Author Topic: Problems centering part is on round stock mach3  (Read 1315 times)

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Offline bilingham

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Problems centering part is on round stock mach3
« on: March 31, 2017, 10:29:03 PM »
I am making small (.67" diameter) scale model wheels.  I use blanks cut from aluminum bar stock.  I prepare the blank on the lathe, face and cut to length.  The blank is clamped to the table, and the spindle is centered over the blank using a needle point.  The X&Y dro's are set to zero.  The z height is set with the end mill and  is zeroed.  I run the part, and the final product is off center by about .04.  what am I doing wrong?

Offline Tweakie.CNC

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Re: Problems centering part is on round stock mach3
« Reply #1 on: April 01, 2017, 01:30:42 AM »
Perhaps check that your CAD/CAM generated Gcode does in fact have the origin X0, Y0 at the true centre of the wheel.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline bilingham

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Re: Problems centering part is on round stock mach3
« Reply #2 on: April 01, 2017, 09:15:01 AM »
How would I check that?  The set up of the model has the center selected.  Do I look at the open lines of the g code?  I used fusion360 for CAD Cam.

Offline Tweakie.CNC

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Re: Problems centering part is on round stock mach3
« Reply #3 on: April 01, 2017, 10:08:06 AM »
If you attach (or send me a copy) your Gcode file I will check it here.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline bilingham

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Re: Problems centering part is on round stock mach3
« Reply #4 on: April 01, 2017, 10:43:44 AM »
Here is the file. Many thanks!

Offline Tweakie.CNC

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Re: Problems centering part is on round stock mach3
« Reply #5 on: April 02, 2017, 02:35:04 AM »
The dimensional problem appears to be in your Gcode.

The datum (X0, Y0) is not in the centre of the circle.
You also need to check that you have your G54 fixture offset 1 set correctly.

I have never used Fusion 360 but with Z0 set at the surface of the work your generated Gcode is expecting to start cutting at Z0.0482. This is not correct.

Mach3 will only do what it is instructed to do (bar exceptions) and if the Gcode is not absolutely correct to start with then the finished work is unlikely to be correct.

Hope this helps.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline bilingham

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Re: Problems centering part is on round stock mach3
« Reply #6 on: April 02, 2017, 09:41:08 AM »
Thanks very much.  I will go to the fusion360 forums and hash this out.

Offline garyhlucas

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Re: Problems centering part is on round stock mach3
« Reply #7 on: April 02, 2017, 11:54:48 AM »
Learn how to pick up center using a dial indicator to sweep the OD of the blank, much more accurate than what you are doing.