Re: [CAD_CAM_EDM_DRO] Ball screws

I read online that a ball screw is a must if you want to build a CNC machine.The reasons being that the backlash or 'Play' that is always present in other screws is not tolerated.I also read that requirements are a little bit flexible for homemade CNC lathes.

 

My first question is,How are ball screws made?

There are rolled ballscrews and ground ballscrews.  There is a thread rolling machine
that rolls the screw stock between two form tools that also look like ballscrews.
The stock is heated (I think) and hot-rolled between the form tools to press
the thread form into the material.  The thread pitch is approximate, but a
properly set-up machine can produce repeatable thread pitches within a few
thousandths of an inch per foot.  The thread pitch can vary slightly from one
end of the screw to the other.

The thread grinding machine can produce threads of very high accuracy, but it
is much slower than rolling.  Therefore, the ground screws are quite a bit more
expensive than rolled.

The nuts for ballscrews have an internal thread similar to the ballscrew thread,
with a generally rounded form.  The old way to make an anti-backlash ballnut
was to have two separate nuts with Belleville washers (somewhat conical and springy)
between them to apply a preload against the threads.  Newer ballnuts have
two ball tracks with an offset between them that makes the short length
of ballscrew between them the spring.  This takes very accurate pitch on
the screw and in the nut to work.

My second question is,Can I bypass ball screws and use simple lead screw and nuts to retrofit a steel turning lathe into CNC?

Sure!  Lathes are a good case, as the cutting is all on one side for each
tool.  A mill, for instance, cuts some on the left side then some on the right
side, so backlash will cause an offset between these cuts.  When turning,
each tool is set for a specific operation (outside turning, inside turning,
facing) and therefore it would be a rare case for backlash to have an
effect.

I am asking this question because i do not have the funds to make a small prototype CNC lathe and then implement to a larger lathe.And ball screws cost a bomb to acquire.

Chinese ballscrews are a bit more affordable than the "name brands".

Jon