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Wrong Arc
« on: January 01, 2008, 04:39:55 PM »
When Mach3 decides which arc to choose between two point (X1,Z1) and (X2,Z2) with a given radius, it chooses the wrong one! see below
It takes the right direction, but it choose a different arc (any two points have two circles with the same radius going through them)
I'm not even sure how it's supposed to know which one to choose. Is it supposed to choose the shortest one?
Have can i fix this? Is it a Mach3 problem, or a Gcode problem.

Aleks.


Gcode:

%
O0000
(PROGRAM NAME - TURNING HOLDING POST 21)
(DATE=DD-MM-YY - 01-01-08 TIME=HH:MM - 15:47)
(MCX FILE -)
(NC FILE - C:\DOCUMENTS AND SETTINGS\ALEX\DESKTOP\TURNING HOLDING POST 21.NC)
(MATERIAL - ALUMINUM MM - 2024)
G21
(TOOL - 1 OFFSET - 1)
(OD ROUGH RIGHT - 80 DEG.  INSERT - CNMG 12 04 08)
G28 U0. W0.
G50 X30.669 Z19.972
G0 T0101
G97 S3600 M03
G0 X-.454 Z1.758
G50 S3600
G96 S550
G99 G1 Z-.242 F.2
X13.993 Z-7.655
G2 X20.122 Z-15.192 R10.8
G1 Z-35.66
X22.951 Z-34.245
G28 U0. W0. M05
T0100
M30
%

Offline Hood

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Re: Wrong Arc
« Reply #1 on: January 01, 2008, 04:50:53 PM »
Go to Ports and Pins then Turn options and take the check out (or  put it in) of the reversed arcs box.
Hood
Re: Wrong Arc
« Reply #2 on: January 01, 2008, 05:01:40 PM »
That reversed the direction of the arc... but the problem is that it chooses the wrong arc
This is what the piece should look like:

Offline Chip

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Re: Wrong Arc
« Reply #3 on: January 01, 2008, 06:21:36 PM »
Hi, Aleks

What cad and post processor are you using ?

Could you post the DXF file

Thanks, Chip
Re: Wrong Arc
« Reply #4 on: January 01, 2008, 06:36:01 PM »
Hi,
Im using Mastercam X and the MPLFAN.pst post processor which came with it. I had to modify it by changing the Y scaling from 2 to -2 because it was inverting my X axis output and i wanted positive values.
This might have something to do with the problem.
But i'm wondering how MACH3 is supposed to know which arc to take, considering there are two to choose from?

As for the DXF, i didn't save it. But it's basically what you see in the GIF above. The problem will occur with any outer radius.

Any thoughts?

Offline Chip

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Re: Wrong Arc
« Reply #5 on: January 01, 2008, 09:52:57 PM »
Hi, Aleks

Try drawing it in the upper left quadrant of your cad and set the post back to default setting.

Using BobCad V22 hear, Having some posting issues my self.

Try this DXF "top" and Txt " last" Download

Thanks, Chip
« Last Edit: January 01, 2008, 10:09:26 PM by afn09556 »