Brittle parts are more fragile than expected and may break under stress. Each Formlabs resin has its own material properties that are important to consider when choosing the right material.

• Parts break or crumble under stress
• Parts with lower than expected strength
• Parts with lower than expected flexural modulus

Any of the following factors, or a combination of them, can cause prints to become brittle:

• Improper resin storage
• Expired resin
• Material properties of the resin type
• Deviations from the recommended steps for post-processing
• Improper part storage
• Custom print settings

Step 1: Check the resin cartridge storage

Improperly stored resin cartridges may lead to brittle parts.

• Store resin according to the SDS, away from direct sunlight in a dry, cool, and well-ventilated area.
• Before starting a print, shake the resin cartridge and stir the resin in the tank with a tool that has rounded edges.

Step 2: Check the resin expiration date

Towards the end of a resin’s recommended lifetime, its photoreactivity may decrease and prints attempted with the resin may fail. A resin may also print successfully for a longer lifetime than indicated, depending on handling, use, and storage.

Check the lot number on the bottom of the resin cartridge to ensure the resin is within its recommended lifespan. The lot number on most resin cartridges is formatted YYYYMMDD or YYYY-MM. If the lot number begins with 2020 or an earlier year, the resin is most likely past its recommended lifetime and may not print properly.

Step 3: Check the material properties for the resin

Each Formlabs resin has its own material properties. For example, parts printed in Rigid 10K Resin may be more brittle than those printed in less stiff resins. Refer to the Safety Data Sheet (SDS) and Technical Data Sheet (TDS) for the specific properties of each resin.

Step 4: Follow the recommended steps for post-processing

Post-processing requirements vary based on resin type. Follow the recommended steps for washing and post-curing parts for your specific resin. Any modifications can lead to brittle parts.

Ensure parts are completely dry before post-curing. Damp parts may not post-cure properly.

Step 5: Store parts properly

Do not store printed parts in direct sunlight. Parts may become more brittle and change color due to the 405 nm light and heat in sunlight. Parts may also become more brittle with age.

Step 6: Check for custom print settings

The PreForm Print Settings Editor allows you to customize print settings for Formlabs materials and certified third-party materials. Custom print settings may affect the material properties of printed parts.

If you have an issue with brittle parts when printing with custom print settings, revert to the Formlabs default print settings. Due to the complex nature of custom print settings, Formlabs is unable to assist with fine-tuning or developing custom print settings.

Step 7: Contact Formlabs Support

If the issue persists, contact Formlabs Support or your authorized reseller and upload diagnostic logs to speed up resolution.