If it feels like you can’t escape 3D printing at the moment, well you’re probably right. Pick up a magazine, visit a website or turn on the TV and you’ll see somebody talking about something they printed. The thing is, while 3D printing is relatively new, additive manufacturing – the idea of putting something together rather than whittling a shape from solid – has been around forever. We’d even argue that some common metal fabrication techniques are the original additive processes. Here’s how we’d make that case.
3D, Additive and Subtractive
Watching a 3D printer can be quite hypnotic. The bed performs a little ballet in x and y axes as the print head deposits powder, liquid or a spool of plastic. Gradually the bed lowers, (or the head rises,) and your CAD model becomes a shape you can touch and feel.
The thing is, 3D printing is really just a subset of what technology gurus call additive manufacturing. Additive is any process that makes a part or product by putting things together. Don’t confuse it with assembly though. In additive there’s an assumption the part is one integrated whole, almost always using a single material, rather than a collection of different pieces put together.
The opposite of additive is subtractive, or what we “old timers” might call “machining.” It’s when you mill, turn or drill material, creating the final product by cutting away. And that leads us into how some of the most common metal fabrication techniques are additive.
The Most Common Metal Fabrication Techniques
Eastwood, who make small-scale metal fabrication equipment for jobs like auto body repair, list the main fabrication techniques on their website. While they cover quite a number we’d argue they can be merged into five distinct types. These are:
Here’s a closer look at each.
Okay, we’ll hold our hands up: this isn’t exactly additive. The reason we put it top of our list is that every metal fabrication project starts with some cutting. Either tube or bar goes under a chop saw, we get the angle grinder out or we spark up the plasma cutter to produce the pieces we need.
When it comes to sheet metal, our main cutting techniques are the shears, for large pieces, and the turret punch for multiple small pieces. Between the two there’s also the laser cutter and the waterjet.
Not exactly additive either, but neither is it subtractive. Bending is when we shape the sheet metal blank or length of tube or bar into the form we need. Sheet metal usually goes through a press brake machine that uses a straight-edged tool to put in individual bends. Tube goes on a rolling mill that puts in a radius.
The alternative to a press brake is a press, like our Minster or Bliss presses. The cool thing with these is that by using tools shaped like the form we want to create, they can put in non-straight bends. However, when we do that we’re really stretching as well as bending, so on to the next type of process…
Forming operations take a flat piece of metal – a 2D shape – and make it 3D. This, we’d argue is additive in the sense that it’s adding a third dimension to the part. Most of our forming is done on a press, where tooling stretches sheet into a different shape.
In an extreme example we could form a cup or can from a flat metal blank. More typically, stretching is done to put curves into flat sheet. Think of dimples or small embossments.
In the car restoration world skilled artisans use an “English wheel” to create new body panels. This produces radii by stretching the metal. (An interesting challenge with this is that most metals harden as they’re worked, something the artisan has to take into account.)
A piece of sheet metal can be made smaller in three ways. These are tucking, using a shrinker or heat shrinking. In each case the basic approach is to scrunch the metal up on itself, effectively folding it so it takes up less space.
Being honest, shrinking isn’t done very often. In fact we’d view it as more of a way of rectifying fabrication mistakes. That said, there are occasions when some folding or shrinking is needed to provide a satisfactory appearance.
Undoubtedly, this is the most additive of all metal fabrication techniques. There’s bolting and screwing and even gluing, (adhesives have a growing role in fabrication,) but the big one of course is welding. Welding is when two or more adjacent pieces of metal are partially melted and the metal allowed to flow together. Depending on the type of weld and the join being made, additional “filler” metal might be added for increased bulk and strength.
Any heating method capable of taking metal beyond it’s melting point can be used for welding: think lasers, oxy-acetylene gas torches and resistance welding. Probably the most common welding technique in fabrication however is gas metal arc welding (GMAW.)
In GMAW a welder strikes an electric arc between workpiece and welding torch electrode. This is hot enough to melt the workpiece and create a molten weld pool. The two main forms of GMAW are metal-inert-gas (MIG) and tungsten-inert-gas (TIG.) The major difference is that in MIG the electrode is the filler wire while in TIG filler is added separately, or not at all. TIG is advantageous with thinner materials, which is why it’s the primary welding process you’ll see here at Wiley Metal.
To stress welding’s additive credentials, skilled welders regularly build up shapes or add metal. This might be to repair a damaged tool, or maybe to bridge a particularly wide gap. Interestingly, well to us anyway, a process called “Wire Arc Additive Manufacturing” was patented back in 1920. Proof indeed that additive has been round a while!
The Original Additive Processes
Everyone’s talking about additive as if it’s just been invented. As we’ve discussed here, it really isn’t new, although in fairness, there are some new techniques, 3D printing being the most obvious. Most common metal fabrication techniques are, arguably anyway, additive, especially welding. If you’d like to learn more about what we can do by putting pieces of metal together, call, email or use our “Contact Us” button.