On Sun, 5 Oct 2003, Stefan Trethan wrote:
> thanks, but this is way of what i asked.
>
> i know there are other options, i know there is drill rod.
>
> but i hoped you may tell me which surface your gas pipes have.
>
> the tpi of metric allthreads is about in the range of 20tpi (~1,2mm
> rough guess) and i hope i find a software which compensates for wacky
> fractions. i really think they will work for now. even if i don't manage
> to have the software recalculate it i can still change my drawings. and
> at least i can test the machine, only to see it working it doesn't
> matter if the output is out of scale. i can still buy better threads
> later.
As far as drill rod goes:
There are some non-drilling machines at the place where I work that use
drill rod as a bearing surface. It works, but it's prone to flexture.
If you're going to use drill rod, go for some beefy rod. 1/2" or 12mm is
ok for something of reasonable size (typical PCB). But if you're
interested in milling stuff that's on the order of 300mm or larger on a
side, go for a thicker rod.
As far as leadscrews go:
Allthread is fine, but you are prone to having leadscrew errors. If you
can find a supplier for precision threaded rod, go for it. If it's
precision ground threaded rod, all the better. There's a US supplier that
will ship Imperial or metric precision threaded rod for not much more than
hardware store allthread. There are bound to be suppliers on every other
continent that'll provide similar products.
As far as software goes:
I run my CNC tooling on TurboCNC from DAK Engineering. It's a DOS
program, and as a result the motor pulses are quite smooth. It'll drive
up to eight axes. This may seem like overkill (it is), but it lets you
put things like a material changer or a toolchanger onto your machine, and
gives you the tools to control them. TurboCNC will let you define the
machine in metric or Imperial numbers, and will run parts programs in
either measurement system. It also has backlash compensation, so if you
are using a decent leadscrew and nut, it will give very good results
without requiring ballscrews.
The one catch with TurboCNC is that it is designed as a general purpose
CNC controller. As a result it talks G-code instead of Excellon. You
need to find software that will generate the G-code for you. Someone has
written some Eagle scripts to export G-code drill files as well as trace
isolation milling files. You can also get software that will take Gerber
and Excellon files and do the transation for you (DeskPCB is a good
example).
Lots of options.
Tom