Defects
This page tries to list various problems that can occur while printing.
The goal is to have a representative picture for each defect, a description for the reason and maybe a solution.
Contents |
Movement Defects
Lost Steps in XY
If the stepper motor would need more torque than they can deliver to overcome the resistance of the system to complete a move, it will "loose steps" and change position. The motors torque is decreasing with rotational velocity, while also the resistance of the system due to friction increases.
The Microcontroller has currently now way of knowing that it lost steps. Methods to know about lost steps is re-homing each layer, causing excessive oozing, having an optical or mechanical encoder in the system, or monitoring the current. The latter is sometimes done by special stepper drivers.
Reasons and solution:
- This can be caused by too high acceleration or too high velocity. Depending on your firmware, you can limit the velocities and accelerations. You can also try to just print slower.
- Also the stepper drivers can fail due to overheating. In this case they will remove the power to the stepper motors for a few seconds to cool down sufficiently, and the corresponding axis will not move. Typical, thats a couple of seconds. In this case, either decreasing the stepper current or better cooling will help.
- If there is too much material deposited, the head might hit a hill of material while moving. Of course this causes higher resistance, if not a full stop of the head. The spring system of the table and the mechanical weakness of the z axis help a bit. But you might want change the settings of the gcode-generating program.
- Loosing steps can also occur if a endswitch is triggered unexpected. The unintentional triggering may be caused by interference signals from the stepper motors. This can be solved by twisting the endswitch-wiring, or by placing capacitors on the endswitch-terminals on the main PCB.
Lost Steps in Z
Sudden Pauses
If driven by USB RS232 emulation, the machine sometimes receives garbled transmits. E.g. by electromagnetic noise, random bits flip. The firmware might or might not recognize this, but the correction needs time. Hence the machine pauses. Thereby, the overpressure in the hot end relaxes, causing a big blob of material. If the machine later on continues, it initially deposists too little material, and might loose steps while hitting the blob. Try using a shorter USB cable, a lower or less jittering transfer rate (requiring a manual compile of the firmware.
Z rib
Segment pausing
- Serial latency
- Processing in Firmware
- Buffer under runs.
Corner excess material
Backlash
Extruder defects
Grinding
Bowden Popping
Lost Steps
Overpressure relaxation at deposition changes
After a transition from a move with large extrusion rate to a slow extrusion rate, too much material will be deposited due to the overpressure in the nozzle. Also the other way round.
Oozing
- Overpressure
- Gravitation
- Pulling
Too much material
- Problem: Occurs when PLA is pushed up on a horizontal printed plane. When this actually happens you can see the nozzle stirring in PLA.
- Cause: too much material per surface, can be caused by too high fill density.
- Containment: Turn low the Extrusion Material Multiplier in 'Real time control and tuning' from 100% to 90%,80%,70% or even 60%
- Solution: Manage your build style in Netfabb. Increase the Width factor with steps of aprox 5%.
- Netfabb->Style->Manage build styles->Buildstyle definition->edit [your profile]->Region Definition->Downskin/Upskin->Width factor
Thermal Defects
Bubbly PLA
Overtemperature causes dissolved water to form light scattering bubbles.
Smearing PLA
If the PLA is too cold for the print-speed, random increases in height will cause additional deposition of material in the layer above, while groves will obtain less. This positive feedback causes finally a a column structure of 1-2mm distance, that is even more pronounced with overhangs.
