Reply To: Bearing gaps



I have somewhat the same issue, not quite as bad but still with small amount of play in the new MPCNC I’m building.

The printer is well calibrated, and several different test prints are well within tolerance for X, Y and Z on the printer.

All of the MPCNC pieces printed with perfect bolt holes (not too tight and not too loose), and the bearings fit snuggly where there are pockets for them as opposed to just going on a bolt. Also all the pieces for the middle aligned perfectly as far as putting them together, it just appears that some of the inner bearing holes were not positioned where they need to be for a tight fit with the conduit that I have.

As a cross check I ordered a router mount from the shop and compared what I received with the same parts printed here. The both match 100%. But there are somewhat less massive than the middle pieces.

Also the Better Middle Z pieces printed perfectly and the bearings there all grab the conduit just fine, its’ only the other middle pieces that are problematic.

But at least one of the rollers printed with more slop that I would like, and a couple of the middle pieces were problematic, with more slop than I would like to see. For the roller I was able to coax the bearing bolts at a very slight angle (they were that close) and tightened the up and that appears to be working well at least for now.

I did some measurements of the conduit (got from Lowe’s before spotting the comment that the Home Depot conduit might be stronger/better. There appears to be a bit of difference in diameter over the length of conduit (2 feet in my case) but probably within tolerance, just combined with the printing the tolerances add up to give some slop.

I suspect that it has to do with difference in the filament and ambient temperature when printing, but right now that is only a guess.

So for a hack, and it is definitely a hack, I put a couple of layers of blue tape to the Y conduit since that appeared to be the worst for slop. That makes the middle solid as a rock. I know that over time it is likely that the tape will wear down, but for now it beats reprinting only to maybe have the same problem again. But I do plan on reprinting, but before I do I’ll make an enclosure for my printer to keep things more controlled as far as ambient temperature goes. And I may go ahead and install the heated bed I was going to to for a while to minimize any warping. The problematic pieces had some very slight warping, and I almost never get warped pieces anymore with my PrintrBot Simple Metal, so I think it is a temperature variation that contributed to the problem.

The good news is that I have the gantry and Z Axis installed and I was able to do a rough test with a magic marker pen taped to the holder and it drew a square 100 x 100 mm and did it fairly well given that the pen itself wobbled a bit due to the tape. I’ll do a more secure holder for some more tests while waiting for my DeWalt router to show up.

Also I used the ShapeOko Grbl settings calculator to compute the GRBL settings for X Y and Z. My X and Y are almost perfect, but Z appears to only move about 1/2 of what it should (e.g. about 5mm when I expected 10mm). I suspect that I forgot to change the number of microsteps on Z from some earlier testing.

In any case adding the blue tape hack to the Y conduit really made things tighten up rock solid for me. I may even see if I can find some teflon sleeving that would tightly fit the conduit and that would save me reprinting. Just a thought..

I guess this is a long way around saying that maybe you are experiencing some ambient temperature effects on printing the beefier parts like I appear to be seeing. So keep that in mind if you go to reprint anything.

If you are committing to reprinting and you will be tossing the current parts there might be one other trick you could try, but it is iffy. That would be to redrill the offending holes at an angle such that the bearings would hit the rail and then put some shim plastic in to hold the bolt at the proper angle when tightened, but that would be a fair amount of work and would have to be done carefully. But you might try it to see if you can salvage the parts you already have printed.