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Author Topic: Backup on Path for Plasma and Waterjet  (Read 4073 times)

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Backup on Path for Plasma and Waterjet
« on: June 06, 2011, 03:59:49 PM »
I'm considering using Mach 3 for a CNC plasma and waterjet system but I don't know what "backup on path" capability Mach 3 has. This can be especially important in plasma and waterjet if the torch/cutting head crashes into the plate and you need to "re-cut" where the collision occurred. This functionality is standard on many plasma and waterjet CNC controls (Burny, Hypertherm, Flow, Omax, etc). So, does Mach 3 have backup on path capability? Are there any limitations?
Re: Backup on Path for Plasma and Waterjet
« Reply #1 on: June 13, 2011, 01:40:03 PM »
If you don't use "kerf compensation", then you are able to go back in the path (fully back untill the start of the program).
To do that you should include at the start of your code: G40 (cancel kerf compensation).
The procedure looks like:
1. You hit "pause" button (wait until the machine is stoped - also "plasma start" command will be deactivated)
2. Hit "reverse run" (the machine goes back on the path)
3. Hit "pause" button again to stop reverse running.
4. To start the plasma arc again at this position, you can create a button that will activate "start plasma" command,
    will wait until the plate is pierced and will start forward running.


Hope that helps...
John
Re: Backup on Path for Plasma and Waterjet
« Reply #2 on: June 13, 2011, 11:26:25 PM »
I think you'll find that Mach will not stop in the middle of a command.  IE: If you give it a command like "G1 X10" and the arc quits 5" in, you can't back up to where the arc quit, but you can go back to the point where the command began.  Not real useful in plasma cutting as in this case you would be cutting air for 5" before the torch reached the point where it previously failed.

Offline BR549

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Re: Backup on Path for Plasma and Waterjet
« Reply #3 on: June 13, 2011, 11:45:29 PM »
You don't restart the torch at the begining of the line you back it up several lines before the point and "watch" it move then hit the fire button a sqeek before it gets to the point you need to restart  at. Do it all the time. You also can use FRO to slow it down as it gets to the spot fire the torch and hit reset FRO. AND off it goes

ALSO have you played with shuttle mode ?????

 (;- ) TP
« Last Edit: June 13, 2011, 11:48:44 PM by BR549 »
Re: Backup on Path for Plasma and Waterjet
« Reply #4 on: June 14, 2011, 04:12:31 AM »
Sounds very strange to me, while i never faced such problems.
I have found some solutions and i would like to share.

You can create 2 macros. One for starting the plasma arc and one for switching it off.
You put them in your code for starting and stoping the plasma arc.
It's not necessary to place them manualy inside the code. (You can touch the post processor of your nesting software).
The first macro also reads the "piercing time" from a DRO and waits until this time ends. Then starts the motion.
Also you create a button which executes this macro.

The program starts normally and can switch ON and OFF the plasma arc at the start and the end of a shape.
Now you have come to a point where you have lost the cutting. Press pause. Hit "run reverse". Hit pause again to stop reverse.
Press the button which executes the first macro. The plasma arc starts at this point exactly where you have stoped.
You don't have to go the start of the line, or start the plasma arc while moving.

So, finaly, yes, Mach3 can "backup on path".
The only "problem" i can see is that the pause button is not immediately executed, while Mach buffers the motion commands.

Hope that helps...
John
Re: Backup on Path for Plasma and Waterjet
« Reply #5 on: June 14, 2011, 08:52:51 AM »
You don't restart the torch at the begining of the line you back it up several lines before the point and "watch" it move then hit the fire button a sqeek before it gets to the point you need to restart  at. Do it all the time. You also can use FRO to slow it down as it gets to the spot fire the torch and hit reset FRO. AND off it goes

ALSO have you played with shuttle mode ?????

 (;- ) TP

I haven't played with shuttle mode.  I'll have to give it a try.

To do what you describe, you must have to turn off THC mode, back up to previous command, resume forward motion, then fire the torch just before turning THC mode back on.  As long as THC mode is on, Mach won't move without a good "OK To Move" signal.

Offline BR549

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Re: Backup on Path for Plasma and Waterjet
« Reply #6 on: June 14, 2011, 02:15:59 PM »
iF you go back  to a previous line  then hit  run from this line then RUN it will take off following the path. YOU DO NOT have to reverse to get there,MACH will move back to the position called for in the CODE(;-), just cursor back up to the line where it failed. Then back up a few more lines to give you some time to react and do a FRO to slow down the machine.The THC is not in play until the M3 calls for the torch to fire and at this point it was NOT called yet SO yes it works . When the path of the torch crosses the restart point HIT the fire button and the torch will fire , then hit the resetFRO button and MACH continues on it way as thought nothing ever happend.

I have 2 buttons on the hand pendant that does just that purpose. 1st one sets the run next line MINUS 20 lines from the next line DRO value and FRO to 10% then RUN.  The 2nd fires the torch M3 and resets the FRO to 100%


I USE IT ALL THE TIME, It certainly works for me.

(;-) TP
« Last Edit: June 14, 2011, 02:27:29 PM by BR549 »
Re: Backup on Path for Plasma and Waterjet
« Reply #7 on: June 14, 2011, 10:38:41 PM »


I USE IT ALL THE TIME, It certainly works for me.

(;-) TP

I can't say I have occasion to use this feature often, but on those off occupations where things just don't go right, it would be useful.  I'll give it a try.  Thanks for the explanation.