just tried the backlash off, still the same result.

Out of interest, what are your acceleration settings. If it losing steps at the end, or start, of a line of code when in exact stop, this could still indicate acceleration problems. You have a huge difference in leads between your X and Y axes and your Z axis. I would expect you to have to have a large difference in your acceleration setting between these also. With a 1" lead on Z, it takes a very large amount of energy to get it moving and it could just be that it is too much.

Mike

In addition to Mikes question,
Which axis is losing the steps?
What type of drives do you have?
What type/size of machine?
What size motors?

Hood

X an Y axises is loosing steps.

I use step motor drive from gecko

what type of machine ? I built my self... it's a router with about 1 meter square travel

motor size is ... the diameter of the motor is about 4 Inch. forgot the nema size.

Mike,
I think what you said is make sense, I will check the acceleration between those 3 axis, and try the result.
here is the acceleration setting I had

XY steps per 157.48, Vel 1999.8,    Accel  200
Z  Steps per  100,     Vel 1999.8,    Accel  100

Out of interest, what are your acceleration settings. If it losing steps at the end, or start, of a line of code when in exact stop, this could still indicate acceleration problems. You have a huge difference in leads between your X and Y axes and your Z axis. I would expect you to have to have a large difference in your acceleration setting between these also. With a 1" lead on Z, it takes a very large amount of energy to get it moving and it could just be that it is too much.

Mike

Mmmm, I would expect it would be the Z axis losing steps if it were acceleration issues. However, it still could be. Could your X and Y axes be binding anywhere or stiff to operate? This too could cause missing steps.

How long has this been happening? Is it just on this job or has it always lost steps?

Mike

if I do the radial cut with Z depth, it's 90% loosing.

if I do only circle/pocket cut it's like 30% loosing.

but never loose on Z !.

X Y binding or stiff ? I have no idea how to check, but I never bind nor stiff X and Y, I don;t know how to.

very notice loosing when cutting  radial on Sphere object, reading the lines sometime stop for split second, it's not smooth reading the gcode lines.

I don't think I have backlash on XY or Z.
the result when cutting sphere is not always the same spot (loosing step)
it's never on Z, I don;t think Z ever loose step, as far as I know.

this been happening since the beginning, but I never notice I though my feed rate is too fast.
now I know is not the feedrate.
I rarely cut Sphere, but since I found this problem I got to solve this by cutting sphere for testing.

I presume, from your steps per and previous info on screw leads, that you have some gearing or belt reduction on your axes? Can you let us know? Also, what type of screws do you have ballscrews, acme, etc.?

You might want to try lowering the acceleration way down on all axes and see what happens. Mach will take care of the coordination.

I've just read your latest and it is well worth trying the lower acceleration.

Mike

mike,
I will do test tomorrow the acelration.
I use Ballscrew with 5 mm lead on X and Y.
I use ballscrew on Z with I think about 1 Inch lead.
I use step motor with NO gear ratio nor belt reduction, it's a direct drive from motor to ballscrew.

mike,
I just tried... I can not wait till tomorrow.
the result is still the same.

I decrease the acceleration to 25% on each axis. so it's 50 on XY and 25 on Z.

no good