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Weird PC Freezing Issue
« on: December 12, 2010, 08:47:21 AM »
Hello guys,
Before starting this topic, I have read all similar posts, but couldn't find the answer so I have to ask for help here.

Machine (brand new) was working for about 5 days and after that, during rest machining PC suddenly freezes (axis, spindle) and I couldn't move mouse or hit Stop/Reset... After 10-20 sec, the PC unfreezes, Spindle starts spinning up and G-Code continue executing normally. Than I was able to hit feedhold (pause), but machine stops after 5-6 sec. Also, I have noticed that Machine looses its coordinates for few mm each. After that the same issue happens randomly with different tools, codes, but at the same way.

Also this one thing might be helpful in finding the cure: when jogging at rapid (12m/min) w/o G-Code loaded, it runs smoothly, but with G-Code loaded it sometimes shakes a little, like it got uneven pulse train for a while. Bridge is over 200Kg weight, driven by AC Servo, which makes very unpleasant behavior.

The PC is brand new, with the following config:

Intel Celeron, Dual Core E3400 2.6GHz
1GB DDR2 RAM
GigaByte GA-G41M-ES2L rev1.1
Win7 Starter

Any hint will be helpful.

Cheers

Offline Hood

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Re: Weird PC Freezing Issue
« Reply #1 on: December 12, 2010, 09:13:27 AM »
Are you using the parallel port or one of the external motion controllers available?
If using the parallel Port what have you got the Kernel set to?

Also if you want to attach your xml I can have a look and see if there are any issues with the config.
Hood
Re: Weird PC Freezing Issue
« Reply #2 on: December 12, 2010, 02:56:25 PM »
Thanks Hood,
I am using parallel port (got a lot of headache to find configuration with onboard LPT). Kernel in Mach is set to 45KHz. Here is the .xml, but I doubt that it is causing the issue. I will try to add extra RAM or graphic card tomorrow to see is there any changes.

Cheers

Offline Hood

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Re: Weird PC Freezing Issue
« Reply #3 on: December 12, 2010, 05:30:29 PM »
Does the frequency on the Diags page stay fairly steady and is it close to 45KHz?
What is the Time in Int?
Have you run the driver test at 45KHz to see if you get a smooth line

Might also be worth looking at the CPU usage when you are getting the problem.
Hood
Re: Weird PC Freezing Issue
« Reply #4 on: December 12, 2010, 06:15:46 PM »
I've had Mach installed on 5 different PC's running plasma tables, mills and routers...and on all of then, anything over 35KHz locked up the PC.  The driver test always showed a smooth line.  Sometimes it would lock up right when Mach loaded and sometimes it would wait a few minutes, but it always locked up within a few minutes of starting mach.  No problems at all running at 25 or 35KHz.  I always run at 25KHz just to be on the safe side.

Offline Hood

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Re: Weird PC Freezing Issue
« Reply #5 on: December 12, 2010, 06:27:45 PM »
I always run at 25KHz just to be on the safe side.

It is usually best to run at 25KHz if you can get the rapids required at that kernel but with servos it is often necessary to set it higher. In this case however, looking at the xml, it would seem 25KHz would be plenty so might be an idea to try as rrc1962 suggests and set it to 25KHz.
Hood
Re: Weird PC Freezing Issue
« Reply #6 on: December 12, 2010, 06:30:09 PM »
Thanks a lot fellas,
I'll try this in the morning and see what will happen.

Cheers

Offline Hood

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Re: Weird PC Freezing Issue
« Reply #7 on: December 12, 2010, 06:42:54 PM »
Heres a bit of info Art wrote with regards to this, it a good read and gives a good insight into things.
Hood

Here's the deal with kernal speed.

Lets say you select 25Khz, and then tune your motors. While tuning, you find
you have the velocity slider up all the way, but would like to go faster than
you can tune.. you then must select the next higher kernal speed, and retune all
motors. If while tuning, you find you cannot go fast enough, repeat till the
kernal speed is such that you CAN select the speed you need.

The reason is this..

In 25Khz mode, the computer interrupts every 40us.. in 35Khz, every 28.5us ,
in 65Khz, every 15us , and for 100khz, every 10us.

Now, the time-in-int is the amount of time spent servicing that interrupt. One
of the secrets of the printer port driver, one Ive never discussed , is that
all drivers in windows are told to do their thing fast, and get out. My driver
breaks that rule..heck it breaks most rules. :) . SO it takes the time it needs
to
do 1 step pulse, read input, set outputs, unset the step pulse, jog if
necessary, etc.. and then exits to wait for the next interrupt. The time-in-int
is the time it takes to do all that.

So lets say your in 25khz, every 40us an interrupt will come along, and your
machin has a time-in-int of 15, that means your cpu has 40-15=25us to do its
normal windows activity. Your computer is now 37% a pulse driver, and 63% a
windows OS..

Time-in-int doesnt vary from kernal speed to kernal speed, only computer to
computer. Lets say yours is 11us. ( a bit high ), if your in 65Khz mode, your
now interrupting every 15us.. , so Windows now has 3us every 15 to do its thing,
its now a cpu that is 20%windows, and 80% pulse engine.

The windows component runs Mach3, so you now have 20%Mach3 ( plus windows
fucntions) , and 80% pulse engine. As the pulse engine % goes higher, the chance
of lockup goes higher.

So higher kernal speeds give you higher criticality, which can be defined as
your sensitivity to random bad events affecting the computer. The lower the
kernal speed, the higher your immunity. As youve noticed, your 45Khz machine
doesnt lock up as much as your 65Khz machine. That follows the logic Im
explaining. (Im almost willing to bet your machine at 25Khz will never lock up ,
or would be very very rare, (Im assuming this from your statement about the two
machines correlated to hundreds of very similar conversations over the years
with lockup victims. Fully 80% of them didnt realize the connection, and tuning
lower in kernal speed stopped the problem.

Now sometimes you NEED higher kernal speeds, ( high step count machines
typically), but fully 90% of people who have set high kernal speeds
dont really need them, they do so simply as a result of the very human instinct
to have the highest possible speed selected. ( "Yeah boys, my engine has triple
hedenstock carbs with dual-hemi semi-octagonal rebuf cyclinder hose accessory
packs!".. :)

You may wonder..why the heck dont I tell people this more forcefully, since
it will stop most lockups. Fact is, higher kernal speeds DO have a smoother
motion just as a result of granularity, and Ive found the vast majority CAN use
higher speeds with no problem. ( I am limited here to 65K ), I use 25K though
for reliability. With over 25 thousand machines out there, the number of
overall lockups is extremely small, and thats including the tendancy people have
to select the higher speeds,so as a result, I try to keep my nose out of their
selections, unless they have trouble.

The final question you should be thinking about now is.. "Why didnt you ask
me this when I complained about lockups.. :) ), the answer is that the
subject comes up so infrequenctly now that even I forgot to ask this basic
question about the kernal speed. I used to post it periodically on this group,
but stopped quite a while back. In retirement I guess Im getting forgetful is
my only excuse. Hopefully, youll find 25K never locks up.. Im suspecting this
is true in your case. I hope so.

For those that want maximum reliability, I suggest this, use as low a kernal
frequency as you can live with. On many machines maximum cutting speed is easily
achievable in 25Khz, the only sacrifice in using 25Khz is perhaps a slower rapid
speed. Rapids are nice, but not as nice as perfect stability, so I tend to give
up some rapids to put their power into stability. Look at kernal speed as a
trade-off, you can go real fast, or real stable.. (This is only if you have a
lockup problem, many can have both and use higher kernal speeds. )

My own suspicion, again based on time and numbers, is that many people would
have lockups, but most leave the kernal at the install speed of 25Khz.. I rarely
hear form them. I hear most from 65Khz, and Ive heard quite a bit from 100Khz..
this is because those that can run 100khz are a rare breed, very fast clean
machines with extremely stable operating system installs. For 65Khz, you better
have a nice fast computer. 45Khz isnt bad, lockups on those indicate a computer
suffering some periodic problem that slows the time-in-int too much..

None of this incidentally explains a random move. The driver is pretty much
incapable of it, it canot move unless commanded, and it takes quite a sequence
normally to command it. Youd have a better chance of winning a lottery than
getting uncommanded motion.....unexpected..yes. :), that happens to all of us..
usually at our unknown request, but uncommanded...near impossible in the drivers
context.

Let us know how 25Khz works.. do you have to sacrifice much speed ( or any )
to use it? And what IS your time-in-int number?

My average time-in-int is 5-7us by the way, which is pretty normal for a 2Ghz
machines, by dual core is only 3-4us, meaning it will take much higher
kernal speeds without reaching any high level of criticality. My 1.2Ghz was
around 15us.. ( pretty bad, but ran fine..)

Sorry for the ramble, I guess it was time for one anyway, for some reason there
are some that actually like my rambles. lol

Thanks,
Art
www.gearotic.com
« Last Edit: December 12, 2010, 06:44:39 PM by Hood »
Re: Weird PC Freezing Issue
« Reply #8 on: December 13, 2010, 06:11:44 AM »

None of this incidentally explains a random move. The driver is pretty much
incapable of it, it canot move unless commanded, and it takes quite a sequence
normally to command it. Youd have a better chance of winning a lottery than
getting uncommanded motion.....unexpected..yes. :), that happens to all of us..
usually at our unknown request, but uncommanded...near impossible in the drivers
context.


Actually, there is no random move. The weird thing is that after few (5-25) seconds of being freezed, the program continues executing normally as nothing bad happened. This is problem because spindle starts accelerating through material, and work zero is moved. Shouldn't watchdog be activated in this case and reset the engine?

I have installed a new LD (there was R3.042.020 earlier) and set kernel at 25KHz. Here is the situation:

- Time in interupt was 2.5-12, now stays unchanged.
- Pulse Freq was 38.5-45KHz, now is 22-25.1.
- Buffer was around 20%, now is 13% (Look ahead set to 500)

There is one more thing I have discovered: When I tried to backup xml, I have noticed that it doesn't contain soft limit parameters, but in Mach it looks like set properly. At the profile line, name of correct xml is shown. But when I open it using Notepad, I can see that it contains different values. Off course the same wrong values are seen in the new Mach when I pasted this xml. In Mach3 folder, there is no xml file with fresh modify date which confuses me more and more???


Cheers

Offline Hood

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Re: Weird PC Freezing Issue
« Reply #9 on: December 13, 2010, 07:37:56 AM »
Yes the attached quote from Art was in response to some other guys issues and I just posted it to show the relation between Kernel and the way Mach can run.

So presume its still not working even at 25KHz?

Have a check in the BIOS that there is no power saving settings.

Hood