Welder High Frequency Box help please?

[ShawnR]

I have recently acquired a high frequency stabilizer which allows an AC welder to weld aluminum using TIG equipment. I am new to TIG welding but want to learn more about it and this seemed like a good way of getting into it. I have been having a tough time welding with it though. I have had some input from a welding friend and he bounces ideas off of a good tig welder but together we have had no luck. After troubleshooting all of the typical Tig type problems, I am starting to suspect the HF box, although it does appear to work well. I get a great arc from the tungsten to the material and can melt the base material just fine, and run the arc along the material. But the material does not seem to "mix" ...it seems to blow away like I am using DC but I tried another power source (welder) and it does the same thing. The HF box uses a spark gap to generate the HF. I know very little about this but the manual does suggest a spark gap of 0.007". I set it to this, and a little more and a lot less and none make a diffence. The HF at the tungsten is very strong (ie jumps quarter inch or more ) so it appears to work but the welding part does not.

Sooo, after all that, my question is this. In the large coil that the welding current flows through in the box (in and then out), there are three wires going into the coil. One comes from either side of the spark gaps and the third goes to one of the output terminals. I get no continuity on any of these wires. I have no diagram so am guessing but I would think there should be something there...? The confusing part is that I have great arcing on the output and can maintain the weld. I have labelled the wires I am referring to as A, B and C in the attached photo. I think these wires are supposed to super impose the HF on the welding current which it appears to do but thought I would throw this out there and see if anyone has any experience with this sort of thing.

 

[MaxHeadRoom78]

Why not try and get an experienced TIG welder to test and decide if it is the M/C or your technique!
Max.

 

[kubeek]

As you say the HF works correctly, so no worries there. Have you measured the connection between the top left and top right terminal, and between bottom left and bottom right? Those should be a dead short. I hope I am not stating the obvious, but you cannot make it weld unless you have a welder connected.

 

[ShawnR]

Max..working on that. Trying to learn as much as I can till I get someone over.

I have an idea. Will report back. Does anyone know how the spark gap affects the hi frequency, ie max voltage and or frequency?

Kubeek, I did not but since the welding current passes through, it should be good. ..I will check anyways. ☺

 

[shortbus=]

Sounds like your trying to weld the aluminum on DC. Aluminum has to be welded with AC, to "scrub" off the oxides on the metal. The high freq is just usually to get the spark to start without having to "scratch start" the arc. Many old machines didn't have high freaq but did have AC - DC output and could still weld aluminum. Also what gas are you using for the shield?

 

[ShawnR]

I found a friend with a 004 model, very similar. I was able to compare the two models and also take readings on the coil. No difference so the problem must be with me! Bummer. Nothing to blame.

Next step is to find someone to pop over and show me how it is supposed to work. The idea is to add some features to this basic setup like a foot pedal for power control, gas flow solenoid, HF control, etc. I nice project for a microcontroller. This has all been done before by others.

Thanks for the input.

Cheers,

 

[ShawnR]

Had a friend over last night. He was able to run some nice beads after a while to figure out the machine and set up It was a combination of things. I had too much current, not enough gas flow for this set up and technique needing tuning up. I can see how a foot pedal control will make it much easier. Thanks for the input.

 

[gary350]

I use to weld all the time at work. Do you have the correct tungsten tip rods? One type rod is for aluminum another type is for other metals.

Be sure to grind the tungsten rod tip to about a 30 degree angle point. Make sure the grind lines are parallel to the rod. Do not spin the rid and grind it so it has spiral grind lines around the tip this makes the arc spin line a mini tornado.

What gas are you using for aluminum? If you using a mix gas it is a little harder to weld but not too bad for horizontal welds.

Make sure you are using the correct tips in the handle. If your tip is too small or too large it is harder to weld. If your using an old melted ceramic tip or chipped ceramic tip trash it and get a new one.

Our welder at work had a polarity switch. It was switched one way for aluminum and the opposite direction for steel. I don't remember which was was which that was 10 years ago.

Aluminum oxidizes not anything you can actually see very easy. The older the aluminum is the hard it is to weld. Old aluminum needs to be sanded at the weld to remove oxidation.

Thin metal is harder to weld than thicker metal. Aluminum is a bit like soldering with lead. The heat setting is very important. I like to set the dial on the welder with the foot pedal all the way down so it barely has enough heat to weld. After welding a few minutes heat builds up now slowly release the pedal to reduce the heat.

Welding aluminum is a bit tricky everything has to be just right and it takes practice. If you get the metal too hot it melts a hole in your part. If it is not hot enough it looks like little blobs of metal stuck to your part. Aluminum melts at a low temperature and aluminum has a high heat transfer rate that sucks all the heat away from the weld spot.

I have a hard time welding aluminum 1/16" thick but I know better welders than me can weld this easy.

I hope this information helps. Miller makes a nice small hope welder. Go to an INDUSTRIAL WELDING SUPPLY STORE they have lots of welders and they can give you good information. Most other stores only sell welders they have no clue how to use them. The local IND WELD SUPPLY STORE here will take you in the back and let you weld with several different welders to see which one you like best for our application. Not only is this good to learn what works best for you they teach you how to weld aluminum. The tell you about the different gasses, the tips, the tungsten rods, the feeder rods, heat, setting, etc. It is like free welding class.

 

[dr pepper]

The hf start is usually a marconi oscillator with a spark gap, and couples to the tip via a transformer, if you see a spark chances are it ok.

Sounds like you need a true ac weld set, an ac set is able to adjust duty cycle, also they have a clean function which keeps the electrode from fouling.
With practice though, maybe lots of it you'll be able to get an acceptable weld with a dc set.

 

[shortbus=]

Sounds like you need a true ac weld set, an ac set is able to adjust duty cycle, also they have a clean function which keeps the electrode from fouling.

Not sure but that isn't quite like how the newer AC Tig's with freq/duty control work. Or at least not how they were explained to me. The variable duty cycle is really being oscillated between plus and minus DC polarities. So it isn't a "true" AC. The older AC Tigs I've used over the years couldn't vary the duty cycle because the were "true" AC. They bought a high end Miller Tig right before I retired, and that explanation is how the Miller rep said they differ, between old and new.

 

[dr pepper]

I was classing pos and neg squarewave as ac, strictly speaking it is, however I nkow what your saying in the world of fabricators ac is what comes out of a mains transformer.
The positive half of the cycle gives you the electrode clean, and the neg side penetration of the base material, you can tell when clean has been used as there is a dark line each side of the weld (depending on gas used), some sets dont specify 'clean' on the panel, miller for one call it 'balance' same thing.

If its any use to you shawn I built a hf start to run from 12dc (for a 4x4), at the time I was looking at some that ran from 240v and used very little parts, let me know if your interested.

 

[ShawnR]

Thanks for the input. Thanks too for the offer Dr pepper. I am good with this setup for now. All my work (play) is in my shop.