Rashing is a print failure in which a rough surface texture forms on one or both sides of an otherwise successful print.
For prints created on Formlabs printers, rashing produces an uneven or bumpy surface finish on one or both sides of a part.
Any of the following factors, or a combination of them, can cause rashing in prints:
- Expired resin
- Debris/clouding/damage in the resin tank
- Contaminated optical surfaces
- Restricted resin flow due to improper model orientation or overly dense supports
Successful troubleshooting first requires identifying the root cause. Follow the troubleshooting steps below to isolate and resolve the print failure. The steps check for possible causes, moving from the most likely cause to the least likely cause of the print failure.
Step 1: Check the resin’s expiration date
Expired resin can produce surface finish print failures such as rashing and ragging. The typical shelf life for Formlabs resins is one year in the cartridge. Learn more about resin lifetime and storage.
Step 2: Check the resin tank
Any debris, clouding, and/or damage in the resin tank can cause the laser light to diffuse, limiting the printer’s ability to fully cure the resin.
- Inspect the resin inside the resin tank for debris using a Form Finish Kit scraper and a fine-toothed comb. Remove any debris and cured resin in the tank using the scraper and the fine-toothed comb, or filter the resin.
- Inspect the PDMS (silicone) layer of the resin tank for clouding. Excessive clouding means the resin tank needs to be replaced with a new tank.
- Inspect the acrylic tank window on the underside of the resin tank for dirt, dust, and/or fingerprints. The clear tank window must be perfectly transparent for the best print results. To clean the tank window, only use Formlabs recommended steps and supplies.
TIP:Keep resin tanks clean and well-maintained between prints for reliable and successful printing.
Step 3: Check optical surfaces
Any contamination, dust, or debris on the printer’s optical surfaces can cause the laser light to diffuse or weaken, resulting in a print failure. Contamination is most likely to occur on an exposed optical surface in the printer.
On the Form 2, the primary exposed optical surface is the glass optical window, which sits below the resin tank and protects the mirrors from external contamination. Visit the interactive 3D Form 2 Glossary to learn more about the optical window and its location in the printer. On the Form 1+, the primary exposed optical surface is the large mirror, which sits below the resin tank.
- In the case of contamination, clean the contaminated surfaces using Formlabs instructions. Whether cleaning a Form 2 or a Form 1+, be sure to follow the instructions carefully because cleaning optical surfaces is a delicate process.
WARNING:Follow the optical surface cleaning guides exactly. Failure to follow instructions could result in returning the printer to Formlabs for repair.
Step 4: Check for restricted resin flow
On the Form 1+, and to a lesser extent on the Form 2, restricted resin flow can cause rashing. “Resin flow” describes the liquid resin’s movement throughout the resin tank during the print process.
Restricted resin flow can occur during the peel process or resin dispense attempts, oftentimes due to either improper model orientation or overly dense supports on the model.
- To resolve improper model orientation in PreForm, manually reorient the model so that the longest axis is parallel with the front of the printer.
- On the Form 1+, the parallel orientation allows resin to flow downstream during the peel process, which lowers the right side of the tank.
- On the Form 2, the parallel orientation, while less critical, also aids with resin flow in the tank.
- Both the part and the build platform displace resin when the printer lowers them into the resin tank. Overly dense supports trap resin, restricting resin flow in the tank and causing rashing. To resolve overly dense supports using PreForm:
Contacting Formlabs Support
If attempting the troubleshooting steps above does not resolve the print failure, feel free to contact Formlabs Support! Please provide as much of the following information as possible when submitting a support request:
- Describe the troubleshooting steps attempted so far. (Example: “I re-oriented the model in PreForm. I also inspected the resin tank and did not notice any damage, clouding, or debris.”)
- Resin type used and resin lot number. To find the lot number, look inside the skirt of the resin cartridge or on a sticker on the resin bottle. (e.g. Resin Type: White v2, Grey v3, etc.; Lot Number: This will be either in YYYYMMDD-## or YYYY/####### format.)
- Layer Thickness of the print. (Example: 0.100 mm, 0.05 mm, or 0.025 mm.)
- Relevant .form files of the model. If available, attach .form files of the model to the support request.
- Number of previous attempts printing the part and any instances of successful prints. If available, please share the .form file of the model. (Example: “I printed the file part2.form three times previously. The first and second were successful. The third one failed.”)
- Send diagnostic logs.