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Offline JVG

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Tangential Control
« on: February 22, 2016, 02:46:14 PM »
Hi.  I'm trying to control a cutting knife using the Tangential Control feature in Mach3.  

Everything is working well with one exception; at corners in the cut geometry, where the A axis needs to re-position to be tangent to the upcoming XY move, the Z lift and A re-position are a blended movement.  

Normally, as with a true milling operation, this isn't an issue but in this case the knife I am using has an offset blade tip.  So, when the Z begins to lift and the A begins to rotate, the tip of the blade is dragged through an arc gouging the material.  What I need to for the Z axis to lift to zero and then rotate the A.  

I can't figure out how to do this.  Any ideas out there?  

Thanks.

Offline BR549

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Re: Tangential Control
« Reply #1 on: February 22, 2016, 04:01:34 PM »
I do believe that is a bug in the current versions. It will never be fixed. You MAY be able to back up enough version Numbers to find one that it did work correctly.

Offline stirling

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Re: Tangential Control
« Reply #2 on: February 23, 2016, 04:36:58 AM »
can you post some example code of where the issue is happening?

Offline JVG

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Re: Tangential Control
« Reply #3 on: February 23, 2016, 01:47:11 PM »
Here is some example code.  The behavior is at the two lines "G00 Z0.0000", which I've separated with spaces from the rest of the code.

G00 G49 G40.1 G17 G80 G50 G90
G20
(2 1/2 Axis Profiling)
G00 Z0.0000
X-1.2292 Y-0.3717
G01 Z-0.3000 F100
G17
G02X-0.1397Y-0.5086I0.5129J-0.3220 F100
X-0.4167Y-1.4766I-0.7741J-0.3020
X-0.7216Y-1.7075I-5.2693J6.6393
G03X-1.2241Y-2.2658I1.2598J-1.6394

G00 Z0.0000

X-1.2586 Y-2.2238
G01 Z-0.3000 F100
G03X-2.0651Y-1.4633I-2.4982J-1.8414 F100
G02X-1.9607Y-0.1278I0.4639J0.6355
X-1.1878Y-0.4262I0.2264J-0.5639

G00 Z0.0000

A0
X0 Y0
M30

Offline BR549

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Re: Tangential Control
« Reply #4 on: February 23, 2016, 03:26:08 PM »
IF you recode it with lines insteadd of arcs then it should work correctly. The bug was with ARCS and tangential control.

Just a thought, (;-)

Offline JVG

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Re: Tangential Control
« Reply #5 on: February 23, 2016, 03:36:02 PM »
Thanks.  I have tried coding just XY moves while relying on Mach3 to provide the tangential control of the A axis.  The resulting movement is very jerky.

I have not tried to compute the associated angle (hypotenuse leg) of each XY pair and add that in to each XY move command.

Offline BR549

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Re: Tangential Control
« Reply #6 on: February 23, 2016, 06:06:38 PM »
From what I understand about teh problem IF you break teh arcs down to segmented line that represent teh arc THEN it works OK.  That would mean NO arcs used in teh code.  But that mode ios normal for a lot of Cams as they put out line in lue of arcs.

(;-) TP

Offline stirling

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Re: Tangential Control
« Reply #7 on: February 24, 2016, 11:59:45 AM »
try this and let me know how it goes

Code: [Select]
G00 G49 G40.1 G17 G80 G50 G90
G20
G17
(2 1/2 Axis Profiling)
G00 Z0.0000
G00 X-1.2292 Y-0.3717
G01 Z-0.3000 f100
G4 p0
G02 X-0.1397 Y-0.5086 I0.5129 J-0.3220 f100
G02 X-0.4167 Y-1.4766 I-0.7741 J-0.3020
G02 X-0.7216 Y-1.7075 I-5.2693 J6.6393
G03 X-1.2241 Y-2.2658 I1.2598 J-1.6394
G4 p0
G00 Z0.0000
G00 X-1.2586 Y-2.2238
G01 Z-0.3000 f100
G4 p0
G03 X-2.0651 Y-1.4633 I-2.4982 J-1.8414 f100
G02 X-1.9607 Y-0.1278 I0.4639 J0.6355
G02 X-1.1878 Y-0.4262 I0.2264 J-0.5639
G4 p0
G00 Z0.0000
G00 A0
G00 X0 Y0
M30
%

Offline Vogavt

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Re: Tangential Control
« Reply #8 on: February 25, 2016, 06:24:40 PM »
Have you looked at Donek Tools website?

If you have software the will read a Microsoft Excel format file, there's a free download of their xls spreadsheet that will convert your GCode to one that works well with a free swiveling knife blade.

Yeah, I know you're wanting to control the rotation with the A-axis, but the file may be worth studying if you have the inclination to do so.

Look here and then back out to their home page.

Pretty cool stuff and hardware.

Offline BR549

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Re: Tangential Control
« Reply #9 on: February 25, 2016, 08:39:53 PM »
HIYA Ian , I see what you did  (;-) .  Does it work ???

(;-) TP