RE: 5 axis controller

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

John

You are doing some pioneer work as you set up the EMC for a five axis
machine.  Some of the answers to your questions may stretch us all.  

On Thu, 11 Jan 2001, John F wrote:

>Does the emc controller have soft limits to prevent to
> prevent the machine 
> from crashing into the mechanical travel limitations of the machine? 

These are settable for each axis in the ini file that you reference in your
run file.   The specific variables are;

MIN_LIMIT =			-10.0
MAX_LIMIT =			10.0

and would be figured in inches if you do not change the units in the
ini file.  They are computed from the 0 position -- home if you set it to
be zero.  I think that these soft limits become active as soon as the
control has been homed out.

Running verify on a file before you run it will tell you if that file
exceeds the soft limits.  Otherwise running the file will cause an error
and e-stop when the program gets near the command that exceeds a soft
limit.

Provision has also been made for limit switch input that should stop the
axis drives short of mechanical disaster.

>Some basic PC questions for this
> control.  How fast
> should the PC be?  How much ram is recommended?  How large should the
> hard drive be?  

There have been a number of good posts, both on this list and on the
CAD_CAM lists that deal with how much PC you need.

Most of this answer depends on whether you plan to use steppers or servos.
Servos do not require nearly as much computing power as do steppers.
 I believe that Jon E is running 100mhz on his servo system and reported
plenty of processing left over.

With steppers you might want to get 500Mhz or so because that will give
you reasonable good stepping rate.  

I'd recommend 64 Meg ram so that you have something for the x-windows and
window manager if you use linux-2.0.36 up to 2.2.14.  The newer stuff
seems to want more memory or it will do a bunch of swapping.  But with
the price of 128 Meg sticks coming down to <$60 us, hey!

When I visited Till in Stuttgart, he was running his little six-stepper
hexapod with a 486.  EMC will run on a wide variety of PC's. The most
important thing is not to under-power it if you run steppers and want much
speed. 

>Which emc files would I need to install for this system? 

For the full five axis you will need the latest anonymous download from
sourceforge and even with that, your use of 4 and 5 will be somewhat
limited for now.  Will has been working vigorously to get the full six
going.

> What  would be the recommended linux files to install? 

Any!  But if you pick a very recent version, or non RH or Mandrake, you
will become one of those bleeding edge folk who will spend more time with
linux and rtlinux than you will making parts.  Installs are documented for
Red Hat to 6.2, for Mandrake to 7.0, and some info is available for Suse,
Debian, and ZipSlack.  A zipslack CD that installs EMC on a windows
partition is available.  Paul Corner is preparing a CD to install
linux-2.2.17 and rtlinux-3.0 and a year-end set of EMC files but this has
not been independently tested yet.  This will be a very limited linux but
you could then add packages.

My advice is still to run RH5.2 if you just want a dedicated machine to
make chips.  

If you write a spec sheet (wish list), something like:
 - RH5.2
 - Parport stepper control
 - Aux parport for lube, coolant, ultrasonic plastic welder, etc
 - serial interface for machine control panel using tcl/tk
 - Ethernet 10/100 for file transfers from MS machine
 - winmodem
 - Rhino in a wine window for drawing while cutting parts
 - Vector in a wine window for cad to cam conversion 
 - Latest (brand) 3d video driver 

the answers that you get will get you a little bit closer to scribbles
on the the order pad than more generalized questions.  You could make up
such a list if you close your eyes and imagine all of the things that you
want your machine to do.

A list like this will likely provoke a good discussion of almost every
item.  (note that some items on the list above will not work, at least not
very well right now)

>Your patience is appreciated.

If you take a little time and search the EMC archives, and the list of
links on linuxcnc.org for answers to some of the basic questions and to
help you formulate detailed questions for those areas that are not covered
in previous posts, You'll do just fine.

When I met Jan in Belgium, I saw that he had a pile of papers at least 4
inches tall that was the documentation of his systems and that he had used
while setting up and getting the EMC ready to run production there.

I trust that you will be willing to take good notes as you set the
system up and make those notes available to others through a page on
linuxcnc.org? -- 

Ray