Re: Re: Re: CNC Control software recommendations

Alex, Matt, Brian +

Forgive the shotgun approach. Response to this ought to be snipped by
topic.

Just to expand the playing field a bit, I've been running the EMC as a
common user for some time. You can find details of how to do this in the
faq at linuxcnc.org. By setting the permissions on files it is possible
to create several user levels of access that are fairly secure. I tried a
system here with operator, programmer, maintainer, and su levels and can
develop clear distinctions between.

When you talk about access to stuff like the parameter file and the ini
for axis config and so forth, all of these specifics can be locked out
from most levels of user. If you need to allow some kind of parameter
access to a common operator, perhaps for variables in a g-code program, It
should be possible to use these from a separate file rather than "THE"
emc.var file. I've thought for a long time that a separation needed to
made in this and use different files for operator, programmer and machine
levels.

It is also rather easy to get access to any of the parameters in a
commercial machine. I've done it hundreds of times with several different
controls makers. Until recently, a full set of parameters, and the
access procedures for them were included in the electrics books that
shipped with most machines.

One shop I do some work for has several different kinds of indexers that
they rotate around on their mills. These require different machine
parameters for M45 signals. That shop made a page telling operators how
to change the relevant parameters for each type of indexer. And yes it is
possible to change any machine parameter using the instructions, and yes
there is a kind of operator that likes to screw with these things. I
think the pilot in the movie "Never Cry Wolf" said it best, "The problem
is boredom, Tyler." This shop even had a night foreman who would play
with parameters things trying to make parts faster. Hey it was good money
putting them back right!

With open source systems, it is easily possible to create log files that
keep track of changes to any of the files which are likely to be involved
in liability issues. A module that you as the cnc maker/seller cause to
be run at startup can encript and bury copies of these log files any place
you want. I don't much like the idea of it, but your on-line service
module could give you access to these log files. "ET call home!."

Thin client networks have taken a bad rap because of some of the early
experiments with them at Bell Labs but there is a Linux movement afoot
that promises to revitalize this concept. You would not need any storage
beyond ram at the machine. A "machine server" that served all of the
machines in a shop could have a boot directory with sub directories for
each machine. When a machine powers on it boots from it's sector on the
server, and loads all of it's configuration information. When an operator
logs in to the linux on that machine, it can start up a clean copy of the
proper setup. Errors introduced by one operator need not carry over to
the next.

A second advantage of this is that with proper heat sinking, there need
not be fans or any other moving parts in the computer that resides on the
machine tool. Your cnc is now apporaching the level of reliability of
proprietary hardware without the associated costs. If you use an SBC
(newbie - Single Board Computer) you get hardware watchdogs that you can
easily and correctly wire into your estop circuit.

A third advantage is that you do not need any floppy or cdrom on the
machine tool through which an operator can introduce problems, viruses, or
games.

HTH

RayH

On Friday 21 December 2001 03:29 am, you wrote:
> Message: 21
>    Date: Fri, 21 Dec 2001 00:56:57 -0800
>    From: Brian Pitt <bfp@...>
> Subject: Re: Re: CNC Control software recommendations
>
> Alex
>
> > Ok, I understand but how available are these tools on the internet for
> > a free download?
> >
> > I agree but due to access speed and other factors I would prefer to
> > have the system on the hard drive. Is it possible to use a parallel
> > port type key with Linux?
>
> you might look into one of the solid state flash drives ("disk-on-chip")
> for embeded system use
> (upgrade the same way as flashing a motherboard BIOS chip)
> the operating system disk could be read only and just big enough for
> the OS ,a snapshot of the original disk image can be compaired to the
> customers disk to prove tampering
> the user settings and programs could be stored on a 2nd writable disk or
> flash chip partition
> these are at least as fast as a normal hard drive ,more rugged and are
> available as "off the shelf" items
>
> > Fanuc parameter setting aren't readily available on the internet for
> > download like Linux and its tools. Fanuc charges big money for their
> > parameters so they can fall back on - No proof of payment for
> > parameters, no liability.
>
> yep Fanuc normaly loads the full version then selects the options with
> parameter settings ($$$)
> for a modular system like EMC you just wouldnt load the optional modules
> so there is nothing there to enable thru the parameter list
>
> > That's allot to have to prove he/she did. Might be easier for the
> > hacker to prove that my system was bad?
>
> Linux offers alot of flexability and security from tampering and can be
> set up to be just as fool proof as any propriatary system
> also I think most people who pay for a CNC control are not likely to
> want to screw it up by fiddling with things
> nor would most shop owners want to compile the upgrades from source
> code ( there are exceptions of course :-)
>
> and the EMC licence allows (encourages) use of the code in propriatary
> systems so binary-only flash upgrades would be no problem
>
>
> Brian