RE: [CAD_CAM_EDM_DRO] Re: VISUAL BASIC & CNC

All printers (serial & parallel) have a problem keeping up with the speed
that the computer ports can output data. They use a technique called
handshaking (in conjunction with a buffer in the printer. When the printer
can't take any more data, it places voltage on one (or more) lines which
communicate back to the computer to stop sending data. When the buffer
empties, the handshaking signal goes low and the computer is able to send
more data. In this way the printer's stepper driver always gets data at a
constant acceptable rate.

There is generally no feedback used to keep track of the location of the
stepper motor in a CNC system with a PC controller (I think encoders can
address this, but haven't gotten there yet). The speed the data is
transmitted is controlled by software and lost steps are not accounted for.

Regards,
Jeff


-----Original Message-----
From: luisguillermo98 [mailto:luisguillermo98@...]
Sent: Saturday, April 12, 2003 5:58 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: VISUAL BASIC & CNC

So how come some PLC manufatures and other automation companies run
their system on windows? I am wondering how printers works since they
never loose step when printing documents..

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Art <fenerty@h...> wrote:
> Louis:
>
> The Mach1 or Mach2 ocx can be used by VB developers to write
applications
> to do pulseing. Mach2 is stable at 35Khz with no more than .000040
second
> jitter in Windows on most systems. Mach1 is as stable at 25Khz .
The OCX
> interface of each allows a VB application to do stepper motor
control from
> windows as easily as calling routines like LoadGCode() or
> StraightFeed(x,y,z,a,b,c) from your application.
> It is still a commonly held belief that Windows cannot step in
a stable
> fashion, but the diagnostics screens in Mach2 (cuurently released
in alpha)
> will show you in detail the stability of the pulseing. It is no
longer true
> that Windows cannot do smooth movement in real time. My 1Ghz
machine is
> stable within 5uS at all times in its pulseing. It can even read
and send
> email and maintain this stability. Mach2 even has a screen designer
to
> design screens to mimic your application's needs and you can use VB
to add
> more buttons you control.
> If your in XP or Win2K I suggest you download the demo and give
it a
> shot. Even the demo can be used to develop your own application.
>
> (Just an unabashed plug to clear up this "Windows can't do it
thing...)
> Art
> www.artofcnc.ca