Cracking - Bulk

12 min

Bulk Cracking

Cracks/fissures form during the thermal curing process at high stress points.

How to Identify

Bulk cracking can be diagnosed as follows:

Cracks appear as thin, dark lines in the part, occurring at stress points such as a corner
Lines appear after baking. Parts look fine off of the printer and after washing.

Bulk cracking is differentiated by other types of cracking by where it occurs on the part. This is a geometry-based form of cracking that occurs solely at stress points.

Reference Cracking - Medial Axis and Cracking - Excessive Solvent for other types of cracking.

Cause - Inconclusive

Troubleshooting

It is recommended that you review all the possible solutions before taking action to ensure you are pursuing the best course of action.

If the best course of action is not apparent, try the troubleshooting options in the order listed. Refer here for more tips.

Process, Material, and Hardware Checks

If any of these conditions apply to your print, take the corrective action and reprint to see if the problem is resolved.

Print Preparation or Part Design Adjustments

The following solutions will address print or part-related causes of the defects. Choose among the suggested actions below and select the best approach for your application. Usually only one type of adjustment is needed.

If problems persist, please reach out to Carbon Support.

Explanation & Causes

Explanation

Bulk cracking occurs when stresses build up during the print and are then released in the bake. The most susceptible conditions of bulk cracking are:

Sharp inside corners
Excessive solvent exposure
Brittle resins: EPX

Causes

Post-Processing

How the part is handled in post-processing is causing the defect.

Root Issue	Problem	Why Defect Presents
Washing	Solvent exposure	Too much solvent exposure weakens the material, making stress points weaker.
Baking	Wrong bake schedule	The most common resins for bulk cracking are the brittle resins (EPX) that use a ramping program to raise the temperature slowly and prevent thermal shock.

Print Preparation or Part Design

How the part is oriented, supported, or designed is causing the defect.

Root Issue	Problem	Why Defect Presents
Design	Sharp inside corners	Stress points such as sharp inside corners are weaker under thermal shock.