Re: Max stepper motor speed - rpm

> There are lower cost spring loaded acme nuts and screws that work
> pretty well for router applications. Your accuracy on a router is not
> as critical as a milling machine where you are expected to be able to
> make parts that will hold .0005 to .001 tolerance on a daily basis.
> Wood is more forgiving and if you can hold .005 overall you have a
> good machine. Wood will shrink and grow that much with just changes
> in humidity. While there is a level of self satisfaction in building
> a highly accurate machine, accuracy you don't need is just wasted time
> and money.

All things being equal, buy the thing that is most accurate. At some
point however, there are diminishing returns. There are classes of
ballscrews that have some super high accuracy, but you can spend 10
times the cost to get only marginally better. but, all that goes away
with a sloppy mount. OR, it gets rid of some problem. and besides
NASA needs to justify some of it's budget.

I did some work at a duPont nylon mill and they were chasing microns
in nylon manufacturing. It's been 20 years, but they said something
like one micron on a nylon thread was worth $100,000 a year. If they
made it too thick, they were giving away product. too thin and they
were risking product failure. Some people can justify the high costs
of things.

There is ACME thread, and leadscrew and precisonion leadscrew. Each
will cost more and each will offer better accuracy. Leadscrew will
also offer lower friction from it's smoother finish.

There are different accuracies of ball screws as well.

I often suggest looking at each type and getting the measurements and
then designing so they all will fit. (see tom's statement at the very
ends of his post)

> As you have probably seen,
> accuracy of your machine is a function of
> all the errors summed so you have to work
> at each stage to get the
> smallest amount of slop.

IIRC, accuracy is the sum of the squares of the errors.

>
> There are hundreds (maybe thousands) of us that have built routers,
> engravers, CNC mills, CNC lathes and plasma cutters. Each time we
> build one we immediately start mentally designing the next one!
> There is always something you would have done differently.