MIG beginner and I need advice

[mrn2obelvedere]

Hello all,

So I am about to embark on my welding project this weekend. I purchased a Miller 140 a couple of weeks ago and I made some practice welds last weekend. (I know its the small one but I think it will fit my needs until I can afford something bigger)

All I can say is that compared to the other welders I have used in the past, this thing is super easy to use. The autoset feature kind of works, but the built in reference chart gets you very close on a variety of material thicknesses, usually I can just adjust the feed rate a little bit to dial in the weld after using the reference chart.

What I am planning to do this weekend is fabricate an upper shock crossmember and weld it into place between the rear subframe rails. I have to do this because the panhard mount on the diff has a clearance problem with the right shock, and thus I have to relocate the shock to the front of the differential.

As far as design I am planning to butt weld a 1.5", 0.080" thickness square tube to a .060" sheet, and then weld this sheet to the frame rails (which are probably a little thinner than the .060, but I am not too sure what is the exact thickness of the subframe material. If I get some time at work today I might sketch up a concept of this in solidworks and post it here to give you a better idea of what I have in mind.

The questions I have are:
1) What power/feed settings should I be using when welding two pieces of different thickness? Should I bias the power to suit the thinner or thicker material?
3) Are there any techniques you can recommend, like angling the tip to direct heat to the thicker piece?
4) Do you think it will be better to use this transfer plate or just directly weld the tube to the subframe?

[oestek]

You'll have to bias the power to burn the thicker material, and be careful not to burn through the thinner piece. I think there's an example of this technique in the second video on this page, which covers a bunch of MIG and TIG welding techniques.

http://v8tvshow.com/content/view/123/45/

Good luck, and I recommend setting up a few test pieces of the exact materials you plan to use to get the settings right.

[parsonsj]

Right. Set up for the thicker material, and roll the puddle into the thinner material. Your material thicknesses aren't that far off from each other, so you shouldn't have much difficulty getting a decent weld, if you've been practicing and using proper technique.

Be sure and check out Kevin's videos... they are excellent.

jp

[mrn2obelvedere]

Who is kevin?

[parsonsj]

kevin == Kevin Oeste, userid oestek, who responded before I did.

Which reminds me:

https://www.pro-touring.com/forum/showthread.php?t=50566

jp

[mrn2obelvedere]

So I got a chance to draw this up in solidworks and my idea looks like this:

https://static1.pt-content.com/images/pt/2010/02/ForwardShockMount-1.png

Note the following:
1)The cross member is 2X2 mild tubing, .083 wall thickness
2)The shock mount itself is fabricated from the same material
3)The screw spacers are .125" thick, .5" inner diameter, .75" outer diameter. These will be welded into place also
4)The end plates are 1/16" thickness (thinner than the tube, similar in thickness to the sub-frame rails)

The purpose of the end plates in my design is to make it easier for me to weld without burning through the sub-frame rails, and also to give an initial attachment point (hence the screw holes, I was thinking I could initially attach the frame with sheet metal screws and check for fitment, squareness, etc before really committing to welding it in.

Any criticism of my design is welcome. Thanks!

[Mathius]

Is it necessary for that crossmember to be bolted in place? I.e. does it have to be removable? Or did you include those holes for plug welds? I would weld it in place if you don't see a need for it to be removed to access something or remove something. I can't think of any reason to need to remove a cross member that's over your axle. Not like you're gonna mount your fuel tank there or something.

Mathius

[mrn2obelvedere]

I have decided not to bolt it into place. The only reason I had that idea was basically to hold the part into place before I commit to welding it in. However I have decided to remove the holes. Also, after talking with QA1 they very kindly gave me dimensions on the eyelets for their shocks and I designed around these dimensions. I went ahead and revised my design to better accommodate the type of loading the mount will see. Since the shocks are very much staggered from the factory, the mount needs to be designed with this in mind. You can see that the shape of the mount mimics the angle of the shock; this spreads out more of the load in the direction that it needs to be in. I'm about to go cut these pieces out right after I post this.

https://static1.pt-content.com/images/pt/2010/02/shockmountschematic2-1.png

[mrn2obelvedere]

Ok so I started welding this up over the weekend and I am discovering very quickly that welding a thick plate to a thinner gage frame rail in the overhead horizontal or vertical position is a very tricky endeavor. Please I need tips.

I have been trying this out using 1/8" blanks welding to some scrap sheet metal and it's a serious pain.

[DRJDVM's '69]

No expert here but..... set the machine for the thick stuff (ideally dial it in on some scrap first).... then concentrate your arch on the thicker plate and let the puddle roll down onto the thinner stuff....or you can quick "dip" it down onto the thin stuff and quick back up the thicker stuff. The goal is to try and keep the heat/puddle more on the thicker plate and let the heat of the puddle melt the thinner stuff

I do short sections at a time since the thin metal will get hotter and hotter as you move along and make it real easy to burn through

[Mathius]

I have decided not to bolt it into place. The only reason I had that idea was basically to hold the part into place before I commit to welding it in. However I have decided to remove the holes. Also, after talking with QA1 they very kindly gave me dimensions on the eyelets for their shocks and I designed around these dimensions. I went ahead and revised my design to better accommodate the type of loading the mount will see. Since the shocks are very much staggered from the factory, the mount needs to be designed with this in mind. You can see that the shape of the mount mimics the angle of the shock; this spreads out more of the load in the direction that it needs to be in. I'm about to go cut these pieces out right after I post this.

Large c-clamps will hold it in place for you to weld. If you want to go cheaper, get a buddy to hold it, and tack. Done.


Ok so I started welding this up over the weekend and I am discovering very quickly that welding a thick plate to a thinner gage frame rail in the overhead horizontal or vertical position is a very tricky endeavor. Please I need tips.

I have been trying this out using 1/8" blanks welding to some scrap sheet metal and it's a serious pain.

Try lowering your wire speed and see if that helps you. As long as you keep your voltage (heat) up, you will still get penetration, but you will have to keep closer watch on your weld pool to make sure you're laying it down properly.

One of my instructors taught me once to turn the wire feed down, even to where the torch makes a "spudder" when welding, but if you just sit in the puddle, it will build up like normal and you will still lay down a solid weld that way as long as your voltage is up. I passed my third welding certification that way using his method with him watching. It was 3/8" steel and qualified me to 1" or 2" on the cert, I don't remember which. I don't recommend it for everything, and I don't weld that way normally, but if you're having trouble with too much heat, it's an option. Using that method, I could actually sit in the puddle for a count of 4 on one side of the joint before dragging the puddle to the other side of the joint (v groove). Obviously on 1/8" material you can't just sit there in the puddle forever, but the concept is the same. Try lowering your wire feed to see if less metal in the pool helps you.

Welding is really just about watching the puddle, and the tighter you keep the welds, the better luck you're gonna have. Also, whenever possible bevel or design your parts to give yourself a joint to weld. It's VERY hard to lay down a good weld without a joint.

We do a lot of flange to flange connections on black iron (slang for cold or hot rolled steel vs. galvanized) in HVAC when running kitchen hoods, and welding the edges of the flanges can make it tough to lay down a nice looking bead because you're essentially just burning away the flanges, leaving nothing for you to actually lay a weld joint on. Whenever possible, I have the shop stagger the seams, making one side of the connection a bit smaller... if one side has a 1" flange, I'll put a 1/2" flange on the other side. Then I have a lap joint, instead of just butt welding the edge of a 16 gauge flange to a 16gauge flange.

If you start spreading out the puddle into a "wash", you're gonna have a lot harder time welding out of position as well. Run a nice tight arc when welding.

Mathius

[cheapta]

I'm no engineer,either but I would weld a "doubler" -a second sheet of thinner material to the framrail before I tried to weld the tubing to it. I've been doing that on my project anywhere the chassis tubing attached to the unibody (rocker panels,rear trunk panel,etc.) This lets the welder think the thinner material is thicker than it actually is,in effect doubling the thin material. Just a thought.

Peter

[mrn2obelvedere]

I'm no engineer,either but I would weld a "doubler" -a second sheet of thinner material to the framrail before I tried to weld the tubing to it. I've been doing that on my project anywhere the chassis tubing attached to the unibody (rocker panels,rear trunk panel,etc.) This lets the welder think the thinner material is thicker than it actually is,in effect doubling the thin material. Just a thought.

Peter

This seems like an interesting idea...too bad I already welded up the crossmember. I'll probably be tacking it in this weekend.

[mrn2obelvedere]

Here's the result: I think it is structurally sound, although not beautiful. I was surprised how easy it was to weld with the Miller 140, even when the fit of the weld wasn't so great (I had a sizable gap to fill between the crossmember and the framerails, maybe 1/16 on either side). I made a few practice welds with scrap in the vertical and overhead horizontal positions, and then I went at it. let me tell you I was fretting over this for a couple of weeks, but now that I have done it it really isn't so bad! Thanks guys for all of your help and input!

https://static1.pt-content.com/images/pt/2010/03/P3130056-1.jpg

[Mathius]

Here's the result: I think it is structurally sound, although not beautiful. I was surprised how easy it was to weld with the Miller 140, even when the fit of the weld wasn't so great (I had a sizable gap to fill between the crossmember and the framerails, maybe 1/16 on either side). I made a few practice welds with scrap in the vertical and overhead horizontal positions, and then I went at it. let me tell you I was fretting over this for a couple of weeks, but now that I have done it it really isn't so bad! Thanks guys for all of your help and input!



Hard to give a definitive answer from that picture, but I think it'll probably hold ok. I don't see any signs of undercut and the beads aren't THAT bad, it just seems like you didn't run them completely into one another, which is kinda like running a bunch of stringers anyways. A lot of the time welding all the way around is unnecessary.

Again, it could be much worse in person and that's not the most close up pic in the world, but the resolution isn't too shabby on your camera and they look _ok_ to me.

Again, in my opinion, best thing you can do is turn the wire feed down until you're comfortable. As long as your voltage is still up you will get the heat you need, but laying down more metal makes a bigger puddle makes gravity that much worse.

Mathius