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Author Topic: Lost steps - again?  (Read 6352 times)

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Offline mTron

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Lost steps - again?
« on: January 27, 2013, 02:28:46 PM »
Hi

New to this forum I need your help in a strange problem I experience in my stepper-motor driven Quantum BF20L mill, controlled by Mach 3.043.022. The PC is an elderly Intel P5 machine running at 512MHz; it is dedicated to Mach3 and has no network connections.

At the very beginning of my work with Mach3, about 3 years ago, the motors just screeched and didn't move. It happened quite rarely, say once in an hour's operation and when doing a G0 rapid move under G-Code control. I never had the problem when jogging, even when using the shift-key. I then reduced the maximum speed on all axes from 1500 mm/min to 1200 and also reduced the ramp to now 60 mm/sec/sec. This seemed to cure the problem or at least reduced it to a tolerable frequency.

Recently the problem reoccurred for no apparent reason, several times in an hour. I further reduced speed and acceleration - no improvement. There seems to be a coincidence: Usually when jogging in Step-mode the speed is very low. After a number of jogging moves in both Cont- and Step-mode with and without shift-key (rapid jogging) the speed in step-mode suddenly equals the last feed speed, which may be much higher. I cannot reduce it unless I terminate and restart Mach3. I have never consciously experienced step-loss under G0 when step-jogging speed was low. It also seems to me that when there is step-loss under G0 the usual acceleration ramp has vanished, which would explain why the steppers cannot follow. However I couldn't really verify that.

I then downloaded and installed the newest version of Mach3.043.066 including its driver. It didn't cure my problem, but since then I have a couple of new problems:  :'(

a) When I pause a G-code run run with the space-key I cannot restart the run, i.e. "Cycle Start <Alt-R>" doesn't work any more.
b) When I zero the X- and Y-axes using an edge-finder in the Offsets-screen Mach3 correctly observes its radius. But when I then manually do a "G0 X0 Y0" command via MDI it has forgotten all about the edge-finder offset - the zero position is not where it ought to be.

Then I scanned this forum, but couldn't find anything that helped so far.

Does anyone of you have an idea what I could do next?  ???

Thanks in advance and cheers!

Peter

Offline Hood

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Re: Lost steps - again?
« Reply #1 on: January 27, 2013, 05:09:30 PM »
Attach your xml and I will see if there is a problem with your config. Regarding the first issue (motors stalling) could be your pulse width is too narrow, try increasing that or even putting in Sherline mode if your kernel is just 25KHz.
Oh and BTW a 512meg computer may be struggling with Mach.
Hood

Offline mTron

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Re: Lost steps - again?
« Reply #2 on: January 28, 2013, 02:15:10 PM »
Hi Hood
Thank you for your rapid and helpful reply.
Please find attached the current xml-file. As you will see, the pulse width is already at its maximum of 5 us. The kernel runs at 25 kHz as you suspected. During the installation I ran the DriverTest which showed "excellent" pulsing up to 65 Hz. This BTW confirmed to me that the computer was fast enough for the job - maybe that conclusion was a bit premature. Anyway I shall take my office computer to the workshop to see if the "screeching problem" disappears. However this must wait till the weekend, because my job keeps me too busy. :(
What is the Sherline mode? (I couldn't find that term in the documentation.)
Peter

Offline Hood

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Re: Lost steps - again?
« Reply #3 on: January 28, 2013, 04:12:06 PM »
Pulse width can be set as high as 15 if I recall correctly, even though it says 5 on motor tuning page.
Sherline mode makes the pulse half width, ie 40Us, that is why you can only use it at 25KHz.
Was the line flat in the driver test?
Hood

Offline mTron

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Re: Lost steps - again?
« Reply #4 on: January 29, 2013, 02:34:07 PM »
At the time I thought that the line in Driver Test was reasonably flat, but judge for yourself in the attachment. Comparing the details between the office PC with the workshop PC makes me hope for a clear improvement.

Regarding Sherline mode: How do I set it?

And regarding the other weirdies I encountered using Mach3.043.066: Would you suggest that I go back to 3.043.022?

Peter

Offline Hood

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Re: Lost steps - again?
« Reply #5 on: January 29, 2013, 03:31:43 PM »
You set sherline mode from Config menu then Ports and pins, its over to the right on the first page that pops up, the one where you set the kernel.

Your driver test isnt bad but its not great either, ideally you want a very flat line with almost no disturbances.

I found weird happenings with 066 and Turn, not seen any with Mill but maybe go back and see.
Hood

Offline mTron

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Re: Lost steps - again?
« Reply #6 on: January 29, 2013, 04:48:09 PM »
Found Sherline mode - cheers! :D

So I'll reinstall version 022 on my office computer, drag it to the workshop and give my project another try. As I said from next weekend onwards. I'll keep you posted. Thanks so far!

Peter

Offline Hood

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Re: Lost steps - again?
« Reply #7 on: January 29, 2013, 05:25:00 PM »
Ok no problem :)
Hood

Offline mTron

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Re: Lost steps - again?
« Reply #8 on: February 03, 2013, 06:15:44 AM »
I did as I said: Using Mach3.043.022 on an Intel Pentium 4, 3 GHz with 2.5 GB RAM the mill ran as the famous Swiss clockwork. The first stress test was

...
m98 p2 l50
...
o2
g0 x0 y0 z0
g0 x100 y100 z100
m99

It tested not only the program's parameters but also the stability of the power supplies. When this ran well I started the maching program which crashed at the beginning of this thread. OK, for safety reasons I milled lots of air, but from time to time I stopped the run to verify that the real coordinates matched those of the DROs.  Well, I didn't wait some 5 hours till it came to the end, but within the first hour everthing was perfect.

So I went out and ordered a new/old workshop computer: a DELL Optiplex 755 2 x 2.33 GHz. I expect it to be delivered some time this week.

Again, many thank for your support which led to the solution of the mystery.

Cheers,
Peter
Re: Lost steps - again?
« Reply #9 on: February 05, 2013, 10:07:12 AM »
Hello
I am facing a similar behaviour.
Everything is normally running fine... and seems the problem appears (to loose steps) only if am loading large G-codes (over 10 MBytes), could this be a cause also ?
Thanks!

Sam