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JohnCNC
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« on: February 11, 2018, 09:50:16 PM »

Hi
I am new to cnc having just built my own.  I am using fusion 360 for cad and cam and Mach3. My machine is running great and cuts squares about as perfect as I can measure.   My problem is that when cutting a circle it’s cutting about 2/100 small. I am not leaving any “stock to leave”or any of that.  Any ideas on what could be happening?  Thanks in advance.
John
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dude1
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« Reply #1 on: February 11, 2018, 11:39:44 PM »

What is the smoothing and tolerances settings and are you use R (radius arcs in the pre post dialog) or I and J
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JohnCNC
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« Reply #2 on: February 12, 2018, 07:07:31 PM »

Thanks for the help -

Smoothing .0004
Tol .004
Radius Arc is not checked and I do not see an I or J.

I am attaching the G Code file.
It cuts a 4x4 box and puts a 1" hole in the middle.
Totally appreciate the help.  I am going to recut it now.

John

* BoxwithHole.tap (5.03 KB - downloaded 90 times.)
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dude1
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« Reply #3 on: February 12, 2018, 07:12:00 PM »

Try doing it with the feed and speed reduced for the circle have it at 15 in/min 
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JohnCNC
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« Reply #4 on: February 12, 2018, 10:19:24 PM »

Same problem.  Tomorrow I am going to try to run a 1, 2 and 3 inch hole and see the errors.  I'll let you know.
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dude1
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« Reply #5 on: February 12, 2018, 11:08:36 PM »

cut the circles realy slow like 5 in/min if it's still out run a Vcarve toolpath of 5 letters if this is out you have big problems or backlash
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JohnCNC
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« Reply #6 on: February 14, 2018, 12:09:19 AM »

I made an adjustment to what i am guessing is a step correction?  I moved a fixed distance on the DRO and put in the difference.  It was not supper precise but I then ran a test of 4 circles, 1, 1.5, 2 and 3 inch all came to within 4 thousands.  I think if I work on the setting a little more i can get that even better.  I did run it at 5 in/min.  wow too slow.  I need a new bit, I plunged it in on another test way to far and fast and toasted it!  Nothing like learning.
Thanks for the help!
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