Re: Missing link

The location part of your question is simple.

steppers spin with 200 steps per revolution (many different rates but
the most common are 200)

your unit will use a gear rack I would assume. Assuming you create a
gear ratio so the stepper spins 5 times for each inch of travel, it
would take 5x200 or 1,000 steps per inch. that would offer a
theroetical accuracy of 0.001"

you design your part, say your name in a piece of sheet metal. you
use your favorite CAD program and make a DXF file. then convert that
into a file than can be read by the contorl software. this generate
the G-code to tell the software what to do.

you run your contorlling software that runs on the pc for your table.
it connects to the drivers (Gecko's, Xylotex etc ?) and the software
sends out step and directon signals. one pulse for each step, or if
the unit is a microstep drive, one pulse for one micro step.

the software counts the steps and 'knows' where the unit is by the
theoretical total count. A stepper can miss a step and be off, but
more often it is exactly where you would expect.

there is a home posistion that sets everything back to zero.

If you added some sort of posistion measuring, you would increase
instrumentation cost, but with a plasma cutter, not gain much.
Plasma cutting paths are not always as accurate as your table.

Also, your plasma table does not have anything that would make it
skip or miss steps. A milling table has a better chance of hitting a
solid object and missing a step. of course gunk in the drive gears
will make you miss steps too.

The breakout box that Tim mentioned allows you to connect your
parallel port to the breakout box, then from there send signals to
sensors like the home and end switches or to relays to turn things on
and off like vaccumes, and of course to the steppers to tell them
what to do.

Hope that helps



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Steve <timbercutter@y...>"
<timbercutter@y...> wrote:

> Hello, I am new to this group as of today. The archive here is huge
> and having trouble searching through it all, but will continue to do
> so. My question is: I am wanting to build a 3 axis gantry machine

such

> as the Torchmate. It will run plasma and a wood router. The

mechanical

> part is something I can figure out, but the electronic is something
> still a bit confusing. I know you have a Computer running some CAM
> software, a power supply, some drive controllers such as "Gecko" and
> some Stepper motors. Does the computer send a signal to the gecko
> directly, or is there another piece that I am missing? I am

wondering

> exactly what part of a CNC system does the computer hook to and
> communicate with. And also will a gecko provide feed back to the
> computer to keep track of what step it's at to keep from losing
> position? Thanks.