--- In
Homebrew_PCBs@yahoogroups.com, Alan King <alan@n...> wrote:
> If room isn't an issue, there is also a very simple way for
stepper
> control for a drill..
>
> H H
>
>
>
>
> D SM
>
>
> Looking down, H and H are two hinges on a triangular piece of
wood.
> Come out about a foot, and D is the drill with SM being the
motor. At a
> foot out, the arc of the circle is very close to a line. Get the
bit
> aligned so it's tangent where it's drilling, and the error is
probably
> less than a couple percent for .2" of drilling through a board.
Use two
> standard $1 door hinges, mount half to the bottom and slightly
cock the
> other half against it when attaching the triangle and you will
have near
> zero play. If you come out 3 or 4 feet, this is almost exactly
linear
> for short depths while being very easy to construct, I've used it
for
> simple manual guidance on several occasions. Since it's so
simple, I've
> also looked at ways to correct it to truly linear, but haven't
found one
> yet that was viable over a rail system.
Perhaps the thing to do is NOT convert it to a linear system but
instead work within the constraints of the rotary coordinates. You
may be interested in this page:
http://techref.massmind.org/techref/idea/lccam.htm which is a redux
of
http://freeandeasy.sourceforge.net/ Thier java simulation at
http://freeandeasy.sourceforge.net/rotsim.php is really worth
looking at.
The links describe a method of moving the table using two rotary
joints. I had not considered just using a pair of hinges, but I
wonder why that wouldn't be perfectly acceptable...