Multiplaz-3500 Evaluation, Part 12: Comparing the Welding Torch
DISCLAIMER!
Let me emphasize that I will not be able to tell you whether the Multiplaz-3500, or any other piece of equipment, will be a good investment for you. Only you can decide that. My intent is to provide as much factual information as I can about the Multiplaz-3500 so that others in our company can make an informed decision about that. The company has no objection to my sharing the information with you as long as I leave their name out of it and make it clear that I am not endorsing any particular product.
DISCLAIMER!
As mentioned in Parts 05 and 06 of this Evaluation, comparing units using performance standards (i.e., how well do they do a certain operation) is usually more satisfactory than comparing units on the basis of design. In the case of the Multiplaz-3500 welding torch, comparing units using performance standards is really the only choice, as I do not know of any other constricted plasma welding torch designed for manual use that is still on the market. Constricted plasma welding torches are widely used in industry, but all of them tend to be fully automated in order to make the best use of of their properties. From about the middle 1970s until about 1990, there was one other such torch that was marketed as a manual torch. It was produced by the Linde Division of Union Carbide, the company that invented the constricted plasma torch. (See Part 01 of this Evaluation.)
That torch was called the “Plasma Needle Arc Torch” and was designed as a sort of miniature version of a conventional (and much more powerful) commercial constricted plasma torch. The torch is much more complicated mechanically than the Multiplaz-3500 welding torch and only uses gases. The design of that torch, and of most commercially used constricted plasma welding torches today, is basically the following:
The cathode is a pointed tungsten electrode, similar to a traditional TIG electrode. The pointed end of the electrode is surrounded by, and centered in, a copper nozzle with a small orifice (hole) just ahead of the point of the tungsten. The plasma gas (usually pure argon at a low flow rate) flows between the electrodes and out of the nozzle. A pilot arc is struck between the two electrodes by moving the tungsten until it touches the copper nozzle and then withdrawing it. The copper nozzle is surrounded by a second nozzle that guides the shielding gas (usually a mixed gas at a high flow rate) through a gas lens and toward the workpiece. Unlike the Multiplaz-3500 welding torch, this torch does not function as a heat source with only the pilot arc. The pilot arc is only that: a pilot arc for the transferred arc. The pilot arc in the “Plasma Needle Arc Torch” was operated from 3 A to 7 A DC electrode negative (DCEN) and the transferred arc operated from 15A to more than 100 A DCEN. The whole assembly was water cooled. A very complicated assembly indeed, and an expensive one. It worked well, especially for thinner material. But by the 1990s it could no longer compete with the capabilities of the improved TIG torches and switched power supplies, and so was discontinued.
In fact, this is still Miller Electric’s opinion today. When asked whether Miller would consider making a small constricted plasma torch welding system, the answer was that they feel that there is nothing that such a system could do that a modern TIG or MIG system can’t do better and at a much lower cost. So, at least in Miller Electric’s opinion, the appropriate units to compare with the Multiplaz-3500 welding torch are their small MIG and TIG units.
When one considers the various manual electric arc welding systems available in the market today, the one unique feature of the Multiplaz-3500 welding torch is the ability to use a liquid, rather than a compressed gas, to produce a smoke free plasma. If manually arc welding steel without compressed gas is important (or essential) to you, then you basically have 3 choices:
Stick welding
Self-shielding flux-core MIG welding
Multiplaz-3500 constricted plasma welding.
The problem with the first 2 choices is that they produce lots of smoke. Flux-core MIG actually produces less smoke than stick welding per pound of metal deposited, but MIG puts down metal a lot faster (~10 times as fast), so the rate of smoke production is higher for the flux-core MIG than for the stick welding.
Let me also point out again, as I did in Part 10 of this Evaluation, that the absence of smoke does not mean that there is any less toxic vapor being given off. The toxic vapors are given off primarily by the hot metal in the workpiece and the filler rod. In fact, the smoke can actually reduce the concentration of some of the toxic vapors before they reach your lungs. In any event, you really don’t want to breathe any of this stuff. Protect yourself by breathing as few welding fumes as you can.
If you want no compressed gas and no smoke, then you should look seriously at the Multiplaz-3500; especially if you weld mostly mild steel. If the use of compressed gas is acceptable, then MY PERSONAL OPINION is that you will be more satisfied with conventional technology, especially MIG. Regardless, try to test the unit you are interested in before you buy. That may be difficult with the Multiplaz-3500, as there are a lot fewer around than there are MIG units. If you are desperate, send me a private email. We may be able to arrange something for the cost of transportation from me to you and back again.
to be continued
larry lee
