Silicone 40A Resin is a pure silicone, without added monomer or acrylate, which combines the material properties of cast silicone with the benefits of 3D printing. Use Silicone 40A Resin to fabricate soft, pliable, and durable parts.

Printing with Silicone 40A Resin eliminates the need for tooling and labor-intensive casting processes, enabling you to produce custom silicone parts with isotropic properties and complex geometries that aren’t possible with casting or molding.

To learn more about the performance or specific material properties of Silicone 40A Resin, refer to the Safety Data Sheet (SDS) and Technical Data Sheet (TDS). Always consult the SDS as the primary source of information to understand safety and handling of Formlabs materials.

Made by Formlabs:

• Compatible Formlabs SLA printer with up-to-date firmware
• PreForm software (most recent version)
• Build platform
• Resin tank
• Silicone 40A Resin
• Form Wash or Finish Kit
• Form Cure or Form Cure L

Made by third parties:

To familiarize yourself with the Silicone 40A Resin workflow, Formlabs recommends printing simpler parts like this watch strap or lattice (FORM file, STL file) that you can print directly on the build platform without supports.

As you start to print your own models, be sure to follow our design guidelines for Silicone 40A Resin and to properly orient and support your parts.

In particular:

• For best results, print parts directly on the build platform with no or minimal supports, or with custom designed tearaway supports. If your parts require additional supports, use auto-orient and default supports in PreForm.
• Ensure that the build platform is clean and properly aligned for improved adherence.
• Models with no radius or a small radius around the base print more reliability than those with a larger radius.
• Print parts with overhangs and large cross-sectional areas close to the build platform when possible.

When orienting parts in PreForm and generating supports:

• Orient parts according to Formlabs best practices.
• Print directly on the build platform when possible.
• Formlabs recommends having a dedicated build platform for printing with Silicone 40A Resin, since cross-contamination with other resins can cause print failures.
• Orient parts so that the bulk of the part or feature is closer to the build platform.
• Angle important surfaces away from the build platform.
• Orient long parts parallel to the build platform. The maximum aspect ratio recommended for printing perpendicularly to the build platform is 8:1.
• Orient to avoid cups, which PreForm highlights in yellow.
• If surface finish is a concern, you may wish to reduce the size of support touchpoints, although this may increase the risk of print failures.

To prepare a model for printing in PreForm:

1. Open a model.
2. Select the resin, resin version, and the desired layer thickness.
3. Orient to preserve fine details.
4. Generate supports.
5. Send the print job to the printer.

Follow the instructions in the Silicone 40A Resin IPA sonication wash guide for best results with washing Silicone 40A parts.

Alternatively, Silicone 40A parts can be washed in a mixture of 80% IPA and 20% n-Butyl Acetate. For example, if using the Form Wash V1, add a 2 L bottle of n-Butyl Acetate to the wash bucket and then fill to the maximum fill line with IPA. The Form Wash V2 has multiple fill lines on the wash bucket, corresponding to 7, 10, and 14 L, so use 1.4, 2, or 2.8 L of n-Butyl Acetate, respectively. Formlabs has not tested the efficacy of this solvent mixture with other materials and does not recommend using it to wash parts printed in other Formlabs resins. Do not wash with IPA alone unless following the Silicone 40A Resin IPA sonication wash guide.

The Form Wash agitates the solvent bath and removes parts from the bath after a set time. Wash parts according to the support article Form Wash time settings. Pay particular attention to information that affects mechanical properties or biocompatibility requirements.

If the model is hollow or has internal channels, ensure liquid resin is flushed out thoroughly from these features. Allow parts to fully dry before post-curing.

For the best results, Formlabs recommends removing supports after washing but before post-curing. For the best surface finish, pull gently at support structures and slide a sharp hobby knife along the part surface. Take care not to damage the part itself. You may wish to use an ultrasonic cutter for greater precision.

It may be possible to simply pull off supports connected to thicker parts, but remove supports on fine features or thin walls using flush cutters or a hobby knife.

You may also wish to use miniature mounted Scotch Brite wheels and a rotary tool to grind down support marks on green or post-cured parts.

Silicone 40A Resin requires post-curing to reach its optimal mechanical properties. Post-cure Silicone 40A Resin in water in a glass beaker placed inside the Form Cure.

Post-cured silicone parts have a harmless odor that dissipates with time. To mask this odor, add Febreze HD to the water in the glass beaker before post-curing. For each 500 mL of water, add 12.5 g of Febreze HD. To measure the amount of Febreze needed, spray around 12.5 grams of Febreze HD into an empty container on a tared scale.

Refer to the support article Form Cure time and temperature settings for post-curing recommendations.

Before using adhesives, ensure that parts have been thoroughly washed and dried and that no surfaces are tacky or dusty. To ensure successful bonding, Formlabs recommends using a primer such as the DOWSIL 1200 series or a medical primer before using adhesives. Follow the manufacturer's instructions for using these primers to ensure best results.

After the primer has dried, use a silicone adhesive such as DOWSIL 734. Do not use cyanoacrylate glues, as they are brittle and leave a crust on the silicone.

• Design guidelines and tearaway supports for Silicone 40A
• Advanced tips for printing with Silicone 40A Resin
• Troubleshooting issues with parts printed in Silicone 40A Resin
• Silicone 40A Resin safety data sheet (SDS)
• Biocompatibility certification (ISO-10993) for Silicone 40A Resin