Lathe Threading Support

[FritzX]

Just found:

G33 (lathe threading) support had recently been added to EMC2, rigid tapping might follow later:
wiki.linuxcnc.org: Spindle Synchronized Motion

Regards,
Fritz

[RotarySMP]

What spindle encoder format is it looking for?

[acondit]

Mark,

In the discussion and pictures that he posted it looked like he was using a quadrature rotary encoder on the motor.

Alan

[RotarySMP]

Thanks Alan, was EMC trying to sync at every encoder puls (which would seem like an enormous calculation overhead) or were they just using the one/rev indexing puls that encoders also deliver?

[acondit]

Mark,

Chris Cradek wrote:
{Hi all, I got a spindle encoder working on my mini mill, so I now have
the crappiest sideways CNC lathe ever. However I was able to cut a
thread using many very light passes moving in at 29 degrees. The exit
and entry cuts were at 45 degrees to Z and lined up beautifully.

Since I can't use a tailstock and I used a small rod, you can see that
there was bad vibration in the cut, and I didn't turn it true before
starting, but nevertheless the multiple passes (dozens of them) lined
up and made a thread:

http://timeguy.com/cradek-files/emc/thread.jpg
}

I went back and read the thread. I believe that he was using a full quadrature encoder that had an index pulse. I haven't yet seen the actual GCode that he was running.

Alan

[RotarySMP]

Hi Alan,

I have been using TurboCNC which only syncs to a one per rev indexing pulse. My machine is wimpy little 7x12 lathe but the thread I have cut with it have been fine from 12x0.5 (micrometer) to a .936 x 16 tpi internal thread to hold a Roton ball screw nut. The use of one per rev works. Actually if you are set up for one per rev, you could easily double the resolution to two per rev by using a 180 degree target and syncing off both the rising and falling signal.

The down side of 1/rev syncing is that you really need a 3 thread length lead in to get sync'ed before entering the work, and the change in load will mean that the first thread will theoretically be the least accurate.

I have downloaded Ubuntu Linux and will be trying a EMC2 load on a laptop.

Mark

[harty]

i have a lathe running turbocnc(dont realy like it much) and a mill with emc2 (love it)what do i need to do to get emc2 to run the lathe (eg get it to see the spindle pulse )

cheers
harty

[andy55]

Originally Posted by harty i have a lathe running turbocnc(dont realy like it much) and a mill with emc2 (love it)what do i need to do to get emc2 to run the lathe (eg get it to see the spindle pulse ) cheers harty

if you already have the encoder on the spindle which gives out a pulse then all you need to do is wire the pulse to an input on your computer, could be a spare input on the parallell port if you are using that.
then you need to setup some HAL in EMC so that the pulse is handled correctly in EMC.

[Bear]

Hi all'
whenever threading with you need to allow lead tim .
not as in thread but in time .
machines cannot go from 0 to .1250 instantly,nor can they stop instantly.
Bear

[harty]

Originally Posted by andy55 if you already have the encoder on the spindle which gives out a pulse then all you need to do is wire the pulse to an input on your computer, could be a spare input on the parallell port if you are using that. then you need to setup some HAL in EMC so that the pulse is handled correctly in EMC.

thanks andy55

its already setup on a spare port i have been testing threading with turbocnc
but editing hal is something i have not done
which file do i need to edit and what parameters do i need to change or add
my setup is running steppers and a single pulse per revolution from the spindle encoder

cheers
harty

[andy55]

Originally Posted by harty thanks andy55 its already setup on a spare port i have been testing threading with turbocnc but editing hal is something i have not done which file do i need to edit and what parameters do i need to change or add my setup is running steppers and a single pulse per revolution from the spindle encoder cheers harty

the fastest way to get EMC answers is usually on IRC, connect to FreeNode and join #emc, usually lots of knowledgeable people around.

The HAL file you are using is usually in the same directory as your INI file. If you are using the standard stepper_inch.ini then the HAL file is probably standard_pinout.hal

the wiki has more information: http://wiki.linuxcnc.org

specifically, the config the guy who is developing this uses is at:
http://cvs.linuxcnc.org/cgi-bin/cvsw...2/configs/max/

if you look in max.hal you should get an idea of what is required.