Interior diameter of prints too small

I've been printing some bushings intended to replace LM8UU bearings, and I find that the interior dimensions are consistently too small. I used several different models, all of them with good reputations (example: [www.thingiverse.com]), and in each case they were very tight on an 8mm chrome rod which a normal LM8UU moves quite smoothly on. Similarly, I printed a model for the Y axis mount for such a bearing (something like [www.thingiverse.com], though not this specific model), and both a real LM8UU and the printed bushings won't quite fit it, though the screw holes look as if they are on the right spacing and everything else is square and measures up.

I am printing in PLA using Repetier host and Slic3r, 0.2mm for the bushings and 0.3mm for the Y mount, on a Folger 2020 i3 variant. Is there some setting I could adjust to help fix this? I could tweak the models, but would prefer not to do that.

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See my blog at [moosteria.blogspot.com].

Holes will always print a bit small due to the way the printers work (it's been heavily discussed many times). That being said you would think that a person that designs a replacement for a bearing they would take that into account. Other things that can affect hole size are speed (too fast can make them a bit smaller) also extrusion amount, if your machine is over extruding then it would also make the hole a bit smaller, this can be fixed by adjusting extrusion multiplier (1 = full extrusion amount while smaller numbers like .85 = less extrusion and larger numbers like 1.1 = more extrusion).

Thank you, good suggestions. I'll try them out. I was printing quite slowly, but I do think my printer tends to overextrude a little.

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See my blog at [moosteria.blogspot.com].

I find that setting 'External perimeters first' in slic3r reduces the magnitude of this problem.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I went a different way with Cura:
I just scale the parts up or down in the direction, where I need it.
Recently I printed a clarinet reed at 75% z-scale to make it swing nice. (80% to make it swing at all)
-Olaf

I just tried a print with both 0.85 extrusion and External perimeters first, and it makes a big difference. Thanks for these ideas.

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See my blog at [moosteria.blogspot.com].

.85 extrusion multiplier or something else?

Quote
msaeger
.85 extrusion multiplier or something else?

Extrusion multiplier, in the filament settings.

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See my blog at [moosteria.blogspot.com].