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Raft silhouetting

“Raft silhouetting” describes a print defect in which the early layers adhere to the build platform, creating a silhouette of the raft or initial layers. After these initial layers that create the raft silhouette, the remainder of the part does not print.

Contamination, dust, or debris on the printer’s optical surfaces can diffuse or weaken laser light, causing a print failure where only the early layers of the print adhere to the build platform.

Visual symptoms

Only the first few layers adhere to the build platform.
The rest of the part is missing from the build platform, and may be present as cured resin in the tank bottom or absent entirely.

Common causes

Raft silhouettes are usually caused by optical surface contamination that blurs or weakens the laser light before it reaches the resin.

The early layers of a print receive additional laser curing, so these layers can cure successfully even if contamination or clouding weaken the laser. Further layers may fail to cure, either partially or completely.

Any of the following factors, or a combination of them, can blur or weaken laser light:

Debris/clouding/damage in resin tank
Contaminated optical surfaces
- Resin tank acrylic window (Form 2)
- Flexible film (Form 3/Form 3B, Form 3L/Form 3BL)
- Glass optical window (Form 2, Form 3/Form 3B, Form 3L/Form 3BL)
- Main mirror (Form 2)

Troubleshooting steps

Successful troubleshooting identifies symptoms and systematically narrows down the root cause of an issue. Follow the troubleshooting steps below to check for possible causes, beginning with the most likely cause of the print defect.

Note:

Make sure that your firmware and PreForm versions are up to date. To check your printer’s firmware version, refer to the support article Checking the firmware version for Formlabs SLA printers. To update your PreForm version, refer to the FAQ article How do I update PreForm?.

Step 1: Check the resin tank

Any damage or debris in or on the resin tank can block the laser at that location, preventing the resin directly above it from curing. Inspect the inside and underside of the tank for dirt, dust, and/or fingerprints. The bottom of the tank must be clean for the best print results.

Form 2	Formlabs LFS printer (Form 3 or later)
Inspect the resin tank for debris with a scraper. Remove any failed prints and cured resin with the scraper, being careful not to gouge or cut the elastic layer at the bottom of the tank. Filter the resin to remove any contamination or cured resin. If using Resin Tank LT, skip this step. Inspect the elastic layer of the standard resin tank for clouding. Severe clouding means a standard resin tank needs to be replaced. Inspect the acrylic tank window on the underside of the resin tank for dirt, dust, cured resin, or fingerprints. Clean it with Formlabs recommended steps and supplies.	Inspect the resin tank for debris with the tank tool. Remove any failed prints and cured resin using the tank tool. Form 3/Form 3B Form 3L/Form 3BL Alternatively, remove any failed prints and cured resin by printing a cleaning mesh. Form 3/Form 3B Form 3L/Form 3BL Filter the resin to remove any contamination or cured resin. Form 3/Form 3B Form 3L/Form 3BL Inspect the flexible film at the bottom of the resin tank for scratches or wear. Excessive wear means the resin tank needs to be replaced. Form 3/Form 3B Form 3L/Form 3BL Inspect the underside of the flexible film for dirt, dust, or fingerprints. Clean it with Formlabs recommended steps and supplies. Form 3/Form 3B Form 3L/Form 3BL

Form 2

Formlabs LFS printer (Form 3 or later)

Inspect the resin tank for debris with a scraper.
Remove any failed prints and cured resin with the scraper, being careful not to gouge or cut the elastic layer at the bottom of the tank.
Filter the resin to remove any contamination or cured resin.
If using Resin Tank LT, skip this step. Inspect the elastic layer of the standard resin tank for clouding. Severe clouding means a standard resin tank needs to be replaced.
Inspect the acrylic tank window on the underside of the resin tank for dirt, dust, cured resin, or fingerprints. Clean it with Formlabs recommended steps and supplies.

Inspect the resin tank for debris with the tank tool.
Remove any failed prints and cured resin using the tank tool.
- Form 3/Form 3B
- Form 3L/Form 3BL
Alternatively, remove any failed prints and cured resin by printing a cleaning mesh.
- Form 3/Form 3B
- Form 3L/Form 3BL
Filter the resin to remove any contamination or cured resin.
- Form 3/Form 3B
- Form 3L/Form 3BL
Inspect the flexible film at the bottom of the resin tank for scratches or wear. Excessive wear means the resin tank needs to be replaced.
- Form 3/Form 3B
- Form 3L/Form 3BL
Inspect the underside of the flexible film for dirt, dust, or fingerprints. Clean it with Formlabs recommended steps and supplies.
- Form 3/Form 3B
- Form 3L/Form 3BL

Tip:

Keep resin tanks clean and well-maintained between prints for reliable and successful printing.

Step 2: Check the optical window

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.

Form 2	Formlabs LFS printer (Form 3 or later)
The optical surface most likely to be contaminated is the glass optical window beneath the resin tank that protects internal components from contamination. Inspect the optical window on the Form 2 or for contamination. Follow the instructions in Cleaning the glass optical window (Form 2). If streaks are difficult to remove, contact Formlabs Support or your authorized reseller.	The optical surface most likely to be contaminated is the glass optical window, which sits atop the Light Processing Unit (LPU). With the printer plugged in and powered on, tap the wrench icon to access the Settings screen, then tap Maintenance > Motor Moves. The Motor Moves screen appears. Tap and hold Left (<) to move the LPU housing to the middle of the printer cavity. Other controls on this screen fully sweep the LPU housing across the printer cavity and control the build platform carriage. When prompted by the touchscreen, disconnect the power cable before continuing with maintenance. Inspect the optical window for contamination. Follow the instructions for cleaning the glass optical window. Form 3/Form 3B Form 3L/Form 3BL If streaks are difficult to remove, contact Formlabs Support or your authorized reseller.

Form 2

Formlabs LFS printer (Form 3 or later)

The optical surface most likely to be contaminated is the glass optical window beneath the resin tank that protects internal components from contamination.

Inspect the optical window on the Form 2 or for contamination.
Follow the instructions in Cleaning the glass optical window (Form 2). If streaks are difficult to remove, contact Formlabs Support or your authorized reseller.

The optical surface most likely to be contaminated is the glass optical window, which sits atop the Light Processing Unit (LPU).

With the printer plugged in and powered on, tap the wrench icon to access the Settings screen, then tap Maintenance > Motor Moves. The Motor Moves screen appears. Tap and hold Left (<) to move the LPU housing to the middle of the printer cavity. Other controls on this screen fully sweep the LPU housing across the printer cavity and control the build platform carriage.
When prompted by the touchscreen, disconnect the power cable before continuing with maintenance.
Inspect the optical window for contamination.
Follow the instructions for cleaning the glass optical window.
- Form 3/Form 3B
- Form 3L/Form 3BL
If streaks are difficult to remove, contact Formlabs Support or your authorized reseller.

Notice:

Follow the optical surface cleaning guides exactly. Failure to follow instructions could damage the printer.

Step 3: Check main mirror (Form 2)

With the Form 2 cover open, look through the optical window to check for contamination on the main mirror.

If the main mirror appears to be contaminated, contact Formlabs Support or your authorized reseller for cleaning instructions.

Contacting Formlabs Support

If the troubleshooting steps above do not resolve the print failure, contact Formlabs Support or your authorized reseller.

To help us provide the fastest and most effective response to your issue, please follow these steps:

Upload diagnostic logs
- On a Form 2
- On a Form 3/Form 3B
- On a Form 3L/Form 3BL
Serial name of the printer
- The serial name is on the back panel of the printer in the format AdjectiveAnimal.
- On a Form 2: Tap the printer icon on the home screen. The Your Printer screen appears.
- On a Formlabs LFS printer (Form 3 or later): Tap the printer icon on the Home screen.
Troubleshooting steps attempted
- Example: “I reoriented the model in PreForm. I inspected the resin tank and did not notice any damage, clouding, or debris.”
Resin formulation and lot number
- The lot number is inside the skirt of the resin cartridge.
Layer thickness
- On a Form 2: Tap the queue icon on the home screen. The Jobs screen appears.
- On a Formlabs LFS printer (Form 3 or later): Tap Queue on the Home screen. The Queue screen appears.
Relevant FORM files
- If available, attach FORM files of the model to the support request.
Previous attempts to print the part and any successful prints
- Example: “I printed the file part2.form three times previously. The first and second were successful. The third one failed.”