Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

i would use steppers.
much easier than servos i think (cheaper etc).

i would also use lead screws, not timing belts.
i would use standard metric srews (with tapered thread) and use 2 nuts on
the moving part.
on nut fixed, the other in a "sliding" tube (maybe you find hex tube or can
make it.)
i would load the second nut with a strong spring against the fixed one so
that all play is eliminated.
the metric thread is self-centering also if the 2 nuts are spring loaded
against each other.

to couple the allthread rods with the steppers you can use a simple piece
of high pressure hose.
this resists to twist enough for precision... it damps vibrations and
imperfections in alignment will be no problem.
direct drive works fine with strong steppers, i have seen this on the web
often (using m8, maybe m6 allthreads).

you need to bear the allthreads properly. it is important to get rid of any
play.
maybe it will work fine with standard ball bearings with a little side
pressure by spring or so.
(make on side of the allthread beared fixed and the other bearing pull away
to help straightening the rod...
but tapered bearings would be much better (but harder to get, more
expensive).


i have seen rails of aluminium and other material which use multiple small
ball bearings
directly as wheels on which carry the moving part.
one of this wheels if spring loaded sometimes.


i would very like to use round rails and three rolls.
but i have no idea where to get good precicion pipes as rails...


currently i am busy with a lot of things, one of them building my rc
plane...
if i had more time i would definitely think about building such a unit too.
i would like to have it for automated drilling...

i would too like to have a cnc foam wing cutter (hard to do for me by hand)
but this is a different thing... (but maybe use same rails etc....



i did not even know that i have thought about a cnc so much and remembered
all this things i read.....
maybe this evening i will have a look at the steel/aluminium material i
have here and if there are any parts precise enough for rails.
but i fear i won't find anything.......







have you sorted out the software things?
i can make a stepper driver but i WON'T MAKE ANY SOFTWARE!.
not that i couldn't, i simply hate this programming things.. i did a lot
more in the past, therefore i know many languages...
but i hate it now for some unknown reason.....


i would need to have all software ready to accept DXF or HPGL , DXF
preferred and gerber and the standard drill format (excellon maybe?).
if you know of that software (maybe a link) please tell me the name...
i will not start building (like the "plotting with resist pen" ) only to
discover later that all softwrare is scrap...



hmm i start to like the idea of a cnc foam wing cutter and not longer
trying that by hand.....


@markus:
i don't like the drawer slide thing too much... maybe i am thinking of the
wrong slides, may you take a picture with your cam?
thanks....




ok, only a few (long, boring) thoughts...


regards
stefan