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Offline RICH

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Re: Strange motor speed on reversing....
« Reply #20 on: May 07, 2009, 10:41:30 PM »
I am sending you a personal message.
RICH

Offline Hood

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Re: Strange motor speed on reversing....
« Reply #21 on: May 08, 2009, 02:41:23 AM »
It is certainly always a good idea to try swapping hardware around one bit at a time to see if the problem follows the hardware.
Hood

Offline RICH

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Re: Strange motor speed on reversing....
« Reply #22 on: May 08, 2009, 01:03:29 PM »
thedude,
- Your steps per unit: Use the calculated values Z=32000  X=38400
   Yes, you can use a different value, don't want to confuse  ( only when you know why you are doing it ).
   When you checked your steps / unit you were jogging in small incremenntal steps. It would be much better to
    jog a longer distance ( at least an inch ) and use that to confirm settings. Once the steps / unit are confirmed
    then find the backlash setting.

   Reading this post you said you had .0135" backlash in the X and then somewhere else it was .0012" so i am  
   confused.

 - What settings for the pulse & dir time in motor tuning are appropriate for your drives?

   I could not find any recomendations on the Hobbycnc Site and additionaly no instruction sheet for your driver.
   That sucks HOBBYCNC!  
   So if the steppers are working fine with the 0 value, use it . By increasing the value your giving        
   more time for the computer pulse to be seem by your drives.
  
- Your driver has an idle current setting such that it will reduce the current 50% after 10 seconds.
  I could not find how you change that setting on your driver board. Is there a jumper or something
  on the driver board to change that setting ? I couldn't tell from the pictures of your drives posted on the
  Hobbycnc site but it does say it can be changed.
  
  Some time ago, someone else had a problem with that driver and changing it such that there was no current
  reduction solved a backlash and or missed step problem. Just don't remember. It was in the last year or so.

  Can you post your xml file? It's located in the subdirectory where you installed Mach3. Change the file extension to
     .thedude   for posting.


RICH

  
Re: Strange motor speed on reversing....
« Reply #23 on: May 08, 2009, 05:09:03 PM »
Rich,
I won't be able to get to the shop tonight.  I will make some notes and look at my hobby cnc info here.
I will be in the shop tomorrow.  Let me know if you have any time.

Hood,
I'll change out the motor tomorrow and rerun the gcode program.

Thanks everyone.!!!
TheDude,
Re: Strange motor speed on reversing....
« Reply #24 on: May 09, 2009, 08:20:05 AM »
I didn't want to post such a long file so I converted to pdf.

DARNIT!!  DO NOT USE THE XML FILE ATTACHED,,,,(I removed it)
I'm sorry, got in a rush and posted the wrong one.  I hope this hasn't caused any trouble.... :-[


This is the backlash comp. 

Backlash Comp
      Backlash X = .0012 (Per Dial Indicator)
      Backlash Z = .0185 (Per Dial Indicator)
      50%


Idle Current Reduction (From the hobby cnc instruction manual)

Idle Current Reduction
Jumper J4 controls this function on each axis. This allows the current to be reduced to @50% after no
movement for approximately 10 seconds on that axis. This may reduce stepper motor heating. Each axis is
individually settable. Remove J4 jumper to enable this function. Install jumper on J4 to disable it. A word
of caution is in order. Idle current reduction MAY cause lost steps IF your software settings are very
aggressive for the start rate and accel rate. It takes a few microseconds to restore full power when
commanded to move from an idle current reduced condition. Experiment a bit with this.
As an alternate to the 50% reduction, substituting R2,R4,R6,R8 with a 4.7K value (not included) will
allow only @30% current reduction. (3A down to 2A for example). This may allow more aggressive software
se~ups. Note that 20K would allow @75% current reduction.
Synchronous and Asynchronous Mode
Asynchronous function is active for all stepping modes. Approximately 10 seconds after last movement
the stepper driver will automatically switch to synchronous mode. This helps prevent stepper "hiss" when not
moving. The time delay is directly related to the idle current delay resistors (100K) installed in step #2. This
function is always active and is independent of idle current enable/disable J4 jumper setting.

« Last Edit: May 09, 2009, 09:05:26 AM by thedude »
TheDude,

Offline RICH

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Re: Strange motor speed on reversing....
« Reply #25 on: May 09, 2009, 09:06:20 AM »
thedude,
You sent me xml info for the MILL and we are working with the lathe.
That's all right for now.
Can you call me?

RICH

Offline RICH

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Re: Strange motor speed on reversing....
« Reply #26 on: May 09, 2009, 10:20:24 AM »
thedude,
Suggest the following:
Create a new xml file for the lathe. One that has no homing, tool offsets, etc. because
you should start all over again, as if you were just setting up the lathe for the first time.
I think, and could be wrong, that the iddle current reduction caused you missed steps
which screws up your setup.

1. Disable the iddle current reduction
2. Set your steps / unit at the calculated values
3. Disable backlash
4. Check your x & z movements based on calculated values, if required, change accordingly
5. Check backlash to find values, then set at 50%
6. Retune your motors, find where they start to skip using an acceleration value of 3, then use a
   use a value of 50% of were they skipped for the velocity, and also use a shuttle acceleration .05.
   ( You can tweek the system later on )   
7. Enable backlash
8. Run some repetative gcode programs to confirm that the movements are repeatable
   and tweek the backlash if necessary.
9. Test some actual cutting.
10. Tweek the system based on your experience.

Hope this solves your problem,
RICH
Re: Strange motor speed on reversing....
« Reply #27 on: May 09, 2009, 01:57:08 PM »
Thanks Rich,  (yeah, I know I posted the wrong xml file,,,,sorry I edited the post mentioning that but not in time,,, )
Adjusted and troubleshooted your suggestions and it is now cutting DIA within .002"  Not too bad, but I imagine it could be better??

Heres what Iv'e done,
1.) DISabled idle current
2.) Retuned the X to 31900  after cutting and measuring DIAs and tuned with trial and error.  (Many more Devo Hats!)haha
3.) Checked backlash by cutting DIA NOT using my indicator.  Turns out there is ZERO backlash on X.  baclash on Z is same and set to 50%
4.) Switched to exact Stop Mode.
5.) my motors speed and accel are 20 and 0.45.  (I'm sure I could increase the accel but taking it slow for dial in.)

I'm going to make a few more parts working with your step 6 suggestion to have a good accel setting.  (All that "whining up and down was annoying).
I'm going to check the parts and see if anything else is off.  Maybe tweak a bit more.

I'm very happy with the setup now.  You guys have been GREAT Help!!  I thank you all very much!!!



TheDude,

Offline RICH

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Re: Strange motor speed on reversing....
« Reply #28 on: May 09, 2009, 04:18:23 PM »
 :)
RICH
Re: Strange motor speed on reversing....
« Reply #29 on: May 09, 2009, 09:45:22 PM »
Thanks again RICH,,, and Hood.
Feels motivating to be confident in the machine. 
I increased the motor velocity to 30 and accel to 1.5 and it was stable and smooth.
I also decreased the shuttle accel from .15 to .05 (per RICH suggestion)
Worked great.!!!
My motors never got hot.

I also went to radio shack and bought a game controller and set it up for my jogging to setup the part.  Now that is REALLY nice to have for manual maching.
Anyone know what the hotkeys are (if any) for setting x and z part zero?

Made a few parts tonight using the wizards,, nothing special, but rewarding for me.
I know it is silly to post pics of such simple parts,, but for me it was a milestone moment in setting up the lathe.
Yes,,, thats the "Devo Hat" in the pic.  A bit larger than the last 25, and made from aluminum, not delrin.
they are attached.
« Last Edit: May 09, 2009, 09:48:19 PM by thedude »
TheDude,