I got to play with the little machine last night. Got some nice welds with aluminum and 3/32" thoriated tungsten electrode pos. Biggest problems I had was trying to use too much current and too long of arc. Cerium electrodes did not like to run pos..they vaporized :) Still haven't opened the box to see if I can bypass the diodes on the final transformer for A/C .. looks like it should work but there are sens wires connected to the output that may cause some crazieness? The 1/16" electrodes work fine for steel electrode neg. They just don't clean enough for aluminum that way and cook with the other way. Next stage is to play with thinner pieces and see if I can do what I bought it for. Welding lightweight materials. Things it is lacking, Remote current control. HF arc starter/stabilizer A/C or adjustable square wave. Adjustable post flow. A good schematic so I can go in and change things :)
Thanks Ernie, What would the advantage of Lanthanated be over Thoriated in the same size for DCEP? I would have to order the Lanthanated as it is not stocked in either of the 2 welding stores here in town.
As far as the foot pedal all I need to decide is if I want it to be a set lower power with your foot off so you would push down to start the arc and release to go to your set welding power or full power with no pressure (or a set max) and decrease with pressure. The electrical part is no problem. It is the practical part that has me hangin fire right now.
And Tom, I can email a schematic or post it to the drop box. Gotta warn ya though it isn't much of a schematic. The entire control board is a black box and the inputs/outputs are not even named. I do plan to open it up and see if I can get more info from the board and could send pics of that later too. I plan to install a foot switch and see about wraping an HF tickler around the output filter inductor. I want to look into bypassing the output diodes as well but it may not be as simple as it seems. It appears to have some feedback leads from the output that may be messed with if it is outputing A/C. It appears they are sensing voltage rather than current though so it may not matter. Then there is the matter of the big inductor that needs to be gone for A/C and since that is the best place to hang an arc stabilizer coil I will have to couple that up some other way. Send me an e-mail and I will send you a scan.
Just fished a Earnie Ball Volume pedal out of my son's dump box. I gave it a good washing - I think excessive drink material was a dust collector :-)
So I scored it - It contains a high quality Pot - I haven't measured it yet. Two phone plugs provides the three connections - or a new connector added to the
1/4" Al metal 'box'. Two U shaped turned such to have two flats outside. It doesn't jump back when the foot is lifted - that is the why spring needed.
I have run DCEP on aluminum for the last 7.5 years at school , showing my students where aluminum welding started. I find that Lanthanted tungstens work better than any other type for DCEP.
A foot pedal that decreases your power as you push would be the reverse of every TIG I have used, but I suppose it may work.
Works for me :) I will order a box of the lanthanated Monday. So, if I understand this footpedal concept, I would mash the pedal to start the arc and slowly release as things heat up such that with my foot off the pedal it is running at the current I set for the normal running? Or do I need to set both high and low limits? I just can't see using it as the control for the current all the time as being very stable. As you re-position your body your foot moves around and your current goes wonky. I really appreciate your taking the time to gude me a bit here. There are no welding schools here or I would be there now :) The welding shops mostly tell me it is impossible to weld aluminum with DC :) After doing a bit of reading on the web I am wondering if this machine might be of the "Lift arc" type rather than a scratch start? I don't think I would know the difference really.
The most common way to run a TIG in a shop is with a foot pedal. In a normal TIG machine, the first bit of movement of the pedal triggers the contactor, which deliveres welding current to the workpiece, turns on the gas and initiates the high frequency start. As you push down your amperage increases. So you can start off low, and ramp up until your metal melts.
With a little practice it is quite easy to hold a very constant current level with your foot.
The way I run a TIG when weldingh stainless steel on location is to use the Sequencer built into my inverter machine.
I tap a button on the torch handle, and it initiates a sequence that starts with a preflow gas purge of 1/2 second, then initiates the arc with high freq at 5 amps, ramps up over 1 second to whatever my main amperage is set to, and then starts pulsing per my settings. A second tap of the button triggers the downslope over 3 seconds to 2 amps, shuts off te arc and delivers 20 seconds of post flow gas.
Now whenI owned a much simpler Maxstar 140, I just set the machine to the amperage needed for that material, opened the gas valve in the handle, and scratch started the arc on the metal. I would weld along the joint until I reached the end. I would then whip teh torch away from the weld to break the arc, return the torch to the previous position just as fast, wait til the tungsten had cooled, and turn off the gas.
If you don't have a foot pedal, then you need to have a pretty accurate idea of what amperage you need for what thickness of metal.
The basic rules:
1 amp per 0.001" of thickness for steel and aluminum, flat butt weld, full penetration, single pass.
Add 1/3 for inside corners. Subtract 1/3 for outside corners.
Subtract 1/3 for stainless steel and titanium Subtract 1/2 for bronze. Multiply it by 2 for copper.
So an inside fillet weld on 1/16" Stainless steel. would be...
1/16" = 0.0625" = 63 amps - 1/3 for SS = 42 amps, + 1/3 for inside fillet = 63 amps.
Oh and never use a filler rod thicker than your base metal if you can avoid it.
Do a google-groups search on my name in the archives for sci.engr.joining.welding and you will find all my rantings and ravings about TIG.
It's better to be a red person in a blue state than a blue person in a red state. As a red person, if your blue neighbors turn into a mob at least you have a gun to protect yourself. As a blue person, your only hope is to appease the red mob with herbal tea and marinated tofu.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.