Re: Apropriate OSes for CNC (was:Re: Michael Deckel Machine Question...)

cs_posting@xxxxxxxxxxx wrote:
Nick Müller wrote:

To be fair, XP isn't controlling the machine in either case. It
is, however, incorporated as the interface.

That doesn't make a difference.

Sure it does. All of the real time functionality is provided
directly by the hardware.

So what is the reason for an OS that needs such an expensive
hardware to run on, when the software isn't capable of taking over
some of the machine's hardware? What did they gain?

The CPU of a modern PC is increasingly a poor place to do critical
real time control. Part of the problem is that as CPU's get faster
and faster, they have to be more and more isolated from the real
world, and that isolation introduces latency and complexity. Also
available PC components change too fast for the custom interfaces to
keep up with. Pretty soon it becomes simpler to design loosely coupled
semi-autonomous custom hardware, than hardware that will put the PC
CPU inside the servo loop or even just the motion planner.

I would think the real test though is not if the part keeps cutting
once windows crashes, but if the part still stops cutting when you hit
the big red button or trip a travel switch, with windows already
crashed...

Feed hold as well. By the time you have motion, everything is on the machine
tool motion control side of the equation.

The advantage of a Windows operating system interfaced to a machine tool
control is third party manufacturing application support.
SPC/RPC and MRP system integration solutions are either written for windows
or OS's that can talk to Windows. For the most part, control manufacturers
have adopted windows for an interface. or are able to run an emulator. Even
a Fanuc will run compiled C.

For manufacturing professionals, the effect is obvious. You have a lot of
developers writing software you can use to automate every aspect of the
manufacturing process that is both compatable and relatively inexpensive.
Development costs are spread over a larger installed base.
That base also yeilds more robust applications.

High speed/high precision industrial machine tool motion control will be
task specific and proprietary for the forseable future. The state of the
industry comercially today is 16 million discrete pulses per rotation, fiber
optic bandwidth and PowerPC floating point processors.
FWIW, that is right out of the box - not the extreme rigs run by some - and
you are splitting an angstrom at those resolutions.

--
John R. Carroll
Machining Solution Software, Inc.
Los Angeles San Francisco
www.machiningsolution.com


.

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