I'm guessing most of the variation is within 1cm of the build plate (aka bed)? The bottom layer is very hard to get the same diameter as the layer above because of how hard you are squishing the bottom layer. And if you increase the distance between the bed and the nozzle in your leveling then the part doesn't stick as well. So this is the hardest layer to be the same as the layers above but it can be done by using a negative value for "horizontal expansion first layer".
The next few layers above tend to move inward for a few layers maybe 3mm, and then they move outward again, and then by 10mm from the build plate you should see extreme consistency. This bowing in is related to the temperature of the build plate. So now you have more compromises:
You can lower the build plate temperature to say 40C, but now large parts are more likely to warp up at the corners and come off the bed. For small parts if you need perfect cylinders (say under 3cm in diameter) then this might be the way to go (40C bed). But for larger parts - more than 80mm across you need to keep the bed above the softening temp (about 52C for pla).
In addition to all this, note that as PLA comes out of the nozzle it cools rapidly (in milliseconds) and PLA sticks to itself (which makes the prints better than for other materials) while still liquid so all corners and circles on a given layer (all circles drawn as circles by the X/Y movements in a given layer) are going to pull inward as the stretchy-liquid-rubber-band like material is pulled inward. I usually compensate this by, for example, making all my vertical holes about .3mm larger than the goal diameter.
In summary - the variations you are seeing are probably caused by the material and the temperature and the movement more than the machine itself which is consistent to much better than .3mm - probably about 10X better than that (.03mm).
A photo might help though. We may be talking about different things here.
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yellowshark 153
Hi, this has nothing do you with your printer, probably, but is due to the way 3d printers print circles. I.E. they do not draw circles they draw lines and as a result the diameter of a circle will always be smaller. So you have to give your circle a bigger diameter at design. It may take you a couple of goes to get it right but once you have done it a few times you will get a feel for your printer and will know what increase to make.
For straight lines you should be able to hit +/- 0.05mm accuracy. I will not guarantee anything better but can normally hit 0.03 or 0.02.
As long as you are well set up then printing slow is the key to accuracy.
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CS3D 0
Hi,
Thank you for your answer. It is really helpful.
But when I talk about "variation of the diameter of 0.3mm" I mean that the diamater for my 55mm circle varies from 54.89mm to 55.18mm
Thanks
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