Why are you particularly worried about that? Cyclodial gear boxes and
harmonic drives are both basically 0 backlash, with potentially some lost
motion. Most are repeatable well under 1 arc minute, which compared to a
lot of rotary tables already out there. And that's something like a .0017"
displacement on a 12" radius. Angular transmission accuracy would seem to
be almost as big an issue that you'd have to start to think about if
you're concerned about those levels of backlash. Also overall mechanical
stiffness.
-Dave
On Sat, 16 May 2020 01:49:58 -0400, Roland Jollivet
<roland.jolli...@gmail.com> wrote:
I've been thinking about 4th axes;
While motorised reduction drives are readily available, the issue is
obviously backlash.
One way to make a zero backlash drive is to use two identical
gearbox/drives. Place them at opposite ends of the axis, and pit them
against each other by a few encoder counts.
So they will track and retain the zero-backlash.
Of course, the total power available is now less than one drive motor,
but
it is an option to use almost any pair of reduction drives that can be
got.
But there is also the cost of the second servo amp.
On Fri, 15 May 2020 at 14:11, andy pugh <bodge...@gmail.com> wrote:
The normally appear on eBay at up to 6x this price.
https://www.ebay.co.uk/itm/233587431605
The B versions have conventional incremental encoders and hall
sensors, so are easy to integrate. Lots of torque, zero backlash and a
very strong and fancy big crossed-roller bearing make them an
almost-complete 4th or 5th axis just needing a bracket and a drive.
I have no connection with the vendor, if you order one and receive
dolls-house furniture instead don't blame me.
--
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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