why ballscrews???

[50062040]

i am thinking about a mill drill (square column) cnc conversion, my question is why would i want to spend an extra $500 on ballscrews? accuracy? speed?

And another thing, linear rails, it has less friction so wouldnt it be easier to pick up slack on backlash making climb milling imposssible and negating all the good effects of having a heavier table?

the table on linear rails would be easier to move within the range of backlash so this would lead me to buy ballscrews in the first place.

[NC Cams]

Depends on what you want to do and how accurate you want to get and how much cash you want to spend.

Ground acme screws can be made as accurate as ball screws for a cost - don't know the relationship.

Ultimately, it comes down to friction and wear.

The rotating torque of a preloaded (negative ball clearance) zero lash ballscrew is going to be lower (ROLLING friction) that the SLIDING friction of an acme. The lower friction potential of a ball screw facilitates higher operating speeds. In addition, you should be able to any given speed with less power input with less friction in the driving member.

Properly hardened and metallurgically compatible parts that roll with respect to one another have less wear potential than those that slide.

I don't think you'll be disappointed with the screws. It is better to be looking AT them than FOR them at a later date.

[fignoggle]

rockfordballscrew website has some good info on this topic. the only thing i would say about one or the other is that if you intend to maintain manual operation of your mill, it's nice to have that friction of the acme. even then, there are some acme screws that claim to be very efficient (haven't tested yet).