After finding the backlash on X about 0.5 mm, actually not a backlash, it was the X spindle mount that was not tight enough.

so I fixed that and running the real cut.
the result ... still the same, but this time when I go back to Home/reference, X0,Y0 it it Correct 0,0. no shift at all.
that was 3 time testing with checking to reference 0,0. no shift at all.

Now I see a pattern like X pattern of problem from top view, I hope you guys have an idea what's wrong or something worth to check.
what I hear when it cut radial on Diagonal cut it sounds like loosing step/louder.
is this not right ??

I use the motor accelerator at the lowest around 8 on XYZ.

I don't know where to ask for help.

Help 

Calico,
Can you post the Gcode file your using?

There appears to be some repeatability from what i see in the pic's .The four gouge points are somewhat in the same place.
There are differences in the cutting between the pictures. If the gouge points are towards the end of the code that would indicate running time is a factor.

RICH

here is the Gcode.
thank you

Calico,
Based on the pictures "seems " like it's gouging somewhere in the first 2000 to 4000 lines of code.
I assume you have a viewer, so find find where the rough is commanding the moves to that level.
The pic attached shows the rough progression to about 2000 lines.

Deleting all the code past that level would allow you to run a much shorter program to analyze the problem.
Hopefully it's repeatable
RICH

Rich,
Thankyou for yor time helping me on this issue.
I have done using only smooth cut, no rough code, just cutting air, the result is fine.

If I cut the real material that will break my bit.
Smooth gcode cut air have a good result but i had tested good with rough and finishing gcode once.
If the rough cut is the cause of this issue I can use any othrr rough toolpath.

But I'm very curious about this issue, why the rough cut cause this? Assume if is is the problem.

Cal

If i find that line cause the issue then what should i do ?

Calico,
You are loosing position at a number of spots along the way. So it is not only the roughing. You can see it in the pictures.
I wanted to find the worst / first ones that were causing the gouging and that seems to be in the roughing.
Seems that first gouging accurs, approx, after each 1/4 of code run at a particular  depth level when roughing.
So it would be nice to just have that grouping of code to help find the problem, call it a test file.

Then you confirm  that there is no error in the code for the Z depth cuts.
You then air cut with the test file and confirm you are not loosing position.
Have a look at the code and make note of approx how much material is being remove and do some manual straight cuts
in some scrap and see if you loose postion.

I think that over a period of time, you are heating up the stepper motor  and causing the gouge in roughing.
You could reduce the rough cut depth so the motor is not working as hard.
In the finish passes it's also time related as every 1/3 to 1/4 of the code group you are out of position.

Maybe,generate code for a piece half the size and depth and see what happens.

Maybe someone can be more definitive.........

RICH

Rich,
I will try to reduce the rough depth first see what happened.
btw that issue never loose position, after those cutting I hit Home Z and it was the exact position xyz.

so I assume there was no loose step.

but I will reduce the depth, see what happened.

What your after is the code grouping where the big gouges occured.
From that code extract the pathing for a complete rough along one radial out from the center,add the next radial for a complete
rough to the bottom, make a loop out of it in a sub-program. This way you can just vary the number of loops and observe.
This way the file will be very small.

You can do the same for the finish pass.

What is causing it can be a number of things.

RICH

Ian,
here is the photos ... you can see the lost steps on 2 spots.
forget about the dimple, it's a hole on the next cut.

as you can see the Z /edge is very smooth/no loosing steps

that looks like you are missing the code to take out the material.or maybe it is jumping that section of code.