Fuse 1 generation printers display Error 260 when one of the printer's temperature sensors reports readings that are below the minimum acceptable setpoint threshold for a heater after running it for approximately 15 seconds at 100% duty cycle. The printer has three Resistance Temperature Detector (RTD) sensors as well as an infrared (IR) sensor. Each build chamber also has three RTD sensors.

The error message subcode indicates which heater is failing to reach its threshold.

• 260/1: Hopper trough RTD
• 260/2: Buffer trough RTD
• 260/3: Air heater RTD
• 260/4: Build chamber piston top RTD
• 260/5: Build chamber lower wall RTD
• 260/6: Build chamber upper wall RTD
• 260/9: IR sensor

Unlike Errors 258, 259, and 261, this error is not usually associated with a broken RTD.

• Error 260 shown on printer touchscreen
• Print does not start
• Print job fails

• A heater is failing
• The printer is too cold at the start of the print
• A connection issue with the heater or RTD
• The inlet voltage is too low
• Electrical noise or shared electrical circuit
• Underdosing when printing with materials that do not have PrinterWatcher enabled
• IR sensor contamination

Case 1: Heater failure
A heater that is generally underperforming may fail to reach its target temperature. With 230 V units in particular, the most common trigger of this failure mode is an air heater that has fallen below its performance threshold and is thus unable to adequately bring the print enclosure air temperature up to a minimum threshold of 150 ºC. This is also possible, albeit less likely, with 120 V units.

Case 2: Low ambient temperature at the start of the print
Another common cause of this issue is the print environment being too cold at the beginning of the print. In this case, the heater is unable to reach the setpoint by the allotted time. Bring the print environment to 20–27 ºC (68–81 ºF), as outlined in the Fuse 1 generation site preparation guide. Printers in cold environments can also often reach their target temperature by running multiple print attempts in a row, essentially preheating the printer. This is not recommended as a long term solution, as this may impact thermal uniformity of the print or may damage heaters.

Case 3: Connection issue with the heater or RTD
A poor connection with either the heater or RTD can cause the heater to underperform or produce inaccurate resistance readings from the RTD. This differs from a fully broken RTD, which generally does not trigger Error 260. This type of connection issue commonly affects build chamber heaters and RTDs, often due to an improperly seated or contaminated build chamber plug. If Error 260 appears alongside Error 258, 259, or 261, it's more likely that the problem lies with the RTD rather than the heater.

Case 4: Insufficient inlet voltage
If the input voltage to the printer is too low, there may not be enough power to the heaters to reach the set point in the allotted time. This is a potential root cause in any country whose mains electricity is less than 120 V, such as Japan (100 V) and Taiwan (110 V).

Case 5: Electrical noise or shared electrical circuit
Power surges, fluctuations, or electrical noise from other devices sharing the printer’s circuit can disrupt the RTD signals, leading to false low-temperature readings.

Case 6: Underdosing when printing with materials that do not have PrinterWatcher enabled
Fuse 1 generation printers do not use PrinterWatcher to monitor the print bed when printing with certain materials (e.g., Nylon 11 CF and TPU 90A). When severe underdosing occurs with these materials, it can affect the IR sensor readings, causing the bed temperature to drop as the material is farther away than expected from the heater and sensor.

Case 7: IR sensor contamination
If the error is related to the bed temperature, it can be caused by a contaminated IR sensor or IR sensor cone. Contamination can cause the sensor to read the temperature lower than it is in reality. In these cases, the issue will likely occur alongside symptoms of printing too hot (hard caking, Surface Armor that is difficult to remove, dimpling, bed tearing, melting, etc.).

1. Determine which sensor was reporting low temperatures, either by:
• Checking the error subcode on the printer touchscreen.
• Checking the error history on the printer touchscreen.
• Downloading your printer’s history through PreForm and checking the error history.
2. Check the ambient temperature level at the beginning of the print and confirm that it was above 18 °C.
1. If the ambient temperature was below 18 °C at the beginning of the print, increase the temperature of the print environment before trying again.
3. Confirm that you are following all site requirements, particularly that the printer is on its own dedicated circuit.
   1. If you are located in a country that uses 100 V or 110 V mains electricity, consider purchasing a transformer to step the voltage up to 120 V.

Air heater

1. Over time, 230 V Fuse 1 air heaters may experience performance degradation. If the air heater is operational but unable to reach its target temperature, it likely needs replacement. Fuse 1 generation air heaters are available for purchase on the Formlabs Store. Contact Formlabs Support or a certified service provider for additional assistance.
2. It is possible but unlikely for a Fuse 1+ 30W air heater to fail entirely. If this appears to be the case, contact Formlabs Support or a certified service provider

Quartz tube heaters and bed temperature issues

1. If you are printing with Nylon 11 CF Powder or TPU 90A Powder, check for signs of underdosing. When underdosing occurs with these materials the print will still continue, as PrinterWatcher is not enabled for these materials. Because the powder level is further from the IR sensor than expected, the measured temperature will be lower than the actual temperature, eventually leading to Error 260. Follow the steps in the support article Underdosing (SLS) to address underdosing to resolve the issue.
2. Check for signs of the printer running too hot. Hard caking, difficult to remove Surface Armor, dimpling, bed tearing, and melting are all signs of the printer running too hot. If this is the case, refer to the relevant support articles for each specific issue.
3. Check for localized melting:
1. If the powder on the print bed is melting on one side, the quartz tube heater on the side opposite the melting may not be functioning. In this case, the next print is likely to result in Error 180. To resolve this issue, replace the quartz tube(s). Fuse 1 generation quartz tube heaters are available for purchase on the Formlabs Store. Contact Formlabs Support or a certified service provider for additional assistance.

Build chamber heaters

1. Reseat the build chamber plug in the printer, making sure to press firmly in order to make a good connection with all pins in the plug.
2. Clean the build chamber connector as well as the printer's build chamber socket with compressed air.
3. Inspect the build chamber connector and printer's build chamber socket for damaged pins.
1. If there are any damaged pins, contact Formlabs Support or a certified service provider.
4. If the issue persists, confirm whether it happens with one specific build chamber or with multiple build chambers.
1. If the issue is specific to one build chamber, the heater in question may be faulty or damaged. Replace the build chamber.
2. If the issue persists across multiple build chambers, it may be an issue with the build chamber socket harness on the printer. Contact Formlabs Support or a certified service provider.