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Messages - ART

861
General Mach Discussion / Re: Problems threading on the lathe
« on: October 14, 2009, 09:49:12 PM »
Rich:

 Yup, I always find that when the trap is set..the buggers stay away. LOL

Art

862
General Mach Discussion / Re: Problems threading on the lathe
« on: October 14, 2009, 09:36:12 PM »
Rich:

 Each time a G32 is processed, this version will write into the lasterrors.txt file the velocity in units/sec for that thread move. Be interesting to see the velocity it picks each move..

Thx
Art

863
General Mach Discussion / Re: Problems threading on the lathe
« on: October 14, 2009, 09:21:49 PM »
Rich:

   Thanks for the verification. Now that the RPM is measured based on time rather then number of int's, in theory the susceptability to
switching screens should be less, but still there.

   In general operation as the index pulse swings by the sensor, MAch3 will either see it immediately , OR on the next interrupt. So
the typical variation of RPM cant be made better than  + or - 40us at 25Khz. SO a variance of 100RPM to 99.99 is what we should get
typically. Its hard to explain why the spindle may get a planning RPM very different occasionally to make the thread advance so much.

 Hmm, I guess thats the golden question isnt it.. what rpm WAS used for each line. I think Ill make a version that saves a debug file
to show the planned RPM for each pass of the thread. If it shows the RPM has varied greatly on any pass from previous passes, that will
prove the advance was due to planning at a different feedrate.

 Ill post a version soon to do exactly that, youll be able to forensically see what feedrate was the end result just as it was planned.
If that shows very stable, we look elsewhere.


Thx
Art


 

864
General Mach Discussion / Re: Problems threading on the lathe
« on: October 14, 2009, 02:59:49 PM »
Hi Rich:

 One thing I notice while looking to the code, you really need a G0 move between any G32 moves.. With G76 this isnt a problem as it injects g0 moves to pullout, but in yur testing, did you use G0 moves to reposition the passes back to the start?

  The of the g0 makes the next g32 only use the rpm current at end of g0 before it plans the next thread pass speed. Seems I may need to do some work on that..

Thx
Art

865
General Mach Discussion / Re: Problems threading on the lathe
« on: October 14, 2009, 09:03:54 AM »
Rich:

  Thanks to your testing I think I have a grasp of whats going on. What to do about it is more complex.
I'm not as sure as to why the variable lead.. though its pretty close at this point, but I highly suspect
whats going on is the RPM is locking in at variosu values at times. This can be caused by many things.

  Mach3 when it gets a threading command, sets up the pass using the current spindle RPM, a split second later
the driver see's this command and "locks in" the current spindle RPM for the entire pass, correcting if the RPM changes
from the "locked" rpm.

   So one of two things is causing that intermittant bad pass. The RPM is wrong at some point in the process. On the versions
your testing the correction is turned off, that helps narrow this down. It means for sure the RPM is different by a percentage
 from one pass to another. If the locked in RPM is different from the RPM that Mach3 used to calcuate the pass, youll get a
leading or decreasing pitch on that pass. We can see a .001 or .003 or .005 pitch as normal, but then on a particular pass the
RPM gets locked at a wrong RPM.

   I have a few things to check inthe code now.. it could be the planner is processing the next threading pass before the first is done, thus the rpm
could be lower due to load when the next thread command is processed. I need to ensure it locks out the next runs processing till the first one is done.

  You can stop testing for a bit while I digest the numbers and see what I can do to tighten this up. Hopefully , thats all it is,
otherwise it means the RPM is wrong occasionally for some reason.. and that may be arder t find.  :)

I suspect  youll find even the earlier version do as this report suggests, specially if the spindle is cold. I have heard runnign it for a few minutes till stable
helps it be stable through the run.

Thx
Art

866
General Mach Discussion / Re: Tool Changing problems on the lathe
« on: October 13, 2009, 11:08:39 AM »
hmm, if I load your program here, zero the x dro, and regen, I get X limits of 0.00 and 60.0 which seems correct. Did you try it on the release screenset.. I cant think of why its acting differently on yours..

Art

867
General Mach Discussion / Re: Tool Changing problems on the lathe
« on: October 13, 2009, 10:09:54 AM »
Phil:


   Change the t0505 to t0500 , what happens then.

Art

868
Randy:

 Np problem. Have fun.

Art

869
General Mach Discussion / Re: Problems threading on the lathe
« on: October 12, 2009, 01:36:28 PM »
Rich:

 Looking pretty good then so far. I think your right, lets press the envelope and see if we can make it as good as we can. Here's a .001 correction applied to
previous version. Tuesdays fine, and again, as always, thanks for the great results posted. The interesting thing will be how it scales to higher RPM's, if we do achieve zero
runout. 

Art

870
General Mach Discussion / Re: Tool Changing problems on the lathe
« on: October 12, 2009, 11:36:05 AM »
Phil:

  It could be. BAsically the program runs ahead of you, so the tool in the dro is simply the last tool commanded in the program usually.
Typing in a new tool to the dro wont change the offset register, youd be better of enter T0505 in the mdi line if you want to swap a tool
to see the effect. I think theres a config item "Remove offsets at end of program " as well, make sure if thats there, it isnt checked. It could
be the program is removing offsets at end of run.

Art