When reasonably sized harmonic drives with servo motors inbuilt are 250$
on ebay, they are COTS. So the answer is yes. Just buy one of those and
move on to solving a more interesting problem or making whatever the
machine is supposed to make.
-Dave
On Sat, 16 May 2020 02:49:55 -0400, John Dammeyer <jo...@autoartisans.com>
wrote:
Hi Dave,
I think the question being raised is whether it's possible to create a
zero backlash 4th or 5th axis with COTS hardware for less money than a
harmonic drive or the cycloidal gearboxes.
John
-----Original Message-----
From: David Berndt [mailto:ber...@uberwin.com]
Sent: May-15-20 11:19 PM
To: Enhanced Machine Controller (EMC); Roland Jollivet
Subject: Re: [Emc-users] Cheaper than normal FHA-25B
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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>> Emc-users@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/emc-users
>>
>
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