Introduction: TIG-Welded Steel Bowl
This is a large, geometric bowl that I designed and fabricated out of stainless steel. I TIG welded the pieces together and sanded it to a satin finish. A handful of people have asked me questions about how I made them, so I took lots of photos and even a few time-lapse videos. Thought this would be a good project for my first Instructable!
The basic steps here can be used to make pretty much any faceted, geometric form: cubes, vases, planters, pretty much any regular or irregular polyhedron. Use your imagination!
Note: This Instructable assumes that you know how to TIG weld and have access to a basic metal shop.
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Step 1: Materials, Tools, and Safety Gear
- 16 gauge stainless sheet steel (You can use any metal that you know how to weld: copper, brass, bronze, mild steel, aluminum, etc)
- .035" stainless steel TIG filler rod (If you're working with a metal other than stainless steel, make sure to buy corresponding filler rod. .035" is thinner than what most welders use, but it allows for more delicate and precise welds. I ordered mine online because they don't sell it at the welding supply store in my neighborhood.)
- Clear metal wax (You can treat the surface in any number of ways, depending on what look you're going for: patina, gun blue, wax, oil, sealant, etc.)
- SketchUp software (can use any 3D software, or pen and paper)
- TIG welder with 1/16" tungsten electrodes
- Tungsten pedestal grinder
- Variable-speed angle grinder with 40-grit flapwheel disc, 80-grit flapwheel disc, and Scotch-Brite attachments
- 120 grit sandpaper
- Rags for applying wax
- For welding: safety glasses, welding shield, TIG welding gloves, natural-fiber long sleeves and pants
- For grinding and sanding: safety glasses, ear protection, ventilator with particulate filters, face shield
Step 2: Design the Piece
Using either CAD software or pen and paper, design your piece. I used SketchUp to create a simple faceted bowl shape. I imported a regular dodecahedron, then played around with different modifications until I was happy with the shape. Lastly, I scaled it so that it was the right size.
Note that, in my model, I didn't account for the thickness of the material. I've found that when TIG welding fairly thin sheet metal (16 gauge, give or take), I can ignore material thickness when cutting out my pieces, and just kind of fudge it when welding. The pieces might not fit together precisely, but it's close enough to weld and will disappear completely with some sanding. This might not be true if you're working with thicker materials, though -- if that's the case, then make sure to account for material thickness in your model.
Step 3: Cut Out the Pieces
There are a many different ways to cut out the pieces from the sheet metal, each with pros and cons. I outsourced this step to a professional waterjet cutting shop because I was making a lot of bowls, I wanted ultra-clean edges, and since it was a paid job, I could afford the high cost. Alternatively, you could cut each piece out with step shears (time consuming, but clean and inexpensive), or a plasma cutter (quick, but will require lots of grinding to clean up the edges).
To prep the design file for waterjet cutting, I measured the bowl's face dimensions in SketchUp and recreated each shape as a vector line drawing (.001 stroke) in Illustrator. I laid out the pieces, nestled them as close together as possible, included info about the scale, and then exported the file as a DXF to send to the waterjet cutter.
Note: I believe there are easier ways of turning a 3D shape into a series of flat faces than the way I did it. For instance, this Instructable, Gaming dice made from folded, waterjet cut steel, suggests exporting the shape as an STL and importing it into Pepakura Designer, where you can "unfold" the shape. I think there are also SketchUp extensions that enable UV mapping. Would love to hear what ideas you have for simplifying this step!
Another tip for next time: I chatted with the guy who did my waterjet cutting, and he said that if I have multiple identical pieces, I should just draw one of each shape, and then indicate the quantity. They'll do the layout themselves. If you're going to outsource the waterjet cutting, I'd recommend calling the shop to find out how they'd prefer to get the drawings -- I could have saved myself quite a bit of time with the vector drawing layout!
Regardless of how you decide to cut out the pieces, you'll want to end up with precise shapes with clean edges. Grind or sand down any slag, burrs, tabs, or rust.
Step 4: Set Up the TIG Welder
Next, set up the TIG welder. The settings, type of filler rod, and thickness of tungsten will depend on the metal, material thickness, and type of weld you're doing (mostly outside/open corner welds for this project). I used the Miller TIG Welding Calculator to look up the best settings.
For my stainless steel bowl, I used 1/16" lanthanated tungsten electrodes, sharpened to a pencil tip point, and .035" stainless steel TIG filler rod. I set the welder to DC-negative, six-second postflow, 120 amps for tacking, and 60-70 amps for welding.
Having an aluminum or steel block can be helpful for propping up the piece as you work. No need for clamps or vice-grips for this project -- more on that in the next step.
As for safety gear, I wore an auto-darkening welding shield, safety glasses, and natural-fiber jacket with a high collar (didn't want my neck to get sunburned!) and long pants.
Step 5: Tack Weld the Pieces Together
Begin by tack welding all of the pieces together. You can tack on either the outside or inside of the piece -- whatever angle is easier to get to. I set the welder to 120 amps (pretty high), and did a very quick tack with no filler rod to create each little spot weld. I did about two tacks per edge -- just enough to hold the pieces together, while still being flexible enough to bend (or break and start over!) by hand if needed.
As long as the edges are lined up precisely before you tack, you don't need to worry too much about getting the angle right. Since the tack welds are small and flexible, you can just bend the pieces into the correct angle as you work your way through the piece.
I mentioned earlier that I didn't use clamps or vice grips for this project -- as you can see from the photo, I just held the two faces together with a gloved hand while I tack welded with the other hand. As long as your tacks are quick, it won't heat up the metal enough to burn you through the gloves.
Step 6: Weld All the Corners
Once all the faces have been tacked together, you'll want to weld each vertex to join the intersecting faces. I turned the power down to about 80 or 90 for this step. Sometimes a flash tack was all it needed to join all the pieces into one weld, but sometimes there was too much of a gap, and I needed to add filler rod.
I found this step to be very important later on, when welding the edges -- if I hadn't previously welded the corner, I found that I accidentally blew holes in the metal very easily. It's much easier to make a clean weld if each end of the seam is already welded.
Step 7: Weld All the Edges
Once your entire piece has been assembled and the corners welded, it's time to weld, weld, weld!
I turned the power down to 60-70, got comfortable, and welded all the outer edges in the bowl. If a seam was pretty tight, I just fused it without adding any filler rod. I only added filler rod if there was a gap between the two pieces. Since this bowl wasn't going to be load-bearing, I didn't worry about weld penetration or structural integrity -- as long as the outside surface was joined and the bowl would hold water, that was good enough for me.
Check out the time-lapse video I took of myself tacking and welding together a bowl! You can see the order of operations, and how I set up my work.
Step 8: Sand and Buff the Outer Surface
Time for a little elbow grease: Use a variable-speed angle grinder to sand and buff the outside surface to create a seamless, satiny finish. Make sure to wear safety glasses, respirator, ear protection (I used both foam earplugs and heavy-duty earmuffs), and maybe even a face mask. Make sure you don't have anything dangly or loose that could get caught in the wheel (ponytail, necklace, hoodie drawstrings, earbud cables, etc.).
I clamped down the piece to keep it from moving. To prevent it from getting scratched, I'd recommend putting one small scrap of cloth between the clamp and the piece, and one piece between the piece and the work table. Make sure it's a very small scrap -- you don't want it to get caught in the wheel.
I started by using a 80-grit flapwheel disc on the angle grinder to sand down the welds. If I had a particularly messy or bumpy weld, I swapped out the disc for a 40-grit flapwheel disc to remove material a bit more aggressively. If your piece has an open side, make sure to gently sand along the rim so that it's smooth to the touch.
Once I'd sanded down all the welds, I switched to a Scotch-Brite disc and gently went over every edge and every face to create a smooth, satiny finish. Check out the time-lapse video I made!
Edit: I left the inside surface of the bowl unfinished, mostly because I couldn't fit the angle grinder inside the bowl. It would have been nice to clean up the inside somehow, though. Do you have suggestions for how I could have finished the inside of the bowl? Maybe sandblasting? Leave your ideas in the comments!
Step 9: Treat Surface With a Patina, Seal, or Wax
Treating the surface with a patina, seal, or wax is totally optional -- you may want to do this to preserve or alter the finish of your piece, especially if you used a metal that oxidizes or rusts easily (e.g., mild steel, copper, bronze). Since I used stainless steel (which won't oxidize or rust), adding a clear wax wasn't necessary. That said, I chose to apply it to protect against lingering fingerprints on the bowl (I knew it was going to be on display at a conference a few days later). There are dozens of options out there for patinas, waxes, and seals, depending on what look you're going for. I like Sculpt Noveau's selection.
Before waxing, I ran a piece of 120-grit sandpaper along the inner rim of the bowl, just to make sure it could be handled comfortably. Then I cleaned the bowl with household glass cleaner and a rag.
I applied the wax all over the outside surface of the bowl with a small piece of rag, and buffed it off with a clean rag a few minutes later. The instructions on the clear wax said to leave it for up to an hour before buffing, but I found that it hardened too quickly. I believe waxes can also be applied hot, which might give you more flexibility with the timing. I let the wax harden fully overnight before packing up the bowls and delivering them to the client.
Step 10: Ta-Da!
Thanks for reading my first Instructable! I hope it was helpful and maybe even inspiring. As I said earlier, these steps can be used to make any geometric shape out of sheet metal -- the sky's the limit! If you're nervous, start with a basic cube that's just a couple inches wide. Once you're comfortable with the basic process, try a more complex shape!
Looking forward to reading your feedback, questions, and tips.