Different Dimensions on Round Objects

Bambu Lab X1 Series Troubleshooting
1

Hi Community,

im writing you for a problem with the printing dimension.

For a project, i need to print a piston. For general that works, but if i messure the printed result, i messure different dimensions on the object. It looks like that this isn´t round.

Sure i have messure differences on the z-seam. But the other directions should more round.

For example: outer diameter: 26mm → messure: min 25,83 max 25,93
Or outer diamenter 22,2mm → print min 22,02 max 22,12

Inner diameter: 8,2 → messure 8,00, but this is ok because it looks like that all sides are the same size.

I have configured configured a material profil as good as i can, the printing results looks good.

Im wondering where the Problem with the dimension comes from? In this case im not able to use the x/y compensation, or correct the size in CAD directly.

Have anybody the same problem or a solution or reason for that?
Anything else what i can do?

The Z-high should be 10mm. messure: 9,82

I have also print a block with dimension: 25x25x18 (XYZ) i messure: 25,05 x 25,05 x 17,80

Thanks for your assistance

Kind regards
DrCarbon

2

Using the block you mentioned at the end, the .05mm is amazingly accurate for a 3D printer. You should be proud. The .2mm in the Z axis is not too bad but you can probably make it better if you check some of the settings, such as layer height for both the first layer and other layers and whether the layer height is an even divisor of the height. For example if all my layers are .3mm and I print a 1mm high object it will probably only be .9mm high. You can use a process profile with thinner layers and it might be more accurate.

As for the diameter of a circular object being printed, there are multiple factors that affect it. If you save an STL from your CAD program the circle is represented as a bunch of triangles. The circle is approximated by straight lines. Most CAD programs can be configured to produce STL files that are more or less accurate, which makes a big difference in the file size.
The best way to try to get a more accurate circular object is to export the model from CAD as a STEP file which is an accurate representation of your model. This allow the slicer to do the best job it can converting the accurate circular dimensions of the STEP file into G code that produces the best print possible.

BTW, based on your diameter measurements it is round to within .1mm which is again a reasonable expectation for 3D printing.

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