Cura slicer produses wrong dimentions

[MathewOrman 0]

The test file was an array of holes spaced by 2mm but prints less of 1.5mm but outer dimension are correct 20mm x 8mm...

Printer Anet 4...

AKP_test.gcode test.STL

[GregValiant 988]

Bringing the gcode into AutoCad there are two holes that (if the printer could do it) are 1.00mm diameter.  They are 4.00mm apart.

With a 0.4mm nozzle the width of the part shows as 8.00mm and the length is 20.00mm.

This is your gcode dimensioned.  Remember that the gcode describes the PATH of the nozzle, not the outside edge of the extrusion or the inside diameter of a hole.  So with a .4 nozzle, you would add .4 to the width and length and subtract .4 from the diameter of the holes.

 

When the printer moves in a circle the liquid filament wants to stay straight and so it pulls into the center of the circle.  That phenomenon is technically known as the "Snot Factor".  The smaller the hole - the worse the effect.  Little holes tend to disappear.

 

If you use the "Hole Horizontal Expansion" setting at about .2 you will see a difference in the diameter of the printed holes.

Remember that a hole is any vertical feature that has no openings to the outside.  If you were to print a spoked wheel then the axle hole would get bigger, but so would the gaps between the spokes.

[MathewOrman 0]

If that was true than printed part would have 20.4 mm width but it has exactly 20 mm and why the printed hole spacing is 3  mm instead of 4 mm?

[GregValiant 988]

"...why the printed hole spacing is 3 mm instead of 4 mm?"  I think it's between you and the printer.  Some mechanical problem like a loose belt or maybe the steps/mm of the X and Y are off...something.  The printer should be moving to where it is told to go and the gcode commands within the file are spot on for the overall size, the size of the holes, the hole spacing, as well as for the thickness of the piece.

"if that was true than printed part would have 20.4 mm width"   No.  19.60 + .40 = 20.00 and 7.60 + .40 = 8.00 and for the holes 1.40 - .40 = 1.00.

I wrote the script for reading a gcode into AutoCad in order to take Cura out of the picture.  It gives a completely independent view of the generated gcode.  That is your "AKP_test.gcode" that you see it that screenshot.  If your printer isn't printing it that way then the problem is in the printer and you would need to dig into that to see what is really going on.

 

[MathewOrman 0]

2 hours ago, GregValiant said:

I've tested on three different printers with new test.stl and to get 2 mm hole spacing I had to space holes by 2.6 mm...

 

But width is still exactly 22mm as designed in cad program...

 

test.STL

[MathewOrman 0]

1 minute ago, MathewOrman said:

 

test.STL 462.58 kB · 0 downloads

That is huge error...

[GregValiant 988]

The error is not in the gcode.  Consider - this is a very basic part of what slicers do.  If Cura couldn't get this right then no one would use it.  Are you printing from an SD card or though Octoprint or some other intermediary?

 

I sliced and printed your test STL file.  The gcode indicates that the model is 22.00mm long.  It printed at 22.02.

 

I used the 1/2 scale side of the scale because of the finer tic marks.  You can see that the top row holes are about 36.5 apart at 1/2 scale and so at full scale that's 18.25.  18.25/7 hole spaces = 2.607 between the holes.  You designed it to 2.6 and it is indeed 2.6.

 

 

I've attached a 3mf file.  The holes are 1mm dia and the spacing is 2.54mm (0.10 inches) which is the typical spacing on the PCB's and breadboards I use.  Outside is 20.00 x 32.00.

GV Hole Test.3mf

Edited April 2, 2022 by GregValiant

[GregValiant 988]

This is a 4017 chip stuck through the holes in my model and it dropped right in at 2.54 spacing.

 

[MathewOrman 0]

Yes, I apologize had bad caliper measurements...

Thank you for your expert help...

 

May the force be with you...