Re: CNC Controler Software

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Jones, Joseph A1"
<joseph.a1.jones@l...> wrote:

> Paul,
>
> I realize that a RTOS or dedicated signal generator can produce

stable pulse rates, but what I don't grasp is what is the result.
That is to say, if I first machine a part using a CNC controller
running under windows with no signal generator, and then secondly
machine that same part using a CNC controller running under a RTOS or
using a real-time signal generator, what will be the difference in
the two parts?

>
> My initial thinking would be that the first part would be getting

the exact same signals as the second part, just not with a consistant
time interval between each signal.

The difference is that the machine will pause and wait for the
software to send more signals. It is not just a variation in the
purity of a periodic waveform, but an actual interruption in the
sending of the signals. This will cause significant tooling marks in
a work piece, whether contouring in 2D or when 3D surface milling.
If you are working materials such as wood or plastic, the momentary
delays and hesitation may cause parts to be burned or melted as well
as marked by the cutter. If the delays are long enough, they could
even become a safety hazard as the machine suddenly takes off after
appearing to be paused.

Another much less expensive Windows option is the DeskCNC controller
($350). It includes both CAM programming software and a machine
controller on a card ( over 40,000 steps per second on 4 simultaneous
axes). It runs best in Windows 98 or later.

When comparing software controlled step systems with the external
hardware varieties, remember that you will probably need some kind of
a breakout board to actually attach your motor drivers to the
computer port. This function is handled by the external hardware.

Many people are now using step and direction controlled DC servo
systems. These are capable of much higher resolutions and rotational
speeds than stepper systems. When you use an encoder at these higher
rates, it is imperative that you have a clean, fast pulse stream, and
that you can output steps to match the enhanced resolutions available.

Fred Smith - IMService
Discounts and specials are at:
http://www.cadcamcadcam.com/hobby