SIL 30
Soft touch, biocompatible, and tear resistant
SIL 30 is a silicone urethane. It is the first additive material to offer a unique combination of biocompatibility, low durometer, and tear-resistance.
This material opens up the ability to print customized applications for comfortable skin contact products such as headphones, wristbands, and various attachments for wearables.
About the Material Material overview and uses cases
Technical Data Sheet Mechanical properties and data
Safety Data Sheet Login required
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SIL 30 is ideal for skin contact applications, in part, because of silicone's unique breathability with oxygen. While this provides an exceptional benefit in wearable technology, SIL 30 reacts to the UV light and oxygen in the DLS printing process with greater susceptibility to overcure and cure-through.
The benefit this gives SIL 30 is an exceptionally smooth surface finish and soft features that can be well suited to a wearable application. The downside is when accuracy of small features or legibility of text is important.
Small features can be challenging in SIL 30, and is especially apparent with regular shapes and repeating features. Excess curing can range from 0.3 - 0.5 mm, whereas other materials average feature size variation around 0.1 mm.
Design Mitigations
- Provide greater compensation for overcure and cure-through by making features larger (by 0.3 - 0.5 mm)
- Reassess your tolerances and provide a wider range where feasible
- Use organically shaped features with less repetition
SIL 30 will resolve small details with softer edges, which can make small embossed or engraved text more difficult to read.
Embossed text printed in SIL 30
Embossed text printed in a rigid resin
Lattices make great performative parts with elastomeric materials while also reducing print times, consuming less resin, and creating unique parts only made possible with additive manufacturing.
Challenges with SIL 30 Lattices
- Accuracy variation due to small features (see above)
- Difficulty washing due to resin entrapment
- Structural fragility in green state (before thermal curing)
Design Mitigations
Design lattices with larger cell sizes than standard guidelines to promote better solvent flow for easier washing.
Use thicker struts than other resins to avoid strut breakage during processing.
Reassess whether a lattice or SIL 30 is the best choice for your application.
Large cross sections parallel to the build platform can show medial axis flow lines across the surface. This is strictly a cosmetic issue that results from fluid dynamics during printing.
SIL 30's flow lines appear as a yellowish discoloration on the otherwise gray surface.
SIL 30 is great at printing a wider range of geometries than most elastomeric offerings because of increased stiffness during printing.
By printing in a stiff green state, SIL 30 can minimize or eliminate the use of supports that may be needed in other elastomers.
SIL 30 is very flexible after thermal curing, losing the green state stiffness.
When supports are needed, use fence over bar supports (where geometry allows) to minimize tearing when removing supports before curing.
Unlike other Carbon 2-part resins, SIL 30 requires a burn off step with every dispense, not just with a new cartridge.
The viscosity difference between the two components of SIL 30 is exceptional and the plunger for the thinner Part B (clear) component always begins moving before the thicker Part A (gray) component. The clear Part B component therefore gets a head start in the mixing tip.
By burning off the first 10 ml of resin in a disposable foil cup, you ensure that all of the unmixed Part B is not used in the print.
Resin that is not mixed properly will likely result in print defects and compromised material properties.
If you are using the Albion Dispenser, pre-heating the resin cartridge at 60°C for 30-60 minutes is recommended. The pre-heating will facilitate resin flow with a reduction in viscosity.
If using the Cox Single-Drive Dispenser, SIL 30 may experience a mixing issue due to the difference in the two plunger rails. The upper rail is weaker and struggles with the thick viscosity of the Part A component of SIL 30.
The Cox Dual-Drive Dispenser and Albion Dispenser (retired) do not have this issue.
Normal Dispense After following the standard burn off step, a normal dispense will appear smooth and consistent.
Abnormal Dispense The dispensed resin will appear inconsistent: areas of Part A and Part B unmixed are visible.
During an Abnormal Dispense
Bowing upper rail When the thicker Part A component is aligned with the weaker upper rail, movement is inhibited and the upper rail bows while the lower rail moves forward.
Part B Thin and clear, the part B has little resistance and comes out of the mixing tip first (even after a burn off).
Misaligned plungers in cartridge With this restriction in movement, the plungers in the cartridge end up misaligned.
Part A When the stress of the upper rail builds up too much, then the Part A, thick and gray, overtakes the dispense.
Preventing an Abnormal Dispense
Use a fully charged battery
Verify the correct speed setting
Load the dispenser with Part B, thin and clear, in the upper position with the weaker rail, and Part A, thick and gray, in the lower position with the stronger rail.
- Dispense the full cartridge.
- Stir resin until all visual marbling and areas of thick resin are smoothly mixed.
Release Film is recommended with SIL 30 due to its fragile green state. Because of this, parts are easily damaged during removal from the platform.
Release film provides lower part adhesion than the platform, so parts can be removed with less force.
Depending on part size and geometry, parts printed on release film can be removed from the platform with a couple methods.
Peeling Method
Pull up the film with the parts on them* and then remove the film from the parts with minimal handling by peeling it off.
*You can squirt a small amount of IPA between the film and platform to make removal of the film easier.
Scraper Method
Use the scraper to detach parts from the film.
An optimal SIL 30 part is self-supporting. If your part is printed on supports, tearing them off is not recommended. Use a tool either before or after baking.
Before In the green state, remove the supports with a small blade to avoid damaging the part.
After Remove the supports after baking with flush cutters. Note that surface finish at cut surfaces will vary.
