MIG welders

This page provides general advice for safe use of the PS1 MIG welders. For details regarding specific machines, see the individual pages:

• Millermatic 252 has the highest output in its class (250 A at 28 VDC). Can weld up to 1/2" steel.
• Lincoln Electric 3200HD can weld up to 5/16" steel.
• Hobart beta-mig 200
• Lincoln Electric 125HD WeldPak
• Lincoln Electric 100 WeldPak

General operation

Most of the PS1 MIG welders are 20% duty cycle, which means we can only weld 2 minutes out of every 10 minutes at maximum settings. If you weld for 2 minutes, wait 8 minutes for the welder to cool.

MIG welders generally have two controls, one for voltage and one for spooling speed. Every welder comes with a set of guidelines for setting these controls based on the the thickness of the metal you are welding, the gas being used, and other variables. Usually these guidelines can be found on a chart either on the outside of the welder or on an inside panel.

We use 75% argon/25% CO2 gas. We use standard 0.030" wire (not flux core).

Welding tips and contact tips are consumables. You can usually find spares inside the welders.

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Setting up

1. Pull out the machine.
2. Remove the welding tip and clean out with the pliers that have files on the outside of the jaws.
3. Use a wire brush to clean spatter off the contact tip.
4. Put the welding tip back on the gun.
5. Check inside the welder to make sure it's wired for MIG. There's a diagram on the inside of the case. This should not change but can.
   1. The reel of metal wire size should match your recommended diameter.
   2. Wire adjustment is much like the 3D printers' - it flips up and has a tension holder
6. Determine and set the appropriate values for voltage and wire speed.
7. Plug in the welder.
8. Cut the wire tip using the pliers to the recommended length. You usually can get an appropriate length by laying the cutting blades of the pliers flat against the welding tip.
9. Open the main gas valve on the tank. Check that the gas pressure is above 500PSI. If it's below, press the button on the left wall that will tell Ron to order more gas.
10. Adjust the secondary valve so that the pressure reads 10 - 15 CFH (the correct pressure should be marked on the gauge).
11. Attach the ground clamp to either the table or the part, depending on what you're doing.
12. Close the screens behind you.

Use

• When not welding, rest the gun in the holder provided on the welding table to prevent accidental contact.
• Check around periodically for stuff you set on fire. This thing puts out hot sparks. I set a rag on fire the first time I used it. I was confused why the authorizer had brought a smoldering rag for authorization - nope, that was me.
• You may want to brush the joints before welding. Be sure to pay attention to the labeling on the metal brush - steel only.
• It may be a good idea to tack both ends of the parts being welded.
• Make sure there's no crimps in the tube feeding the metal wire. It should be as straight as possible.
• Ideally you would weld at about a 45° angle.
• If welding something perpendicular, you're trying to make a puddle (bead) that equally touches both parts. You'll angle it towards the top piece slightly more.
• Yell "Welding" before starting.
• Remember the duty cycle. Most machines can operate 2 minutes for every 10. That means you can only use the machine for 2 minutes before taking a break to let it cool down. In practice you usually won't have a problem with this, but for longer, and multiple welds, pay attention to this.

When Done

1. Turn off the gas.
2. Set the spool speed and the voltage to the lowest levels possible.
3. Purge the gas by pull the trigger until the PSI reaches 0.
4. Cut off the extra wire you just fed in the above step.
5. Unplug the machine.
6. Coil up the gun and ground clamp and put back the machine.
7. Brush off the mess from the table and then sweep, like the fine, upstanding citizen you are.
8. Put away anything else you got out, like metals, gloves, face mask, clamps, magnets, etc.

Safety

• Wear natural fibers (cotton, wool) only. The welder puts out sparks and can melt synthetics onto your skin.
• Wear closed-toe shoes, unless you like setting your feet on fire.
• Cover all skin - the welder puts out a lot of UV light. You'll get a sunburn, guaranteed. Plus, you can get burned.
• It's a good idea to have a hat or something under the face shield, as sparks will go onto the top of your head.
• There are two screens on wheels - arrange them to block UV light from going to the rest of the shop.
• Use thick gloves and a face shield. The face shield for MIG is pretty handy, it darkens when you start welding.
• Yell "welding" before starting so anyone sneaking up on you is aware to avert their eyes.
• The piece will be hot for a long time after you welded it. You can grab it with tongs and dip in buckets.