[dfox1787]

does anyone know why when im telling to mach3 to move -y20 the dro read outs 19.991?

i zero y before i asked it to move

[ger21]

Could be do to your resolution, or steps/unit setting

[dfox1787]

Could be do to your resolution, or steps/unit setting

im currently calibrating the machine and my digital indicator is saying its moving 20mm but the mdi is reading 19.991 so my steps per unit are correct but the dro isnt displaying the correct value.

concerned when i machine the accuracy isnt going to be there.

[Torchhead]

The resolution of a machine is the smallest distance ONE step produces. That boils down to Steps per unit. You can't make a machine have more resolution that what the steps per unit are. Mach can take fractional steps per unit but it has to average them out of a distance by applying an added step here or there to get that close. To get higher resolution you either change the gearing between the motor and linear drive elements or you get a higher resolution motor (Servo with high line count encoder)
With no information on the motors, linear drive type or any gearing its just a general answer.

[jalessi]

Dfox1787,

The thickness or width of a human hair is seven times larger than the inaccuracy you are worried about.

Jeff...

[dfox1787]

Dfox1787,

The thickness or width of a human hair is seven times larger than the inaccuracy you are worried about.

Jeff...

are you saying you wouldnt worry about it. it is moving the correct distance according to my dial indicator.

[dfox1787]

The resolution of a machine is the smallest distance ONE step produces. That boils down to Steps per unit. You can't make a machine have more resolution that what the steps per unit are. Mach can take fractional steps per unit but it has to average them out of a distance by applying an added step here or there to get that close. To get higher resolution you either change the gearing between the motor and linear drive elements or you get a higher resolution motor (Servo with high line count encoder)
With no information on the motors, linear drive type or any gearing its just a general answer.

Hi torchhead this is a cheap china cnc 3040 machine. its driven by ballscrews and the motors are nema23 265oz 2.8a.

i think i just need to spend more time calibrating and maybe i can get it spot on. The dial indicator is saying the axis is moving the correct distance.

[jalessi]

Dfox1787,

See attached link for a little more insight into what you are experiencing:

https://en.industryarena.com/forum/mach-3-precision-question--212578.html

Jeff...

[jalessi]

I have no idea what your tolerance requirements are however I myself would never worry about a .009 mm discrepancy.

Jeff...

are you saying you wouldnt worry about it. it is moving the correct distance according to my dial indicator.