>Scott Stephens wrote:

>> If you have at least 50 hours (if you know what your doing)...

>        Taken me more than that so far, but I have been "developing"
>if you get that. I have a few projects coming down the line in
>future with this stuff so I will keep plodding along. Definitely
>not a weekend project though! :o)

I've probably spent 100 over the last few months, including fooling around
with old PC's. I found one secret was you can't use over 1/8" thick aluminum
for nylon bushing mounts with 1/2" Thompson rod and around 6" spacing. It is
mechanicaly unstable, and hangs. I now have an appreciation for mechanical
engineers. An engineer I worked with at an ultrasonic scanner company tipped
me off that those systems need to be 'tuned' like electronics.

Unless you need 'lots' of holes drilled quick, its really too much trouble
for a hobby. I could have drilled stacks of boards in the time I've spent.
But I don't want to be deterred from making  plenty of fast modifications
for developing prototypes. Besides one day I'll EDM a red hot, conductive
ceramic and be the first with an axial-flow model turbojet 8^)

>        I looked at leadscrew stuff, but chose the other approach of
>using simple 1mm pitch (x7mm diam) threaded rod. This is slower than the
>leadscrew but much more rigid.

Oh my, and I'm whinning about the speed with a 1" pitch screw. I recently
got a Wholesale Tool catalog and saw ACME rod & nuts for 1/10 the price I
paid, and wished I had made my own anti-backlash nut(s), because I know I'm
gonna be changing them often.

I rely on Thomson Rods for stiffness. But 2 -1/2" x 24" is not stiff enough.
I wish I used 1" or took the time to calculate the beam deflections rather
than looking at a printer and guessing I could just go a size or two up.
Fortunately there is no torsion load on the x-axis (unless I try milling).


>Just need steppers and drivers good for 2000 steps/sec to give 10mm/sec.

You are in no hurry. My motors are rated to 600 pulses/second so I expected
up to a couple inches/second. I think you'll regret the wait, especialy if
you find you need to baby sit the damn bot like I do.

>        From what I have seen, some of the board routers/track cutters use
>a simple roller (like a caster) on the cutting head.

Why didn't I think of that? I would still need to modify the software, and
use an encoder. Last time I drilled holes the Z-axis must of hung in a hole
because it lost counts.

I put LED's on the stepper outputs and noticed the Dremel tool put horrible
horrible line noise that caused false stepping. But I expected it and was
watching for it.

>> Who has/wants a chopping PIC stepper controller?

>        I'm curious, but I have nice big linear cc supplies built and I
>kinda liek them! :o)

Do you need a fan to cool them? A power supply 4 times the size you would
otherwise need? I like PIC's too much.

BTW I've collected lots of app notes on steppers, drivers and mech design
stuff. If anyone is interested I can E-mail them megs of files or dig up the
web sites.

Scott

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