The New Machine

[Ricardoco]

Hi Rick

AH! Confidence truly is that feeling you get just before you understand the problem :heehee:

.001mm is one micron. Standard ball nuts give you 50 microns, shimmed gives you 20, the only way to get 1 is to use double nuts and spring them. Helps if you can hold the screws in tension with more springs. The Belleville washer is your friend. You can compensate for backlash, but you will forever expect the tool to dig in.

Ball nuts bed in, they may feel firm but you are probably pushing against the dust seals and kidding yourself. The seals can't hold it when the tool loading kicks in.

If you bolt the column to a brick wall I would suggest a 5 micron step, 200 steps/mm is optimal for accuracy and speed. Half step is good, quarter step is vaguely credible, beyond that everything gets too springy.

Getting high accuracy is more a problem of rigidity than anything else. You can't mill to 5 microns because the tool will bend, you can't skim 10 microns, it will simply ignore you. To get 5 microns your tooling needs to cut a mirror finish. IMHO 5 microns or better has to be ground.

Good luck :naughty:

Robin

Well as I said if I aim high and do the best i can with what i have its an education and im not sure it will hurt will it. I do wish in my original post i had used the work theoretical...

[Rogue]

.001mm is one micron. Standard ball nuts give you 50 microns, shimmed gives you 20, the only way to get 1 is to use double nuts and spring them. Helps if you can hold the screws in tension with more springs. The Belleville washer is your friend.

By double nuts do you mean the "double ballnut" that somewhere like Zapp sells, or do you mean using two seperate nuts and combining them with the spring?

I've seen the latter in different places around the internet, but I didn't know if the former was simply a commercial version of the latter.

[Jonathan]

I'm pretty sure Robin will mean two nuts sprung, hence the Belleville washers. I think the commercial versions are just shimmed. To eliminate backlash you need them to be pushed apart using a spring applying a force greater than any cutting force plus acceleration, F=ma, you anticipate.

[Robin Hewitt]

By double nuts do you mean the "double ballnut" that somewhere like Zapp sells, or do you mean using two seperate nuts and combining them with the spring?

Either, if you use a double take the shim out