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Offline kf2qd

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Radius to end of arc differs from raduius to start line ...
« on: April 22, 2010, 02:22:57 PM »
I keep getting the error - Radius to end of arc differs from raduius to start line ...

Using absolute I & J

When I go back in and check the difference it comes to less than 0.00001 (1/100,000) error, and is awfully hard to get rid of.

For instance -

startpoin to center radius -
X 1.1682 - I .5713 = .5969, squared = 0.35628961
Y 1,9091 - I.5713 = 1.453, squared =  2.111209
added together = 2.467499
square root = 1.570827365


End point to center radius -
X0.125 - I .5713 = -0.4463, squared = 0.199,183,69
Y1.9622 - I 0.4561 = 1.5061, squared = 2.268,337,21
added together = 2.467,520,9
square root = 1.570,834,46

Difference =
1.570,827,365 - 1.570,834,46 = -0.000,007,095,0

Add 0.0001 to any of the dimensions and the radius grows too much.

Any clues as to how to minimize this problem so Mach3 can tolerate this insignificant bit of error?

I am doing some "artsy" stuff that has many arc segments but have to deal with this only 2 or 3 times in a program.

Pete

Offline ger21

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Re: Radius to end of arc differs from raduius to start line ...
« Reply #1 on: April 22, 2010, 05:56:00 PM »
Quote
Using absolute I & J

Set in Mach3? The g-code? both?

Typically, you'll see this error most often when Mach3 is set to absolute and the code is incremental, or the opposite. If your code is 4 decimal places, as long as those 4 places are correct, it should work.

Can you post some sample code that gives you an error?
Gerry

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Offline kf2qd

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Re: Radius to end of arc differs from raduius to start line ...
« Reply #2 on: April 22, 2010, 10:54:32 PM »
Mach is configured Absolute positioning, Absolute Arcs. I find it much easier to think in absolute, and the G-Code is much easier to read.

Lots of arc segments with much smaller radius, this is an arc with 1.5"+ radius

the code fragment that these numbers came from looked like this -
G90
G92 X0 Y0 Z1
M6 T1
S2000 M3

section of code...
G0 X.1

G0 X1.1682 Y1.9091
G1 Z-.1
G2 x0.125 Y1.9622 I.5713 J.2651
other code.

I pulled these numbers from my CAD program and transcribed some numbers wrong in my first message, the stuff after the equal sign was correct. Like i say - the radius error is out there in the 100,000 ths place and I don't have a lot of influence on it.

At first I thought it was improperly drawn entities in my CAD program, but the only way to get it any more accurate is to go more decimal places as at 4 decimal places it is as accurate as can be had.

Will post the first part of the code tomorrow from work. The machine is in my classroom at the school where i work.
Re: Radius to end of arc differs from raduius to start line ...
« Reply #3 on: April 23, 2010, 12:05:26 AM »
According to your example and the numbers you wrote I testedthis code

G0 X1.1682 Y1.9091
G2 X0.125 Y1.9622 I0.5713 J0.4561


And it works fine, it does not show radius error
Please check if the example is ok

Regards

Offline kf2qd

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Re: Radius to end of arc differs from raduius to start line ...
« Reply #4 on: April 23, 2010, 09:24:57 AM »
Here's the actual code to the point where the error occurs.

G90
G92 X0 Y0
M6 T1
S2000 M3

G0 X0.1250 Y1.9622
G1 Z-.1 F3
G1 X0.3388 Y2.0681
G2 X0.4554 Y2.1763 I0.4992 J2.0121
G3 X0.5444 Y2.2738 I0.4077 J2.3092
G2 X0.6253 Y2.3301 I0.6103 J2.2654
G2 X0.7749 Y2.4246 I0.7759 J2.2573
G2 X0.8486 Y2.4818 I0.9086 J2.3283
G2 X0.9249 Y2.5227 I0.9063 J2.4658
G2 X1.0291 Y2.5469 I1.0096 J2.3945
G2 X1.1100 Y2.5793 I1.0863 J2.5213
G1 X1.3539 Y2.4535
G0 Z.1

G0 X1.1682 Y1.9091
G1 Z-.1 F3
G3 X0.1250 Y1.9622 I0.5713 J0.4561
G0 Z.1

I can get this code to choke if I oload only the last 'paragraph' of code.

It is the start of a Rose. I have a version of it that does work, just that 0,0 is in a different position. I am working on a nameplate for the Principals door here and at one point it does the same thing. And those arcs all start at nice 90 degree positions.

Mach is Version R3.042.029

Pete
Re: Radius to end of arc differs from raduius to start line ...
« Reply #5 on: April 23, 2010, 11:11:22 AM »
Your code works fine on my machine. My mach is 3.042.020

By the way, cab I ask what are you cutting at F3? is it an EDM?

Regards
Re: Radius to end of arc differs from raduius to start line ...
« Reply #6 on: April 23, 2010, 11:15:31 AM »
Heres a snapshot of your code loaded in my machine. the file loads and runs fine

Offline kf2qd

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Re: Radius to end of arc differs from raduius to start line ...
« Reply #7 on: April 23, 2010, 11:39:23 AM »
I am cutting some 1/2 thick countertop material, some kind of plastic. Some scrap I have that works nice for testing. I am using a 1/8 endmill and I could go faster, but choose not to so I lessen my chance of tool breakage. I was working on a project yesterday that gave me errors, and recoded it today witht the same tools,( a Visual Basic app I am working on in ProgeCAD) in the same sequence and had no problems whatsoever. Is there an Odd/Even date randomizer in the arc routines? Or maybe I am holding my mouth wrong. Having written some programs for PC and PLC I have had those things show up that only seem to happen during the right phase of the moon or some other obscure outside occurence.

I have a copy of Mach on 2 machines, both older Dell Optiplex 260's @ 1.8GHz, with the one tied to the Seig XE CNC not connected to the network. So far, when one does something strange the other does the same thing.

Pete

Offline kf2qd

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Re: Radius to end of arc differs from raduius to start line ...
« Reply #8 on: April 23, 2010, 11:44:32 AM »
Decided to take a look at the program those earlier code segments came from and it loads and looks fine today. Don't know what is different, loaded and ran other programs this morning and they were fine.

Have to see what happens tomorrow...

Pete

Offline kf2qd

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Re: Radius to end of arc differs from raduius to start line ...
« Reply #9 on: April 23, 2010, 11:47:23 AM »
And yet another reply... (is there a way I can edit a previous reply? I haven't seen it tif there is.)

I am working in Inches & Inches / minute, Were you thinking mm & mm/min?

Pete