PRUSA i3 MK3 Troubleshooting

The first layer of the print is uneven or is not adhering to the bed.

The first layer of a print may not adhere to the bed if it is unclean. Remove the bed (allow to cool if heated) and wipe down with Isopropyl alcohol.

The nozzle may be too close, or too far away from the print bed. Use the "Live Adjust Z" function to raise or lower the Z distance between the nozzle and the bed. The Z height is too low if the print has major overlaps causing a rough surface. The Z is too high if the plastic is not adhering, or the print lines are not connecting properly. A correctly adjusted Z distance will result in a properly adhered first layer with a smooth finish.

An uneven bed surface may cause problems with the first layer of a print. to ensure an even bed surface, perform a "First Layer Calibration" within the calibration menu on the printer.

The plastic may not adhere properly to the surface if the extruder is moving too quickly. Adjust the speed in settings to 75% for the first couple of layers, then raise back to 100% for the rest of the print.

The plastic will not adhere to the bed if the temperature is incorrect. First, locate the suggested bed temperature on the filament spool, then adjust the temperature accordingly.

The extruder will not push the filament through the hot end.

If the filament is not extruding from the nozzle, it could potentially be clogged. The first step is to attempt to unload the filament from the extruder and visually check its appearance. If the tip of the filament has formed an irregular blob that is unable to be fed through the nozzle, cut off the end of the filament at a 45° angle and reinsert it.

If the filament will not unload on its own, raise the nozzle temperature in the printer settings to 260 °C for PLA or TPU; or 280 °C for PETG or ABS. Wait a few minutes for the nozzle to begin melting the filament inside the nozzle, then manually push the filament through the extruder to clear any blockage inside.

If the filament is not extruding from the nozzle, the temperature may be incorrect. First, check the filament spool to locate the suggested temperature for the filament you are using. If the temperature is incorrect on the printer, go to Settings -> Temperature -> Nozzle -> then raise or lower the nozzle temperature depending on the suggested temperature.

If the filament is not continuously extruding from the nozzle and the spool stops rotating, it may be due to impaired feeding from the filament spool.

First, ensure the nozzle has been heated to the appropriate temperature. To set the appropriate nozzle temperature, see Incorrect Extruder Temperature above. Next, remove the filament from the extruder head and ensure it is wrapped around the spool correctly. The strands of filament should not be crossed over each other. After the strands of filament have been uncrossed, clip the end of the filament at a 45° angle and insert the filament back into the extruder head.

A "Thermal Anomaly Error" appears on the screen and the print is stopped.

The first check to fix a "thermal anomaly error" is to perform a "Thermal Model Calibration" within the calibration settings to ensure the thermistors are reading the temperature properly.

A recent firmware upgrade may cause the printer to display a "thermal anomaly error." View the Thermistor Calibration above to troubleshoot this issue.

A broken or faulty Extruder Thermistor will relay an incorrect temperature back to the thermal model of the printer. See the Extruder Thermistor replacement guide to address this issue.

A broken or faulty Heat Bed Thermistor will relay an incorrect temperature back to the thermal model of the printer. See the Heat Bed Thermistor replacement guide to address this issue.

The layers of the print are shifting horizontally or vertically, resulting in a failed print

Layer-shifting issues can be attributed to an unstable surface or an insecure bed. Some simple solutions for this issue are by making sure the printer is placed on a stable surface that doesn't wobble, or to check the bed and make sure it is cleaned and properly secured in place.

If the layers of a print are shifting, the printer may need to be calibrated. Under the printer's calibration menu, run the XYZ Calibration.

Loose or broken X & Y axis belts can cause layers to shift or print geometry to obstruct. The Y-axis belt is located under the heat bed and the X-axis belt is the horizontal belt the extruder carriage moves across. If the belt is broken, see the X&Y Belt Replacement Guide.

If the X-axis belt appears to be loose, use an Allen key to slightly loosen the top two front-facing screws and make sure they have space to their right to move. While rotating the motor with one hand, tighten the diagonal-facing top screw of the X-axis motor. If the Y-axis belt appears to be loose, move the printer to the edge of a table with the screen hanging over the edge. On the front plate of the printer's metal frame, behind the screen, you will find the orange Y-axis belt idler. If you have a gap between the idler and the front plate of the frame, use an Allen key to tighten the screws. Tightening the screws will secure the Y-axis belt.

A "Crash Detected" message appears on the screen and the print is stopped.

A dislodged part can cause an XY Crash during a print. This can happen when a part becomes unstuck from the print bed and comes in contact with the extruder or its path. See First Layer Issues and re-print.

If an XY Crash is detected, the printer may need to be calibrated. Under the printer's calibration menu, run the XYZ Calibration.

Loose or broken X & Y-axis belts can cause an XY Crash error to appear on the screen. The Y-axis belt is located under the heat bed and the X-axis belt is the horizontal belt the extruder carriage moves across. If the belt is broken, see the X&Y Belt Replacement Guide.

If the X-axis belt appears to be loose, use an Allen key to slightly loosen the top two front-facing screws and make sure they have space to their right to move. While rotating the motor with one hand, tighten the diagonal-facing top screw of the X-axis motor. If the Y-axis belt appears to be loose, move the printer to the edge of a table with the screen hanging over the edge. On the front plate of the printer's metal frame, behind the screen, you will find the orange Y-axis belt idler. If you have a gap between the idler and the front plate of the frame, use an Allen key to tighten the screws. Tightening the screws will secure the Y-axis belt.

A broken bearing on the X, Y, or Z axis can cause an XY crash to show up on the display screen. See XYZ bearings replacement guide to address this issue.