Alright, maybe i'm shooting myself in the foot here by inducing demand and
I won't be able to get any cheap ebay units in future, but here goes...
I bought a used spinea ts200 about a year ago and put a 750w servo on the
back of it, built an enclosure and use it primarily as a fixturing
positioner. It's awesome for my needs. 169:1 ratio. Position holding under
light milling (think 5hp or less is my experience, I don't have a 40hp
beast to test with)
I will say, from my limited 1 unit experience, the efficiency isn't great
if you want to get anywhere near top speed you'll have to swap the grease,
or heat the unit, or just put a honking big servo on there. I have trouble
getting over 10RPM without the servo running beyond it's continuous duty
zone. Maybe mine was filled with some sort of alternative grease in a past
life, never opened it up to investigate. For positioning 10RPM is lots.
I'm impressed with the milling stiffness. I've overhung a heavy walled 5"
square tube about 20" from the face of ths TS200 and use it as a 4 sided
fixture with no far end support and it still mills like a champ. I'm only
doing 2hp or less cuts in aluminum on that fixture, and I'm sure it'd be
better with a tailstock, but it's run for hundreds of hours making parts
without so far. The cross roller bearings in those units are quite
something.
I haven't hooked up a brake of any sort, doesn't seem needed it for my use
cases.
One thing to maybe look out for if you care a lot about positioning is the
these units have an angular transmission accuracy error/window that looks
something like +/- 17 arc seconds, differs for exact units, get specs from
spinea for your model if you like. So if you care about resolutions below
that, or lost motion then another solution, or a high resolution encoder
mounted on the output flange would be the way to go. I believe the strain
gauge units have a similar but different accuracy issue, perhaps software
compensation would even be possible?
I'm also of the impression that the tilting stiffness and torsional
stiffness are significantly superior to the harmonic drives, but I could
be totally off there.
-Dave
On Tue, 31 Mar 2020 23:03:11 -0400, andrew beck <[email protected]>
wrote:
Hey guys.
I have been thinking about my 4th axis I am going to make.
I have my cnc mill working now though there is still a bunch of work to
get
done. But I have been thinking about how I can make the best 4th axis
and
after that 5th axis.
I have narrowed it down to either harmonic drives or Hypocycloidal gear
boxes.
I am thinking the hypocyloidal type looks the most rigid and best to make
as it looks like the it would be very easy to make on a cnc mill and a
harmonic drive relies on a thin strain wave gear that is not the
strongest. I actually have a rather large one which I have been thinking
about using but I would like to go with a the hypocycloidal design
instead.
all you guys out there with awesome cncs sitting in your sheds have you
ever built one of these? I don't want to reinvent the wheel if I don't
have to. And I am on the track to making my cnc a 5th axis when I get to
it. First I will make the 4th axis and pump a bit of work through it and
make some money lol. But 5 axis looks pretty fun and cool and I think it
is finally doable for the pro diy person.
I have all the toys like a surface grinder and lathes etc and of course
the
cnc mill.
also don't mind spending money if needed as it is a business.
here are some links to get the ideas flowing
videos
https://www.youtube.com/watch?v=Eds48L4cJjM
fuson 360 scripts to generate the gear profile.
https://github.com/mawildoer/cycloidal_generator/blob/master/README.md
https://github.com/tapnair/Fusion360HypocycloidGear
and just to show that it has been done before I say that the new Hass
umc500 has cycloidal gearboxes in it so the design must be pretty good.
https://www.haascnc.com/machines/vertical-mills/universal-machine/models/umc-500.html
regards
Andrew
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