Considering a Full Rewire on a Working Schaublin 125 CNC

You are making great progress. Took me a year to get that far

I can't say why it is not working as it is, but I have no linear scales, so my homing is just the home Hal switch and then fine tuned off the motor encoder index, and that is rock solid. Could you ignore the linear scale, and home the same as mine (which I think is original Schaublin)?

Please upload some pictures of your linear encoder installations.
Cheers,
Mark

I don’t think the linear scales are at fault. I tested them over the 20 mm range of my longest indicator in 1 mm steps, and that is flawless for both axes. I also had the axis move over nearly its full range for 5 minutes at rapid speeds and then come back to the indicator, again, no measurable deviation.

To test the motor encoder directly, I would have to solder them in, and I cannot imagine that this will be better, as I already use the index from there. But if I don’t have any other options, I may as well try it.

I can make some pictures tomorrow, do you mean the mechanical installation on the machine or the wiring, or both?

I don't think you need to wire the motor encoder A and B signals in to LinuxCNC to try it. It is a standard LinuxCNC option to home to switch (Hal switch) and then to the next encoder count, which you already have wired in.

I am interested to see how they did the physical installation of the linear encoders. I considered adding them to mine, but didn't.

The previous owner installed a magnetic encoder on the X axis. I did not disassemble it, so all there is to see is a thin cable coming out.

I installed a glass scale on Z. I will make photos tomorrow, there is perfect space for it behind the X-axis motor mount. The installation was really easy.

Oh, and to “home to switch (hall switch) and then to the next encoder count” that is what I did initially. That way I got about 0.4 mm variability on X.

Since there are two Hall sensor triggers on X, do you get the same errors homing off each?

Oh, I had forgotten about that. I will try if that works. Thanks for the idea.

So,

I have a great update. I got the machine working. Using the X-minus hall switch did not do the trick. Testing everything that I already thought was not the problem gave me the solution. The magnetic linear encoder in the X axis was the problem.

I did most of the testing of it at low speeds and short distances, as my indicators obviously cannot measure the length of the full axis. I can remember doing a test running the whole axis at rapid speed for multiple minutes, but I may have done this only on Z, it was two weeks ago. Or it got worse somehow, I don’t know.

In the end, using the motor encoder resolved all the problems.

I also disassembled the X axis to see how the encoder is installed. There is a very small read head in the plate behind the thrust bearing for the ballscrew and a putted scale in the underside of the X-axis slide.

I also made some pictures of the Z-axis encoder.

And then, after I spent all day getting this done, I was able to actually make op 1 on the test parts I wanted to make as test parts.