Invert Axis For Opposite Hand Parts

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26 Aug 2016 15:13 #79500 by fc60
Greetings,

Many years ago (early 1980"s) when I did my time on the CNC machines, most of the machines had a switch to "Invert" an axis for an opposite hand part, very common in the aerospace business.

Is there such a feature within LinuxCNC?

Cheers,

Dave

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26 Aug 2016 16:09 #79503 by Todd Zuercher
No, I don't believe there is any dedicated way to do this (simple G-code). But I think there could be ways you could work around the limitation to get something that might work for what you intend.

IMHO
In this age of CAD/CAM generated code, this sort of feature has become rather obsolete. (Usually easier and safer just to regenerate the code.)

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26 Aug 2016 17:22 - 26 Aug 2016 17:23 #79505 by Todd Zuercher
Such as this, if you're a little creative with your G-code you can make a file that can be fipped simply by changing a parameter value like this.
#1 = -1 (Set #1 = -1 to mirror 1 for normal)
#2 = 0.0 (offset for X mirror axis)
#3 = 3
o100 if [#1 EQ -1]
 #3 = 2
o100 endif

(1/4" End Mill)

G0 X[#1*4.244+#2] Y5.0743
S17300
G0 Z1.
G1 Z0.75F100

G1 X[#1*3.8212+#2] Y4.8068 Z0.F200
G1 X[#1*0.8875+#2] Y3.091
G[#3] X[#1*0.8256+#2] Y2.9831 I[#1*0.0631] J-0.1079
G1 Y0.9725
G[#3] X[#1*0.9506+#2] Y0.8475 I[#1*0.125] J0.
G1 X[#1*6.818+#2]
G[#3] X[#1*6.943+#2] Y0.9725 I[#1*0.] J0.125
G1 Y6.4148
G[#3] X[#1*6.8802+#2] Y6.5232 I[#1*-0.125] J0.
G[#3] X[#1*6.7549+#2] Y6.5227 I[#1*-0.0622] J-0.1084
G1 X[#1*3.8212+#2] Y4.8068
G1 X[#1*3.7348+#2] Y4.7563
G1 X[#1*3.2944+#2] Y4.519 Z0.75
G0 Z1.
%
Last edit: 26 Aug 2016 17:23 by Todd Zuercher.
The following user(s) said Thank You: tommylight

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26 Aug 2016 19:39 #79506 by eFalegname
Flipping parts is a very normal daily procedure in cabinetmaking, it's a shame that Linuxcnc lacks this feature.

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27 Aug 2016 01:56 #79528 by Todd Zuercher
The problem with running code flipped is that it also reverses the milling direction. That can be a big problem with wood, where climb milling might be required to prevent corners from chipping.

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27 Aug 2016 15:12 #79557 by fc60
Greetings,

Forgot to mention, Boeing had a large assortment of Left Hand cutters. So inverting the axis for the opposite hand part just meant using a left hand cutter and editing the M3 to M4.

Cheers,

Dave

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27 Aug 2016 19:19 #79564 by Todd Zuercher
I forgot to mention the above code modification was done to a regular g-code file in 3 find and replace steps using Notepad++ (using regex replace commands). first step modified the X commands to multiply them by #1 and add the offset, 2nd was to multiply the I commands by #1, and 3rd was to make the G2 words variable. It could easily also be done on the fly while opening the file with a script.

I still think it is more trouble than it's worth. We have 7 or 8 machines that do have the capability, to run a mirrored files, and in over 15 years we have never once tried to use it.

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28 Aug 2016 20:34 #79612 by cmorley
I could really use an inverted axis option on my lathe... it has a tool turret on both sides of the center line.
i would use it everytime the lathe was used.

Chris M

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28 Aug 2016 21:15 #79616 by Todd Zuercher
I would think that something useful could possibly be done with some careful Hal trickery and some custom M-codes, But I'd have to think about it a while to iron out the details. I wonder if the problem has already been solved by someone. Some time searching the archives may prove fruitful.

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28 Aug 2016 21:50 #79620 by tommylight
Just thinking out loud here,
What if .......a pyvcp button with the added python script that would get the values from gcode ( outer most values ), invert them adding "-" and then offseting all that for the values it got from gcode, so everything falls in place ????
I wonder...... but i do not have the time nor did i do actual programming in a long while.

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