Messages

831

General Mach Discussion / Re: Problems threading on the lathe

« on: October 23, 2009, 02:36:26 PM »

Hi Rich:

  Yes, I suspected as much. The correction code is still based on number of interrupts seen between index pulses, we now know that using PCI bus time is much more accurate, so the pitch is
correct, but I think Im going to have to swap the interrupt based correction code to time based as well, otherwise it may sense a correction when none needs to be done. Id go back to the non-corrected and see if AL threads are generally OK, or material that doesnt slow the spindle.

  Ill start work on the correction swap to time based, Im thinking that may solve the issue. Im wondering if the current non-corrected gives us any bad passes, that woudl be a clue thats valuable, if there are no screwups in soft material, then I suyspect the correction is now createing its own "whoops" passes..

Art

832

General Mach Discussion / Re: Problems threading on the lathe

« on: October 22, 2009, 11:11:38 PM »

Rich:

 Great so far then.. Woth no correction required the threads now pass muster. And they should on anyone system then in theory.
Ill keep my fingers crossed for correction..

Art
 

833

General Mach Discussion / Re: Problems threading on the lathe

« on: October 22, 2009, 09:53:11 PM »

Rich:

   Hers a driver that turns correction back on..

Art

834

General Mach Discussion / Re: Problems threading on the lathe

« on: October 22, 2009, 08:08:06 PM »

Hi Rich:

  Yes, I was thinking the number crunching was showing too many inferences to the RPM. I'm a bit embarassed
I didnt see it before, the lack of fractional component of the rpm measured seems the pitch culprit.

  Im going to turn on correction again after you run your tests, we'll see if that works as it should if you
apply a bit of pressure to the spindle while its turning..

Art

835

Tempest Trajectory Planner / Re: Tempest Planning - Preliminary information and testing

« on: October 22, 2009, 08:00:23 PM »

Mike:

 If its just sharp corners, then you mnay simply be fighting physics. When you specify a Jerk of 25000, youll telling it
to slow on corners to exactly 25000 units/sec^3 of jerk. So thats the speed. Raise your jerk limit to 100,000 and see
if it goes faster.

Art

836

Tempest Trajectory Planner / Re: Tempest Planning - Preliminary information and testing

« on: October 22, 2009, 03:22:52 PM »

Hi Mike:

  Seems to run here OK..though I only ran to line 700 or so.. Averages about 2450 on the feedrate. I have mine set to 20 line lookahead, 1cv and 25000 jerk. Is thi sthe latest verison?

Art

837

General Mach Discussion / Re: Problems threading on the lathe

« on: October 22, 2009, 01:06:18 PM »

Rich:

  At the moment we have no correction, so that cant be it.. and if Windows was interupted then the pitch woudlnt start properly I think..
The more I crunch the numbers the more I think its the integer RPM.. Oct22-1 will be interesting..

Art

838

General Mach Discussion / Re: Problems threading on the lathe

« on: October 22, 2009, 10:14:29 AM »

Hi Steiner:

  Actually, if averaging is turned on, its averaged over 8 rev's..

Art

839

General Mach Discussion / Re: Problems threading on the lathe

« on: October 22, 2009, 09:43:56 AM »

Rich:

  Sorry to flood you, but crunching has shown me the error may simply be the integer nature of the rpm whcih should almost always have fractions
to it. SO heres a version that should show an RPM of 400.712536753261 or similar..

Let me know if it indeed does so, if Not, Ill have to rehook my spindle sensor ( disconnect for some shop work... ) and test further. I think we're
onto why the .0025 or .003 error. If this works as I hope, that shoudl now be much closer..

Art
( I found more integers , so I resent this message with an updated code base..)

840

General Mach Discussion / Re: Problems threading on the lathe

« on: October 22, 2009, 09:30:30 AM »

Rich:

 Just as a following up. I rechecked your error passes.

We can see that the RPM was seen to change by 1RPM from 400 to 401. The feedrate changed
as a result from 40IPM to 401.RPM. Thats the only difference and its not alwasy there so
I was discountiung it. Heres why..


40IPM at 400RPM.. is .666666 inches per second at 400RPM ( 6.666666 revsper second ) so a pitch of .1 exactly..
40.1IPM at 401RPM is .6683333 inches per second at 401RPM ( 6.683333 ) so a pitch of exacltly .1 again..


  These numbers are as near perfect as one could hope for. NOW lets assuem the RPM WAS holding at 400, and not
really getting to 401RPM.. ( Ive noticed we have a granularity of 1.0 for RPM, Im going to see why that is, we should
have fractional RPM's really, so why is RPM always .000 after the decimal. )

  But before that lest figure out what happens if the RPM was simply wrong at 401, and we were still running at 400.

The difference between 400 and 401 is the diff between 6.66666 and 6.683333 so .016673 inches per second. with
6.66666 revs per second, so the error woudl be .016673 / 6.6666 = .0025Inches per rev. ( Sounds familiar dont it.).

  SO Im suspecting now the RPM , always dropping the decimal fraction may explain the lead/advance errors your seeing.

Ill look now to see why the RPM is always an integer, if I fix that we should see a tighter fit to the pitch. None of this
explains the crazy passes.. but lets see what fractional RPM does.. it shoudl fix the .0025 error ..

Art