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Author Topic: Will Mach3 let me pass the edge of a job past a fixed welding torch  (Read 6078 times)

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Complete newbe, first post.
 I am trying to build a table that passes the outer edge of a rectangular flange with rounded corners past a MiG torch max size 1000x650mm
It's a bit like holding a paintbrush out in front of you to paint a stripe around the outside of a biscuit tin as it passes by.
I think I need X,Y and C rotation. The only way I can work out to do this is to have the job centered on a turntable that is driven X,Y.
I think I have worked out a tool path that would work but it looks like a capital "D" on it's back with a Parallel line inside the "D"
I could move X until I get to a corner then rotate the job around the center of the corner radius by rotating the table 90 deg and moving the center of the job in an opposite arc to the corner at the same time.
This all seems a bit messy, is there a better way of passing the edge of your job past a tool like a grindwheel for example.

Im finding this a bit tough for my intro into CNC, If only I could have started with a 3 axis mill.

Hi there

I think the main reason nobody has responded to your post yet is because the discription is all messy and can't figure out by what you mean ???. Maybe if you make some sort of a drawing by hand or Cad and attach it here, people can understand you and help you setup as there are quite a few clever guys around on this site.

Thanks for your reply, I was very tired and frustrated when I posted.
I have learned more about G- Code and using Mach3. I have started building the system now.
I am building a moving x,y table with a turntable. I have a fixed base 2000mm X 1300mm. On top is my X table 800 x 1300, on that my Y table 800x800 and on that a 1100 x 1100 square turntable.
Mach3 mill would expect me to move my table under a fixed cutter, but I trying to offer the edge of a work piece  centered on the turntable to a fixed welding torch, fixed to the front of my base frame.
I have written G code that looks like it will work, but the toolpath shown is for the centre of my turntable and looks nothing like my workpiece.
I will upload pics and my attempt at G code soon.
Hi Ricky
Sounds good. Will be able to give you some hints when I see the pics. Thats the wonders of cnc as well as Mach. Mach is flexible in so many ways, you can mix and match various tools axis etc. and make it do what you want it to do without too much effort.
I will be waiting for your pics.
Re: Will Mach3 let me pass the edge of a job past a fixed welding torch
« Reply #4 on: June 03, 2013, 03:54:58 PM »
I have tried to upload pics a couple of times but nothing happening.

This is a 10% size g-code the toolpath looks nothing like my 850x600 rectangle with 100mm radius corners.

G54 G90
G00 X0 Y0 A0
G01 X-65 Y0 F1000.
G02 X-15 Y15 I32.5 J-17.5 A90 F6000
G1 X-50 F1000
G02 X0 Y0 I17.5 J-32.5 A180 F6000
G01 X-65 Y0 F1000
G02 X-15 Y15 I32.5 J-17.5 A270 F6000
G1 X-50 F1000
G02 X0 Y0 I17.5 J-32.5 A360 F6000

Re: Will Mach3 let me pass the edge of a job past a fixed welding torch
« Reply #5 on: June 03, 2013, 05:34:00 PM »
Hi Ricky

I'm still not to sure what your setup looks like but from what I understand you're g-code is not going to work. When working with rotary axis in Mach, your toolpath won't look like the profile as suppose to 2 or 3 axis linear moves where the toolpath basically simulates the profile you want to cut, instead you will get a toolpath on the screen, then another after the A axis has rotated but on the same xy plane
 The toolpath window will not rotate the plane after each rotary movement. What will happen with your toolpath is that you will have the same xyz movements copied and pasted, it sounds a bit confusing I know. I need to draw this to give you exact movements, say you start x0 y0, then you will go to where you want to plunge. Z comes down then you do a cut like in your case -65 on x, now remember, with your turntable being square, after a 90 degree turn, where you have stopped at x-65 will now change to x0 y-65. This will not give you 100mm rad corners though but hopefulle you can see how much changes after the 90 degree turn. Give me a day or two then I will send you a sample g-code you can try.


Offline alenz

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Re: Will Mach3 let me pass the edge of a job past a fixed welding torch
« Reply #6 on: June 03, 2013, 08:48:29 PM »
Ricky, See if this is what you had in mind.
The first attached file is the Gcode for an 850 X 600 rectangle with 100 radius corners.
The second is the same drawing with all lines broken into short segments.
The third is the second file converted to Polar coordinates for use with a C-axis rotary table.
Will provide details if it looks like you can use this method.
« Last Edit: June 03, 2013, 08:53:42 PM by alenz »
Re: Will Mach3 let me pass the edge of a job past a fixed welding torch
« Reply #7 on: June 04, 2013, 04:25:16 PM »
Thanks for your replies guys, much appreciated.
I think my biggest problem at the moment is not having my table built so I can see the results. I should be up and running in the next two weeks.

I will try to explain my thinking as clearly as possible. 850x600 rectangle with 100mm radius corners centered on square turntable.
So starting with the first 850 side I move X 650 (850 - two corner radius).
Now I get to the first corner, I need to rotate my job 90 deg on the  100mm corner radius centre.
The turntable must rotate 90 deg every corner to present the next side to me.
I cut out a cardboard shape of my work and pushed a pin in one corner radius, when I rotated 90deg around the pin, I could see this was the correct motion I require, the center of my work was following a large opposite arc, as mach 3 thinks the center of my work is my cutting tool I guessed this was the path to plot.
As the length of the center arc is about 6 times greater than the circumference of the 100mm corner radius, I need to increase feed rate on the corners to match the speed of going along the sides.

Forgive me if this sounds silly but if you put a credit card flat on a piece of paper, draw an arrow on the paper, now pass the entire edge of the card past the arrow tip until your back to where you started. The center of the card being my toolpath.


Offline zarzul

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Re: Will Mach3 let me pass the edge of a job past a fixed welding torch
« Reply #8 on: June 05, 2013, 05:33:18 PM »
the last 2 sentences I understood,   I don't understand why you would build it with a rotating table in the center.
Why not just fix your part stationary and move around it with your x & y?

Offline stirling

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Re: Will Mach3 let me pass the edge of a job past a fixed welding torch
« Reply #9 on: June 06, 2013, 04:59:20 AM »
If I understand your requirements, this sounds very much like a plasma system I once did for cutting square section tube. The torch could move in X and Z and the tube rotated (in A) with the rotational axis parallel to Y.

I think you understand the code needed but aren't getting the display you'd expect in the toolpath window - is that correct?

If this is the case, because you're using X,Y and A (presumably with the axis of A parallel to Z) then make sure you have Config/Toolpath - rotations set to "Z Axis" and "A rotations enabled" ticked.

Without those settings you'll get the "D" on its back type display you've described. A bit like this..

<a href="http://www.youtube.com/v/LmrzaSeGaM8?hl=en_US&amp;amp;version=3" target="_blank" class="new_win">http://www.youtube.com/v/LmrzaSeGaM8?hl=en_US&amp;amp;version=3</a>

But with these settings you should get something like this...

<a href="http://www.youtube.com/v/ZyjOvQV5aaI?hl=en_US&amp;amp;version=3" target="_blank" class="new_win">http://www.youtube.com/v/ZyjOvQV5aaI?hl=en_US&amp;amp;version=3</a>