Hello Guest it is March 06, 2021, 12:33:03 PM

Author Topic: Steppers run rough in program run/ smooth in tuning?  (Read 6571 times)

0 Members and 1 Guest are viewing this topic.

Steppers run rough in program run/ smooth in tuning?
« on: April 23, 2009, 09:14:48 AM »
Hi,
I have a practical cnc router that originally came with Wincnc. I wanted to try Mach on this machine as I use mach on my lathe. The set up is,
Pc Dell desktop, dual core processor, 1 g ram.
Stepper drives IMS 483's running 48v.
Motors Pacsci 270 oz/in motors.

Mach v3.042
Steps per- 2038 on the x and Y (rack / pinion), 10000 on the Z (Ball screw)
Accel 100, Velocity x,y (400) z (100)

The weird thing is that in the motor tuning, These settings work smooth as silk. As soon as I save the changes and go back to the program, Mdi screens the machine runs like crap! However, If I am manually jogging and move the mouse, the motors smooth out! At least while I am moving the mouse.

In Wincnc i can run these motors @ 600"/min rapid. In Mach only about 450"/min before the motors are stalling.

Any help appreciated,
Cutmore

Offline Hood

*
  •  25,838 25,838
  • Carnoustie, Scotland
    • View Profile
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #1 on: April 23, 2009, 10:51:16 AM »
Try the pulse width at 5 and see if that helps.
Hood
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #2 on: April 23, 2009, 11:09:30 AM »
Thanks Hood,
Sorry I forgot to mention,
I tried the puse width at from 1-5, the Kernel speeed at 25Khz- 100khz, Re-tuned the motors each time.  Cv on, Cv off, Step, direction Active low checked, un-checked.

Also I had initially set the machine up with Mach running on a laptop (2ghz processor 2 gig ram) With the same results, which made me think it was worth trying on a desktop system.

the thing that baffles me is that, I was testing a program on the laptop, and when I had Mach on the Program run screen the motors were running 1/2 decent, i switched to the diagnostics screen and the motors were smooth. Every time I moved the mouse the motors would smooth out while moving the mouse,both the laptop and the desktop. i even un-plugged the mouse but the motors were still rough.
 ???
Cutmore

Offline Hood

*
  •  25,838 25,838
  • Carnoustie, Scotland
    • View Profile
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #3 on: April 23, 2009, 11:15:23 AM »
Do you have any sort of CPU power saving mode? Sounds like it could be that is causing a problem, windows thinks the computer is doing nothing due to Mach not working like normal software, you move the mouse and windows sees activity so ramps the CPU a bit. Well its a good theory anyway ;D

Hood
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #4 on: April 23, 2009, 11:25:22 AM »
I did try shutting the screen saver off as well as dis-abling the hibernation mode. Even set the configuration to desktop.

I am stumped! It does sound like some sort of Windoze >:D  sleepy thing though!

Cutmore

Offline Hood

*
  •  25,838 25,838
  • Carnoustie, Scotland
    • View Profile
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #5 on: April 23, 2009, 11:33:29 AM »
Looked in the BIOS, maybe some sort of sleepmode there?
Hood
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #6 on: April 23, 2009, 11:39:53 AM »
Thanks Hood,
i didn't think of the Bios settings.

I want to run a test of Mach vs Wincnc on my router with a 3d file I recently ran. The run time with Wincnc was 6.5 hours.

Hopefully the bios setting idea will help,

Cutmore

Offline Jeff_Birt

*
  •  1,107 1,107
    • View Profile
    • Soigeneris
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #7 on: April 23, 2009, 12:15:26 PM »
Have you done the mach driver test? That is a good way to see how smooth the output wave form will be. You can also turn on 'Sherline' mode. This really stretches the step pulse out. I had to do this one one machine to get good results. Also be sure that you have the step/directions signals set up to the correct state. Some driver switch on the rising edge of the signal (Active Hi) some on falling edge (Active Low). If you get it backwards the drive won't work properly. You can see anything from lost steps to rough running.
Happy machining , Jeff Birt
 
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #8 on: April 23, 2009, 12:20:23 PM »
Thanks for the tips Jeff,
I did do  the driver test and it came up probably the smoothest of any of my Mach pc's yet!
I did try the signals for both step/direction in the active hi, and active low. I changed 1 at a time. man lots of combo's you can test!

I did not however try the sherline mode as i didn't know what that did.

Cool. More things to test!

Thanks,
Cutmore

Offline Jeff_Birt

*
  •  1,107 1,107
    • View Profile
    • Soigeneris
Re: Steppers run rough in program run/ smooth in tuning?
« Reply #9 on: April 23, 2009, 02:12:02 PM »
Check the docs for your drivers to what edge they trigger on and set Mach accordingly. If that is not set properly than any other changes you make won't produce meaningful results.

Also keep in mind that WinCNC uses dedicated external HW to generate the stepper pulses where as Mach uses the parallel port. As great as the Mach LPT driver is it can't match having a dedicated HW built for the purpose. Also, some motherboards just can't actually drive the LPT that fast. The driver test will come out great but the actual LPT hardware is lacking. Sometimes an add-on PCI parallel port card will make all the difference, sometimes not. Take a look at this thread as it may have a few other ideas that you can try. For a more realistic comparison you would need to use something like a SmoothStepper: http://soigeneris.com/shop/Warp9_97624.aspx  or other motion control card.
Happy machining , Jeff Birt