>Ok, all this talk has given me the bug to build a milling machine
>for pc boards. Something that will be semi-precision.
>Maybe some of you guys can offer some good tips for building an X/Y
>table?
>I am a poor person and want to hold cost down as much as possible,
>so ideas like the "Drawer Slide" linear motion bearings are greatly
>appreciated!
>
>Slides:
>I'm not sure how much play are in those drawer bearings. Probably a
>lot. I'll have to look for some good ones, or maybe make my own
>slides from brass or UHMW channels. I've dealt with different types
>of gibs and round shaft/ball bushings before, so can probably figure
>out something that is semi-precision at low-cost.
During the last two months I was lurking around in hardware stores a
lot, keeping my eyes open what of their articles could be used for a
CNC drilling machine. As part of this I also took a close look at
drawer slides. Some of them are definately precise enough to build a
PCB drilling machine with them. Another interesting "slide" kind of
constuction are the slides used for cupboards. All in all I think it's
very easy to build such a machine if the goal is drilling PCB holes or
milling PCB's only. Lot's of options to build a very stiff
construction. I.e. legs of tables, gas tubes, laths like they use to
flatten out concrete (they come in all kind of shapes are made of
aluminium profiles) U shaped aluminium profiles etc. etc. It all boils
down to keep the eyes open.
>Linear Motion drives:
>Stepper motors are the obvious low-cost solution, but I'll need to
>find some good resources for cheap parts that will work properly as
>a complete system.
e-bay. There are always very cheap steppers available on e-bay.
>True servos? Better but not as available as "surplus" ?
I don't think they would be up to the tast torque wise.
>Either one would of course need suitable controllers and software.
>I can write some software (VB and Perl) but I think some
>shareware/freeware is available to handle conversion from different
>CAD programs...
Software should not be the problem as long as you keep the controller
interface (provided you build your own) compatible with what seems
like standard pin layout. There are also enough cheap controllers
available on e-bay and sometimes there are sets consisting of
controllers and stepper motors. Some of such sets even come with the
software to use.
>Then I'll need to fabricate the mechanical drive portions: Leadscrew
>or Timing Belt like printers?
I will start to build my own machine shortly. I decided to use simple
threaded rods, steppers along with drawer slides. Ok, due to the fact
that I'm etching / through hole plating my boards, it boils down to
drilling only which is really not so demanding.
>Design parameters:
>What are the largest boards I should allow for in the x and y axis
>travel? 8", 12"?
This one is easy. Ask yourself what the biggest board will be that you
are doing yourself... :)
>Anyone who has experience with such things, please chime in if you
>know of some good sources for info or parts!
There are MANY sources in the internet. However I get the impresion
that it's not really needed to buy "plans" etc. if you have some
skills with mechanical stuff and if you take the time to see what's
available in your area that can be used. I simply walk through
different hardware stores with my eyes open during the last months and
I must say I saw so many things that can be used that a finished
"plan" may would make things harder. It's all important to understand
the basic principles of how cnc works and there you go. Even if you do
a mistake here and there, if you only use cheap parts from a hardware
store, but do it on your own you will have the skills and posibilities
to correct your design until it works fine.
Just my 2ยข though.
Markus