# Troubleshooting

# Pulleys are loose on the motor shafts

One carriage doesn't move or doesn't always move right. Tighten them.

# Nozzle is higher in the middle vs. the sides (or vice versa)

You need to set the diagonal rod length accurately, then redo the auto-leveling. Diagonal rod length can be adjusted with the curvature buttons, or by sending the G-code M665 L<length in mm>. The diagonal rod length is the hole-center to hole-center distance for the diagonal rods. They all need to be the same length for accurate printing.

  • Make sure bed is clean
    • Wipe the bed with Isopropyl Alcohol a.k.a. rubbing alcohol regurarly
    • Use dishwashing liquid to remove grease from the bed
  • Make sure Z0 height is correct (nozzle isn't too high)
  • Make sure the temperatures are correct for the given filament
  • If necessary, use a brim or raft for extra adhesion
  • If necessary, use hairspray or glue for extra adhesion

# My print is skewed / leaning

  • Make sure that the belts are equally tight. Big differences in belt tension can cause this.

# The QQ-S pauses slightly when I press buttons while printing

Yes, you should avoid doing that. Or change to a different firmware.

  • There's a new board ("Hispeed") available for the QQ-S that features replaceable drivers. You can buy it from Flsun customer service, or check AliExpress for it.

# It doesn't auto-level right, it goes to the wrong height or digs into the bed

You may have the Z-probe offset set incorrectly. This is the height of the nozzle above the bed when the Z-probe makes contact.

  • For the leveling switch, set with G-code: M851 Z-16.2
  • For the leveling pad, set with G-code: M851 Z-1.05
  • Then save by using G-code: M500 Also, if you've adjusted something that changes the height, reset the Z0 height.

# I broke my hot-end!

  • The hot-end parts are relatively fragile, especially the throat
  • You should heat the hot-end before removing the nozzle (otherwise, the plastic inside can act like glue)
  • You should always use two wrenches or pliers: one to hold the stationary part, one to hold the part you're unscrewing
  • When reassembling, first assemble loosely, then push the bowden tube all the way in, then heat and tighten last bit (or, use the Luke Hatfield fix; see above "Under-extrusion")

# Videos

# Heating problems shown on LCD

# TH-error1 or BED-error1

Minimum temperature error at hot-end/bed heater

# Check for

  • (hot-end/bed) thermistor disconnected from the motherboard
  • (hot-end/bed) thermistor wiring is broken
  • (hot-end/bed) thermistor itself is broken

# TH-error2 or BED-error2

Maximum temperature error at hot-end/Bed heater

# Check for

  • (hot-end/bed) thermistor wiring is short-circuited
  • (hot-end/bed) is on fire

# TH-error3 or BED-error3

Hot-end/bed not heating as expected

# Check for

  • (hot-end/bed) thermistor is not attached to (hot-end/bed)
  • (hot-end/bed) thermistor is not making good contact with (hot-end/bed)
  • (hot-end/bed) heater is not working properly
  • excessive cool air is blowing on (hot-end/bed)

# The black coating is coming off from the glass

This is mostly a cosmetic issue. If adhesion is reduced, you can always use hairspray or glue to get it back. In fact, using hairspray or glue can act as a "buffer" to prevent a print from taking off any more of the black coating. If the appearance bothers you, one easy fix is to get a Buildtak, PEI sheet, or other print surface to cover the entire bed with.

# The printer screen comes on when plugged into USB:

  • This is annoying. In order to fix, you need to remove a part from the main board:
  • remove D10 or F4 on MKS Gen L board (QQ)
  • remove D5 or F4 on Robin Mini board (QQ-S)
  • You could also modify a USB cable and cut the 5V power line.

# The fan ducts don't point at the nozzle tip:

You'll probably need another fan duct...

# Diagonal rods fell apart

Several folks have seen the rods loosen or come out of the ball-joints.
Reattach them using epoxy. Make sure the end is rotated and properly aligned with the other end.


CA glue works, but doesn't give enough time to align the parts.

# Under-extrusion, or extruder is clicking without pushing filament

  • Confirm that the bowden tube is tight against the nozzle with no gaps.
  • Consider the Luke Hatfield fix; see https://www.youtube.com/watch?v=7tCxO17XZtw (opens new window)
  • Confirm that the hot-end nozzle is firm against the throat (not the block).
  • Confirm that the hot-end heatsink is being properly cooled.
  • Check the extruder gear spring tension (counter-clockwise to tighten on QQ-S/Q5).
  • Make sure the nozzle isn't too close to the bed (first layer only).
  • Check the nozzle itself for any blockage or deformity.
  • Confirm slicer settings (filament diameter).
  • Calibrate your extruder.
  • Make sure your hot-end temperature is appropriate for the filament you're using.
  • Make sure your print speed isn't too fast for the filament/nozzle you're using
  • (use a lower speed for the first layer).

# Fans stay on, are noisy

  • Add an inline power switch: search "iec cord switch"
  • Add thermoswitches (KSD9700, 45C, N.O.)
    • one for power supply fan (mount it in the donut)
    • one for chassis fan (mount it next to motor driver heatsinks)
  • The fans are 60x60x15, 12V (QQ) or 24V (QQ-S) (except for power supply fan: 12V)
  • You can consider the Noctua mod

# Filament grinding away the extruder inlet (QQ-S)

It's easy to fix this, and there are multiple solutions!

  • put a short PTFE tube into the inlet (yes, it even expects you to do so)
  • install a filament guide, there are multiple on thingiverse
  • install a filament detector (2-in-1 solution)