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Author Topic: Problems threading on the lathe  (Read 330278 times)

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Offline Hood

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Re: Problems threading on the lathe
« Reply #430 on: September 28, 2009, 08:37:28 AM »
Certainly looks like VFD can be taken out of the equation then :)
 So anyone using a PP, what is the pulse frequency on the Diagnostics page sitting at? I seem to remember when mine was using the PP it was very close to the set kernel and I don't think it varied at all day in day out, wonder if that could be a clue?
Even though I don't have an issue and have never had, it would still be great to see this get a resolution.

Hood

Offline RICH

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Re: Problems threading on the lathe
« Reply #431 on: September 28, 2009, 08:54:15 AM »
Hood,
Mine has never been rock solid and varies. This is true for four different computers i have tried.
You can have a good consistant index input, but, as you elude too, if Mach has a bum
input for controlling the steps then you can end up with the lead problem and even when
the the start of the threading cycle should start. 

I'm thinking and that is dangerous.  ;)
RICH

Offline ART

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Re: Problems threading on the lathe
« Reply #432 on: September 28, 2009, 09:32:51 AM »
Hi Guys:

  The threading is being re-investigated as of this coming week or two. John S has agreed to run some tests for me to see where the wander is at. We're goign to start with the
Printer port single pulse threading, then evaluate the multislot again to document the differences. The wander is caused by a varying of the time the computer see's the index time.
It seems on some computers there is an inherent delay and this causes an overcorrrection that creates a wandering Z position. On other computers it seems not to exist. I still
dont know though if its the computer or the machien causing the variance. The multislot gives me statistics to see how much variance. When I feed it a time based generated pulse
I see no variance here, but using my Emco lathe, I see the index pulse varying in time.

 This means either my motor is varying in speed slightly, ( though I cant see or hear it..) or the sensor itself just isnt that solid in terms of when it activates. More test results should be
coing out soon.

  In current versions the driver was modified to a new timing base, which is more solid. My #interrupts display has since read withing a close number of selected kernal speed. 25005 for 25Khz for example, and very solid. I suspect those with further away numbers, and more variance see worse threads. Perhaps future tests will tell us which it is.

Art
 
 

 

Offline Hood

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Re: Problems threading on the lathe
« Reply #433 on: September 28, 2009, 09:41:08 AM »
That is interesting, I can't look at the lathes pulse frequency as it doesn't have a PP on the pico mobo but just looked at the mill when I started it with an old PP profile and the pulse frequency is rock solid. Have also looked at the desktop machine I am typing with and again it is rock steady. Not sure if you actually see it varying in real time though? Have certainly restarted Mach a few times on each and its always exactly the same.
Hood

Edit
 This reply was in response to Rich's last post, Art has since come in, was on the phone while typing so was a bit slow, thats my excuse anyway ;D
« Last Edit: September 28, 2009, 09:43:16 AM by Hood »

Offline RICH

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Re: Problems threading on the lathe
« Reply #434 on: September 28, 2009, 09:50:54 AM »
Art,
I assume that the variance will carry over to the SS. Is that true?
During the driver test for my pc i get 22000 for 25KhZ and it varies by 200.
RICH

Offline Hood

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Re: Problems threading on the lathe
« Reply #435 on: September 28, 2009, 10:05:45 AM »
Rich, do you see that varying in real time on the diagnostics page?

Hood

Offline ART

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Re: Problems threading on the lathe
« Reply #436 on: September 28, 2009, 10:31:20 AM »
Rich:

  No, variance doesnt carry to the SS, it has a fixed period cycle that wont ( or shouldnt ) vary. Your computer shows a sign of instability with a low reading of 22000 and a 200 variance. What does the drivertest show? A stright line? or is it more of a sawtooth?

   Its my suspicion that the variance can be caused by the cpu being less than perfect in when it triggers the interrupts.

Art

Offline RICH

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Re: Problems threading on the lathe
« Reply #437 on: September 28, 2009, 10:53:12 AM »
Hood,
Thanks,
The TURN  DIAGNOSTICS dosen't work for the SS.
I can turn off the drives and  check it out as if i was using the PP and get some info and then will repost
shortly.

RICH

 

Offline RICH

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Re: Problems threading on the lathe
« Reply #438 on: September 28, 2009, 10:57:17 AM »
Art,
The dirver test shows  a straight line, a small spike every now and then.
RICH

Offline RICH

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Re: Problems threading on the lathe
« Reply #439 on: September 28, 2009, 11:07:47 AM »
here is a screen shot of the driver test
RICH