hobbed bolt and extruder have ~2mm offset

Basically, if you draw a centerline down the center of the hobbed bolt’s teeth, it misses the center hole down which the filament must pass in order to reach the hot end. The offset is about 2mm, which is significant since the filament is only 3mm in diameter.

The bodded bolt is set up in the following manner: large gear --> three “large” washers --> one “small” washer --> bearing --> printed frame --> bearing --> “large” washer --> locking nut.

Since I do not wish to cause more harm than good, I have refrained from attempting a f ix on my own. I believe that another washer should be added to the “stack” of four washers in order to shift the hobbed bolt into alignment.

Any suggestions?

Your logic is correct, adding a washer to adjust the hobbed bolt to center it should do the trick. That being said, it should already be lined up from the factory, so if it isn’t, there may be a washer missing or your hobbs might not be in the right spot. If that doesn’t do the trick you might call the lulzbot peoples and see if they have any ideas?

Iwill double check the diameter of the bolt and get a selection of washers to try.

I have done my best to align the hobbed bolt assembly properly. I have had to do the following:

  1. Disassemble the hobbed bolt assembly.
  2. Remove slop from over extrusion in the bearing housing area.
  3. Reorder and replace washers to align the hobbed bolt assembly.
  4. Loosen the set screw that attaches the small gear from the stepper motor in order to align the small gear with the large gear.
  5. Repair delaminates elements in the gears caused by misalignment of the gears.

I put it all back together and while it is not perfect, it is definitely better.

Would you mind taking a photograph of the extruder assembly? We would be happy to help! Send the photograph to Support@LulzBot.com and we’ll see what’s needed and help with whatever needs to be done!

Sorry for the similar replies, but if someone encounters a similar issue, without seeing the other threads, it will be helpful for them to know how to get further assistance.