On 1/4/26 14:53, andrew beck wrote:
thanks for all the replies guys
just answering everyone now
Gene i am using brushless AC servos already (just like your closed loop
steppers only better) your steppers sound pretty cool but you will find
that once you get into the larger kw sizes its best to just go straight to
servo motors my motors are 3.5kw (steppers with the closed loop drives
and encoders kinda become servo motors anyway at that point)
3.5 kw? properly geared that could tun your whole 3 bedroom ranch house
about 5 rpm!
The one time I tried to do a servo from scratch, I found the control had
many degrees of rubber in it,
and when I tried to autotune it, it burned up the motor from violent
oscillation. And did the motor a ~30~ in 20 secs
with lots of smoke.
I was trying to make an A axis out of a chinese BS-1 clone. Stunk the
garage up for a couple gays.
I still needed a fast rotary, so I bolted a 3NM 3 phase closed loop
stepper/servo to a 5/1 rvs30 worm and printed
a chuck for the end of a 2x2 stick. Made a B axis for my rebuilt 6040
gantry mill first. Turns the chuck around
600 rpms in perfect synch with the Y axis while carving the buttress
threads on a hard maple stick into a
woodworkers vice screw long enough to grab a 1x12 by the edges. That
worked so well I made another
for my GO704. Accuracy is the backlash in the RVS30. 10 arc-minutes
maybe. And the psu draw is under 100
watts for that motor. Glad I don't get that light bill for a 3.5kw per
axis setup. Efficiency.
regarding the ballscrew preload. i think i will try the scales first and
then if i have issues i will look at ballscrews. currently i don't want to
put a whole lot of time into this. just want to wire it up and forget
about it and then make parts on it.
i need pretty good accuracy on the z axis for height but currently the x
and y axis don't actually matter too much for the job i have for the this
machine right now
and i already have a spare magnetic scale for the z axis so i will try set
that up in a few weeks and test this dual feedback PID stuff
I have a horizontal mazak 5 axis cnc 22ton beast, that has taken a year and
a half now to get going lol and i know how these projects can stall a bit.
i had a few issues with old tired drives and should have just pulled the
pin and bought new drives early on
but tried to repair them for awhile. because we don't have many people in
new zealand that can repair them and i don't have the skills myself that
didn't go well
once i bought new drives it was easy lol
but between the toolchanger and the pallet changer and something like 20
separate motors on the machine that all need wiring up to contactors or
drives etc there is a lot of work
now finally its all finished apart from the spindle motor. just got this
last one issue. it's a special permanent magnet synchronous motor and i am
having issues getting a vfd to run it
On Mon, Jan 5, 2026 at 5:08 AM Sam Sokolik <[email protected]> wrote:
I would have to look again.. but I think I remember the k&t ball screws
are preloaded to 1 ton of force..
Sam
On Sun, Jan 4, 2026, 10:03 AM Ray Henry <[email protected]> wrote:
Many of these commercial machines have double ball nuts and a linkage
between so that they can be rotated against each other to take up wear.
On Sun, 4 Jan 2026 at 12:59, Stuart Stevenson <[email protected]>
wrote:
I don't know how much preload is considered 'tiny'. The 5 axis Cinci X
travel is 120". The preload stretch is supposed to be .007" measured
with
an indicator on a mag base on the casting beside the screw while
tightening
the nuts.
That sounds very tiny on that length. It pretty much falls off the
bottom of this bolt-stretch calculator.
https://www.engineersedge.com/hardware/bolt_elongation_formula_15777.htm
--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912
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Cheers, Gene Heskett, CET.
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-Ed Howdershelt (Author, 1940)
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- Louis D. Brandeis
Don't poison our oceans, interdict drugs at the src.
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