Homebrew PCBs

--- 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...