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Galinette
(@galinette)
Eminent Member
Retract/expand volume

Hi,

I'm beginning with 3D printing. I want to print custom potentiometer knobs, which I modelled at the exact shaft dimensions. They are too hard to slide on the shaft.

I could remodel the shaft hole to add some tolerance, but is there a way do do this on the full surface in Prusa Slicer? Such as retract the whole volume by 0.1 or 0.2mm without remodeling.

Thanks!

 

Best Answer by Neophyl:

You can apply an x/y size compensation.  Its located under Print Settings>Advanced>Slicing.  positive values grow all perimeters out by that amount (so good for printing thin lines that wouldn't ordinarily slice.  Not so good for screw holes though as they would get smaller.  A negative value shrinks the perimeters in.  Which is what you describe as wanting.  It doesn't effect your height though as Z is not altered.

Holes in parts pretty much always work out being printed smaller.  Its always better to model the tolerance in to the model though if you can. 

You can download or easily model a tolerance gauge (known size pins and cubes) with matching holes that are sized with 0.05 or 0.1 increments then print.  That way you can see which hole your pin/cube fits through to see what you should be aiming for on your printer.

One thing though, make sure you have properly calibrated your filament and extruder before doing so.  Over extrusion can play a big difference in the way parts fit together.  Most people forget to measure their actual filament with calipers at several points and feed that into the filament settings for diameter.  By default filament is set to 1.75 but if your filament is actually 1.76 then hey a bit of over extrusion.  They instead set their extrusion multiplier down when in reality its their actual filament.

Posted : 03/12/2021 11:10 am
fuchsr
(@fuchsr)
Famed Member
RE: Retract/expand volume

I guess you could use the new negative volume feature of PS2.4 and insert a small cylinder into the hole to widen it a bit. But frankly, I wouldn't start my 3D printing career with a kludge like.

Instead redesign the part and add more tolerance. Will make it a lot easier to maintain your models in the long run. In most modeling environments it should be a trivial exercise. E.g. in Fusion 360, you could simply move the inner face of the hole by 0.1mm. Or if you used parametric modeling and defined a variable for Tolerance, just increase it to whatever value makes sense. 

Posted : 03/12/2021 11:59 am
Neophyl
(@neophyl)
Famed Member
RE: Retract/expand volume

You can apply an x/y size compensation.  Its located under Print Settings>Advanced>Slicing.  positive values grow all perimeters out by that amount (so good for printing thin lines that wouldn't ordinarily slice.  Not so good for screw holes though as they would get smaller.  A negative value shrinks the perimeters in.  Which is what you describe as wanting.  It doesn't effect your height though as Z is not altered.

Holes in parts pretty much always work out being printed smaller.  Its always better to model the tolerance in to the model though if you can. 

You can download or easily model a tolerance gauge (known size pins and cubes) with matching holes that are sized with 0.05 or 0.1 increments then print.  That way you can see which hole your pin/cube fits through to see what you should be aiming for on your printer.

One thing though, make sure you have properly calibrated your filament and extruder before doing so.  Over extrusion can play a big difference in the way parts fit together.  Most people forget to measure their actual filament with calipers at several points and feed that into the filament settings for diameter.  By default filament is set to 1.75 but if your filament is actually 1.76 then hey a bit of over extrusion.  They instead set their extrusion multiplier down when in reality its their actual filament.

Posted : 03/12/2021 12:04 pm
Galinette
(@galinette)
Eminent Member
Topic starter answered:
RE: Retract/expand volume

It would definitely not be easier as I would have different models per printing technology. Current model fits well with outsourced SLA, if I can find a setting on the Prusa that allows transposing all shaft tolerances directly this would be much easier. And the shaft is not cylindric, it has a flat on the side and a notch on the top. Remodeling all the knob library would be a real pain, I'd prefer solving this with a setting approach.

Posted : 03/12/2021 12:33 pm
Galinette
(@galinette)
Eminent Member
Topic starter answered:
RE:

X/Y size compensation of -0.1mm worked perfectly! Thanks

This post was modified 8 months ago by Galinette
Posted : 03/12/2021 1:44 pm
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