Newbie looking at 6040 (China CNC) for polypropylene 15mm sheet

[Zeeflyboy]

I wouldn't get overly obsessed with the DRO giving a round number read out - better that it is actually calibrated correctly.

After all, other than for reasons of OCD consider that your 17.9188 from the DRO above is only 0.0012mm away from the commanded 17.92 - 0.0012mm is roughly half the width of a typical bacterium (which are commonly 0.01mm long too for context!) Basically it's a level of precision that your machine couldn't possibly hope to achieve anywhere near so it's irrelevant for all but how neat the DRO looks.

When you correctly calibrate the ballscrews, likelihood is that you will end up with a horrendous number like 321.24 as your calibrated steps per mm which of course means you don't have a snowball's chance in hell of ending up at a round number on the DRO.

I'm not sure how you arrive at your conclusion that you will be working to an error of 0.05 to 0.075mm.... but 0.05mm is nothing to be sniffed at... it's a very good level of accuracy realistically speaking - less than the thickness of a typical human hair.

Increasing the microstepping won't really help... if anything it just makes it harder for your motion controller to keep up at high speeds. Microstepping really only serves to make things smoother, gains in resolution are mostly illusionary.