You need to keep the drive system as simple as possible and keep
backlash in mind.
Also, don't forget about the spring constant of any shaft you run across
the gantry. If you do that, you might want to
run a tube drive shaft rather than a solid shaft for more torsional
rigidity.
There is nothing wrong with running two motors.
Excessive backlash will cause big problems.
Dave
On 10/4/2018 8:47 AM, Leonardo Marsaglia wrote:
First of all, thank you guys for your advices as always!
I'm gonna try an asnwer this on one message because sadly gmail doesn't
have the quote selected text feature anymore.
About the oversized motors. Yes, I also think that for a normal router 1 kw
per side is too much. But the thing is, I'm planning to use round guides
with bronze adjustable bearings. I decided this because I want more
rigidity for an eventual need of machining aluminum, and also because I
think this kind of guides with whipers are much more reliable than the
recirculating ball ones. Also, I don't think I can have the adjustable
feature with the slotted ball bearings. I'm attaching a picture of the
bearing I plan to make, there are no lube channels on the model but they
will be on the final part.
So, to sum up, with these kind of bearings I expect more resistance on the
joints, and also the router is 2 meters x 3,8 meters long so to have enough
rigidity I'm planning to use steel and cast iron, so that's why I'm
oversizing the motors. Besides, there's no much difference between a 400W
and a 1Kw chinese servo motor and drive on ebay.
About how to drive and home the gantry. From what we've been talking and
thinking it through a little more, I'm thinking that the best solution is
the one Gregg suggested. To have a transversal shaft on the gantry driven
by the servo motor by a worm and gear reduction with the timing pulleys on
each end of the shaft driving the pinions. This way I can adjust and square
the two columns and it should stay squared at any time. This is really
important because this is going to be used by a regular operator, so this
has to be as reliable and fail proof as possible.
About the last question. Is there any disadvantage other than may be a
little more mechanical complexity with the one motor and shaft approach?
Because I've seen lots of routers driven with two motors that I almost
think it's mandatory for some reason.
Thanks again!
Leonardo
El jue., 4 oct. 2018 a las 0:03, Gregg Eshelman via Emc-users (<
emc-users@lists.sourceforge.net>) escribió:
The easiest method is mechanically connect the two sides with a shaft
along the gantry and use one motor. Then it *cannot rack* or have any of
the other issues that can happen with driving both sides of a constrained
axis with two motors.
If you need more Z height, you can elevate the racks on the sides. Or run
chains or belts from the cross shaft ends down to stub shafts with the
pinion gears.
On Wednesday, October 3, 2018, 4:03:48 AM MDT, Leonardo Marsaglia <
ldmarsag...@gmail.com> wrote:
Hello to all!
<clip>
About how to drive both Y joints as one axis: I've read that there's a way
of simply adding two Y joints for the Y axis in the 2.8 master branch but I
don't know if there's documentation available already.
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