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Thread

Stepper - ballscrew coupling

2005-05-30 by curt_rxr

Hi All,

A simple method for compensating for slight misalignments is use a
length of vinyl tubing which is a snug fit on the ballscrew. You will
likely have to machine a bushing to fit on the stepper motor shaft.
Since you can do this with one setup on the lathe the holes will be
concentric and the only "gotcha" is the fit of the bushing on the
stepper motor shaft. Try for a slight interference fit and use
Loctite grade B bearing mount on final assembly.

Some further thoughts on PCB drills.

If you cast your machine base out of 95% ( by weight ) mason's sand
and 5% Clark's liquid epoxy ( http://www.clarkcraft.com/ ) you'll a
very strong base that can topped with a final thin liquid epoxy coat
to level everything out at a cost well under $100.

If you make a vacuum tight box under a work surface of MDF a shop vac
will hold the PCB tightly in place. Since you will need some sort of
dust pickup for the drill it makes sense to let the shop vac be your
clamp.

Re: [Homebrew_PCBs] Stepper - ballscrew coupling

2005-05-30 by Esteban Arias

Here you can see this idea: http://www.vertice.cl/cnc1/

Greetings from Chile

Esteban Arias
earias@...

At 05:19 p.m. 30/05/2005, you wrote:

Show quoted textHide quoted text

>Hi All,
>
>A simple method for compensating for slight misalignments is use a
>length of vinyl tubing which is a snug fit on the ballscrew. You will
>likely have to machine a bushing to fit on the stepper motor shaft.
>
>Since you can do this with one setup on the lathe the holes will be
>concentric and the only "gotcha" is the fit of the bushing on the
>stepper motor shaft. Try for a slight interference fit and use
>Loctite grade B bearing mount on final assembly.
>
>Some further thoughts on PCB drills.
>
>If you cast your machine base out of 95% ( by weight ) mason's sand
>and 5% Clark's liquid epoxy (
><http://www.clarkcraft.com/>http://www.clarkcraft.com/ ) you'll a
>very strong base that can topped with a final thin liquid epoxy coat
>to level everything out at a cost well under $100.
>
>If you make a vacuum tight box under a work surface of MDF a shop vac
>will hold the PCB tightly in place. Since you will need some sort of
>dust pickup for the drill it makes sense to let the shop vac be your
>clamp.
>
>
>
>
>
>Be sure to visit the group home and check for new Bookmarks and files:
><http://groups.yahoo.com/group/Homebrew_PCBs>http://groups.yahoo.com/group/Homebrew_PCBs
>
>
>
>
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RE : [Homebrew_PCBs] Stepper - ballscrew coupling

2005-05-30 by Robert Hedan

I LOVE THAT ONE! It's now my new desktop so I can study it when I want. :D

Note the centered screws on every axis, that's the best technique in my
opinion. Even if it is only a drilling station, that cuts down further on
the play. Those motors look powerful, that machine looks capable of CNC
work.

For the clamps, I was planning on cutting scrap PCB into 2 L-shapes, glueing
2 identical pieces on top of those, but making the top layer protrude about
1/16" into the L opening. That way the bottom layer is the exact thickness
as a PCB and aligns it on the platform, and the top layer acts as a clamp.
One set will be mounted permanently on the platform as the 'origin' corner,
and the other set will be held down by a butterfly bolt (nut embedded within
the platform surface).

That rubber hose coupling is hilarious. I wouldn't have thought of such a
simple and effective design.

Robert
:)

Here you can see this idea: http://www.vertice.cl/cnc1/

Greetings from Chile

Esteban Arias
earias@...

Be sure to visit the group home and check for new Bookmarks and files:
http://groups.yahoo.com/group/Homebrew_PCBs
Yahoo! Groups Links

Re: RE : [Homebrew_PCBs] Stepper - ballscrew coupling

2005-05-31 by Alan King

Robert Hedan wrote:

> I LOVE THAT ONE! It's now my new desktop so I can study it when I want. :D
>
> Note the centered screws on every axis, that's the best technique in my
> opinion. Even if it is only a drilling station, that cuts down further on
> the play. Those motors look powerful, that machine looks capable of CNC
> work.
>

It actually doesn't improve play as much as you might think off hand, there
are some advantages but they're not that extreme. My fav is really one high
precision rail with both screw and load near it, and an anti-rotation arm or
plate over to another rail that simply stops rotation and is very non-critical,
it's play hardly affects the other side. Most of the high powered engravers use
this, with a plate across and just a plain ball bearing riding on a rail for the
other side, all the precision is in one rail.

> For the clamps, I was planning on cutting scrap PCB into 2 L-shapes, glueing
> 2 identical pieces on top of those, but making the top layer protrude about
> 1/16" into the L opening. That way the bottom layer is the exact thickness
> as a PCB and aligns it on the platform, and the top layer acts as a clamp.
> One set will be mounted permanently on the platform as the 'origin' corner,
> and the other set will be held down by a butterfly bolt (nut embedded within
> the platform surface).
>
> That rubber hose coupling is hilarious. I wouldn't have thought of such a
> simple and effective design.
>
> Robert
> :)
>

Well likely neither did we, it's been around a long time. Actually Jameco or
someone has some fairly good rubber type connectors. Each end has a circle with
two prongs sticking out, the rubber piece in the middle is cross shaped and fits
between the prongs from both sides. Simple and allows lots of play, yet is
tight in the rotation direction.

http://www.jameco.com/webapp/wcs/stores/servlet/CategoryDisplay?storeId=10001&catalogId=10001&langId=-1&categoryId=754015

Under Robotics:mechanical:couplers if the link doesn't go through well.

Wow their steel coupler is $4.49 that's nuts, mine were $1 retail I think.
The spider couplers must be a nickel since they're selling them for $1-ish.

See if I can look it up real quick..
There we go HH Smith. http://www.abbatron.com/products/part/get/hdw_sha_shco
Shaft accessories shaft couplers.. Have to look around on the net a bit but I
found them for not too much per bag of 25 even retail when I got mine..

Alan