One of the buzziest of buzzwords when it comes to designing and making things right now is 3-d printing. That's because it's new, and a lot of effort is going into making 3-d printing seem like a user-friendly, infinitely useful technology that will soon be in every house. Like a microwave oven, except that instead of warming your coffee it'll make you a coffee mug.
That is not going to happen any time soon. First of all, you need to be able to design pieces that will perform the function you ask of them. This takes some experience and/or some engineering expertise. Clever-looking tuner buttons won't seem so clever if they don't feel nice , are hard to turn, or break. Furthermore, you need the ability to design your pieces in a CAD environment, like RhinoCAD or Fusion360. This is not simple software. It takes some time and dedicated effort to learn it. But us luthiers are not just everyday folks; lots of us already have the necessary skills, and more to the point, have a clear objective in mind. 3-d printing can indeed become part of the repertoire of skills and techniques used by luthiers in certain instances, but like every other method of creation there are many constraints and caveats.
If you're not familiar with 3-d printing, the basic gist of it is that material is spit out of a printhead that moves forwards and backwards, side to side, like a desktop inkjet printer. Then the object being created is lowered ever so slightly, and another layer of material is printed on top of that.
Or you might be familiar with the inexpensive printers out there that will create small objects out of plastic. They really are cheap enough for a home hobbyist to use. The problem is that the parts will have a noticeable texture to them, due to the fact that the material is extruded out of a hot nozzle, rather like a glue gun. They're not smooth and shiny like an injection-moulded plastic part, and the precision and strength of these parts is not the same either.
But you don't have to have your own 3-d printer. The technology was after all invented for industry, so that companies could create accurate prototypes of parts before they went to the expense of making moulds and machinery to produce them in quantity. 3-d printing was not really invented for making end-use objects, just prototypes. But funny enough, as a luthier who makes one-of-a-kind guitars, each one is in essence a prototype.
And as it turns out, there are a few firms that operate high-precision, industrial-grade 3-d printers that can produce parts far better than the little hobbyist ones. And the main virtue of 3-d printing is that unlike most manufacturing processes like machining or moulding, you don't need to do a large run at all, so many places are happy to produce even small single parts. The cost is almost completely dependent on the volume and dimensions of the object, not how many you need. Not only that, but since there are no mould or jigs that have to be made, your creation basically gets built with the click of a mouse, so it can be made and shipped virtually overnight.
But what if you don't want to use plastic? I mean, it gets used for many parts of many guitars, both modern and vintage. But for parts where you need mechanical strength or where plastic would suck out the tone, you need metal:
Being able to use metal vastly expands the usefulness of 3-d printing in my own work. There are a couple of different technologies available here, with different advantages:
The first is good old-fashioned lost-wax casting. This ancient technique involves making a model out of wax, coating it in a heat-resistant mold material, melting out the wax, filling it with molten metal, cooling it, and breaking away the mold. In fact the only part of this is that is 3-d printed is the wax model. Thus, the parts created won't necessarily have perfect dimensional tolerances, and because of all the steps it's not exactly cheap. The advantage is that the surface quality of the metal can be really good, and you can use almost any of them to create the final object, even solid silver or gold. Great for jewelry, not necessarily optimum for guitar parts though.
The second I've tried involves spraying stainless steel powder with a tiny amount of adhesive. The model is then infused with molten bronze, creating a finished piece that is very strong and tough. It's also the cheapest method, especially for larger objects. The surface texture can be a little rough, and may show the print lines from the layering process, but it's an intriguing and touchable texture so I don't mind. There are a few major drawbacks though: Like lost-wax casting, the parts shrink or warp during the manufacturing process, but unpredictably; worse, the mix of steel grains in a bronze matrix is very tough machine, so it's not practical to modify the parts after printing. It can barely be cut or filed, and trying to tap threads for machine screws is tricky and results in sub-optimum threads. Useful, but only for certain parts.
The best technology at the moment is pretty exotic and amazing. It involves blasting fine metal powder with a high-powered laser to melt the particles together. Each layer is hit with enough heat to fuse with the previous layer. It's expensive, and at the moment generally only available for small pieces, but the resulting parts are solid metal, with almost the same strength and density as a forged or machined part. Furthermore, they are very accurate in dimension, and can be machined, threaded, polished or plated, which makes it much more useful for mechanical pieces.
So what's the whole point of this? Why would you got to the trouble of designing a part in a CAD program and having this expensive single part made by a lab that blasts stuff with lasers? The short answer is that you probably shouldn't.
There are only certain scenarios where 3-d printing is advantageous to the working luthier: If you insist on originality, i.e. having your own hardware used by no-one else, then you run into the production-run problem: with traditional manufacturing techniques small quantities are way more expensive per unit than large quantities. But 3-d printing is not exactly cheap per unit either. And in both cases, the time spent designing the parts is a fixed cost, so the more units you make then the design time is effectively spread out across more units. In all cases the expense of truly custom-made hardware means it is only feasible for high-value instruments.
If we're working with small quantities we can sometimes get around the production-run problem by making modular parts. This means, for example, individual bridge units, so if you're building a 7-string instead of a 6, you would just add in an extra unit. This allows us to make many copies of a single part which we can then use in most scenarios. However, it's more difficult to design good modular parts, and if the production run size is equal, the cost of a set of 6 modular bridge units will be more than a single 6-string unit.
With 3-d printing, the production cost per unit is the same no matter how many you make, but what about the design cost? You don't want to have to redesign your bridge from scratch every time you want to, lets's say, change the string spacing. But with CAD software we have the interesting option of being able to make a basic model that is easily modifiable. For example, you might be able take your regular bridge and use a "stretch" or "skew" function to change the string spacing, all with just a few clicks. Making an 8-string? Duplicate a couple of segments and re-loft, perhaps. This way we get the flexibility of modular parts, but the strength and cost-savings of monolithic hardware.
The other interesting possibility with 3-d printing is that it is capable of creating shapes that would be impossible using any other manufacturing technique. Parts can be made with internal voids and very thin sections, in extremely complex shapes. One of the most amazing applications of this that I've seen so far are rocket engines, which require all sorts of internal tubes and a very precise nozzle shape.
Remember also that the cost of a 3-d printed part depends mostly on the volume of material used; a carefully-designed part will be one engineered use as little material as possible. In essence, as designers we have to start thinking more like aerospace engineers, trying to shave off every gram while still retaining the strength we need for things to function. Coupled with the incredible visual possibilities offered by this whole new way of generating metal, we are starting to see a new visual design language taking form, with organic, latticelike forms a visual representation of the force vectors at work:
At this point I'm just a rank amateur. My CAD skills are rudimentary. Still, as the technology of 3-d printing improves and becomes more common, the costs will go down and we may very well start seeing people with some serious design talent taking advantage of the possibilities. Because those possibilities are almost endless- soon our imaginations will be the only limit.