Prusa i3 Common Issues Troubleshooting

1. ATX Powersupply keeps turning off in the middle of a print.

• Most power supplies require a load on their 5V rails, which one is 5V? Any yellow wire to black ground wire will be 5 Volts. (Red to black will be 12Volts) You can either use high power 10 Watt 10 Ohm resistors, or like me, you can just plug in an old CD Burner.

2. PLA prints are coming out very brittle, and they break easily.

• You need to increase the nozzle temperature so that there is better adhesion between layers.

3. First layer is not sticking to the heated bed.

• I’ve found using a 1:10 PVA glue (Elmer’s will work fine) to water solution, and just brushing it onto the bed. Let the glue dry, and then print soon. If you wait too long, it will lose its stickiness.

4. Prints seem to jump and skip steps. This will look like at a spot, the print will shift in the X or Y axis.

• There can be a couple of causes for this.
  • Your stepper motors or motor driver board are overheating. You’ll need to adjust the stepper motor current to the lowest amount where it will still run. On a RAMPS board this can be done by adjusting the Vref. Detailed instructions can be found here: http://www.nextdayreprap.co.uk/commissioning-reprap-prusa-mendel-build-manual/#6zmjtih8gjuo_3 Look under “11.4 Pololu Stepper Driver Calibration”
  • The default acceleration in the RAMPS Marlin firmware is stupid high, so it could be too fast for your machine. You can go into your firmware (Configuration.h), and adjust the following settings. My adjusted values are in red, I put them to 2% of the default values.
    • Original Marlin Defaults
      #define DEFAULT_MAX_ACCELERATION {9000,9000,10,10000}
      #define DEFAULT_ACCELERATION 3000
      #define DEFAULT_RETRACT_ACCELERATION 3000
    • My Version
      #define DEFAULT_MAX_ACCELERATION {180,180,10,200}
      #define DEFAULT_ACCELERATION 60
      #define DEFAULT_RETRACT_ACCELERATION 60
  • To detect any issues with the driver boards themselves, try switching the X-axis & Y-axis boards with those of the Z-axis and Extruder.

5. There are blobs in the print.

• I’ve found adjusting the default extrusion width in Slic3r to 1.2 times the layer height. For a layer height of 0.25mm I use an extrusion width of 0.3mm. This is not an exact science, but a system that seems to work for me.

6. First layer looks awful, kind of like spiraling filament, that doesn’t adhere.

• The Z-home is too far from the glass, adjust the Z-endstop so the nozzle is closer. Use an index card or piece of paper to do the “friction test” where you drag the paper under the nozzle, and adjust the z-home until you feel friction.