My history in welding: I first learned to weld around 2004 from a friend with a MIG welder that specialized in hand-railings and other endeavors for work. I asked for a quick lesson so that I could attach an old snowplow to my huge steel bumper of my ’67 Dodge Powerwagon. After trying to sign up for the Ti, then Steel, TIG UBI framebuilding classes 2 separate times 5 years apart and having to bail out at the last minute both times because of a new job (yes, TWICE!), I missed out on getting an earlier start down this framebuilding path. So around 2005, I was able to take a short after-work welding class at CU Boulder in their machine shop. It was mostly MIG and gas-welding, we had a full 30 seconds on the TIG machine — no joke. Not until 2010 did I get to take a class from a framebuilder in Denver who taught me how to TIG weld, or at least started me on the path to learning to TIG weld. If I had to do it all over again, I’d have told my first future boss that I WILL be gone for two weeks immediately after being hired, so I could have taken that UBI course back in 2001. But I likely wouldn’t have gotten the job…
Anyways, so now what? I’m still struggling with the TIG torch but feel like i kinda know what I’m doing now. For some reason, my first teacher had a prejudice about using the pulser function to TIG weld bike frames. He taught me that if you use the pulser, you are supposed to dab the rod at the peak amps as you move the torch along the joint – not lay the rod in there so that the torch eats it up as you move it along. So at 1Hz, this was not too hard, but at 2Hz it was extremely hard (and still is) not to get the rod stuck in the puddle once the cycle went to the base amps. Furthermore, I was taught it was basically ‘cheating’ and easier than not using the pulser to make a smooth stack of dimes bead. He recommended that I learn to weld the real way first, then if I felt I needed to, then start using the pulser. So, I thought (ignorantly) that nobody used the pulser to weld bike frames and if they did they were taking the easy way out. Oh my, how wrong was I!?
The pulser helps many framebuilders achieve that perfect, consistent, even-width and seamless looking stack of dimes weld. It’s likely that if you peruse the YouTube’s of your favorite builder (if they have any) you’ll see the on/off flashing of the TIG welder instead of a steady glow of light coming from the tube joint. There’s really too much to talk about why one is better or worse than the other, but I am starting to believe that the pulser is a superior method of TIG welding, especially on thin-walled bike tubing. There are many professional sites out there to tell you the same including the Miller website and other pro framebuilders on the message forums. The main gist of the reasoning is that using the pulser gives a flash of high amps followed by a cooling period where the metal can fuse but not overheat in the same way or as easily as when not using the pulser. The settings one uses are extremely important obviously, but in general, when using the pulser you should get a more consistently homogenous fusion of the two tubes, less possibility of the bead itself being a stress riser, and less tube distortion. [Let me say that you can obviously weld bikes just fine without the pulser and they’ll last a very long time. I doubt there’s any long term studies showing a comparison, and I’m doubtful that if you’re a good welder without the pulser that it’ll significantly (or at all?) reduce the longevity of your frames.]
What i do: What I have done on my bikes is NOT use the pulser since that’s how I learned and how I can actually get a good bead as of yet. But if and when I needed to do a second pass to fix a poor looking (poor penetration weld) I’d turn on the pulser and not only make the bead look better but pull the tube in the direction of the weld I just passed. However, I would not use more filler rod and just pass the torch over the bead. It’s not a good practice to continue, but if you don’t starve the weld (lack of filler rod) on the 1st pass, you should be OK with a quick second pass to pull the tube (and frame) more into alignment. This is not just my hot air, but was said on a framebuilding forum by the same person that I got a quick TIG welding lesson from last week when I picked up my new frame fixture. (I’m not sure he said it’s OK to not use additional filler rod though when using this “technique”.)
What I learned from Don: I hope he doesn’t mind me paraphrasing his advice, but please take this as just that: advice from a pro to me. Realize that I may have heard it in a different way then it was intended, or just plain incorrectly. I told Don that I don’t use the pulser and he suggested I should since I have been getting some head tube and BB ovalization when welding my frames. Nothing probably out of the ordinary but I have nobody to help me determine that either way. I know warpage from laying a TIG bead is common, and the extent depends on how tight your miters are, how thin the tubes are, and how hot you are laying down the bead. Anyways, here’s what he recommended I do for using the pulser (keeping in mind this may be nothing earth-shattering or even new for most of you that learned how to weld in a better way than I).
1.) You want to PUSH the filler rod into the tube joint by rolling the rod between your fingers. The thumb simultaneously pushes the rod forward into the puddle as well as twists against your index finger while the other fingers are holding the rod straight. This keeps a constant tension and movement of the rod into the puddle as you move the torch foreward. This is pretty standard filler rod hand technique but it is something I never learned to do and therefore don’t do. I just have been dabbing the rod into the puddle as I move the puddle along the joint, whether I foot-pulse or keep a steady amperage. Since the tube passes aren’t very long, I haven’t felt the need to learn the above technique since I’m not going through a ton of rod.
Believe it or not, this was the biggest eye-opener for me. I have never moved the torch over the tubes and even just laid the filler rod there for the tungsten to melt along-the-way since I was taught that was bad form. Having someone that gets such perfect welds (Don) tell me to use the pulser and PUSH the filler rod into the joint (and puddle)…well, that was totally counter to my current way of thinking.
2.) Keep moving the torch at a constant, and relatively quick, pace along the joint. The stack of dimes happens naturally when the pulse cools the puddle each cycle. When not using the pulser, the stack happens when you add filler at a given interval along the joint and the puddle cools as you move along. I have also paused when dabbing the filler rod into the puddle while moving the torch (pausing only for a milisecond) to get a certain rhythm going and get a nicer stack of dimes. Anyways, this isn’t anything new but part of the whole picture — move the torch steadily along ‘eating’ up that filler rod along the way.
3.) Don’t let the filler rod cool outside of your gas lens (outside of the argon shielding gas). I have always removed the rod to let the puddle cool and let the argon get its full access to the work, but you should keep the rod under the cup protected from contamination. Some leave the rod in the puddle but it would seem to me that that doesn’t work for bike frames when you’re laying 4-6 separate/opposite passes on one tube joint. Proper welding sequence is not to go all the way around the tube at one continuous pass in one direction, but to do something like 12-3, 6-9, 3-6, 9-12, or the like. The welds will then put more equal tension on the tube and keep it in better alignment assuming equal heat control and miter quality.
The other things he said were mostly just confirming stuff I already knew so I don’t remember them as well as the above 3 things. But the pulser settings are something of an enigma for me and I think most new welders. I’ll just come out and say that I have dinked around with the settings a LOT and still haven’t found anything that works really well. Having said that, I usually use something like this:
80 peak amps, 12 base amps, 45% of peak, and at a rate of 2HZ.
Each TIG machine has it’s own way of saying the same thing for these settings so what mine are may have to be translated into what your machine says…i don’t know. But for thicker-walled tubing, I go higher on the peak amps (90-100) and raise the base amps a few too. For 0.6mm walled tubing, I’ll go colder. But again, I just truly stink at using the pulser as you’ll see from the above photo. The left-most weld is my normal way of doing it (no pulser) and the right two practice welds are using the pulser after tacking it in place.
If I’m going to switch to using the pulser full time, I have a LONG way to go! I couldn’t get the pushing the rod into the puddle thing…it’s so counter to what I usually do that I was slowing my pace and overheating the metal and also starving the puddle at other times. Then it’d blob up on the rod and add too much rod the next pulse. UGH…