Outline/Perimeter Shells affecting hole sizes?

[alien2108]

Hello!

I have been fine tuning my Prusa and I did fine tune the extrusion rate so it is perfect....0.48mm comes out 0.48mm (tested with Slic3r, since Simplify3D just doesn't want to handle the test models correctly).

Now if I set Outline/Perimeter Shells = 1 I get proper Hole sizes. But if I set it to 2 holes are too small. Shouldn't this value already take into account all the measure changes and inside diameters of holes should stay correct?

I would also appreciate a tip how to print a single wall object with let's say Perimeter Extrusion Width = 0.48mm for tests (my nozzle is 0.4mm) as most of the calibration object look like.

[jimc]

how off is the measurement? one thing that people usually forget to take into account is the shrinkage of the plastic. usually 1-2% is normal for abs. a touch more for nylon. not sure with pla since i dont print with that. one other thing is you cannot take a measurement on a hole on the first 5-10 layers as those can be affected by the first layer/bed gap.

[alien2108]

I would say things are off for about 0.1-0.2mm...just enough coins do not fit. But if I set the Perimeters shells to 1 it is much better....I also reduced the extrusion multiplier for additional 0.2 and now things are quite ok....But still AFAIK Perimeter Shells should not really affect hole sizes....

[jimc]

good to hear its better. .1mm is really a small amount and i think well within spec of a 3d printer. be sure you have your shells set to print outside first then inside for times when accuracy is really needed. i would say though the little bit your seeing is due to plastic shrinking as it cools. with 2 perimeters i would expect to see a little more shrinking. you will have 2 lines now cooling and pulling inward. sounds like you got it under control though.