Sunday, November 6, 2011

Welding 101: I have no idea what I'm doing

What the fuck is this thing

The Millermatic 211 is a MIG welder. You press the trigger on the gun and it simultaneously feeds wire, vents inert gas, and creates an arc that generates so much heat it melts up to 1/2" thick steel.

The device is actually pretty straightforward to setup: Plug it in. Take the electrical clamp and attach it to whatever you're welding. Put on a helmet and gloves. Turn on the gas. Turn the machine on. Get in position. Press the trigger and try not to be startled.

The wire is fed from a couple pound spool that you put in the side of the machine. It's got a bunch of equipment to auto-feed that spool. Even auto-feeding the first time up into the gun was easy.

The helmet is fairly advanced. It automatically darkens when it detects UV light. Both the sensitivity of the darkening and the opaqueness can be adjusted. It need batteries. One interesting note: Looking at the sun is also enough to set it off. I still get a bit of a sun-spot on my eyes if I stare at the sun through it.

The gas can is 75% argon and 25% CO2. I have no idea why this mixture. The main goal is getting something inert. Why not all CO2? Why not all argon? I forget how much the tank holds but I do know that when I first slapped the regulator on it the dial registered 2200 PSI. Every square inch of the inside of that tank is holding back 1 ton of pressure. It's probably pretty thick. Still, don't drop it. Since the gas and wire didn't come with the welder I picked it up at a local welding supply shop. I get the impression this is mostly what they ever sell. The other gear was notably over-priced.

The welder itself only has two dials. It has some sort of auto-feeding circuit that means you shouldn't even have to touch one of them. That would be the feed-rate. The other dial is the thickness of the material you're welding. I can only crank it up to 3/16" before I'm supposed to be using a 220 outlet.

How hard can it be...

Fumbling my way through it

Step 1: Don't forget the gas. For the first weld, the one that looks cratered, I forgot to turn on the gas. Aside from looking like shit it is actually weaker. I was able to pull the weld apart. The two below it that are smooth and shiny are actually correctly done. I think in both instances here I've got the power turned down too low, however.

I'd previously cut holes in the angle steel and proceeded to weld the bearings into place by putting a piece of angle steel and doing my best to keep them in place. The originally cut holes, however were not perfect fits, nor were the measurements. Combine that with my inability to place the bearings and I got a final product that essentially didn't work.

So I opted to use the power of the milling machine. I made a set of holders out of wood. Milling wood is both simple and fast. This will allow me to hold all the parts exactly in place while I make the welds. Once I've got spot welds on everything I can go back through and re-weld the hell out of all of it.

In the end I worry I didn't give enough tolerance. I noticed after I'd done all that welding that one of the holders was off a bit. I'll have to wait to get more skate bearings to find out.

I've also considered just replacing this whole ridiculous setup with actual manufactured bearings but that immediately jumps the cost up to about $300 for a set (at least when I order from the generally over-priced McMasterCarr). I'd like to see if I can do this for more like $40. I'm willing to take another shot or two at it even after this.

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