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Author Topic: Jerky motion...yes I've read the other posts :-)  (Read 16927 times)

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Jerky motion...yes I've read the other posts :-)
« on: July 01, 2008, 03:20:03 AM »
I posted this on CNCzone today but thought I'd post it here too as I need to get my machine tuned correctly; plus I've watched some vids on youtube and now I know it's not running smoothly.

OK, I've used my cnc for a while now, about 1 year, but now I'm finally cutting my guitar stuff and I want to make sure everything is working the way it's supposed to.

When moving during a run the sound of the motors are jerky sounding and when looking at the ballscrews during the run they move in a somewhat jerky motion. Now the cuts seem pretty smooth and since I've never owned or used a CNC machine before I'm not sure if this is correct movement. So if you all can look at the video and tell me that's normal or not I would appreciate it. The sound is going to be the key as it's hard to see the motion of the machine, it's just cutting air I've turned off the router. The video is 15mb. I'll include my G-code for this particular run that you are watching to see if it's that. Its not jerky during straight runs.

Video: http://www.smokeproductions.com/cnc.avi

A little background on the machine, home built. Keling 425oz steppers, Keling 8078 Drivers, 48V 6.5A PS, Roton Ball Screws, Mach 3 V2.63, 10,000 steps per inch, 72IPM maximum and 10 acceleration for motor tuning. I just thought during a run it would run smooth during curves in a fluid motion?

After reading on here about the CV stuff I went back and took note of my CV settings: Motion Mode CV, CV Dist Tol. 180 is checked and G100 Adaptive is checked.

So what setting should I be using and is that my problem? Thanks so much in advance.

Offline Hood

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Re: Jerky motion...yes I've read the other posts :-)
« Reply #1 on: July 01, 2008, 03:46:29 AM »
Tried Sherline 1/2 pulse mode?

Please attach your xml.
Hood

Re: Jerky motion...yes I've read the other posts :-)
« Reply #2 on: July 01, 2008, 11:33:14 AM »
What does 1/2 Pulse mode do, all my cuts come out with the correct dimentions? Here is the xml file for some reason this forum keeps saying I already have a file uploaded with the same file name so you can view it or download it from my server. Thanks for the help.

http://www.smokeproductions.com/Mach3Mill.xml

Offline Hood

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Re: Jerky motion...yes I've read the other posts :-)
« Reply #3 on: July 01, 2008, 01:13:41 PM »
Sherline mode gives a longer pulse which some drives need.

Will look at your xml in a while but just so you know in the future, the forum only accepts a file once, someone has posted Mach3Mill.xml before so to post your xml you could rename it before posting. Using your forum name helps as well as people downloading the xml can then remember whos it is, so for instance you could rename it Cartierusm.xml

Hood
Re: Jerky motion...yes I've read the other posts :-)
« Reply #4 on: July 01, 2008, 06:01:03 PM »
Thanks, I appreciate the help. I have been using my system for about a year but nothing critical and now I'm realizing it needs some tweaking and I have no idea how to start.

Offline Hood

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Re: Jerky motion...yes I've read the other posts :-)
« Reply #5 on: July 01, 2008, 06:03:53 PM »
Looked at the xml and it looks ok from first glance. Have you tried Sherline ?

Hood
Re: Jerky motion...yes I've read the other posts :-)
« Reply #6 on: July 01, 2008, 06:40:30 PM »
Yes, I just tried sherline and turning off all the CV things on the config page, all that has no effect whatsoever, it runs the same.

A separate question, I just upgraded my PS to 48 V from 24V and now I get limit switches tripping after a couple minutes. My motor cables are shielded but not the limit and home switch cables, do you think it's just electrical noise, emi or rfi? And the CV problem was the same with the 24V PS I just switched over yesterday to get more torque.

P.S. I don't think I tried sherline with the CV enabled, Gerry at CNCzone told me to try turning off the CV as sometimes it messes things up, so I'll go try the sherline and CV together.
« Last Edit: July 01, 2008, 06:42:04 PM by Cartierusm »

Offline Hood

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Re: Jerky motion...yes I've read the other posts :-)
« Reply #7 on: July 01, 2008, 07:21:42 PM »
OK have you run the driver test? its in the Mach3 folder, see what the graph looks like, you dont have QuickTime on your computer by any chance?.
 Also make sure your power supply doesnt dip in voltage when all the axis are moving.
Limits should really be shielded, you may get away with increasing the debounce.
Dont think CV would cause that problem but then again......
Hood

Offline ger21

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Re: Jerky motion...yes I've read the other posts :-)
« Reply #8 on: July 01, 2008, 10:05:57 PM »
Yes, I just tried sherline and turning off all the CV things on the config page, all that has no effect whatsoever, it runs the same.
......................

P.S. I don't think I tried sherline with the CV enabled, Gerry at CNCzone told me to try turning off the CV as sometimes it messes things up, so I'll go try the sherline and CV together.

Actually, I said turn off the CV options on the Settings screen and the general config page. I didn't say turn CV mode off. See if CV feedrate and CV Distance are turned off and see if that helps.
Gerry

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Offline Chip

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Re: Jerky motion...yes I've read the other posts :-)
« Reply #9 on: July 01, 2008, 10:37:07 PM »
Hi, Cartierusm

All in All, With small line segments, (short x## Y## moves), Your motors will Sing, Can you name that Tune !!.

But it dose sound, Sorta spread out and out-a little, No lost steps as far as you now. (Done a G00 X0 Y0 move to home after you finish the cut, Is it OK.

Moving your Acceleration UP till you start losing step's then back it off 10% or so, This will help close the Gap on achieving your F20 Speed, Ac-cell/De-cell (Closer Together).

On the Diagnostic Screen, Is the "Pulse Frequency", Locked in to a solid Value, "Should be", If your using 25K it should show a value above 25,000.

If it "Isn't",

A quick test is to run your G-code and move your mouse around in the Mach screen till the Pulse Frequency stabilizes to a solid value (Continue moving the mouse as necessary to keep it locked in during the Test).

It's a indication that you'll need to Optimize "Windows" for Mach"s use.

Hope this Helps, Chip
« Last Edit: July 01, 2008, 10:38:58 PM by Chip »