Hole dimensions in printed parts

Mostly Printed CNC - MPCNC Troubleshooting
1

Hi there,

I started work on an mpcnc before the new design was announced, but now that I have printed a few pieces it seems that my 3d printer is not dimensionally accurate or that I am worrying about nothing.

I am waiting on Grainger for the hardware, but when I put the conduit into the feet, it is pretty snug. Attached is an image of the roller and stepper mounts being wobbly, should it be like this? I am printing in petg and performed a 100mm test, which I was .05 of a millimeter.

Sorry if there are any spelling errors or if it’s worded weirdly, I am working off of a phone. Thank you!

15892266129478530493059544818755
158922661294785304930595448187553024Ă—4032 1.82 MB
1589226623833537166530466454999
15892266238335371665304664549993024Ă—4032 1.99 MB

2

Just to double check the simple first, did you use the print for the diameter of your tubing?

3

Yes I did, I used the “C” parts (Which I think is for 23.5m) and checked my conduit OD before starting printing.

4

I don’t recall with this part specifically, but there are some parts that have gaps between surfaces and use screws/bolts to clamp them together, making a tight fit but never actually meeting surface to surface.

2 Likes
5

I don’t think that roller piece ever touches the top to the bottom. The bolts hold it snug, and the gap ensures that’s possible.

1 Like
6

Beat me to it!

2 Likes
7

Thanks for letting me know, maybe I am just being paranoid then…

1 Like
8

Thank you! I don’t have the bolts yet so I can’t try it out, but for some of the holes it shows as 3.75mm instead of 4 (for the M4 bolts) on my calipers. Do you think that is correct?

9

Wouldn’t be enough to make me worry. Maybe the bolt will be hard to turn through, but the plastic will carve out once you start tightening it.

10

Thanks. I’ve never made such a large scale project with my 3d printer before so sorry if it seemed like a stupid question.

11

Ask away. I found so many answers because people already asked the questions, it kept me from having to ask any until I got mine all together. It doesn’t just help you.

3 Likes
12

Yeah when I noticed the same issue in my parts, I just thought “eff it”, worst thing that’ll happen is it won’t work right and I’ll have to print the parts again anyways.

13

The corners are that way too. There is supposed to be a gap and if you try to get the parts to touch, you are likely to crack the parts.

3 Likes
14

What Jamie said, and to add to that, if the bolts don’t fit, you can ream them out with a drill. Don’t oversize them, use the same size as the bolt that’s going through the hole.

15

Did the prints work out for you? I got my hardware in today and ended up having to thread the larger holes (and the ones closer to the bed…), since I can’t get that much filament due to COVID, I want to make sure before I start printing again.

16

Yeah everything works. I had to ream most of the bolt holes. A couple bearings were stiff so I had to ream a couple holes a little extra. The conduit was especially tight, but I just carefully deburred each end of the conduit

Other than that, everything seemed to fit together pretty nicely. I posted by build yesterday MPCNC Saskatchewan