On 7/16/25 08:00, Stuart Stevenson wrote:
What is the difference between:
1: stepper/servo (Hanpose, et al)
This I am becoming convinced is the next, fine grained method of
positioning a stepper motor. Considerably more precisely than the usual
pid and such. and given the increase in voltages capability of the
drivers allows all this to be done on a microsecond basis, potentially
to the encoder count accuracy. An accuracy amply demonstrated by 3d
printers as the errors a motor makes in trying to microstep it are at
least 5x more controlled when the evidence of a fractional full step
error is preserved in plastic for later analysis.
2: BLDC servo
3: A/C servo
Neither of these have been explored by me other than an attempt to do it
in my hal file while attempting to control a Chinese BS1, with a
stepper/servo motor that was intended to run a gate blocking a gated
community access road. which had a 90/1 output strong enough to turn the
worm of the BS-1. I did this about the time LCNC did away with the PID
in favor of the ATPID. But I found the doubled geardown presented time
lags this new ATPID wasn't able to self calibrate, so it hunted about
half a degree until it smoked a 24 volt motor running on 24 volts. 2 of
them before I gave up, at a cost of $125 a copy, and it was about
1/1000th of the speed I needed nearly 3 minutes to turn a full 3b0
degrees. Not a usable solution.
So still needing to solve the problem of carving a buttress thread ( and
not reallt famous for thinking inside that box) I next put a 3NM 3 phase
closed loop stepper on the input flange of an RVS30 5/1 worm drive from
fleabay, printing the output chuck. I put a 7 degree wedge under the
motor so the load side of the tooth was cut by the side of a 1/16" RN
mill with a .250" DOC. and wrote the gcode to carve the rest of the
tooth profile. only 4mm tall, 6 mm back angle but 12mm pitch by carving
one thread of a 2 start going down the length of the thread for one
start, withdrawing the bit, adding 180 degrees to the B axis, moving the
bit back to cutting depth and cutting the 2nd start coming back to a 180
degree stop. This results in the B axis turning about 500 rpms during
each stroke. Beautiful buttress threads in hard maple. Turned off the
water to my mister on that mill to just blow the sawdust away. Then I
modeled that same shape for the half nuts which are identical pairs in
OpenSCAD and printed them as 2 copies of the same g-code but offset on
the build plate. Now my problem is the speed of the printers so I'm
about 50% done building a 2nd even bigger one. I can make 3 screws a
long day on the mills, but it takes a hobby priced printer about 2 weeks
to print the rest of the parts to make one vice screw so a 2nd bigger,
faster printer is under construction. The target is a screw a day ready
to ship. If I last long enough. . .
It seems to me to be describing the same technology.
It might well be, but it seems to me to be the better and cheaper way to
get a well tuned implementation, just rip the PID's of your .hal and
bolt these in. Readjust the TP's speed and accells, Problem solved.
Machine can be moved with precision up to 10x faster. With less total
power from the wall. Whats not to like?
Thanks
Stuart Stevenson
4638 Farmstead Ct
Bel Aire, Kansas 67220
316 258 0953
stus...@gmail.com
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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