First, pick the CAD software tool of your preference to design the mold insert. We’ll use the open-source Blender, but the workflow should be fairly similar in any other CAD software.

At Fabrik Molded Plastics, Inc., we offer custom two-shot plastic injection molding capabilities. Other service offerings include precision plastic injection molding, insert molding, CT scanning, scientific plastic injection molding, automotive lighting, tooling transfers, and custom automation services.

Before purchase, make sure to evaluate the injection molder carefully against your production requirements. For large parts, industrial processes will still be necessary. This DIY injection molding technique is best optimized for producing small parts at low volumes.

Injection molding is ubiquitous as a manufacturing process—in fact, the majority of plastic products in the world today are manufactured by injection molding. While it is an ideal technique for large-scale production needs, traditional CNC machined metal molds have prohibitive high costs and long lead times for low-volume production.

Based on internal testing and case studies with our customers, we suggest to choose the 3D printing resin based on the criteria from the table below. Three stars means the resin is highly effective, one star is less effective.

Depending on the geometry and the size, multiple molds can be printed at once on a build platform to increase printing efficiency.

A 3D printing material that can withstand the temperature and pressure on the mold during the injection molding process. We recommend the following materials for Formlabs SLA 3D printers:

Want to learn more about injection molding with 3D printed molds? Download our white paper for detailed guidelines for using 3D printed molds in the injection molding process and see real-life case studies with Braskem, Holimaker, and Novus Applications.

Setting up the print only takes a few seconds in PreForm, the print preparation software for Formlabs 3D printers. If your mold design requires support structures for printing, make sure to orient the mold halves in PreForm so that the cavity faces up. This will simplify post-processing and ensure a high-quality surface for your molded parts.

You have a wide variety of materials to choose from for injection molding. Formlabs and our customers have tested the following materials with 3D printed injection molds:

Two-shot plastic injection molding is an injection molding process used to create multilayer, multicolor, or multi-material parts in a single process. This process is also sometimes referred to as two shot injection molding, 2-shot molding, 2K, multilayer, multi-shot injection molding, or multishot molding. Multi-shot manufactured products eliminate steps in the manufacturing process while creating a more cost-effective, enhanced finished product.

In Blender, use the eye icon in the scene explorer to toggle off one half of the mold. Once your workspace is set up to your liking, set both halves of the mold to the “wire” draw type under the Object menu, as in the image below.

Commonly used materials for two-shot injection molding include thermoplastics, thermoplastic elastomers, and liquid silicone rubber.

A benchtop injection-molding machine, such as the Galomb Model-B100 or the Holipress. There are a number of benchtop injection molders on the market that vary in cost. Many of the lower cost molders use a hand-driven plunger, while some of the more expensive units use a screw or pneumatic system. Some of our customers have recommended systems from Minijector, Morgan, APSX, or Micromolder as well. Desktop automated molders such as the product line from Babyplast are good alternatives for mass production of small parts.

Depending on the injected material, adhesion of the part to the mold can cause deterioration of the mold during extraction, in particular with flexible materials such as TPUs or TPEs. Using a mold release agent is a good solution to help separate the part from the mold. Silicone mold release agents are compatible with Formlabs Grey Pro Resin, High Temp Resin, and Rigid 10K Resin.

In this guide, we’ll walk you through the process of DIY injection molding and share all the tools and tips necessary to utilize plastic injection molding in-house using 3D printed molds.

If designing for an aluminum mold frame, add .125 mm of extra thickness to the back of the mold plates to account for compression forces and to ensure a complete seal.

Download the blank mold insert design files—you’ll use them to create your injection mold design. The designs can also be easily scaled to accommodate most injection molders and mold frames. Alternatively, you can also design your own mold insert for the using the cavity diagrams of the master mold frames.

Now that you’ve designed and 3D printed your mold, you can mold the parts on your benchtop plastic injection molding machine.

Building a setup for DIY injection molding does require some investment. It takes both money and time to acquire the right equipment and to master using it. However, these costs are in many cases still lower than the cost of a single metal mold, so the eventual time and cost savings, once you’re up and running, will easily offset the initial effort.

Stay updated with the latest 3D printing news, interviews with experts from around the world and tutorials on how to leverage 3D printing.

Download our white paper for guidelines for using 3D printed molds in the injection molding process to lower costs and lead time and see real-life case studies with Braskem, Holimaker, and Novus Applications.

If you have more questions about the workflow, make make sure to check our article FAQ: Injection Molding With 3D Printed Molds.

Also called multi-shot or double-injection molding, two-shot injection molding is an over-molding process that adheres additional material—like thermoplastic elastomer (TPE)—to plastic substrates to improve the appearance, grip, handling, environmental resistance, or impact resistance of injection molded components. Two-shot injection molding is typically performed by multi-barrel injection molding machines, which add extra material shortly after forming the substrate to create strong bonds between the materials.

Fabrik Molded Plastics, Inc. is a custom injection and insert molding provider of thermoplastic products. We use the latest molding technologies and automation equipment in our full-service offerings to ensure we compete at the global level. Because we use the latest molding technologies and a  scientific approach in our molding processes, our clients can reap the benefits of our competitive advantage. Contact us today or request a free quote to start your custom project.

For prototyping and low-volume production (approximately 10-1000 parts), 3D printed injection molds provide a time- and cost-efficient solution. They also enable a more agile manufacturing approach, allowing engineers and designers to test mold designs, easily modify them, and then continue to iterate on their designs much faster, while being orders of magnitude cheaper than traditional CNC machining.

Rigid 10K Resin is an industrial-grade, highly glass-filled material, which provides a solution that can cope with a wider variety of geometries and injection molding processes. It has an HDT of 218°C @ 0.45 MPa and a tensile modulus of 10,000 MPa, making it strong, extremely stiff, and thermally stable.

Creating custom molds using a stereolithography (SLA) 3D printer, like the Form 3, is simple and convenient, allowing you to leverage the benefits of both 3D printing and traditional molding techniques.

The exact approach to DIY injection molding will vary based on your desired design and volume, but these tips and tricks will help increase your success rate.

To 3D print the mold, it’s essential to pick a material that can withstand the temperature and pressure on the mold during the injection molding process.

Grey Pro Resin has a lower thermal conductivity than High Temp Resin or Rigid Resin, which leads to a longer cooling time, but it is softer and can wear hundreds of cycles.

A high-performance desktop SLA 3D printer, like the Formlabs’ Form 3. The Form 3 can produce accurate molds with crisp features, and a smooth surface finish that will yield high-quality final molded parts. Beyond DIY injection molding, an SLA 3D printer is also a valuable asset for prototyping and other applications throughout product development.

Interested in other applications of 3D printed molds? Download our white paper that also covers thermoforming and casting with elastomers.

Turn the visibility of your current mold core off, and turn the other side on. Repeat the process to ensure that the object fully intersects with the inlet of the other half of the mold core. With your object lined up, you’re ready to subtract the area of two intersecting objects by using the “boolean difference” function in Blender.

For bonding to occur, the two parts undergoing the two-shot molding process must be chemically compatible. Fabrik consults with customers and material suppliers to ensure proper material selection for the specific application.

High Temp Resin offers a heat deflection temperature is 238 °C @ 0.45 MPa that is suitable for injection molding. This material is more brittle, but is recommended for materials with a high molding temperature and to reduce cooling time.

Adding two to five degrees of draft on surfaces perpendicular to the direction of pull will allow the part to be removed more easily and will minimize degradation of the mold.

Now, you can position your mold. Ensure that the object fully intersects with the inlet for the molten plastic during the injection molding process. Use orthographic mode, engaged via “toggle perspective/ortho,” to make this more straightforward.

Select the first half of your object, and choose the boolean option under the Modifiers Menu. Select the object you’re cutting, and make sure that the “difference” operation is selected. Apply the operator, and do the same for the other side. It should look something like the image below. If you get stuck here, this tutorial on adding interlocking components to a design may be helpful.

Your mold is now ready for printing. Export each half, making sure to check the “Selection Only” box in the Blender exporter.

Consider the desired properties of your object and the capabilities of your injection molder before you make your choice. From there, simply follow the bespoke instructions on your injection molder to quickly and efficiently produce your parts.

The two-shot molding process improves the final product in terms of feel, color, and functionality. There are many design opportunities to suit specific preferences. Examples of two-shot injection molded products include toothbrush handles, buttons, switches, caps and closures, and hand and power tools.

To reduce the visibility of print lines on the finished part, print the mold with a smaller layer height (50 or 25 microns per layer instead of the default 100). Note that this increases print time.

The two-shot injection molding process consists of two main phases. Similar to traditional injection molding, the first phase involves injecting resin into a mold, which is then cooled to form a solid part in the shape of the mold. The second phase involves overmolding the 1st shot by transferring it to a second cavity by robot or rotating platen. The two plastic resins will form a molecular bond and, once cooled and ejected, becomes a finished multi-resin molded part.

The conversation around 3D printing and injection molding is often oppositional, but it’s not always a question of one versus the other. By directly 3D printing parts or using 3D printed molds for injection molding for prototyping and low-volume production, you can leverage the benefits of both technologies. This will make your manufacturing process more time- and cost-efficient and allow you to bring products to the market faster.