Re: [CAD_CAM_EDM_DRO] Toolchanger

Carol & Jerry Jankura wrote:

> Jon:
>
> This often seems, at first blush, as the right way to implement a system,
> and may well be if it's for a hobby that you will be the only maintainer and
> absolute minimum costs rule.
>
> But consider - You're running a CNC G-Code interpreter under what many (not
> necessarily me) would consider to be an arcane operating system (that is,
> not many know much about it). Now, you're going to add either another module
> or separate program written in a language that most maintenance folks don't
> understand. So, it follows that when the machine quits, it's this system
> that's first blamed. And, guess who's going to be called to diagnose and fix
> the machine whether this system is the actual cause? No, I think that
> partitioning the CNC into its own computer and adding a low cost PLC running
> a ladder logic that most maintenance folks (electricians, that is) know
> something about is the preferable solution.

Well, since EMC would have to be modified for EITHER the PLC or direct
control way, the PLC just adds more complexity to it. If EMC was already
set up for a PLC, that would be different.

The OS (Linux) is not the issue at all. The limitations of the real time
methods and great complexity of EMC is what makes all of this difficult.
Just finding the routine that is responsible for some function in EMC is
a 2 hour exercise, or worse. Linux is better documented than most
OS's, especially Microsoft. Yes, if you are a registered developer, and
subscribe to the $2000/month developer's service, you can have vast
amounts of internal system documentation. I've never talked to anyone
who has had access to that stuff, so everybody works in the dark, and
wonders why things don't work. At least with Linux, there IS publicly
available documentation, and the source code is available with just one
command.

If you are going to BUILD your own CNC machines, you have no business
turning them over to plant electricians, at least without a LOT of documentation
being made and kept with the machine.

If you do it directly from the computer, you can have diagnostic programs and
diganostic screens that can show what is happening every second. This could
be very helpful in diagnosing any problems. I'd much rather work from a big
screen that has meaningful labels like "spindle in posititon=TRUE" and
"transfer_arm_parked=TRUE" than trying to read a bunch of LEDs marked
IN01 through IN16 and figure them out on a ladder logic diagram.

Jon