How to fix MakerBot Error 81 due to false-positive filament jam

1 points by syllable_studio 5 years ago | 1 comment

I recently got an old MakerBot 3d printer on craigslist. I could not get the print to work. It would print a tiny amount and then give me Error 81 - filament jam. Here's a note on how I fixed it. I just want to document it somewhere so others can find it. Not sure if there's a good MakerBot forum, so just leaving this here.

The printer model is MakerBot Replicator Mini - it's more than 5 years old I think. the print cartridge is a "Smart Extruder", not a "Smart Extruder +" which fixes this issue I had. This issue is discussed here: https://www.theverge.com/2016/1/4/10677740/new-makerbot-smart-extruder-plus-3d-printer-ces-2016

This Error 81 in my case was caused by the "encoder wheel" getting stuck, which triggered a false error. This is discussed in the MakerBot support page, but the page doesn't tell you the right way to fix it (at least not for me): https://support.makerbot.com/troubleshooting/makerbot-replicator-mini/error-codes/error-81_10672/2902

See next comment on how to fix it (i hit a character max)

syllable_studio 5 years ago |

Here is how I fixed it.

(Error 81 due to a false positive filament jam -- occurs because the encoder wheel gets stuck and isn't turned by the moving filament)

The problem was indeed the encoder wheel getting stuck which triggered a false error. Your instructions do discuss the encoder wheel here. They say to move the encoder wheel to the "back side." This was confusing to me for a few reasons: - I didn't know which side was the back side - I didn't know why this would help - The wheel didn't seem to move when I nudged it anyway.

If this is indeed the right fix for some people, can I suggest that the instructions give a little more detail? Like: - Check if the wheel groove is not aligned with the top plastic hole. If necessary to fix the alignment, use a flat head screwdriver or a similar tool to gently push the wheel closer to the back side of the Smart Extruder.

_The real problem_ For me, the real problem was that the wheel didn't turn because there was a combination of too much wheel axle friction (between the wheel and its axle) and/or not enough wheel groove friction (between the wheel groove and the plastic filament)

_Verifying this problem_ While the printing is in progress, shine a light through the top or right side of the 3D printer case. You can watch the encoder wheel. It should turn in sync with the filament passing through the wheel groove. If there is an error, you can verify that the error happens because the encoder wheel stopped turning while the filament was flowing. This was happening for me in one particular sticky part of the encoder wheel's rotation.

_The solution_ 1: I applied lubricant to the encoder wheel axle. - I didn't even need to take the cartridge apart, I just used a needle to carefully apply some to the axle and manually turned the wheel while letting it drip down into the bearing.

2: I roughed the plastic of the encoder wheel groove. - I used an exacto knife to make tiny scrapes all around both sides of the inside groove of the wheel.

3: Test that these steps are working by holding the (cooled down) extruder in your hand, and manually inserting a small length of plastic into the top hole. Move the filament in and out and ensure that the wheel is turning smoothly in sync with the filament passing through the wheel groove inside the cartridge.

I hope this helps others! I know it's a very old product now, but maybe there's still some people out there still having this problem. Good luck :thumbs-up: