Confused

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KenW
Posts: 44
Joined: Tue May 23, 2017 11:49 am

Re: Confused

Postby KenW » Sat Jul 22, 2017 1:42 pm

Ok, so here is what is happening. I set my workpiece in position based on my offset defined by g55.
I home the machine, then move my bit to the surface and set the Z axis.
The following program is a test to cut a simple 4mm deep slot, but the final depth comes out to about 1.88mm.
I'm stumped. When the cnc stops the Z axis moves up to around 73mm and I measure it and that is correct.
Any help? Here is the code:

%
(TEST PANEL 7-22)
(T16 D=3.175 CR=0. - ZMIN=-4. - FLAT END MILL)
N10 G90 G94 G17 G91.1
N15 G21
N20 G53 G0 Z0.
(2D POCKET1)
N25 M9
N30 T16 M6
N35 S18000 M3
N40 G55
N45 M8
N55 G0 X1.587 Y106.787
N60 G43 Z15. H16
N65 G0 Z5.
N70 G1 Z2.5 F1000.
N75 Y107.854 Z2.463 F333.33
N80 X177.976 Z-3.697
N85 G2 X186.495 Y106.412 Z-4. I0. J-25.888
N90 X203.865 Y81.965 I-8.519 J-24.447 F1000.
N95 G1 Y25.536
N100 G2 X202.04 I-0.913 J0.
N105 G1 Y81.965
N110 G3 X177.976 Y106.029 I-24.063 J0.
N115 G1 X1.587
N120 Y107.854
N125 X177.976
N130 G2 X186.495 Y106.412 I0. J-25.888
N135 G1 X186.296 Y105.842 Z-3.94
N140 G0 Z15.
N150 M9
N155 G53 Z0.
N160 M30
%

KenW
Posts: 44
Joined: Tue May 23, 2017 11:49 am

Re: Confused

Postby KenW » Sat Jul 22, 2017 1:59 pm

So, I removed lines N20, N60 and N155 that had reference to G43 and G53 and the cut was perfect. 4mm depth.
Now can anyone explaing why this worked? I looked up the G codes but don't quite follow what they mean.

Thanks,
Ken

beltramidave
Posts: 214
Joined: Fri Aug 21, 2015 8:54 pm

Re: Confused

Postby beltramidave » Sat Jul 22, 2017 2:02 pm

Are you zeroing z to the top of your material or to the bed surface?
Are you sure when you set z zero that you have G55 coordinate system selected?

KenW
Posts: 44
Joined: Tue May 23, 2017 11:49 am

Re: Confused

Postby KenW » Sat Jul 22, 2017 2:31 pm

Yes, I set G55 in mt MDI and am setting Z to top of material.

When I removed those three lines 20, 60 and 155 it makes the cut properly, so perhaps it has
something to do with the G43 in line N60 ?

beltramidave
Posts: 214
Joined: Fri Aug 21, 2015 8:54 pm

Re: Confused

Postby beltramidave » Sat Jul 22, 2017 2:55 pm

G43 is a tool offset. Make sure that you use a g49 (cancel offset) before running another toolpath with a different tool. I believe that LinuxCNC remembers that offset even after restarting your PC.
Here is a good read.
-programming-tips.blogspot.com/2014/12/g43-g44-and-g49-tool-length-compensation.html

KenW
Posts: 44
Joined: Tue May 23, 2017 11:49 am

Re: Confused

Postby KenW » Sat Jul 22, 2017 4:22 pm

Not sure that I need a tool offset as I'm changing the tools manually and mostly using the same tool from one panel
to another anyway.

What I'm still unclear about is in my program I have an offset of G55 and executes the file just fine. However, after the program
has ended and I hit the button "return to x-y" it doesn't go back to the 0,0 point that I set in G55.
Could the M30 be resetting the modes? If I run the same file again, it does go to the correct position because of the G55 on
line 40. Just curious.

beltramidave
Posts: 214
Joined: Fri Aug 21, 2015 8:54 pm

Re: Confused

Postby beltramidave » Sat Jul 22, 2017 5:19 pm

I would not think you would need any tool offset either unless you are using multiple tools in the same toolpath and using the Probotix tool sensor.
Where does it go when you click on go to xy? Some of those buttons are hard coded in the .in file.
M30 should not matter.

beltramidave
Posts: 214
Joined: Fri Aug 21, 2015 8:54 pm

Re: Confused

Postby beltramidave » Sat Jul 22, 2017 5:26 pm



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