Re: EMC plc intergration

[Ray Henry <rehenry-at-up.net>]

Hi Lee

I wrote this before you called but will send it to the list because there may 
be others interested.  I can't answer your first question about using a 
commercial PLC but have a few suggestions based on experiments I've done here.

During the phone conversation you indicated that this is an older K&T machine 
with switchable pole motor.  Indexing of the spindle for tool change is done 
by ramming a pin into a hole in the spindle drive train.  

As it sits now, the EMC does not have any provision for program control of 
multi-speed spindles.  If you didn't need four speeds (2 motor and 2 gear) it 
would be easier to handle by doing a gear change and running the VFD that you 
are thinking about getting.

Tool change commands are available from the interpreter and will be passed to 
IO programs like bridgeportio and tkio.  Fred Proctor once remarked that if 
someone was holding a gun to his head, he'd write the PLC in Tickle using the 
existing iosh.  In fact the sample program tkio is just about equivalent to 
bridgeportio.  Both are software logic controllers that use an extra parport. 
The principle of each could be expanded to include most any tool changer or 
pallet changer or whatever logic you wish to build into your machine.

There are quite a few inexpensive digital IO boards available now.  It is 
possible to access pins directly from programs like tkio and iosh to pull 
relay coils and sense switches.  www.bsof.com or www.winford.com come to mind 
as sources for inexpensive ISA buss cards.  

Tool Command Language (Tcl/Tk) is a rather easy language to learn at the 
level you would need for machine logic.  I see that activestate.net has been 
changing around their site to make it more difficult to get free info and 
easier to sign up for their paid services but there is still quite a bit of 
information available at

http://www.activestate.net/Solutions/Programmer/Tcl.plex

The best way into that info now is to use www.scriptics.com or go directly 
into the wiki at http://mini.net/tcl/

>From there you will find links to many different resources to this language.

In the www.linuxcnc.org/handbook, there are at least four sections that deal 
with iosh and emcsh.  Both of these programs connect Tcl/Tk scripts to the 
EMC.  Iosh is used by tkio.  Emcsh is used by the tkemc and other graphical 
interfaces.

Hope this helps.

Ray



On Wednesday 02 April 2003 10:22 pm, you wrote:
>  To the List;
>        Has anyone intergrated or used a plc with emc? I want to use a
> software or external plc to control  my spindle and tool changer. The
> spindle has a two speed motor with VFD and two gear shifts.
>                 Thanks; Lee Kissner