The hot-end assembly of the Me2 extruder is mounted onto the underside of the extruder and fixed in place using a grub screw. In the course of normal operation this shouldn't come loose, but accidents like repeated head collisions may loosen the tip. With a loose grub screw, the action of extruding plastic pushes the hot end down and away from the extruder body, throwing your calibration off.
If your Z-axis calibration seems to constantly be too low, resulting in failed prints, poor first layer infill, or the nozzle scraping against the build tray and recalibration doesn’t fix the issue, you may have a loose grub screw.
Confirm the Problem
Have a look at the extruder from the side. You should be able to see the top of the feed tube extend through the mounting block and butt up against the underside of the extruder drive housing (see figure 1). If the tube is all the way up then a loose grub screw is unlikely to be your problem.
Making sure the hot end is cold and the power is off, unplug the printer and lay it on it’s back so the X-axis is supported and you can get to the extruder nozzle by hand.
Grab the extruder body and try to wiggle the hot-end and nozzle and pull it directly downward from mounting block. If the hot-end and feed tube don’t move easily then the grub screw is fine and you just need to re-calibrate. If you can get the feed tube to move with hand pressure alone, then the grub screw holding the hot-end into the extruder may need to be tightened.
- With power off, lift the X-axis up and support it with something, leaving the extruder suspended (a filament box works quite nicely)
- Using a 2mm hex key, undo 3 of the screws on the fan on the front of the extruder as shown in figure 2, and rotate the fan out of the way. You should now be able to see the grub screw and the bottom of the hot end mounting block. Make sure the grub screw isn’t missing or destroyed.
- Push the hot-end up into the extruder assembly and make sure the top of the feed tube butts up against the extruder drive housing.
- Using a 1.5mm hex key, carefully tighten the grub screw. Take care - excess force may ‘round off’ the screw, making it almost impossible to remove. If you have wick in threadlocker (such as Loctite® 290) apply a small amount directly to the grub screw thread.
- Rotate the fan back into place and replace the screws removed in step 2. Be careful not to over-tighten the fan screws. If you hear a rattling or buzzing noise from the fan when printing you may have overtightened the fan screws and need to back them off just a little.
Before you jump straight back into printing, it’s a good idea to try the hand tests from the ‘Confirm the Problem’ section above. If you can pass those, try a quick print on draft quality (0.2mm layers), carefully watching for scraping or abnormal behaviour. Once the print is finished, check to see if the feed tube has slipped at all. If not, you’re all good!
If you’re still having trouble, raise a support request and we’ll figure out how to get you running again.