NOOB 3D PRINT - Inner Diameter prints out smaller than specified

I’m new to this world of CAD & 3D printing, so please excuse me.

I’ve done a drawing of a part & it all looks fantastic on the screen however, when I print it, any inner-diameter specified for a hole, is printed much smaller than specified.

I’m not sure if it’s something with SketchUp or something with my uPrintSE+ that I’ve missed but I’d really appreciate any advice to understand how to overcome the issue.

Many thanks in advance,

Could you share the SKP file so we can inspect it?

This seems to be a function of the slicer software … some will follow the inside profile with the extruder nozzle centered on the line. For a 0.4mm nozzle, this means that a hole will be 0.4mm too small. By the same token, outside dimensions will be off by the same amount. Slic3r says “Slic3r insets contours by half the extrusion width, no more no less.” Not sure what CatalystEX does (if that’s what you’re using). There is also the issue of the diameter of the hole versus its location in machine steps that can cause the hole to be off. And don’t forget the one or two percent shrink factor.

In general, if the accuracy of a hole is critical, deliberately make it slightly smaller and drill/ream it to size when done.

Sorry for the delay, I missed the update, I hope the files uploaded correctly

PC Holder V6.skp (1.2 MB)
PC Holder V7.skp (1.2 MB)

Thanks jimhami42,
I was leaning towards it being a problem with CatalystEX but that was just a guess.

It’s great that people here are willing to help new-comers like me.

Thanks heaps

If your flow rate is set too high relative to the table feed rate, you will lay down wider passes which will also cause the holes to be too small. If your holes are way undersized, this may be the problem.

You need to add a clearance margin to the diameter in order to prevent this from happening and this value is calculated in consideration of the flow rate and the material properties as it will affect the shrinkage.

If exact hole size is important, something that I have done before is to print small, add an extra shell, then drill out the holes with a proper size bit. Best solution as plastic changes size as it cools.