imperfect circle

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31 Jan 2012 23:30 - 31 Jan 2012 23:32 #17309 by submicro
imperfect circle was created by submicro
Hello


I've been testing and running simple parts on my X2. I've noticed it does not make perfect circles or arcs. i made a simple test program to make a 1 in circle. It measures 1in wide and 1in tall but it's not a perfect circle! It's very noticeable, but it's repeatable. I can run the circle several times and it's exactly the same in the same location. You can't even tell it was run several times it's that repeatable. I don't feel any backlash. Any ideas?

submicro

p.s. in stepconf 2 is for halfstep is 3 or 4 for 1/4 step?
Last edit: 31 Jan 2012 23:32 by submicro.

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01 Feb 2012 00:40 #17312 by BigJohnT
Replied by BigJohnT on topic Re:imperfect circle
Imperfect circles are backlash and or loose couplings.

John

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01 Feb 2012 09:53 #17313 by Rick G
Replied by Rick G on topic Re:imperfect circle
I would suggest you use a dial indicator and check your backlash again.
What you are seeing as John stated is most likely backlash and or flex.
Double check your machine for backlash and try cutting the circles at different (slower) speeds and perhaps both cutting directions.

Rick G

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01 Feb 2012 12:07 #17314 by Rick G
Replied by Rick G on topic Re:imperfect circle
By the way there is a ngcgui sub to help measure backlash..

backlash.ngc

Rick G

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01 Feb 2012 19:25 #17323 by submicro
Replied by submicro on topic Re:imperfect circle
Thanks for the ideas guys.

I'll measure the backlash as soon as I put the machine together. I decided to put larger balls in my ball-screws. My thought being that they might be the cause of my problem. I had them lying around anyway:-)

BUT as usual nothing goes as planned :-( Even though I'm using the same size ball-nut, and balls as the one in the video I watched, they don't want to co-operate!

I'll get back to ya as soon as I fix this mess I made.:S

Thanks
SubMicro
A.K.A Robert

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02 Feb 2012 01:21 - 02 Feb 2012 01:26 #17329 by submicro
Replied by submicro on topic Re:imperfect circle
where do I find this file? it's not in the examples folder

Also I managed to solve the ballscrew mystery. :cheer: It just took a little more force! :pinch: Now that ballscrew is perfect no backlash that I can tell by hand. Now tomorow I'll put it back together and measure..


SubMicro
Last edit: 02 Feb 2012 01:26 by submicro.

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02 Feb 2012 12:21 #17338 by BigJohnT

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02 Feb 2012 12:41 #17340 by Rick G
Replied by Rick G on topic Re:imperfect circle
To test for backlash without it you can..
Turn backlash compensation off.

Make a negative move, then a positive move. set your dial indicator to zero.

Then another positive move. Check to make sure the move is correct and your Scale is right.

Now make the same move negative. Your dial indicator should be back to zero if there is no backlash. If not zero this shows the backlash.

Repeat several times.

G1 X-1
G1 X0 ; SET DIAL INDICATOR
G1 X1 ; SHOULD BE CORRECT SIZE
G1 X0 ; SHOULD BE BACK TO ZERO

Rick G

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02 Feb 2012 20:08 #17346 by submicro
Replied by submicro on topic Re:imperfect circle
Ok thanks for the file John. where did you get 2.5? I didn't know it was available yet. I would like to upgrade to 2.5 I'm using 2.4.6.

Thanks for the how to Rick, I'm on way tothe shop to begin reassembling my mill and take measurements.

SubMicro

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02 Feb 2012 23:04 #17349 by BigJohnT
Replied by BigJohnT on topic Re:imperfect circle
You can get the deb from the buildbot.

buildbot.linuxcnc.org/

John

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