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3D_MD
(@3d_md)
Active Member
Printed object is not the correct size

Hi all,

I have printed many calibration cubes that are a known dimension. They always print well and are within 1% of the expected size. For example, a 20 mm cube will be 20.02 mm, and so on.

Recently, I have downloaded a model from Thingiverse, imported and sliced it using PrusaSlicer, and printed it. It has a dimension that is supposed to be 2.2 mm. In Blender, I verify that the measurement is correct. Yet, when I print it using my Mini, it has different dimensions. The error here is significant. The measurement is meant to be 2.2, and yet is 2.34-2.39.

Can anyone tell me why this is happening and what I could do to fix it?

Thanks!

 

Posted : 06/12/2021 3:22 am
jsw
 jsw
(@jsw)
Noble Member
RE: Printed object is not the correct size

How does the total length/width of that object compare to what it's supposed to be?

At small values, like a 2.2mm object, things like the width of the bead of molten filament can be very significant in dimensional accuracy.

Posted : 06/12/2021 4:47 am
3D_MD
(@3d_md)
Active Member
Topic starter answered:
RE: Printed object is not the correct size

Thank you for your reply.

The total length and width (80 mm nominal) is correct (79.92mm for both).

When I zoom in on prusaslicer, I do see the "column" in question is comprised of five passes. Am I correct that a 0.4mm nozzle always puts out a bead of filament equal to its diameter? If so, I guess I am curious why this cannot be 20 mm (0.4 x 5).

Thanks for any help!

Posted : 06/12/2021 12:22 pm
fuchsr
(@fuchsr)
Noble Member
RE: Printed object is not the correct size

Am I correct that a 0.4mm nozzle always puts out a bead of filament equal to its diameter?

It's actually defined by Extrusion Width in your print settings in Prusaslicer. The default is 0.45.

Posted : 06/12/2021 12:30 pm
3D_MD
(@3d_md)
Active Member
Topic starter answered:
RE: Printed object is not the correct size

Oh! That’s interesting. I guess I should play with that value (decrease it, if possible) to see if I may be able to get this a little more dialled in. Thank you.

Posted : 06/12/2021 12:33 pm
BogdanH
(@bogdanh)
Honorable Member
RE: Printed object is not the correct size

 

Posted by: @3d_md

...Am I correct that a 0.4mm nozzle always puts out a bead of filament equal to its diameter? If so, I guess I am curious why this cannot be 20 mm (0.4 x 5).

 

If  you look at Prusa Slicer (Print Settings>Layers and perimeters: Vertical shells), you will see, that "recommended" single line width is about 0,42mm. But that's just for reference. For example, for a wall made of 5 lines of equal width, total wall width should be 5x0,42=2.10mm.
In your case wall width is 2.2mm and so center line will be slightly wider (see this ).
The thing is, if you use Ensure vertical shell thickness in slicer (which is "yes" by default), then you don't really need to worry about outer wall dimensions.
There will always be some deviations in final printed dimensions (which mostly depends on extrusion accuracy and filament shrinkage).

[Mini+] [MK3S+BEAR]...
Posted : 06/12/2021 1:10 pm
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