OK did that test.
Im moving forward against the dial indicator in X in steps of .010'', these are halved on the dial indicator as in DIA mode.

I moved 5 steps of .010'' forward and 5 back, so from 0 to .050'' and back to 0 again.

Here are the measurements for each tap od .010''

forward movement of .010''  moved .0045'' on indicator, so .0005'' short of .0050'
forward movement of .010'' (.020'')  moved .0095'' on indicator, so .0005'' short of .010''
forward movement of .010'' (.030'') moved .0140'' on indicator, so .001'' short of .015'
forward movement of .010'' (.040'') moved .0195'' on indicator, so .0005'' short of .020''
forward movement of .010''  (.050'') moved .0241'' on indicator, so .0009'' short of .0250''

I then reversed the taps to move X away from the dial indicator

backward .010'' (.040''), dial reads .0200'', spot on half.
Backward .010'' (.030''), dial reads .0149'', so .0001'' short of half .0150''
backwards .010'' (.020''), dial reads .0102'', so .0002'' over half .010''
backwards .010'' (.010''), dial reads .0050, so spot on half again.
backwards .010'' (return to zero), dial reads 0.

Mach is version R3.043.066

Ok I would suggest you try 057 version you will find it on the ftp site. There have been issues with 066 and 067 versions especially with Turn but I am not saying that is your issue but worth a try.
The other thing I can thing of is change the X Step pins active state.

To find the ftp site go to Downloads tab at the top here then to Mach3 then you will see it says for older versions click here.

Hood

Hi Hood

Just turned Exact Stop on, as we had it set to Constant Velocity and an X-1 move error has gone from being .0015'' short to .0008'' short. Nearly halved it just with that option. Will download latest version. Is there a way to keep all the settings we have right now?

CV should not make the slightest bit of difference with a single axis move but it could be 066 version, will be very interested to know
Hood

Got 57 installed but it wont let me do an x-1, says 'Cannot do G1 with zero feedrate'

You are in G95 mode, feed per rev, change to G94, feed per min from MDI and it should work.
Hood

Gave it a feed value and its happy now. An X-1 move with Exact stop enabled gives an error reading of .0018'', so worse than version 66
Constant Velocity gives an X-1 error of .001'' better (not as good as version 66). Will see what the G54 commands do now.

Once you gat the steps per unit set based on calculating or using Mach to set them you then measure to confirm that they are correct.
Rather straight forward but then there is usualy some error that one finds .........that sillly few thou. So i will call it the refinement part of finding the steps per unit.
A lot of things come into play when looking, accounting, and thus adjusting for the small inaccuracies.

Chances are that MAch or the software are not the culprits for the inaccuracies. As stated before, Mach gives the commanded instructions for the move and the axis will move as instructed.

It is fruitless to addrress backlash until you have rationalized out the refined steps per unit. You will have backlash, it can't be zero, just a matter of how much.
The refinement of the steps per unit requires that the user be very meticulous in whatever measurement they make and use. Said a different way the simple question is .....What did you measure?

Just a few thoughts that come to mind:
- The indicator is not calibrated or repeatable or not placed well for the measurement
- The ball screw is not linear
-  Coupling has backalsh ( if solid one not a problem but if anything else can affect the reading / repeatabillity)
- Thrust bearing loading ( and this can apply to the stepper motor itself especicialy if directly coupled to the screw)
- Any axis component inaccuracy ie; belt tension, gearing, bearing., etc)
- The motor itself in how well it will microstep.

 All of the above come into the refinement and one needs to know what is causing the error and what if anything can be done about it.
Some are easy and some are a real bear to isolate.

FWIW, back to the side ...........,
RICH






 

 

Ok sorry I misread your previous post, was for some reason thinking you said no spindle feedback message

Hood