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Author Topic: Dead ... or alive.  (Read 10967 times)

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Dead ... or alive.
« on: March 06, 2014, 11:16:18 PM »
Just wondering, anyone here know if the encoder spindle lathe threading thing with the SS is at all possible/probable ?
Any progress at all ?
Not much going on on the SS forum. (about a year  ::) )

And what we might expect in the quick pull-out ? Unlike the CS Lab and (EMC)

Just curious.  :)
Thanks,
Russ
Re: Dead ... or alive.
« Reply #1 on: March 11, 2014, 08:46:10 AM »
Can you explain what you mean by 'quick pull out'?

sam
Re: Dead ... or alive.
« Reply #2 on: March 12, 2014, 12:26:48 AM »
no Z axis pause at the end of the thread before the X retracts the tool from the thread, preferably completed within 1/2 to 1 revolution of the part while maintaining the pitch with the Z axis.
Mach does this quite well, some others ... not so good.
Russ

Offline RICH

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Re: Dead ... or alive.
« Reply #3 on: March 12, 2014, 06:46:02 AM »
Russ,
Don't have an answer for you but do have dumb question.

From a "fastener use" viewpoint....... Why does it matter if the pitch is maintained or is gradual?
The stress point is moved and intensification factor would still be subjective, and in calc's, the  max loading  would still be based on the thread geometry.
Even the max loading is subjective.

Just wondering if you are needing to address someones spec for the bolt........

RICH
Re: Dead ... or alive.
« Reply #4 on: March 12, 2014, 07:47:31 AM »
Hi Rich,
  I'd say it doesn't really matter that the pitch is not maintained "exactly", actually with one routine here at 1000 rpm Mach pulls out in 1 revolution while the 48 tpi pitch diminishes roughly 30-50% (by eye) which is pretty good and eliminates cutting the annular groove.

Good point, thanks,
Russ
 :)
Re: Dead ... or alive.
« Reply #5 on: March 12, 2014, 07:48:49 AM »
Linuxcnc has always done this...

https://www.youtube.com/watch?v=Z_LxyosF2yc

http://www.linuxcnc.org/docs/2.5/html/gcode/gcode.html#sec:G76-Threading-Canned

You can specify an entry or exit taper - this move is synchronized with the spindle.
Re: Dead ... or alive.
« Reply #6 on: March 12, 2014, 04:08:00 PM »
Thanks Sam, I might look into that.
Other emc  vids I've seen show what looks like a groove, maybe I didn't see correctly.

Thanks again,
Russ

Offline Hood

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Re: Dead ... or alive.
« Reply #7 on: March 15, 2014, 06:40:10 PM »
Russ,
 dont know if its been done or not but suspect not. However even if it has then I would say its unlikely to work as it seems using full encoder sync with Mach3 will always produce that delay in pull out. I talked with Steve (Smurph) about this issue and he said he had exactly the same issue with the Galil so had to revert to single index. Rufi of Vital systems said to me it works fine in DSPMC/Hicon but neither he or anyone else could show me video evidence of it so......
 

Sam,
 does LinuxCNC still do tapered threads wrong or has that been sorted?

Hood
Re: Dead ... or alive.
« Reply #8 on: March 15, 2014, 08:32:36 PM »
Hi Hood, thanks.
  Watching a thread on encoders running now at the W9 forum. Looks like it may get worked on, will be interesting to see how it transpires.

Thanks again for sharing your research,
Russ
Re: Dead ... or alive.
« Reply #9 on: March 15, 2014, 10:21:31 PM »
Well - it isn't really that it does it wrong as it doesn't do it like any other control and no one has made a canned cycle to fix it yet..  (that I know of anyway)

G33 spindle synchronized motion in linuxcnc was made to be very flexible..  You are not limited to z axis moves.  ie - you could cut a scroll if you wanted to.  or a fusee.  That though required that the pitch be calculated along the move.  So if you move x and y the same amount (45deg angle) the pitch is along the hypotenuse.  If you are cutting a taper - you have to specify the pitch along the xz move - not the z move.  (clear as mud?)  People have made some gcode subroutines to do the calculations..  Here is a good thread (no pun intended).

http://www.linuxcnc.org/index.php/english/forum/40-subroutines-and-ngcgui/13006-ntp?limitstart=0

Here is G33 from the manual
http://www.linuxcnc.org/docs/devel/html/gcode/gcode.html#sec:G33-Spindle-Sync

sam

Sam,
 does LinuxCNC still do tapered threads wrong or has that been sorted?

Hood
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