I just print the cube with Acceleration Control and Jerk Control disabled, Horizontal Expansion = 0mm and Initial Layer Horizontal Expansion = -0.25mm. Unfortunately the measured X & Y error is almost the same as before. The measured dimension is 10.19x10.10x9.90mm. It looks like Acceleration Control and Jerk Control don't matter in this cube test.
Then I enable Acceleration Control and Jerk Control again, set Horizontal Expansion to -0.07mm & Initial Layer Horizontal Expansion = -0.32mm. This time I get 10.00x9.98x9.93mm (excluding the elephant foot). The result is pretty good since the error of all axes are smaller than 0.1mm.
So, the current Horizontal Expansion option should be enough for me. The only problem is the elephant foot. The 2nd Layer Horizontal Expansion option should completely solve the issue.
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gr5 2,224
All the other "initial layer" parameters override settings for the first layer and don't sum. So you probably want -.32 in this cae.
When measuring the error of the part make sure the micrometer doesn't touch any corners! Corners have their own error caused because the print head is slowing down. In fact if you want high precision then make sure you turn off:
1) acceleration control
2) jerk control
And make sure all the printing speeds are the same (because when it switches from (for example) infill to shell if it speeds up it will underextrude for a few seconds or if it slows down it will overextrude for a few seconds.
vertical cylinders are indeed going to be small because the filament is like a liquid rubber band and is pulled inward. I usually add 0.4 or 0.5mm to all my vertical cylinder holes in cad (but not to horizontal cylinders.
You can add a chamfer at the base of your part to compensate for all of the horizontal expansion/elephants foot. I know it's not as easy as using initial horizontal expansion. Sorry - that's all I have for you.
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rcfocus 0
Thanks gr5 for comment. I will try to turn off acceleration control and jerk control.
I have used the "chamfer trick" for many years (since UM2). But it is really very very inconvenient for my case. I design 3D models for customers and use UM3 to verify the design. Finally customers will make the mold according to my design. I hope the design is consistent. If I add chamfer then there will be a risk that I forget to remove it before sending the model to customer.
In fact, chamfer is also not perfect solution. I have tried chamfer from 0.2mm to 0.8mm, 45 degree. The result is not good enough. Theoretically fillet should give better compensation but it is not suitable for printing.
I think an option to tune the 2nd layer expansion would be the ultimate solution.
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