Cura turns round hole to oval

[shaulb 0]

Hi

 

I printed a design with small holes on the X and Y axis
the holes came out oval, I've mesured the prints height, depth and length, all match the design

I've checked Cura (4.8) and turns out it slices the holes as oval
anyone have an idea why that's happening and how it can be corrected?

[gr5 2,167]

I think this is round as is possible given that the hole is sliced into layers.  If you ignore that flat top and bottom it looks very round to me.

 

Regarding "printing oval" - it's probably the top of the hole that is sunken a bit downwards.  This overhang is almost horizontal here and that's difficult to print.

 

Do you care about the "look"?  Or do you care about the functionality (is there something that doesn't quite fit).

 

One solution is this (skip to part about horizontal holes):

https://support.3dverkstan.se/article/38-designing-for-3d-printing

[shaulb 0]

Hi, thanks for the answer

 

I'm worried about the screws I'm suppose to use with this print, 

I'm pretty sure they'll be loose.

 

but what I'm a little surprised about is that the slicer won't make the hole rounder even with 0.1 or 0.05 layer height

 

[gr5 2,167]

It should be PERFECT dimensions in the slicer.  Unless you have "horizontal expansion" set to something other than zero.

 

It's the printer that may or may not print it correctly due to many reasons - for example PLA shrinks like a liquid rubber band as it comes out and wall edges can move inward (towards the solid area - away from air) which can make your hole wider than asked for.

 

Are you saying it looks visually wrong or the final printed part is wrong (In 0.1 and 0.05 layer)?  It should be perfect.  Any errors are probably your eyes but to be sure you could upload your project file.  In cura do "file" "save" and upload that project file and I'll look at it.  But I'm pretty sure it's as perfect as cura can possibly make it.

[gr5 2,167]

By the way, when I have critical dimensions - I usually print slightly small and then drill it out with the correct size drill.  This may seem crazy but it's very easy and quick to do.  The part guides the drill perfectly and you get perfect precision every time.

 

Usually people complain about vertical holes (not horizontal).  they tend to print 0.4mm too small due to liquid-rubber-band effect.  I always make my holes about 0.4mm larger than desired and I *still* often drill out the most important ones.

[GregValiant 1,246]

If you were making parts using a conventional machining method, screw holes would have clearance.  There would be a "body" drill size and a "tap" drill size.  You would uses dowels or maybe flat head screws to locate the piece that had the body sized holes.

You're trapping a hex shape there.  If the nut or screw is positively located by the hex shape, then you are good on that side.  Positively locating the other side will require some thought.

 

The previews that Cura shows are pretty good, but I always consider them a cartoon.  The Gcode instructions and the printer itself (and it's calibration) will determine if the final shape is round or out-of-round.  Horizontal holes are really hard to get round.  The bottom and the top are going to have flats.  It's the nature of the process.