Sieg X3 stepping its cut

[brento]

Yet another problem with my mill. As it steps down on the z axis to begin each cut, it is shifting over a few thousands each time along the x axis. this is causing the sloped cut in the photo. What could be causing this? I checked all the lines of g code and they are fine and there is no discernible backlash in any of the axis. The fixture is tight and there is no movement there.

[wendtmk]

Perhaps posting this question in the "Benchtop Machines"forum might get you an answer. This forum is dedicated to LMS CNC machines. In other words, CNC machines that LMS sells, not conversions.

Mark

[brento]

This is a LMS mill that I purchased less then 10 months ago.

[wendtmk]

Was it a Little Machine Shop CNC mill or a conversion? If a conversion, that's what the Benchtop Machines forum is for. This forum is for machines that come from LMS as CNC machines.

Mark

[LUCKY13]

It sounds like your spindle is out of tram. Have you check for tram?


Jess

[brento]

It was purchased from LMS as CNC. I just checked their website, apparently they no longer sell this model, but it is not a conversion. I have checked the tram and it is good. I was wondering if a bad stepper motor would do this?

[rpovey]

His tram would have to be miles off to see that amount of slope.
I think it's more likely a wiring issue, his x axis picking up some noise when his y axis moves down?
Or possibly he's just losing steps in x or y because of a mechanical issue.

If you cut a circle repeatedly at the same depth, is it circular?
Does the cutter correctly repeat the path?

[brento]

I will try the circular cut, but as far as cutting the part in the picture, it appears that it is shifting a few hundreds to one side at every pass and that is where that slope is coming from. I just ran the same program cutting a piece of wood instead of stainless steel and it came out perfectly. I am interested in this electrical interference possibility, how would I go about testing for it?

[brento]

Here is a picture of a waterproof ipod case I made a little while ago. if you look at the bottom of the cut to the right on the last few passes you will notice that it stops cutting steps.

[rpovey]

Originally Posted by brento I will try the circular cut, but as far as cutting the part in the picture, it appears that it is shifting a few hundreds to one side at every pass and that is where that slope is coming from. I just ran the same program cutting a piece of wood instead of stainless steel and it came out perfectly.

Then it's much more likely a mechanical problem and you're dropping steps while making the cut, rather than the axis moving when you step in Z.

You don't say if you are using Mach or EMC, but try changing the axis acceleration and velocity to extremely conservative values (1/2 what you have now or lower) and try the cut again, you can worry about increasing the settings once you identify the issue.

Edit - Just read you we're cutting stainless, try the cut with less depth and speed, you may just be being too aggressive and losing steps.

[brento]

I am using Mach3. I will try being less aggressive, but that ipod case was cut in aluminum with the same results. What I can't pin down is why sometimes it is staggered and sometimes it is not. An example is when it is near the last few passes and it is cutting the material support, it tends not to make those steps. If it is a mechanical problem, would the lack of resistance when running the program on a wood block indicate that? Is it perhaps a problem with the ball lead screw?

[rpovey]

Could be almost anything, gibs could be too tight lead screw could be binding, etc etc.
But I'd start by reducing acceleration and maximum velocity in the mach axis setup.
There isn't a lot of point in speculating until the issue is identified.

The fact it's not doing it in wood, just suggests to me something is very borderline there is less resistance to the cut in wood, that AL or obviously stainless.

You can usually hear stepper miss steps, do you hear anything odd when cutting?