. The added benefit of hardened steel inserts is that, in most cases, they can be revised and groomed to be used in full production tooling.

Prototyping Considerations

What size or dimensional considerations impact prototyping processes?

The simpler the part geometry, the easier it is to prototype, as well as a tool that doesn’t require side actions to achieve a specific feature. Some features can be molded by using a hand-load for a part up to 4″ square.

What secondary operations can Forum provide for prototypes?

Forum offers a full suite of secondary services for both prototypes and production including pad printing, threaded inserts, machining and assembly.

What limitations are there for prototypes to be a representative sample of production?

A 3D printed cavity does have some limits on surface finish and may require wet sanding, polishing, painting, or other post molding operations to achieve a desired texture or smoothness.

What lead-time advantages can I realize by using Forum’s prototyping services?

The typical lead-time for SPI Class 103 tools is 6-8 weeks not including validation.  By leveraging 3D printed inserts Forum’s prototyping solutions can produce tools and parts within 2-4 weeks.

Get There Faster With Forum

To provide our customers with industry-leading product design and development, Forum Plastics continues to expand and invest in technologies and solutions. Our people and our capabilities take you from prototype to production. Learn more about the benefits of prototyping with Forum Plastics.

For more information, please contact Doug Hungerford, Director of Engineering.

Appendix: SPI Mold Classifications

Note: These standards do not constitute a warranty or guarantee by the Society of the Plastics Industry, Inc., or its members for the classifications or specifications set forth herein.

Source: SPI Standards Handbook: The Society of the Plastics Industry, Inc. 1801 K Street, NW, Suite 600K Washington, DC 20006-1301

Cycles: One million or more

Description: Built for extremely high production. This is the highest priced mold and is made with only the highest quality materials.

  • Mold design required.
  • Mold base should be a minimum hardness of 28 R/C.
  • Molding surfaces (cavities and cores) must be hardened to a minimum of 48 R/C range. All other details, such as slides, heel blocks, gibs, wedge blocks, etc., should also be of hardened tool steels.
  • Ejection should be guided.
  • Slides must have wear plates.
  • Temperature control provisions to be in cavities, cores and slides wherever possible.
  • Over the life of the mold, corrosion in the cooling channels decreases cooling efficiency thus degrading part quality and increasing cycle time. It is therefore recommended that plates or inserts containing cooling channels be of a corrosive resistant material or treated to prevent corrosion.
  • Parting line locks are required on all molds.


Cycles: No more than one million

Description: Medium to high production mold, good for abrasive materials and/or parts requiring close tolerances. This is a high quality, fairly high-priced mold.

  • Mold design required.
  • Mold base to be minimum hardness of 28 R/C.
  • Molding surfaces should be hardened to a 48 R/C range. All other functional details should be made and heat treated.
  • Temperature control provisions to be directly in the cavities, cores, and slide cores wherever possible.
  • Parting line locks are recommended for all molds.
  • The following items may or may not be required depending on the ultimate production quantities anticipated. It is recommended that those items desired be made a firm requirement for quoting purposes:
  1. Guided Ejection
  2. Slide Wear Plates
  3. Corrosive Resistant Temperature Control Channels
  4. Plated Cavities

Cycles: Under 500,000 cycles

Description: Medium production mold. This is a very popular mold for low to medium production needs. Most common price range.

  • Mold design recommended.
  • Mold base should be a minimum hardness of 8 R/C.
  • Cores and cavities must be 28 R/C or higher.
  • All other extras optional.

Cycles: Under 100,000 cycles

Description: Low production mold. Used only for limited production preferably with non-abrasive materials. Low to moderate price range.

  • Mold design recommended.
  • Mold base can be of mild steel or aluminum.
  • Cores and cavities can be of aluminum, mild steel or any other agreed upon metal.
  • All other extras optional.

Cycles: No more than 500 cycles

Description: Prototype only. This mold will be constructed in the least expensive manner possible to produce a very limited quantity of prototype parts.

  • The mold base may be constructed from cast metal or epoxy or any other material offering sufficient strength to produce the minimum prototype pieces. This tool is only for prototype purposes only.
  • All other extras are optional.