The workflow for low-volume injection molding includes the following seven steps:

1) Mold Design

Design the mold for your part in the CAD software of your choice. Adhere to common design rules for additive manufacturing and injection mold design. Learn some Design recommendations specific to polymer 3D printed molds.

Upload your design into 3D print preparation software. Prepare your print and send it to your 3D printer.

2) Mold 3D Printing

Choose a 3D printing material and begin your print. Rigid 10K Resin at 50 micron layer height is an ideal choice for most mold designs as it combines high strength, stiffness, and thermal resistance.

When possible, it is advised to print the mold flat, directly on the build platform without any supports, in order to reduce warpage.

After washing and post-curing, your 3D printed mold is ready to be integrated into your injection molding process.

 3) Mold Assembly

Prior to assembly, you may choose to finish the mold to meet critical dimensions with hand-sanding, desktop or CNC machining.

It is recommended to place the printed mold inside a standard metal frame, or a Master Unit Die, to support against high pressures and extend the lifetime of your printed mold. Carefully assemble the 3D printed mold inside the metal frame. Add ejector pins, inserts, side-action parts, and other components as needed.

Install the assembled mold in your injection molding machine.

 4) Mold Clamping

Insert the plastic pellets, input the required settings, and begin production.  A lower clamping force is suggested, particularly if the printed mold is not protected by a metal frame.

A broad range of thermoplastics can be injected with 3D printed molds such as TPE, PP, PE, ABS, POM, ASA, PA, PC, or TPU.

 5) Injection

It may take a few shots to identify your ideal process conditions as many factors are at play including part geometry, choice of plastic, injection temperatures and pressures, and other parameters. Reduce injection pressure and temperature as much as possible.

With one printed mold, some users are usually injecting 100s of parts in easy-to-process plastics such as TPE, PP, and PE with temperatures up to 250°C. With plastics that require higher injection temperature such as PA or PC, the 3D printed mold might have a shorter lifespan.

 6) Cooling

The cooling time of a polymer printed mold is longer than that of a metal mold, as thermal transfer occurs slower in plastic than metal. As such, adding cooling channels to your printed mold is generally not suggested. Instead, cooling can be accelerated by applying compressed air to cool the mold, or using interchangeable stacks.

 7) Demolding

Demold the part either manually or automatically with ejector pins. Apply a release agent for thermoplastics with high viscosity. Mold releases are widely available and silicone mold releases.