Sooooooooo, I have had this machine for a few months now and have been ****ing around with the settings on AC to see what all the hype was regarding the variable polarity feature. I have decided that I really like the VP capability but I would also like to stress that by no means is it necessary to successfully tig weld aluminum. I think Miller actually dropped the ball BIG TIME by doing away with the Dynasty 300. They may have something else in store but as it sits, there is a huge gap in their inverter tig lineup between the D200DX and the D350DX.
For those not in the know, the Dynasty 350 has 50 more amps and a few more bells and whistles. The real improvement was supposed to be on the AC side where you could independently set the amperage values for each half of the electrode positive and electrode negative cycles. The values can, according to Miller, be set to "provide enough cleaning while putting more amperage into the part". It is also supposed to give better penetration and faster travel speed. Tungsten life is also supposed to be better using more EN amperage.
This is a tool holder I made for my lathe this afternoon. I used the VP feature on the 350 to make these welds. The settings were as follows:
Machine set at 250 amps
EN Amperage = 268
EP Amperage = 143
Balance = 75
Frequency = 120
3/32" blue tungsten using a gas lense and #7 cup
The material was 1/4" 6061 and the filler was 1/16" 5356. The ratio of EN to EP was 2 to 1. What you do is set your EN amperage to 200 and your EP amperage to 100. Then, set the welding amps to whatever you want and it will maintain that 2 to 1 ratio. The 2 to 1 ratio is also just a recommended starting point. You can basically set the thing to any ratio you want for any given welding task. The balance setting will also have an effect on the "average" that the welding amps end up at.
The first thing noticable was that the puddle formation on the 1/4" material was almost instantaneous. It took maybe 3 seconds before I was ready to add filler and then it was just "get after it". The etched cleaning zone was also substantially smaller than it would have been on the 300 with the same settings, sans polarity adjustment. The really remarkable effect was the lack of tungsten degradation. I welded 6 two inch long beads and the tungsten looked like I had just sharpened it. That would never have been the case if I were using the 300DX or a conventional machine. I pretty much had the pedal maxed, or slightly less, for this project.
The pics are as follows:
1. The toolholder I was making. there are 3 two inch long welds on the top and the bottom.
2. Weld close-up. The wet in at the toes on these settings was awesome.
3. Another close-up of a different weld at a different angle.
4. Tungsten close-up after the 6 welds.
5. Same as #4.
I have more work and testing to do but my preliminary results are super positive. If you have any questions, I will do my best to try and answer them.
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11-09-2007, 10:18 PM #1
Dynasty 350 DX: Variable Polarity