Has Bondtech Gear Alignment Been The Source Of My Issues All Along?
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Has Bondtech Gear Alignment Been The Source Of My Issues All Along?  

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Has Bondtech Gear Alignment Been The Source Of My Issues All Along?

Hi guys,

The quick summary of what I'm asking in this thread: My Bondtech Gears were out of alignment with filament path by approximately 1-1.5mm when I assembled the printer. I did not think this was a big deal as the filament path still looked okay to my eyes (I'm a biology nerd, not an engineer). Is this most likely what caused my symptoms in 1) through 3) below? Or was it the cold pulls that I performed before re-aligning the gears? Or a combination of both? My printer is now printing marvelously after alignment of the gear and cold pulls (which weren't tested independently of each other.)

So, I've had my MK3 kit built for ~1 month now, and have been seriously struggling with trying to get it to produce acceptable prints. I took a long time to level the bed finely, then after that I ran into the problem I'm now posting about. I will include image(s) showcasing what I'm talking about. However, the essence of the problem was:

1) My first layer would go down just fine at low speeds. (This has all been with PLA at stock Prusa Slic3r PE settings.)
2) Once my first layer was done and print speed increased, I would get very erratic extrusion. Infill would be horrible, and even some of the perimeters would go missing at random points. Small parts printed just fine, but medium-large parts had horrible issues. Slowing down a lot (like 50-75mm/s on infill) helped the issue a lot, but not entirely. The end products on larger prints would also be extremely weak.
3) Eventually, after enough time of messing with this, I started encountering erratic extrusion on the first layer at low speeds!
4) I never found any threads or info mentioning bondtech gear alignment as being able to cause this.
5) I also never contacted Prusa about this (I'm in US and the time difference + lack of wanting to just be told to make sure it was assembled properly dissuaded me)

Now, my first thoughts after reading about this issue was that I had a bad underextrusion issue, so I went to a calibration print and optimized that, which helped a little. I also switched filament by this point to an old MeltInk3D roll of PLA I had because I was afraid I was going to run out of the roll of Prusa Silver PLA that came with the printer. I also raised print temps all the way up to 220C later on, which had some slight benefits it seemed, but didn't fix the problem. After doing that for a few prints, my first layer became erratic.

After that point, I found a YouTube video by Ron's Place where he also mentioned that he was having weird extrusion issues with his MK3 kit, and he mentioned that cold pulls with ESun's cleaning filament fixed his issues (link: ). I decided to just try standard cold pulls (note that I don't think I saw any chunks or weirdness come out of the two cold pulls I performed using the method he described, whereas he did). Since I opened up the extruder door for this, that's when I decided to re-align the bondtech gear with the filament path and lube them as well. When I opened up the extruder door and looked at the filament's path, it looked a lot worse than I thought it did originally.

After re-aligning the bondtech gears with the filament path and the cold pulls, my MK3 is now working amazingly well. I am ridiculously happy with the prints I'm getting. I have tried two different brands of PLA, now, and am getting excellent prints (in my opinion) with both. No missing layers, infill prints pretty well at 200mm/s (a little underextrusion there still, but not print-ruining). The extruder also no longer clicks at all, which it would do sometimes before (I did try loosening tension on the bondtech gears prior to re-alignment, which had no effect.)

I personally think that mainly the gear alignment caused my issues. If anyone can be sure that it did, Prusa should really put some giant red text in E-Axis Assembly, Step 14 saying that you should take the time to align these gears with the filament path as accurately as you can, for ignorant first-time builders like myself. Also, in the second image they show in that step, doesn't it look kind of like a poor alignment in their image? That filament is clearly slightly curved, even though it's in the center of the teeth. That is actually part of what made me say it didn't need to be super accurate at this step when I assembled the printer. Link to image I'm referring to: https://d17kynu4zpq5hy.cloudfront.net/igi/prusa3d/pXZDeYpdqMvpjmos.huge

If this was my issue and I was ignorant, I mainly want to bring this up so others can find this in case they may be struggling in my boat, because I was insanely frustrated with this problem.

Thanks for taking the time to read all of this, and thank you for any responses!


Posted : 12/04/2018 8:55 pm