On 11/23/23 16:19, 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?
This is true under known conditions, but when boring a slightly over
19mm hole for a 3/4" oak dowel with a 1/2" router bit, the slop is
bidirectional depending of which blade is where so if the stick isn't
held, the slop is explored to its limits by the cutting forces from the
router bit as it turns. I've also tried a forstner bit, same comment
because the skirt slicers aren't the same height. Much easier to make
the right sized hole with the router bit guided by linuxcnc.
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.
So is mine, but is also call a surveyer and have him set stakes slow.
This A axis can do 500 rpm.
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.
*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.
--
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soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
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