Welding Tips and Tricks

Multiplaz-3500 Evaluation, Part 09: Testing 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!

The performance of the Multiplaz-3500 welding torch was measured by moving the torch manually to weld butt, lap, and tee joints in the flat position using no filler rod (autogenous welding). It is felt that this gives the best view of the puddle and the best determination of penetration. Welding was done on 1.5 mm (1/16”) to 10 mm (3/8”) thick 1018/1020 mild steel and 304 stainless steel. The completed welds were visually examined for surface oxide, porosity, etc. The welds were then sectioned at right angles with a band saw and the pieces were visually examined to determine the degree of internal fusion. A section of a butt weld of each thickness was tested by bending it along the length of the weld until the angle through the weld was 90 degrees or more. If the weld failed, the break was examined to try to determine the cause of failure (e.g., lack of fusion, crystallization, etc.).

Depending upon the thickness of the metal, the welding torch was operated either in Mode I (electrical arc internal only; heat carried to the workpiece by the hot plasma gas) or Mode II (electrical arc transferred to the workpiece). In mode I the plasma has a diameter approximately that of the nozzle opening (1+ mm) and a length of about 1 cm. Welding is similar to that using a very small oxy-fuel torch. In mode II the plasma is constricted to a diameter of less than 0.5 mm (0.020”) and extends to the workpiece. The arc transfers when the distance between the nozzle and the workpiece is reduced to about 6 mm (1/4”), but once transferred the arc can be lengthened to about 12 mm (1/2”) before it drops back to Mode I. Welding in Mode II is quite different than welding with a TIG torch. The small diameter of the arc makes the local heating intense and it takes some getting-used-to to keep from overheating the puddle. On the other hand, one can get complete fusion to a depth of more than 6 mm (1/4”) between two pieces of 12 mm (1/2”) thick mild steel in a butt weld with no clearance. With a backing bar to keep the metal from melting out of the joint, one could probably get complete fusion for the full depth at maximum current (Mode II, Position 6).

Inside corners are a problem (tee joints) because the nozzle is relatively large and the transferred arc jumps to the nearest surface, rather than into the corner where one wants it. (Of course, this is true for many other torches as well.)

The appearance of the surface depends upon the metal. For mild steel, the surface looks much like that of a weld made using an oxy-fuel or MIG torch. There is an oxide coating, but it cleans up easily with a wire wheel. For stainless steel, the surface looks significantly more oxidized and porous, but the fusion below the surface looks O.K. The lower thermal conductivity of stainless steel makes it more difficult to keep from overheating the puddle with the intense, small diameter arc. Also, because of the other elements incorporated in stainless steel, it is much more subject to crystallization after heating, and especially so after overheating. As a result, the welds on the stainless steel not only looked worse, but also were not as strong. Sections of the stainless steel welds all cracked at less than 90 degrees and showed crystallization at the points of failure. None of the welds of the mild steel failed, even at much greater than 90 degrees.

The welding torch is less tedious to use than the cutting torch. One must still go through the “cool, refill, restart, stabilize for 2 or 3 minutes” cycle after each 10 minutes of welding, but the cathode-to-nozzle distance does not need to be readjusted each time. In the welding torch, the cathode-to-nozzle distance for starting the arc is about the same as the distance for welding and it normally requires little, if any, adjustment. The life of the cathode and nozzle were found to be in excess of 10 hours, in agreement with what is stated in the Multiplaz manual (10 to 20 hours).

As mentioned in Part 01 of this Evaluation, when using the welding torch in Mode II, one must use a ground clamp on the filler rod in order to protect the operator from electrical shock. The filler rod ground clamp provided with the Multiplaz-3500 unit is rather large and awkward. If you are used to feeding the filler rod by sliding it between your fingers you probably will not like using the ground clamp supplied. I suggest a small alligator clip on a more flexible (but same current capacity) wire instead.

The tables in the Manual that give recommended welding conditions are somewhat confusing until you realize that no entry in the “flux” column means that you DO need to use flux. Only if it says “none” is it suggested to weld without it. The recommended fluid is (50% water / 50% alcohol) for mild steel (and under some conditions stainless steel) and (40% water / 60% alcohol) for stainless steel under most conditions. We used isopropyl alcohol in all of the welding tests.

There is a design flaw in the torches that causes a problem with the welding torch. The nozzle is held in place by a steel clamp that goes over a ridge at the base of the nozzle and then screws into the torch body. For some of the nozzles, the ridge is not wide enough and the clamp seats before the base of the nozzle is fully sealed. As a result, some of the vapor from inside the nozzle leaks out around the base of the nozzle. With the cutting torch, the vapor is normally just steam and is only a minor nuisance. But with the welding torch, the vapor contains alcohol which ignites from the plasma and the hot work piece. This does not affect the welding, but the flame extends out a few inches and the smell of hot alcohol vapor is quite noticeable.

We did not try to weld aluminum (using flux) because in the welding that we do, the use of flux is not allowed. Residual flux (always present within the weld, no matter how much you try to clean it off after welding) makes the weld more susceptible to corrosion. This cannot be tolerated in the welds that we do, so we use AC TIG for aluminum and DC TIG for most other metals.

to be continued

larry lee

Larry, have you tried using a cutting tip nozzle with the smaller orifice as a welding tip with the 50/50 solution on Mode 1 at the lowest setting? Leave the cathode adjusted as if you were welding not cutting.

I got to thinking about this welder and I was always getting way too much heat for some of the jobs that I was doing, so I wondered what would happen if the nozzle orifice was smaller. This would be the equivalent to selecting the proper sized tip on an oxy/actylene torch. Well, to my surprise I finally got what I was looking for, a torch with plenty of heat but within the heat range for work that I was trying to do. At first, I thought that the smaller orifice would just make more pressure and not work like I expected it to, but by selecting the lower settings, it worked just fine. I kept the voltage under 170volts. (Just for fun, I tried to tame the torch even further by running it on straight water for welding. This cut the heat down even further and allowed me to weld some pretty thin stock.) Photos attached.

The other thing that I noticed was that the nozzle orifice loses its nice round shape from time to time and gets a bit of a buildup inside. I use a pin vise with the appropriate sized drill bit, to ensure that the nozzle orifice is always clean and round. This is most noticeable when the flame starts to form a strange shape. I listen to the sound of the gases coming from the nozzle and when its adjusted properly it suddenly goes quiet. Watch the flame color and make sure that there's no green tint at your setting. (this is copper burning). The gas flame should be a nice blue color, (sometimes white) and the noise level of the gases should be minimal. If the torch is set wrong, it will be as noisy as a Victor gas torch.

I can see having to replace the cathodes when they wear out, but the nozzles can easily be welded over and redrilled to any size that works for the application at hand. This torch is designed to weld copper and the nozzles are made of copper, so why waste copper by replacing nozzles, just recondition them. I plan to experiment with a wide variety of nozzle orifice sizes to see what works best for me.

I already know that as a plasma cutter, this torch is lacking but as a clean burning fusion torch, I'm still very impressed. I haven't tried stainless yet, but now that I've figured out how to control the heat a bit better, I might give it a try. Its all experimental on my side. This is a hobby for me and I'm a very curious person.

I weld in my basement and there aren't any fumes. The smoke detector is within 8ft of my welding area and its never gone off from welding. (I've set it off a few times with some of my electrical experiments.) The torch is clean burning and I like this very much. BTW - There are 6 smoke detectors in my house at strategic locations. I feel much safer using this welder indoors, (compared to anything else) because there are no dangerous high pressure gases being used and I can shutdown the torch with the flip of a switch. When I'm done welding, I turn off the inverter and put the torch nozzle in a glass of water to cool it down. (This is standard procedure from the manufacturer.)

WerkSpace,

Thank you for your comments. I agree that there are improvements that can be made in the operating procedures that are recommended in the Multiplaz-3500 manual. However, for our testing we first test the torches as stated in the manual. My evaluation is also from the perspective of using a machine for commercial or production purposes. Hence, for each set of tests, we put a new cathode and nozzle on to minimize any effect of wear on those parts and to obtain the best results for the evaluation.

For personal use (and perhaps in production, too), one would, as you have said, try to clean up and reuse the consumables as long as possible.

I also agree with you about the advantages of not having to have compressed gas tanks for personal use. This is really the major advantage of the Multiplaz-3500, and for some it outweighs the disadvantages. My intent is to present as much information as I can and let each reader decide.

As for the issue about fumes, I wrote Part 10 of this Evaluation before I read your comment. I think that it gives my perspective on the issue.

Best regards,

larry lee

Thank you for the insight, Larry.
As a result of your latest post, I will cease welding of any type in my home.
Good ventilation makes sense, whether I can see or smell any fumes.
You are absolutely right, it's what we can't see that can harm us the most.