Re: CNC lathe threading?

["Barry A. Boes" <bab-at-boesusa.com>]

Funny, I have a shoptask 3 in 1 as well.  Back to threading...


I tried writing a g code program that would just cut the threads with
multiple passes assuming a particular machine RPM.  The problem that I
ran into is that EMC doesn't seem to have a constant time between task
starts, even if I set bridgeport CYCLE_TIME to 0 and others to 0.001
and no machine load.

I've now "discovered" emcsh.  I've modified the code to cut the
threads based on an assumption of constant spindle RPM.  It cuts a
pass by sending MDI commands out.  After the pass, it just does a
(while(ewait() != the_right_time +- some_small_number)) then sends the
MDI code for the next pass.

I'll use it like this :
     start up tkemc
     get the machine running
     at a command prompt, type "thread -r machinerpm -d thread_depth -t tpi..."
     Then watch the tkemc gui follow the thread cutter's commands

I'm going to see how that works today with very low spindle RPM's
(120).  I've already ordered a hall effect sensor in case that doesn't
work.  I figure I'll modify the above code to watch a parallel port
input pin for transitions, calculate the feed rate based on it, then
start the MDI code threading passes by clocking on the magnet.

RT-linux is what's giving me the most trouble.  It's not nearly as
simple as some other RTlinuxes.  Could anyone out there give me an
example that will run emcsh at a real-time priority so I can translate
it to my thread cutter?

   On a positive note, it's really awesome how emctask, bridgeportio,
etc are all separated and communicate.  It makes it really nice for
someone like me who wants to get in the middle and play with things.




jmkasunich-at-ra.rockwell.com writes:
 > 
 > 
 > 
 > Ray:
 > 
 > AFIK, axis names, etc, aren't all that important.  Especially since I have
 > a Shoptask 3-in-1, so I will be using it as both mill and lathe.  I'll
 > probably
 > stick with the mill axis names, because most lathe work that I anticipate
 > is relatively simple, and I'll probably write the lathe G-code by hand.
 > 
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