Re: [CAD_CAM_EDM_DRO] Backlash

Hi Jon,

> The problem is your existing screw has differential wear. That means
> the thread
> in the most used part of the screw is thinner than at the ends. It is
> impossible
> to make a fixed anti-backlash nut for a worn screw. The only way to make

it

> work is by making one of the nuts spring loaded. This will greatly
> accelerate the
> wear on the screw and nut. If you replace the screw with a hand-made one

or

> one made from commercial screw stock, then you will at least eliminate the
> variation in the thread. (Note that crossslide screws are usually
> LEFT-hand thread!)

I don't think differential wear is the problem as the machine has done no
real work. I took it to bits because there was still some delivery grease on
the machine, although it is 10 years old. It was in a technical college and
never used past the first few weeks.

I can adjust the nuts to give me 0.1mm of backlash and the slide remains
free over all its length, but if I adjust the backlash tighter than this the
fast traverse loses steps. This is the speed the controller uses for all
fast moves and is not setable/changable in the software.

It was ok before the strip down but I think it might need some bedding in
before it will be that way again and I can't wait. I'd rather change the
design of the nuts. I will be putting a ballscrew on it but not just yet.

Regards,

Terry