Actual limit on encoder frequency

[kreutz]

Henrik;

Have you tried with a different PC? Or the same PC driven by a (free) DOS/Linux based CNC program (for testing only)? It is a little bit odd that nobody complained before about this issue...

About PC optimization:

Did you try stopping the networking/remote access/firewall/print spooler/cryptographic/ related services on your PC? I assume that no anti-virus or PC fix/monitoring software is running (Norton/iolo/etc).
What amount of RAM? What is the virtual memory size?
Do you use a fixed size swap-file, or is it Windows controlled?
Is the higher priority assigned to foreground processes or background processes?
What type LPT port is assigned on the BIOS?
Have you tried a different LPT port (PCI card)?

Regards,

Kreutz.

[contactirfu]

Hi henrik ,

U are not alone, though I tried to get the O parameters tested at different speeds today, I sort of was confused.

here is my story.

today after setting up the delay switch i set of putting together both the X and Y to their paces and here is what I discover, at around 4000mm/sec and 45KHz there were around 8 O's and then as I wnet on reducing the speed I had to settele down of 3200mm/sec. thats real bad. Also considering the fact that the place where i have my workshop located has a night time voltage of 195 to 200 volts on each phase I had to derate my speeds to 3200mm/min and then there were no O values anymore.

thats what I could make out today. If it is a possibility for increased speed and reliability with smooth stepper then I would in all case go for it sooner or later!

let me know if you want me to do more tests and let me know how bcos I also don't have a oscilloscope.

Thats it from me today.

RGDS
Irfan

[H.O]

Hi guys,

Kreutz,
I agree it's odd, that's why I'd like to know what others are getting.....Perhaps they simply haven't used speeds above ~13kHz with Mach3 or never actually checked the O-parameter, or it's simply a problem with my setup, I don't know...... Odd, yes....frustrating, yes.....

This is the second PC that I've tried with, the first was a laptop and this one is a purpose built machine, dual core Athlon CPU at 2.2GHz, 2GB RAM and it boots from CF-card so the swap-file is turned off. Only other software installed is AcrobatReader and CUBLOC studio but none of those have any services running at startup. There's no antivirus, no printer-drivers, no firewall software or anything else running except the touch screen driver.

Mach3's drivertest program shows "excellent" stabillity even at 100kHz kernel frequency as can be seen in an earlier posted screen-shot.

Right now I don't know what mode the onboard LPT-port is set to as I haven't touched that part of the BIOS, I'll check it though. I have not yet tried with a another LPT-card but I guess I could order one just for the heck of it.

I have yet to try disabling the network card, thanks for remindning me of that.


Irfan,
Thank you for doing those tests! Let's see if I got this correct....

** You have the kernel speed in Mach3 set to 45kHz, correct?
** You have the axis velocity set to 3200mm/min, correct?
** If you raise it above 3200 you start to get false transitions acording the O-parameter?

Questions:
** Do you have the M-setting in the UHU set to anything other than 0?
** How many steps/mm do you have Mach3 set to?

Thanks guys!

[contactirfu]

Originally Posted by H.O Hi guys, Irfan, Thank you for doing those tests! Let's see if I got this correct.... Thanks guys!

** You have the kernel speed in Mach3 set to 45kHz, correct?

yes thats correct

** You have the axis velocity set to 3200mm/min, correct?

presently yes thats right

** If you raise it above 3200 you start to get false transitions acording the O-parameter?

That I am not sure! but at 4000 mm/min I got the max at 8 counts

** Do you have the M-setting in the UHU set to anything other than 0?

yup M is zero - not tried anything else.

** How many steps/mm do you have Mach3 set to?

X axis 400 steps / mm

Y axis its 450 at present - i havent calculated teh exact yet.

[LZ1TWB]

Hi Henrik ,

If you can really achieve only 13Khz I think you may be having some problem with your drive or the encoder/motor. I is much lower that I have made /and I think I've not made that much /.

And when I say 75KHz I mean encoder steps. With a 25KHz mach3 kernel it means that my M parameter is something like 3 or 4. I tend not to push the computer more than 21-22Khz as it seemes to have problems as slower screen updates and such latency stuff /Driver watchdog triggers also when I got as high as 25Khz/. My CNC PC is PentiumII 733 128 RAM, driving simple steppers so far 3 axis with no problems.

Have you tried to change the board? Or the motor with different encoder? I have experienced some other problems with electronics and found it very useful if there is another equipment to be able to change and therefore compare the results.

Todor

[H.O]

Irfan,
Thank you! If you run 3200mm/min at 400steps/mm you are stepping at 21.3kHz which is close to twice what I'm getting - that's a lot better but still not good at all.... I'll need to have another look at my computer, turn off the auto negotiation on the network card etc.

Todor,
Yeah, I'm not ruling out anything but since I CAN step it at 65kHz with the signal generator I'm having a bit of a problem seeing it be the drive (electronics) or encoder. Your 21-22kHz seems to match Irfan's numbers pretty good. I'll swap back the encoder to my 3600lines one and see what numbers I'll get with that one.

I really need to be able to step it at atleast ~35-40kHz (with M set to 1) or preferably ~70-80kHz (with M set to 0). Even if I can get 20kHz it's way to slow....

Yes, a 733MHz for Mach3 is a bit on the slow side, I've heard about people running on 500Mhz but I can imagine the GUI gets a bit slow....

Thanks guys!

[LZ1TWB]

Originally Posted by contactirfu ** Do you have the M-setting in the UHU set to anything other than 0? yup M is zero - not tried anything else.

Irfan is using M=0 which means that encoder frequency is equal to input frequency. In my case M=3 which leads to 4 times the input frequecy, for example 20x4=80Khz. So I think I've managed 80Khz not 20. Just a thought to make sure we don't mess up the numbers here.

Anyway what type of signal generator are you using /I missed that/ - desktop function generator, simple 555 type or smth else?

Thanks,

Todor

[H.O]

Todor,
The signal generator is a desktop type - not a very advanced one but it's OK.

We have to separate the encoder frequency and the step-input frequency here or we won't get anywhere..... The problem doesn't seem to come from the encoder frequency at all but from the step frequency. (Or rather the jitter the in the pulse-stream)

I can get ~13kHz with Mach3, 65kHz with signal generator
Irfan can reach ~21kHz with Mach3
You've reached ~21kHz with Mach3

Only reason I asked Irfan about his M-setting was to calculate what step-frequency he was running.

The UHU manual/FAQ/website states that you should be able to reach 100kHz in "any case" but that step frequencies as high as 300kHz have been achived under optimal conditions. (Depenading on the M-setting, recalc-interval etc etc)

If 100kHz should be possible in all cases how come none of us have been able to get above ~21kHz?

Even if the jitter is as bad as it possibly CAN get with Mach3 set to 25kHz pulse frequency there's still 40uS between pulses when the UHU clearly should be able to "see" them if there was as little as 10uS between them.....

Anyway, have to run now, will try to switch encoders and have another look at the computer tonight.

Thanks!
/Henrik.

[LZ1TWB]

So here are the results from my latest test I did this morning. I used my home PC as it is much faster than the previous mentioned - Dual core athlon 2.2GHz, 2GB RAM;
/assuming my encoder is 1024steps/round x4=4096 and 10mm pitch screw/

(1)
Mach3 set to 100Khz
M parameter = 0
409.6 steps/mm
F11000mm/min

This speed is equal to an output frequency of 75093 Hz comming from the parallel port. No problem at this point. I cannot move higher as the Driver watchdog triggers and takes mach3 into a reset condition. The PC is not made for cnc use with all the stuff that has to be turned off so maybe that's the cause.

(2)
Mach3 set to 75Khz
M parameter = 0
409.6 steps/mm
F10000mm/min > f=68226 Hz, No problems

(3)
Mach3 set to 75Khz
M parameter = 1
204.8 steps/mm
F15000mm/min > f=51200 Hz /par. port/ ; f=102400 Hz/encoder/,No problems
Single errors triger above F16000 which is f=109226 Hz/encoder/

I almost got to the end of the motor speed with this voltage having some errors. Motor is 2000rpm max.

(4)
Mach3 set to 25Khz
M parameter = 4
81.92 steps/mm
F15000mm/min > f=51200 Hz /par. port/ ; f=102400 Hz/encoder/,No problems
Errors come above F16000 which says it makes no difference if I use mach3 at 100Khz with M=0 or 1 and if I use it at 25Khz with M=4. The results are all the same - I get stuck at around 100Khz.

This is for now that I have done here.

Todor

EDIT: I forgot to mention but I am using the old board design. Since we are discussing processor power here I thought it makes no difference.

[H.O]

Thank you very much Todor!

Your test prooves that the processor is capable of handling Mach3's pulse-stream at 75kHz, which is way more than what I'm getting.

My computer is also a dualcore 2.2Ghz with 2GB RAM so it should be on par with what you have. Mine, on the other hand, does not have any extras on it so it should be performing better than what it is.

** My tests with the signal generator shows that the HP-UHU drive, the UHU-chip and my motor/encoder is capable of speeds at or above 65kHz step-frequency.

** Your tests shows that the processor itself, when driven by Mach3, is capable of 75kHz step-frequency or more.

** The above prooves that it's not a general problem with Mach3's pulsestream but rather something with MY computer/Mach3 setup. I'll keep on digging.....

Again, a sincere thank you for doing the tests!

/Henrik.

[krazatchu]

I briefly scanned the thread so perhaps someone has already mentioned this...

As it runs fine from the signal generator, the problem seems to be either the parallel cable, the pc, XP, or mach 3....

From my own experience, I 'm guessing it's a combination of XP and Mach3...
I had jitter problems until I turned off ACPI...

Anyhow, have you setup the pc as per the Mach3 optimization guide?
http://www.cnczone.com/forums/showpo...64&postcount=1
There might be other version of this around, this one looks similar to the checklist I used...

Most importantly, Step 6 ...
Hope that helps!

[H.O]

Hi,
I agree - it has to be a computer/software thing. Todors tests prooves that the chip is capable of handling Mach3's pulse stream and since I can't match his results by a long shot the problem must be my setup.

The strange thing is that Mach3's drivertest application shows excellent timing results but obviously it's not as good as it could be. This computer has an onboard graphics card which is generaly advised not to use but again, since the drivertest app shows good results I've thought it worked OK - may not be the case....

AND this IS the second computer I've tried the last one was a much slower laptop but I got basicly the same results from that one.

Thanks!