Different calibration interior/exterior dimensions

Hello,

I'm calibrating my prusa and I had this issue while printing. Printing a piece of 26x16x16mm and a 8,1mm diam. vertical tube hole I got a 26,5x16,65x16mm exterior dimensions and a 7,2mm diametre tube hole.

Acording to the calibration steps, if I attend to the exterior dimensions calibration I should get around a 69 steps BUT if I attend to the tube dimensions I should calibrate with around a 79steps value.

Where is the problem? How should I solve it?

Regards

26.5 - Plastic Expansion - steps/mm probably correct
16.65 - Plastic Expansion - steps/mm probably correct
16 - Not much expansion in this direction or steps/mm is off
7.2 - Hole Shrinkage - Quite severe (Slic3r?), you need to account for this in your models if your steps/mm is 100% correct.

Try out this model to make sure XYZ are correct - read the description about material expansion:
[www.thingiverse.com]

Have you measured bed/head travel as opposed to a printed object? It is far more accurate (provided you measure it accurately!)

Also make sure you run a single wall test and verify you're actually getting the extrusion width you are requesting.

@yydoctt measuring bed/head travel I should correct the steps following the external dimensions of the piece (decreasing the steps value to correct the 26.5 and the 16.65mm), but if I decrease the steps then I will get more narrow hole.
How should I correct this issue if it would be a plastic expansion problem?

@Pollygonhell I also printed single wall cube and the walls are 0.5mm as the requested dimensions on Slic3r 8.4.

Pikelo, I am saying your steps/mm are probably correct. Hole shrinkage is very common especially with slic3r. You should measure the head/bed travel and make that result your steps/mm - as this is more accurate than measuring printed parts.

Then to counter material expansion you can try reducing the temperature during print or use a fan.

Unfortunately I doubt you can do much about hole shrinkage other than altering the model - try changing the fill pattern or density. I think it is more a problem with Slic3r, though I haven't been following its development in a little while.

I have been using slic3r from a long time ago without this problem. I just changed T5 belts by T2.5 and got this issue.

With T5 belts didnt have this smaller diametre with the same stl model..

Definitely there is NO way of calibrating this issue. Always a mistake on exterior OR interior sizes. But the thing is before I was printing fine with this problem!!

Are you using the same version of Slic3r you were before changing the belts?
There was a bug in one of the 0.8.something versions of Slic3r where it would do what your seeing, though I think the error was only 0.1mm in each direction.
Have you looked at the GCode to see if it's doing the right thing?

I'm using the latest version the 8.4. How could I check the GCode to see if it is doing the right measures??

Slice something simple like a box, the distance between the paths one either side should be W-extrusionWidth where W is the expected width of the box.