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Problem with work offsets & Cutter Compensation
« on: January 12, 2015, 02:18:41 PM »
Problem with work offsets & Cutter Compensation

I made a plate with the following code;

G17
T1 ( <Tool escription>"/ )
M06
G43 H1
G90
G54
G1 X1 Y-0 F19
M3
G42 D1
G1 Z.003
G1 X-.250 Y0
G1 X-1.9 Y-.868
G1 X-4.25 Y-.868
G0 Z2.0
G1 X-4.25 Y-3.11
G0 Z.25
G1 Z.003
G1 X-2.12 Y-3.11
G1 X-2.12 Y-3.48
G1 X0 Y -2.41
G0 Z2
G1 X1.0 Y-0 Z0
G40


Everything went well.  No real issues.  I need to make 4 of these plates so I wanted to use the G55 in order to cut 2 plates at a time.  I am having some issues and was wondering if anyone can help.  The following is what I did;
I set up the stock on the mill.  Zero’d  x,y,z on plate 1 using G54 and plate #2 using G55.  I checked both were working correctly using the “go to zero” button.  Everything was fine.
I ran the program and plate #1 ran good.  The program went to plate #2 BUT when it started G1 X-1.9 Y-.868  it went in an inverse postion.  It seemed like all the y postions needed to be negative. 
This was weird b/c:

•   in the little screen that shows the parts both parts lined up on the same plane.
•   I copied and pasted the same code from part #1 to part #2
•   I ran part # 2 in a separate program using G55 only and the part ran fine.
•   When I negated all y values the Mach 3 screen showed the part in an inverse position but the tool cut the same was as if the Y values were not negative.

I tried using G10 P1(G54) & G10 P2(G55) but for some reason the tool path ran G10 P1 fine but when it ran G10 P2 it ran the SAME exact path in the G54 position.  It did not go to G55.
I am just starting with G code and have exhausted all my knowledge tring to fix this issue.  Thanks for your help in advance.   
I have attached the code using G54 & G55 and also using G10 further below;

Method #1 (G54 & G55)
G17
T1 ( <Tool escription>"/ )
M06
G43 H1
G90
G54
G1 X1 Y-0 F19
M3
G42 D1
G1 Z.003
G1 X-.250 Y0
G1 X-1.9 Y-.868
G1 X-4.25 Y-.868
G0 Z2.0
G1 X-4.25 Y-3.11
G0 Z.25
G1 Z.003
G1 X-2.12 Y-3.11
G1 X-2.12 Y-3.48
G1 X0 Y -2.41
G0 Z2
G1 X1.0 Y-0 Z0
G40
G55
G1 X1 Y-0 F19
G42 D1
G1 Z.003
G1 X-.250 Y0
G1 X-1.9 Y.868
G1 X-4.25 Y.868
G0 Z2.0
G1 X-4.25 Y3.11
G0 Z.25
G1 Z.003
G1 X-2.12 Y3.11
G1 X-2.12 Y3.48
G1 X0 Y 2.41

Method #2 (G 10)
G17
T1 ( <Tool escription>"/ )
M06
G43 H1
G90
G10 L2 P1
G1 X1 Y-0 F19
M3
G42 D1
G1 Z.003
G1 X-.250 Y0
G1 X-1.9 Y-.868
G1 X-4.25 Y-.868
G0 Z2.0
G1 X-4.25 Y-3.11
G0 Z.25
G1 Z.003
G1 X-2.12 Y-3.11
G1 X-2.12 Y-3.48
G1 X0 Y -2.41
G0 Z2
G1 X1.0 Y-0 Z0
G40
G10 L2 P2
G1 X1 Y-0 F19
G42 D1
G1 Z.003
G1 X-.250 Y0
G1 X-1.9 Y.868
G1 X-4.25 Y.868
G0 Z2.0
G1 X-4.25 Y3.11
G0 Z.25
G1 Z.003
G1 X-2.12 Y3.11
G1 X-2.12 Y3.48
G1 X0 Y 2.41

Offline BR549

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Re: Problem with work offsets & Cutter Compensation
« Reply #1 on: January 12, 2015, 08:10:49 PM »
Just glancing at the Gcode, You are making it hard to read by using 2 quadrants to program in  +XY and -XY. It would be much easier to follw if you stay in 1 quaudrant  +XY .

Next I do NOT see where you have used a leadin for the tool offsets. YOU MUST use them or you may get some very weird moves as Mach3 trys to compensate for the LACK of the leadins.

Same for Z comp you must give it room to be able to comp the toolheight before it starts to cut.

What have you set the G54 and G55 offsets to ??

(;-)TP
Re: Problem with work offsets & Cutter Compensation
« Reply #2 on: January 12, 2015, 08:26:40 PM »
TP.  Thanks for the reply.

Not sure if you noticed but this is my first code.  I am reading Smid's book and I may have missed something's.

First,  what do you mean by +XY and -XY.  Did I use a G code for -XY and +XY or can you tell from my coordinate?  How do I keep my code in 1 quadrant? 


Second, what is lead in?

I set my G54 & G55 using the work offsets tab in Mach 3.

John

Offline BR549

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Re: Problem with work offsets & Cutter Compensation
« Reply #3 on: January 12, 2015, 09:05:13 PM »
AS to =/- XY if you noticed you moved from a +XY position to a -XY position . To start out it is BEST to keep all the points in the +XY quadrant where all numbers are Positive.
It is NOT a must do but makes it much easier to read and understand the moves.

Read up in Peters book on tool offsetting G41/42/40 it talks about the leadin /leadout moves reqiured to do tool comp. Basically you are giving the machine ROOM to do the compensation move to create the offset around the part you must also Leadout a move to uncomp the toolpath.

With Mach3 IF you do not use a leadin/out move Mach3 will do its best to make a comp move with the moves you give it to work with MOST times it creates some very unusual moves to try and make it work. Normally it does not work.

(;-) TP

(;-) TP

Offline BR549

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Re: Problem with work offsets & Cutter Compensation
« Reply #4 on: January 13, 2015, 07:19:30 PM »
OK I took some more time to recreate your code AND you have run into one of the Mach3 bugs dealling with Tool Comp.

Ther is NOT way around it and Mach3 will never be fixed for that problem. 

Sorry, (;-) TP
Re: Problem with work offsets & Cutter Compensation
« Reply #5 on: January 13, 2015, 07:29:54 PM »
Thanks for your help.

I will definitely take your advice on keeping the code in 1 quadrant.  That makes sense.  I just need to put more thought into where my origin is going forward as I write more code.

I read the chapter on tool comp and will make sure to include lead in and out when doing tool comp.

Question:  I have seen other posts where people have issues with work offsets(G55 etc) and tool comp.  Is that the bug you are referring to?  Or is it something else I need to be aware of?

Thanks. 

John

Offline BR549

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Re: Problem with work offsets & Cutter Compensation
« Reply #6 on: January 13, 2015, 10:25:40 PM »
There are just some combinations of Tool Comp and Fixture offsets that Mach3 cannot deal with(BUG) Other combinations will work fine. It just depends.

(;-) TP