Re: [CAD_CAM_EDM_DRO] Re: How to convert a Grizzly 1006 Mill to CNC

At 05:43 AM 10/19/2007, you wrote:

>Can the computer run 2 parallel port simultaneously,

Well, no, but the execution will make it appear to be so. A PC
historically has had three port addresses available, only two of
which were "full featured." The third was on, originally, the MGA
(Monochrome Graphics Adapter) or Hercules card and did not have as
many registers. The other two can support bidirectional, ECP and EPP
standards. The computer will support them successively and the
program determines the delays. Let's say you are driving the port at
a 10 KHz rate (100 uS) and the program takes 10 uS per update. One
port will be 10 uS behind the other, but both ports will output the
signals at full speed.

>and will 2 parallel port be enough for 4 axis?

Maybe. It depends on what you feel the ports must do. You need a
step and direction for each axis (4 axis x 2 bits/axis = 8 bits) plus
some inputs like limit switches and emergency stop. If the spindle
is software controlled, you need at least two and want three bits
unless there is feedback (e.g. servomotor and tach.) Tool
changer? at least step, direction, home and release clamp.

Two ports will do it but there will be issues with combined limit
switches. If you hit ANY of them, there is no way to tell which you
hit. Home is another issue. On the "A" axis, an encoder can tell
you where "home" is, on the "Z" axis, having the tool tip touch a
target works, but "X" and "Y" may need a reference which is not
trivial and a reference so tool size can be determined.

Basically, yes, put two cards in the PC and yes, it will be (barely) enough.


David G. LeVine
Nashua, NH 03060