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Author Topic: Lathe Threading - RPM inconsistent  (Read 4107 times)

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Lathe Threading - RPM inconsistent
« on: February 21, 2014, 03:39:18 PM »
Hey folks,
  I have a new problem.
Been threading with this set-up for several years, thousands of identical parts.

I'll have to retrieve the version, but think its 22.

Suddenly, the rpm is bouncing around +/- 4 onn the Mach screen and about half that on the VFD readout.
This of course ruins a 48 pitch thread (5 passes).
It used to only fluctuate 1 rpm.... maybe 2, but mostly 1 and made acceptable threads. Sometimes 1600 pcs. non stop.

Quite by accident, I noticed that closing Mach, then restarting the rpm was stable again.
Then I checked the diagnostics, not sure though if it was fluctuating or not at the time. But, here is what it reported:
Time in int. 4 > 11
CPU speed  2018.0
Pulse Freq.   44023

The kernel is set a 25

This is PPort, PMDX 122 BoB - PMDX 106 Spindle control.

I'm trying to narrow it down to .... the PC ?  the 106 ? ... or the inverter ?

We opened the pc case and blew it out (was very dirty) thought the cpu might be overheating .. didn't help.
Never know when it might happen, sometimes instantly ... might be good for a day or two. Regardless, much too frequent now.

Any help troubleshooting would be much appreciated,
Thanks,
Russ
« Last Edit: February 21, 2014, 03:52:26 PM by Overloaded »
Re: Lathe Threading - RPM inconsistent
« Reply #1 on: February 21, 2014, 06:49:15 PM »
One other little anomaly.
More frequently than before, Mach will hank up when clicking on certain buttons. One being Load Code or sometimes (iirc) Edit Code. But LOAD for sure.
Requires a manual kill and reboot. No other way.

Russ

Offline RICH

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Re: Lathe Threading - RPM inconsistent
« Reply #2 on: February 21, 2014, 09:22:34 PM »
Russ,
I would go with at least version 3.042.033. or .034.

+- 1 rpm is ok, but +-4 is not good as  mach can't account for an increase in spindle speed  ......adjustment for rpm slow down only if i remember correctly.

Maybe remove spindle control and set manualy ( which should be done anyway ) and see what the rpm readout is giving as that may give you a clue on what is the culprit.

RICH
« Last Edit: February 21, 2014, 09:25:41 PM by RICH »
Re: Lathe Threading - RPM inconsistent
« Reply #3 on: February 21, 2014, 10:32:58 PM »
Good points Rich !
 I hadn't thought of bypassing the spindle control for a test.
That would certainly narrow it down.
Will check and try the newer versions.
Will be back at the machine Monday or tuesday. I'm making a list. Might take along a new VFD and a newer PC too.
Thanks a bunch Rich,
Russ

Offline Hood

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Re: Lathe Threading - RPM inconsistent
« Reply #4 on: February 22, 2014, 01:54:49 AM »
Time in int. 4 > 11
CPU speed  2018.0
Pulse Freq.   44023

The kernel is set a 25

Would look there first.
Hood
Re: Lathe Threading - RPM inconsistent
« Reply #5 on: February 23, 2014, 01:40:21 PM »
Thank you Hood.

What do you think might cause this to suddenly happen to a machine that has run very well and basically untouched for several years ?
And, what to do to possibly fix it ?

I don't have a scope, but plan to try to check the PWM out from the pc with an analog meter. Not expecting that to work very well though.
Also planning to check the analog IN to the drive (from the pc > 106) to see if it is wavering.
Will be back where the machine is Monday or Tuesday.

Thanks everyone,
Russ

Offline Hood

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Re: Lathe Threading - RPM inconsistent
« Reply #6 on: February 23, 2014, 02:11:08 PM »
If the pulse frequency is way out compared to the kernel and it has just recently happened, then I would say hardware could be the  likely culprit.
Look at the mobo and see if any caps are bulging, look in the BIOS and see if the voltages and temps are close to where they should be. If you are having crashing problems with the computer (not sure if you are or not) then could be memory.

Hood
Re: Lathe Threading - RPM inconsistent
« Reply #7 on: February 23, 2014, 03:05:13 PM »
OK Hood, thanks.
I'll prepare another pc, just in case.

Russ
Re: Lathe Threading - RPM inconsistent
« Reply #8 on: February 23, 2014, 05:19:42 PM »
Russ,
I would go with at least version 3.042.033. or .034.

 
RICH

Hi Rich,
   My lathe here is running 3.043.022, not sure which "22" is on the other machine yet.
Would you kindly verify that the 3.042. stated above is correct ? Just to be sure.

Thanks Rich,
Russ

Offline RICH

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Re: Lathe Threading - RPM inconsistent
« Reply #9 on: February 23, 2014, 06:03:14 PM »
Russ,
3.042 is corrrect. 

RICH