On 11/10/19 8:21 PM, Gregg Eshelman via Emc-users wrote:
Some ballscrews have every other ball slightly undersized so only half the balls are
taking any load. If there's enough wear, replacing the "spacer" balls with ones
the same size as the load bearing ones can take up the slack, and increase the load
capability of the screw. In some cases one or two balls may need to be removed to make
room. I've seen some screw rebuilders selling sets of bearing balls in a wide range of
diameters for the DIYer who wants to find the best size to take up the wear.
Problem is that won't help with a screw that's unevenly worn. You have to make
it run right at the ends where wear is the least, but it'll still be loose in
the middle. Some screw rebuilders will grind the screw to precise dimension the
full length then replace the balls with whatever larger diameter works best.
Having that done can make a rolled screw as precise as a ground screw, because
it will be a ground screw.
Last I looked into that (some years ago) I saw companies offering that
service as low as $40.
On Sunday, November 10, 2019, 4:34:26 AM MST, Gene Heskett
<[email protected]> wrote:
On Saturday 09 November 2019 21:44:20 Thomas D. Dean wrote:
I measured several rotations of the Z-axis lead screw on my Sherline
4400 CNC lathe.
The BACKLASH setting is 0.0035
Thats bordering on looking to see if it can be tightened up. Start by
checking the screws end play. I've added reynolds wrap between the outer
races of thrust bearing assemblies and their seats in the bearing
housings in brand new screws. Might have to replace the balls with
oversized balls, or figure out how to add ball thrust washers, I've done
both.
The Sherline 4400 Lathe is equipped with a threaded lead screw, 20tpi.
It does have a backlash mechanism that I have not adjusted, yet.
The Sherline 2000 mill does have a ballscrew update, which I have.
I was hoping for some understanding of the CNC software that would allow
for for a proper damping of the response. My lathe/software combination
seems to not be critically damped. There is some over/undershoot.
Tom Dean
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