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Problem with G01 G91 A360
« on: December 16, 2006, 05:39:03 PM »
Hi
I'm trying to mill a dish shape for a loudspeaker using XZ and C axis.
I have a cross section from Gcodeout, changes Y to Z then I ad G01 G91 A360,that I got form HuFlungDung @Cnczone. When I bring it in to Mach3 it gets very big and losing its shape. What am I doing wrong ? please help.
Thank you in advance

(in parabol3.nc I have only used G01 G91 A360 in the last 6 rotations)
first time in some time

Offline Graham Waterworth

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Re: Problem with G01 G91 A360
« Reply #1 on: December 16, 2006, 05:57:15 PM »
Is the x and z moving in an arc?

If so have you got G17, G18 or G19 in your program?

Graham.
Without engineers the world stops
Re: Problem with G01 G91 A360
« Reply #2 on: December 17, 2006, 09:58:38 AM »
Its not an arc, I cut up a spline into 27 segments, hoping that I found a efficient way to work around a center.
/gunnars
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Offline Graham Waterworth

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Re: Problem with G01 G91 A360
« Reply #3 on: December 17, 2006, 10:07:47 AM »
How much too big, 25.4 times?

Your code has no G21 and if Mach is set to inches it will be big.

What type and size of cutter are you using?

Have you allowed for the cutter dia and ball radius if its a ball nose.

Graham.
Without engineers the world stops

Offline Graham Waterworth

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Re: Problem with G01 G91 A360
« Reply #4 on: December 17, 2006, 10:28:39 AM »
Load this code into mach and see if this is more like what you expected.

Graham.
Without engineers the world stops
Re: Problem with G01 G91 A360
« Reply #5 on: December 17, 2006, 03:51:47 PM »
Thank You,
The way that I used G1 made it grow for every 360, now it looks very nice :) I don't understand it yet, but I will.
/gunnars
first time in some time

Offline Graham Waterworth

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Re: Problem with G01 G91 A360
« Reply #6 on: December 17, 2006, 05:04:24 PM »
G91 is an incremental move, it moves a measured distance from where the tool is at that moment.

G90 is an absolute move, it is a measured distance from the datum point.

Thats what was wrong with your code, you were doing incremental rotations of the A axis and then also on the X and Z, the X and Z should have been absolute moves.

Graham.
Without engineers the world stops
Re: Problem with G01 G91 A360
« Reply #7 on: December 20, 2006, 05:16:06 PM »
I have bin trying to figure out 2 other options with  similar shape files, first the interpolation of XZ and A making a continues spiral. I made a try and the only time it sort of worked, where when and made it grew with 1 then 2 then 3 .....turns. This can not be the right way to go.
G91
G0Z1.0000
G0 X0.0000 Z0.0000
G1 Z0.0000F1000.00
G1 X11.9288 Z-0.2738 A360
G1 X23.8326 Z-1.0923 A720
G1 X35.6871 Z-2.4492 A1080
G1 X47.4694 Z-4.3334 A1440
M5

Then the pizza slice code. XZ down to the end, A a couple of degrees then reverse the XZ and back up and a couple more degrees........
Not much luck with this either.
Can I find simple example files somewhere?
/gunnar
first time in some time

Offline Graham Waterworth

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Re: Problem with G01 G91 A360
« Reply #8 on: December 20, 2006, 06:21:34 PM »
I think you are getting confused with G91 and G90.  Try the code like this:-

G91
G0Z1.0000
G0 X0.0000 Z0.0000
G1 G90 Z0.0000 F1000.00
G1 X11.9288 Z-0.2738 A360
G1 X23.8326 Z-1.0923 A720
G1 X35.6871 Z-2.4492 A1080
G1 X47.4694 Z-4.3334 A1440
M5

Graham.
Without engineers the world stops