On 11/23/23 17:22, marcus.bow...@visible.eclipse.co.uk wrote:
On 2023-11-23 21:18, Chris Albertson wrote:
Yes, a magnet and a steel disk is the simplest possible design. If
you don’t need indexing. Nothing would move. The disk could slide
over the magnet and then when energized the sliding would stop.
The slop issue is normally solved by always rotating in one direction
so maybe it could be controlled?
I can’t believe a 1/2 degree error is acceptable. On a 100mm radius,
a 0.5 degree error amounts to mislocating the hole by almost 1mm.
My cheap made-in-India rotary table is way better than 0.5 degrees error.
My rotary table was not expensive, but it has an adjustment on the depth
of engagement of the worm, to allow backlash to be reduced.
I thought that was a fairly common arrangement.
Marcus
On Nov 23, 2023, at 12:11 PM, Ryan McIntosh <r...@pebkac.ca> wrote:
If you are going to clamp a metal disc with anything, use an
electromagnet... But if it's a worm drive with that much slop, I
guarantee
there's some improvement to be found by controlling the thrust
movement of
the pinion gear. Inserting a shim (could be punched out of an old
set of
feeler guages) under the gear where it shoulders up to the case can
probably reduce the backlash by a significant amount.
True of the indian rotary tables but yiu are also saddled with the slow
speed of the 90/1 geardown, with a nema 23 spinning it, a half turn
takes at least 15 seconds. These are cheaper Chinese 5/1 gears designed
to be driven by nema 23 or bigger steppers, and they are not adjustable.
*Ryan McIntosh*
E4F Designs
(204)770-3682
r...@pebkac.ca
On Thu, Nov 23, 2023 at 1:25 PM Chris Albertson
<albertson.ch...@gmail.com>
wrote:
On Nov 22, 2023, at 1:06 PM, gene heskett <ghesk...@shentel.net>
wrote:
I'd have to agree Andy. I need to design a disk brake for my A
axis as
there's half a degree of slop in the worm drive which if it gets to the
motor will be held, but the slop in the worm makes for sloppy looking
holes, but the activation method is still in my head. Even that is only
important when drilling a hole for the handle. I'll come up with
something.
Would a simple disk brake work? I think it might clamp the part any
place
within that 1/2 degree of slop range. Ideally, you would have an
index
plate and some way to place a pin in a hole to lock the table. But you
could only have a few holes and not enough holes for one at every
place you
might want to stop.
What if the disk had “V” slots cut in the edge. Like a very large US
Quarter Dollar, but with maybe 360 grooves. Then you could wedge a
shape
(like a tiny axe head?) into the slot and force the disk to stop on
an even
degree. You could use more than one wedge, space them around the disk.
A wedge would need a lot less clamp force than a brake disk pad
because it
is a mechanical lock almost like an index pin
If you still want a “disk brake” why not use an actual disk brake
from a
bicycle? They are about the right size, have huge holding power,
and don’t
cost all that much. The ones you would want to use are hydraulic
so the
electric actuator could be a couple feet from the rotating table. They
still make cheaper ones that use cable but avoid those, they are too
hard
to adjust.
Or maybe both, Use the slot and wedge to aligh the table to the
nearest
degree and then clamp it with a hydraulic disk brake. Cost is under
$100.
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Cheers, Gene Heskett.
--
"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)
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