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Author Topic: CNC seem welding????  (Read 11729 times)

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CNC seem welding????
« on: May 24, 2009, 10:03:14 AM »
Has anybody here used their plasma table for an automatic welder?  I have a bunch of 1/4"aluminum plates to weld up and keep thinking about using my table.  Any suggestions would be great!

Thanks

Tom

Offline Sam

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Re: CNC seem welding????
« Reply #1 on: May 24, 2009, 11:26:03 AM »
I have mounted a mig gun to a bridgeport table, and used the power feed to travel. It worked just dandy. I would not want to do the same on my cnc machine, however. I would be to worried that all that current would fry something in the electronics, but that's just me being overcautious I suppose.
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."

Offline Jeff_Birt

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Re: CNC seam welding????
« Reply #2 on: May 25, 2009, 12:40:27 PM »
For automated welding the first hurdle is keeping your parts accurate enough. Humans can account for misfit parts, machines can't. The next task is properly fixturing the parts. Automation won't change the basic properties of the type of welding you are doing; if you couldn't weld vertically with the material/filler that you are using when welding it by hand automation won't change that.

For seaming there are two basic type of fixturing. One uses a continuous series of fingers on each side of the seam that hold the material down and in registration with each other. You close one set of fingers, run one plate up against them to square it, and then close the other set on top the inserted plate to hold it in place. Next you open the first set of fingers and push the second plate up to the edge of the first and then close the fingers on top of it. This should give you a pretty straight seam but some tracking adjustments might need to be made depending on length. Many times this is done manually with a joystick, etc.

The second basic type is used for situations where the seams are less perfectly aligned. It uses some sort of seam tracking to keep the torch on track. Seam tracking devices can vary from laser tracking, to mechanical probes to through arc seam tracking (with specialized equipment.)

To control the welding process you will need to at least sense that you have established and maintained an arc (similar to plasma cutting). Some newer welding power supplies will have an output for this. If you don't have one you can use a current sensing relay. You will probably also want to have better control of the gas flow if your going to do it a lot. That way you can turn the gas on a second or two before starting to weld (pre-flow) and keep it on several seconds after the weld (post-flow). Fancy welding controllers will also let you set different current profiles for starting and finishing the weld.

Happy machining , Jeff Birt
 
Re: CNC seem welding????
« Reply #3 on: May 25, 2009, 02:04:37 PM »
Thanks,  The parts are all water jet cut so fit up is good.  My thought was to just use stops on each panel and some hold down clamps.  The G code would be very simple, just point to point at a set speed and the starting/stopping of the torch would just be by hand.  A pretty crude setup I know but there are only 60 or so welds each 6 feet long.   If I can do it and end up with less cleanup in the end I think it might be worth it.

Thanks Again for the responces and I'll post pics if it works ;D

Tom
Re: CNC seem welding????
« Reply #4 on: June 04, 2009, 08:52:43 AM »
Hey I like this topic.

I did this on a few scrap bits of steel.  Here look at these pics, pretty good for only one go at it mucking around.

Peter
http://www.learn-how-to-weld.com

Offline Jeff_Birt

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Re: CNC seem welding????
« Reply #5 on: June 04, 2009, 09:17:58 AM »
That looks good, appears that you got the welding power supply up into spray mode. One nice side effect of welding automation is that is almost impossible to do by hand, like spray transfer on thinning materials. If you add a bit of dwell at the end of the cycle you can reduce the crater/low spot caused when welding and motion stop together.
Happy machining , Jeff Birt
 
Re: CNC seem welding????
« Reply #6 on: June 04, 2009, 01:54:26 PM »
Looks great Apples!  I'll be doing my samples next week.  its 1/4 inch aluminum 6 feet long,  do you think I should tack it first by hand or just go for it?  Well clamped?

Tom
Re: CNC seem welding????
« Reply #7 on: June 04, 2009, 05:57:26 PM »
Tack and clamp as much as possible.  That is sort of the cardinal rule when welding anyway.

Put it this way.  There is a machine called a "beam welding machine".  Basically it welds 3 bits of flat steel together to make them into an I beam.  This particular machine is being used for welding the chassis rails for low loader truck trailers ( to put heavy bulldozers etc on).  And on this machine they use rollers with hydraulic rams pushing and clamping it all the steel together.  Then there is a welding machine either side of the plates of steel and away it goes. 

There must be some serious clamping forces there with those hydraulics. 

But yeah, heat makes metal expand and get bigger and warping and twisting is very common.

Re: CNC seem welding????
« Reply #8 on: June 19, 2009, 03:37:15 PM »
Did some tests and they look pretty good.  Will be doing the actual parts next week.

Re: CNC seem welding????
« Reply #9 on: July 01, 2009, 03:36:24 PM »
It's working great!  here is some pics of of the set up.  I'm useing 3/64 wire with a travel speed of 70 ipms.  Tacks and welds both "legs" in 1 min!!