Homebrew PCBs

>> Roel, Andrew and others wrote:
>> <Stuff about a drum plotter>

> Loco labs wrote:
>
> im building a small CNC type machine using
> steppers and belts to move a dremel in 3
> axis, controlled from parallel port. I will
> use eagle pcb and then create a gcode file
> for mach3 to route the isolation.

Have you tried the dremel tool to mill
fiberglass PCB ?

I beleive the speed (20K rpm or so) is a bit
slow and that they also have a bit much run
out to do a nice job of it.

The comercial machines you quite fast (60K)
low run out spindles.

Post pics when your dont though.  We like to
see this kinda stuff being done.

> for moving a laser diode around you will
> not need any torque at all, so it would be
> possible to get away with using a few
> small stepper motors from printers or
> using the assembly from flatbed scanners
> to perform x and y movement. but it will
> be very slow.

We only need a Y axis for the stepper motor.

X axis is around the drum as it spins.

Yes stepper will only need to be very small
as all it needs to move is the carraige for
the laser.

There is one thing I have no idea about and
no one else seems to have posted any
thoughts.

Am I going to have a problem with sticktion.

Sticking-Friction which is the friction that
is higher while something is at rest.

You can have a problem that you tell the
stepper to move one tiny step.  The head
sticks and does not move.  You tell it to
do another step.  It is still stuck.  You
keep giving it steps then all of a studden
it will jump X steps fwd and stick again.

You can get over sticktion by moving the
carraige back and FWD each time - but that
slows things down a bit.

15 minutes for a print is a bit slow - but
not too bad if the quality is good.

> if you google up 'orbit
> picstep' you will find a very nice stepper 
> driver that has step, direction & enable
> signals.

Driving one stepper is pretty trivial so
I shall just do it out the main boards AVR
(saves people looking at me funny for using
a pic as well)
 
> I know of UV sensitive boards, where can
> i get the red sensitive ones as mentioned
> before?

No red sensitive boards - only film.

Use red laser to print on to film.

Develop film.

Use developed film to expose board with UV.

BTW - welcome to the group - where in OZ
are you (just in case I need to rib you if
QLD manages another 30-6 next wed night)