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Unload Failed

If your printer pauses during a toolchange and displays an Unload Failed message on your printer's display, follow this guide to recover the toolchange and to diagnose the cause of the failure.

What the error means

An Unload Failed message means that while the Chameleon was trying to unload the filament, the printer's filament sensor still detected filament.

How to recover it

  1. Unload your filament from your printer's extruder
  2. Detach the Chameleon's PTFE tube from your printer's extruder
  3. Cut off the filament tip with side cutters
  4. Manually pull the filament into the Y splitter and out of the way of other filaments
  5. Check the Klipper console to see what the next tool is. For example, if T0 -> T1 was the most recent toolchange message in the Klipper console, your printer was trying to unload T0 and load T1
  6. Load in the corresponding filament manually into your printer's extruer
  7. Load the filament to your hotend using your printer controls
  8. Reconnect the Chameleon's PTFE tube to your printer's extruder
  9. Resume your print

Congratulations! You just recovered a failed toolchange.

Why it failed

To prevent future unload failures, here are some common causes and fixes for failed unloads:

Faulty filament sensor

This section applies only to setups using 3dchameleon-klipper with a filament sensor

If your printer's filament sensor is giving faulty readings, it can cause false alarms of failed loads and unloads. There are too many types and variations of filament sensors to cover them all, but here are some tips to diagnose the failure:

  • Check filament sensor wiring
  • If mechanical sensor, check the filament sensor for filament debris
  • If optical sensor, the color of the filament may not work well with the sensor
  • If optical sensor, lighting may also mess with detection reliability

Printer's extruder didn't unload

This section applies to all setups. However, the solution described here may be slightly different if not using 3dchameleon-klipper

If your printer's extruder doesn't unload far enough before doing the toolchange, it might still be gripping the filament while the Chameleon is trying to pull it out. To fix it, change the G1 E value to something higher at the end of QUICK_TIP_SHAPING in 3dchameleon.cfg.

Example before:

G1 E-60 F2000

Example after:

G1 E-100 F2000

3DChameleon filament grip

This section applies to all setups

If the 3DChameleon can't grip the filament properly, it won't be able to pull it out through the Y splitter. To fix this, print out and install Tension Tuning Sliders for the problematic filament paths. Under Files -> Tension Sliders, pick the appropriate slider:

  • The first value is the distance between the drive gear and the bearing. Smaller values here make them closer together.
  • The second value is the tension of the springs pushing the bearing and the drive gear together. Larger values here make them pushed closer together with greater force.

Tip Shaping

This section applies to all setups. However, the solution described here may be slightly different if not using 3dchameleon-klipper

**This section applies to all setups. However, the solution

If your filament tip is improperly shaped, with a blob or string at the tip, it will require excessive force to unload it through the tube. In extreme cases, you can get the dreaded hook of death.

As a general rule of thumb, for QUICK_TIP_SHAPING, a larger MOVES value will result in cleaner tips. However, the most reliable method is to install an Auto3DClippy. See Configuration for config changes. Note that you will need to switch to the dev branch for Auto3DClippy support as of time of writing.