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#1 2017-04-20 23:48:00

jamesarm97
Member
Registered: 2017-02-02
Posts: 69

Rounding error when moving z up and down on the z calibration page

The printer I am using uses gcode to move the z axis (standard G1 Zxxx). Normally I print in absolute mode but then the buttons to move up and down go to that height and not up or down by that amount so I changed the manual move gcode command to switch to relative then move then back to absolute. I noticed that if I home to floor Z gets set to 0 on that screen. If I move up by any amount then move down by any amount that number seems to have a rounding issue. Moving up 50 then down 10 will end up with 40.007 then If move up then down again the number changes again in fractions instead of whole numbers. It only seems to have rounding issues when I move down. I don't know if that is cosmetic or not but we have seen complains of objects that seem to have different z heights than they should.

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#2 2017-04-21 07:23:54

Shahin
Administrator
Registered: 2016-02-17
Posts: 3,536

Re: Rounding error when moving z up and down on the z calibration page

Will try to fix manual movements on absolute mode.

To keep current position and movements accurate, NanoDLP internally keeps everything in pulses.
So when ask the printer to move 50mm up and 10mm down. NanoDLP convert numbers to pulses. In reality RAMPS also convert them to pulses.
So current position on NanoDLP is more accurate. But at end differences are so small you should not notice anything on models.

The real achievable resolution is depend on ballscrew and motor degree. (microstepping is not accurate) Optimum layer height must chosen using these two value otherwise both surface quality and models height is could be effected.

Absolute positioning is much more reliable in case of RAMPS.

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