Cracking - Medial Axis

cracking medial axis cracks/fissures form along the medial axis flow lines how to identify medial axis cracking can be diagnosed as follows cracks appear as thin, dark lines running along medial axis flow lines along medial axis flow lines medial axis flow lines occur on surfaces parallel to the platform, facing the window lines appear after baking parts look fine off of the printer and after washing medial axis cracking is differentiated by other types of cracking by where it occurs on the part this is an orientation based form of cracking that occurs solely along medial axis lines on flat surfaces facing the window reference cracking bulk docid\ njxfq6vzx7uurgxntaipy and cracking excessive solvent docid\ wyb5x 5127poknom ljjw for other types of cracking cause inconclusive cause inconclusive 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 part defects 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 washing follow solvent exposure times closely in the resin post processing protocol do not exceed maximum solvent exposure times and reduce exposure time when possible if parts are fully clean use swabs to remove excess solvent along medial axis lines after washing, dry parts on a blue towel or raised mesh (with air flow around the whole part) until all solvent is evaporated prior to baking baking check that the correct bake schedule was used per resin protocols resins most susceptible to cracking use a bake schedule that ramps up temperature gradually 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 orientation orient parts to keep window facing surfaces at an angle (recommended) keep surfaces parallel to the platform smaller than 10 mm across print plan adjustments reference print plan adjustments docid\ nxuk0dltz vemeau0dipn (login required) for guidance on the following parameters 1 pump up stage pump height parameters minimum pump height minimum distance from peak distance from peak multiplier force peak motor stop percentage if problems persist, please reach out to carbon support explanation & causes explanation medial axis cracking occurs along the medial axis flow lines on surfaces parallel to and facing the window resin flows in from all sides of a part, and where those varying flow directions meet is the medial axis flow lines these lines act as weak points in the material where stress during the chemical changes of baking can cause cracks the most susceptible conditions of medial axis cracking are large surfaces parallel to and facing the window excessive solvent exposure brittle resins ce and epx causes post processing how the part is handled in post processing is causing the defect post processing 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 medial axis 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 print preparation or part design cause root issue problem why defect presents orientation surfaces parallel to and facing the window medial axis lines only occur on surfaces parallel to and facing the window these lines are weak points that can crack under stress print plan adjustments print plan adjustments print plan adjustments adjust the print plan to optimize mid to high volume production and/or address part defects in doing so, adjustment may both prevent or cause defects below are adjustments that can cause this defect printing stage parameter type type of adjustment why defect presents 1 pump up pump height decrease decrease a shorter pump height may not provide enough time for resin to relax into the medial axis flow lines, leaving them weaker as a result