COLUMN | Click to build [The Bow Wave]
Readers will probably be aware of the impressive gains made in 3D printing in recent years. For those who’ve been out at sea or don’t have any teenage relatives, 3D printing is where you design an object on a computer and it is printed, layer-by-layer until the entire design has been completed.
Shipbuilders will be used to CNC machining where a computer controlled drill and grinder turns a block of metal (or wood or foam) into a shape designed on a computer. This is known as “subtractive” manufacturing because you’re starting with a large volume of material and removing parts of it to reach the desired shape.
By comparison, 3D printing is known as “additive” manufacturing because you are building up the object piece by piece using materials such as thermoplastics, polyamides, ceramics and various metal alloys.
Initially the process was undertaken by firing lasers into a resin that would turn solid wherever two laser beams met. The process has since evolved to the two primary methods which are dry powder forming, where an object is built by lots of thin slices that are fractions of a millimetre thick, and extrusion where the building material is a spool of plastic or metal wire that is heated and laid down in layers and built up.
Many people around the world, and off it too, have been experimenting with what can built by these machines. So far, creations range from model ships and houses to working firearms and even a spanner that was printed on the International Space Station.
Objects that would be impossible to make with traditional methods are simple now, such as printing complete gearboxes with the gears already inside, or ball bearings in their sleeve and even rocket engines.
A really exciting example of 3D printing can be found from the engineers from GE who have built a small jet turbine entirely from 3D printed parts. (https://www.youtube.com/watch?v=W6A4-AKICQU)
So far some problems have arisen with 3D printed objects where the bonding between layers isn’t as strong as the material itself and has resulted in structural weaknesses, particularly in extrusion derived objects.
A Norwegian company, Norsk Titanium, has developed a system for metal extrusion printing that should overcome this by producing what is referred to as a 90 per cent completed object. Using what is effectively a computer controlled welding gun, a titanium wire is extruded during the argon welding process and is used to build up an object. During this process the material is heated high enough that the deposited metal bonds at a molecular level just as it would during welding.
The resulting object is effectively an object made of welding wire, albeit one that was very carefully deposited and is a little rougher than the laser controlled printers that use powder as a building block. The final step is cleaning up the edges and so the object is sent for CNC machining to produce the final product.
It shouldn’t be long before the process is expanded to utilise aluminium, or even steel, as a printing material at which point I think the marine application will become apparent. How about a small boat shed with a couple of computer controlled welding arms and a library of boat designs on a hard drive.
It’s early days yet, but perhaps soon we’ll be able to design a vessel and press print. Just make sure the IT guy is available to fix those printer drivers.
Any comments, or perhaps you’ve come across something interesting? Feel free to contact me at [email protected]