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Author Topic: pockets out of size, need help  (Read 1725 times)

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pockets out of size, need help
« on: April 16, 2011, 01:09:48 AM »
after review all parameters on my machine: (motor tuning, displacement precision in X and Y axes and execute the axis calibration), and review the G code generated from my Cad-Cam program (BobCad V24), I have this problem: all pockets are undersize in diameter (not in depht), the Gcode created starts with following instructions:
line N1  G21 G40 G49 G54 G80 G90 G91.1 G53 Z0...

the line which indicate the start position for the controlled point as sample: (for a pocket with 15mm diameter 12.7mm depth, with center coordinates X=25mm, Y=100mm, tool diameter 4.7625mm (3/16"), as I calculate the point x=30.118 and y=100. has to generate a exact 15mm diameter hole:

 N11 X30.118 Y100.
N12 G01 Z-12.7 F2540.
N13 G03 X30.118 Y100. I-5.118 J0. F2135.
(the machined pocket has 14.2mm diameter.)
what can I do or change in the configuration in Mach???
thanks in advance. Eduardo
Re: pockets out of size, need help
« Reply #1 on: April 16, 2011, 02:38:05 AM »
Look to me that your end mill have a diameter of 5/32 instead of 3/16

If you take your program and use the .156(5/32) end mill, you will end up with a 14.2mm diameter hole.

Maybe I'm wrong


Offline ger21

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Re: pockets out of size, need help
« Reply #2 on: April 16, 2011, 07:31:49 AM »
The diameter of your toolpath is 10.236, so it should be the correct size when you add the tool diameter.

As Jeff said, are you sure the tool is the correct size?

Have you cut other parts that are the correct size?

If all your parts are the wrong size, then your steps/unit could be set wrong.

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Re: pockets out of size, need help
« Reply #3 on: April 17, 2011, 12:52:10 AM »
Jeff, Gerry :
thanks for your reply, but no, the cutter diameter is 3/16" it has a micro waste after about 2000 pockets, also I changed the tool for new one... and Gerry, yes in the past I get many pockets whit exact size, the sizes of my pockets are: 5mm, 8mm, 15mm, 20mm and 34mm. in diameter, today I checked again the axis calibration ( X and Y) and the most exact aproximation was about .0005" (checked with a Starret dial indicator). the tool is a spiral 2 flutes from Onsrud.
Also, Today I make some trials doing profile circles with zero tool compensation and results were excelent (using a V tool 30 deg. 0.05mm depth). diameters were exact.
I have the feeling the trouble comes from the configuration of my Mach3.
but I can not find where do I can make the changes.
Thanks again and expecting your news...
yours Eduardo