Desktop Fabrication – 3D Printers and how they work

Colin Gearon, Phil Charlesworth & Chris Robinson

Colin opened a triumvirate of presentations with the byline “from concept to object”; this covers not only 3D printing but all aspects of digital modelling and fabrication. It combines 3D modelling or computer-aided design with additive and subtractive manufacturing. 3D printing is an example of additive manufacturing, and various types of machining and cutting are classed as subtractive manufacturing. Applications include dental implants, prostheses, automotive applications, hobbyists and schools, aerospace and armaments manufacture (in Ukraine mass production of over 1000 drones a day via 3D printing of components has largely rendered artillery redundant). There are at least two 3D printers on the international space station.

Computer aided manufacturing (CAM) is the stage that connects computer-ready or computer-aided design (CAD) via the generation of code to a machine that makes stuff. This code is called Gcode, the G standing for geometry. Examples of manufacturing machines might include computerised numerical control (CNC) machines, laser cutters and 3D printers

3d printing (AKA rapid prototyping) uses a filament which is heated and extruded through a nozzle to build up complex shapes one layer at a time. The filament can simulate wood, plastic, glass and other materials. It’s important to understand that 3D printing is not precise; laser cutting on the other hand can be precise, and CNC manufacture is precise.

Colin handed over to Phil, who described practical applications of 3D printing in the construction of rockets at the University of South Wales. A PhD researcher in Phil’s group is currently working on a 3D printed metal rocket motor injector, but more common examples of 3D printing in rocketry include the nose cones. Centring rings, which transfer thrust from the motor to the body of the rocket and have to be highly concentric and accurate to 0.1 to 0.2 mm, are made using CAD/CAM/CNC techniques. At the University of South Wales, open source software is used to design rockets and simulate performance, and the design transferred into a CAD package, in this case Fusion 360, which can generate Gcode for a CNC router to make centring rings directly.  To generate Gcode for a 3D printer from the CAD model of the nosecone, another stage, called a  slicer, is used to generate layer-by-layer instructions.

Phil’s group have achieved great success with their rockets, taking second place out of 22 teams in a national inter-universities completion with a design that attained 1722 m of altitude, a maximum velocity of 294 m/s and an acceleration of 13.4 G (according to the simulation that the design software generates).

Phil then gave another talk on behalf of the absent Chris Robinson, describing some of Chris’s successes with 3D printing. Chris started out using 3D printing to construct model railway buildings and moved on to theatre props, including an entire full-sized ham and the accoutrements to make a wooden box look like an Aga. He is currently enjoying himself 3D printing lids for open yoghurt pots.

Phil Chadwick