Tuesday, April 15, 2014

Getting a better electrical ground for welding

Label says it's made in China 

I found the above copper wool in a store and snapped up a pack. When I reached home the first thing I did was to grab a big magnet and check whether this is pure copper or just plated. What do you think? Well, it clung to the magnet but not as strongly as ordinary steel so I suspect the base metal is some type of stainless steel.

Well copper or not, metal wool makes an excellent "sponge" to create lots of small good contact points between the ground clamp and the workpiece to be welded or the welding table. I now use the copper plated wool whenever I weld. It gives me greater confidence while welding in that it completely eliminates one variable--bad ground connection--when the weld isn't going well.

Couple of months ago I hacked my MIG ground clamp by cutting and stripping several feet of AWG#14 solid copper wire, folding it at the middle and then looping that around the screw that secures the lug of ground cable and then finally winding the rest of the wire around one of the jaws of the clamp. The idea is to have the copper get clamped onto the workpiece.  The wool now further increases the area of contact thus further decreasing electrical resistance.

How I use the copper wool. It gets squished between the copper-wire-wound clamp and the workpiece. In this example I've folded the wool around the flat iron so that the bottom jaw of the clamp also presses it into the bar.  

This wool is rather course and I would think that a finer one would be even more effective. And given a finer grade's greater pliability, it can be folded and pressed/crushed far easier than this one I'm using.

Hat tip goes to Jody Collier of weldingtipsandtricks.com. In one of his vids he talks about using flexible heavy gauge welding cable and stripping the insulation off and using that with the ground clamp to increase the surface area in the interface between clamp and work piece. Jody has some of the best if not the best welding vids on Youtube. His tips are beyond valuable. Go watch and subscribe.

Monday, April 14, 2014

My MIG welder

I got this CIGWELD WeldSkill 150 second hand late last year. The wire speed control is infinitely variable (you can set it to 7.75 for instance) but the voltage control has detents which allows only 4 settings. The machine works very well for 1/16" thick steel and thicker. However, I still can't get it to properly weld thinner gauge sheet steel. I can't get good continuous welding with wire speeds lower than #7 even with voltage turned down to its lowest setting of #1. Not yet sure why.

Auto-darkening helmet in the background and an AC stick welder which I haven't used in months

Load with a new spool of 5kg 0.9mm flux cored wire

Red and black wires need to be swapped depending on whether you're using flux cored or solid wire

Flow meter for the shielding gas when I'm using solid wire. The masking tape with blue mark indicates the 10 liters/min (equiv to around 20cfh) level. Did this to make sure I don't set the flow incorrectly. I'm using 80% argon 20% CO2. Can't find 75/25.

LPG bottle dollies

The LPG bottle we use has an empty weight of around 1kg and filled weight of around 25kg. So lifting the cylinder isn't really that good for aging backs. I usually lay it on a thick rag and drag the cylinder when I have to move it. Gets the job done with much less strain but it isn't the most efficient nor elegant method. I recently saw a round dolly at a home depot and instantly decided to make one myself. It was one of those "why didn't I think of that?!" moment. Ah well.

Design #1: Square Frame

With a good number of second hand 1/16" x 1-1/4" square tubing (but actually 1-3/16") laying around I chose this as the material of choice for the dolly. I cut four pieces of 9-5/8" lengths with 45-degree miter cuts using a 14" chop saw. The bottom of the gas bottle has a nominal outer diameter of 12" and inner diameter of 10". The diagonal of a square is equal to L√2, where L is the length, so with each side 9-5/8" the diagonal comes out to around 13-5/8" which is long enough to accommodate the 12" diameter of the cylinder.

2-1/2" lengths of angle irons were cut and welded to the inner corners of the square. These prevent the bottle from slipping off or from being knocked off the dolly. One side (the top side) of each angle iron piece is miter cut at 45 degrees. This diagonal eases mounting of the bottle on the dolly since if the cylinder lands on that incline it can slide down (or push the dolly off a bit) so the bottom of the bottle lands on the corners of the platform.

1" diameter casters were tack welded to the dolly. Their mounting plates were simply too thin and had too little surface area to weld continuously so they're held by a good number of tacks. Had a problem with one of the casters--it won't swivel freely anymore. A dingleberry must've landed in the ball bearings while I was MIG welding the caster to the frame. Lesson learned--shield moving parts and protect sensitive components from spatter.

Photos shown it already built and painted with red oxide primer.

Brought the dolly to my sis when I visited her and since she liked it and found it useful I left it with her. Can't find any photos of it after painting it black. Must've forgotten to shoot one.

Design #2: X-Frame

Since I need a dolly for myself I had to build another one. But  I found the aesthetics of the above design more than wanting. Looking at it puts a pout on my face. Surely there are far better looking designs I told myself, although I had to work within constraints--my greenhorn abilities, ease/difficulty of fabrication,. limited equipment (no tube bender, press brake, band saw, etc.), and materials available in the garage.

Still using 1-1/4" square tubing,  I cut one 14" and two 6-3/8" pieces. MIG welded the two latter to the center of former to form an X. Using a 4" angle grinder I ground the butt joints flush with the surface while leaving the fillets as they are. Used the same-sized casters as with the first dolly but with nylon wheels. Black plastic end caps close the holes on all four ends.

Because of my experience with the first dolly--having a dingleberry or two land and weld themselves in the bearings in one of  the caster's swivel mechanism--I used masking tape and some scrap paper to encapsulate each of the casters to prevent any spatter from getting into where they shouldn't. The paper did catch fire a couple of times and I put it out simply by patting it with my leather-gloved hands. After tack welding the casters onto the frame I removed all the (partially burned) tape and paper and wrapped the casters again right before painting. One coat of red oxide primer and two coats of yellow quick dry enamel.

Future Make

Except for the general  X shape, am still not satisfied with this second build. I was working within material constraints. I'd rather use 1/8" x 2" flat bars as the platform and then weld on 1/8 x 1" flat bars as vertical supports, thus forming a T section. And I find the 1" casters too small for ease of rolling and too flimsy for the heavy load. 1-1/2 to 2" diameter wheels would be far better. And instead of casters with mounting plates that have 4 holes for screws, I'd use something like these and have those vertical pins go under the LPG bottle to secure it in place on the dolly. And if it isn't yet obvious, the tack welds on the casters are absolutely godawful! They're hideous. I'd rather not resort to welding them unless they've got much beefier steel plates.