Re: Still a little unclear

In a message dated 5/20/99 1:24:23 AM Eastern Daylight Time, pencad@...
writes:

<<
Am I right in assuming that there are many various ways in getting a DXF
file or whatever format to the machine for processing. From what I
believe thus far, I can produce with my CAD a file that can be
translated into code by a CAM program and then at this point I become
unsure of the "various" means of getting that information to the
machine. I have downloaded many demo programs from the CAM side of the
house, and these have helped me to get somewhat comfortable with the g
and m codings.

>>

Probably the simplest and cheapest way to get into the CNC/CAM game is to use
a program such as "stepster" (freeware) or DeskNC (cheap shareware). Both
these programs (and others I haven't tried or mentioned) convert the G code
file into a series of pulses that are sent to the parallel port. These pulses
at the port are very weak, the purpose of the driver board which connects to
the parallel port is essentially to amplify the pulses to a voltage and
amperage adequate to run a stepper motor.

You basically tell DeskNC how many pulses in which direction it takes to move
your machine one inch in a given axis. In my particular case it takes 4000
pulses/inch in the X and Y axes and 8000 steps per inch in the Z axis, keep
in mind that these numbers are determined by the characteristics of the
motors themselves (how many pulses per revolution) and by the characteristics
of the machine to which the motors are connected (how many revolutions of the
motor shaft to move one inch). DeskNC then reads the G code file and converts
a command for a given move (eg: 1 inch left on the X axis) into the correct
number of pulses and the direction signal to "make it so"..

The flow of the overall system is rather like this:

(in your computer) CAD program outputs DXF file >>> DXF file converted to
GCode >>> GCode to DeskNC >>> DeskNC to parallel port pins >>> (now we move
out of the computer) >>> parallel port pins to driver board/amplifier >>>
driver board/amp to stepper motors >>> stepper motors to translation
mechanism in your machine (can be ball screws, belts, gears, steel cable
wrapped around a drum or what have you.

Hope this helps... I've spent a considerable amount of time puzzling all this
out pretty much by myself and wish that I had a forum such as this during the
process.

The problem with much of the hobbyist/inexpensive hardware/software is that
it is often rather sparsely and cryptically documented, assuming a great deal
of knowledge of the subject that the beginner (those most likely to be using
such wares) usually lacks.

Jon Croad in Atlanta, GA