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High accuracy applications?
I am planning the rebuild of my Schaublin 135 lathe.  I am not happy with my current dro installation and would like to use something more flexible.

I want to try anyway, to move the cross slide and compound scales inside (with very small magnetic scales) and add an angular encoder to the compound with a conventional protected scale for the long axes. I don't know if I can keep the internally mounted scales clean enough but it seems worth a try as the extrenal mounting options are not ideal.

This project is far from cheap (the rebuild alone will cost at least 4k Euro for grinding etc and hundreds of hours of labor never mind the machine purchase or the climate controlled workshop I have built for it) so if I need to go with Heidenhain I will but TouchDRO is an appealing option if it will do the job as it should be far more flexible and obviously less expensive.

The question is, given the same quality of scales (up to micron resolution anyway) should I expect any actual difference in accuracy with a commercial counter/display?

This is a cool project and if not this application I am sure I will end up using it on one of my machines. 


All of the accuracy is in the scales that you use and how you mount them, at least for linear movements. The accuracy of Yuriy’s math when you combine linear and rotational axes I can’t speak to.
How much if any difference would be in,

1 . The circuitry and its resilience to stay signals, partially this needs the board to well designed but also how you wire it in and how close the wires get to motors etc.

2. The 1 micron scales need to output a A B and =A and -B which can then be compared and used to recognise stray signals.

3. The board needs to receive and use these -A and -B .

This can be done with Yuri's boards.

The only feature I have seen elsewhere is variable calibration, ie where you can divide the scale range and calibrate each zone differently from the other zones. But if you are using new scales this should not be needed.
the counter is not the problem, the scales, and how they are mounted is what is important.  Keep reader head wires away from motor and vfd's. look at scales from mitutoyo, they make all sizes and precision to meet your needs

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