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backlash help please
« on: March 01, 2009, 07:07:31 PM »
i have a vertcal cnc mill and i have .015 backlash in x,and 10 or .011 in y. i have looked at the old post on backlash and tried everything.so far this is what i have done. backlash ,put amounts in and hit ok and restart. that did not work so i went to configure ,shuttle accel and matched that wiith same amounts. i have been on this for about 3 hours. i have never checked backlash in this machine since i had it ,seemed to always cut at decent tolorences it is a bridgeport series one 30 years old with a new contoller.    thanks for the help in advance

alex

Offline Chaoticone

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Re: backlash help please
« Reply #1 on: March 01, 2009, 08:07:02 PM »
Alex, try this. Set you backlash amounts to what you are showing you have and set the speed to 200% and enable backlash comp. Then go to general config. and set the shuttel accel to .01, restart Mach and see how it does.

Brett
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Re: backlash help please
« Reply #2 on: March 02, 2009, 08:05:44 PM »
thanks ! i did everything you said and i could not get it out,so i lowered the speed to 50 percent and it seems to have done the trick.i just picked 50 and it worked could you tell me why it worked at 50?  i left the shuttle speed at .01 like you said at 50 percent also .does it need to be changed?

thanks alex

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Re: backlash help please
« Reply #3 on: March 02, 2009, 09:11:12 PM »
Alex, are you running steppers or servos?

Brett
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Re: backlash help please
« Reply #4 on: March 02, 2009, 10:01:09 PM »
steppers.

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Re: backlash help please
« Reply #5 on: March 02, 2009, 10:17:40 PM »
I think what is probably happening at 200% is it was trying to move that fast but would skip steps. Ususally you can get away with this because while takeing up backlash the only load it should be trying to move is very small but depending on where the backlash is comeing from, I can see where it may cause a problem. Those suggestions are only the ones I have seen a lot of sucess with and they are only a strating point I suggest. All set ups are different so lots of times the settings will vary.

Brett
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My guard dog is not what you need to worry about!

Offline RICH

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Re: backlash help please
« Reply #6 on: March 02, 2009, 10:27:39 PM »
You may need to play some with the shuttle accel. It determines how fast the backlash will be done.
If too fast you may skip steps. Just don't remember as it's been some time ago.

Brett can correct me if wrong. I can change % frorm  50% but never had it over 100%.

RICH
  

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Re: backlash help please
« Reply #7 on: March 02, 2009, 10:42:11 PM »
Your right RICH. Both the speed setting and shuttel accel effect the speed it takes up backlash. I'm not exactly sure how each relates but are both related to it. I wonder if the shuttel accel sets the ramp or time it will take to get to the speed set in the backlash config box? Art or Brian suggested the shuttle accel setting once I'm pretty sure and it was one of those things that stuck. LOL

Brett
« Last Edit: March 02, 2009, 10:44:06 PM by Chaoticone »
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My guard dog is not what you need to worry about!

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Re: backlash help please
« Reply #8 on: March 02, 2009, 10:53:30 PM »
Haven't the foggiest idea Brett. But I remember I just started gradually changing the shuttle speed till i was happy it wasn't "crawling along" or seemed fast enough.

BTW,  Think that was one that Brian mentioned at the seminar, they didn't know where to put the settiing and it just ended up being thrown there.

RICH
« Last Edit: March 02, 2009, 10:55:47 PM by RICH »
Re: backlash help please
« Reply #9 on: March 02, 2009, 11:53:22 PM »
You can also temporarily set the backlash distance to a large value so you can more easily see the effects of the shuttle and speed settings.
rc