How Does 3D Printing Work?
3D printing, commonly known as ‘Additive Manufacture’ is a form of rapid prototyping where models are made layer by layer without the use of moulds. It is a WYSIWYG process where the virtual model and the physical model are almost identical.
There are many forms of additive manufacture which all work in slightly different ways, but essentially they all follow the same principals. Each different method has its advantages and drawbacks, whether it be better surface finish, stronger model for working prototypes or full colour models for display models.
What are the basics?
All 3D printers work from the bottom of the model up. The first layer is placed down on the build tray.
Much like an inkjet printer, the machines ‘draws’ out a cross section of the model across the X and Y axis. Once this has been completed, the build tray is lowered (i.e. the model moves down the Z axis) by a fraction of a millimetre and the process of drawing out another layer on the X and Y axis is repeated. This is performed over and over again until the entire model has been built.
For any part of the model where there is an overhang or gap between moving parts, a support material is layed down (as it would be impossible to onto thin air!). Look at the example to the left of the 3dprintuk logo, notice how the support material is printed below any overhanging part, and how there is none above it, a good example is to look at the difference between the letter ‘n’ and the letter ‘u’ – they are the same shape, yet one uses far less support material than the other.
Different printing techniques
Depending on the material used, how many colors you want, the resolution you require, and how much money you’re willing to fork out, there are at least five popular 3D printing methods to choose from. Some are very similar, but some are really rather crazy (or brilliant).
- Fused deposition modeling – The most common 3D printing method is fused deposition modeling (FDM). The raw material with this process is a spool of plastic or metal wire, which is melted and placed by the printer’s nozzle. It quickly hardens, and then the next layer can be added. As far as commercial printers are concerned (like the MakerBot), FDM always uses plastic wire (filament) and is usually called “thermoplastic deposition” in layman’s terms
- Inkjet printing — Using special inks (resins and binders) it’s possible to build up a 3D model using a device that’s very similar to a home or office inkjet printer. Layer upon layer of resin and binder are added until an object is created. This is the only 3D printing process that allows for custom colors.
- Selective laser sintering – Sintering is the process of creating solid objects from powders, and in the case of selective laser sintering (SLS) the powder can be metal, plastic, ceramic, or glass. Basically, SLS uses a pulsed laser to “draw” the desired cross-section. The powder fuses, and then then the laser form the next layer on top. This is very much an industrial method, as it requires a rather strong laser.
- Digital light processing – With DLP (yes, the same technology behind DLP projectors), a vat of liquid polymer is turned into a very strong solid by exposing it to light. Very high accuracy/resolution can be achieved with this technique — and again, this is an industrial method. Stereolithography is similar to DLP manufacturing, but a lot more expensive.
The others – Finally, there are a few 3D printing techniques that aren’t used extensively, but could be in the future. Resin can be cured using LEDs (similar to the DLP approach); 2-photon photopolymerization can be used to create ultra-small 3D-printed features; laminated object manufacturing uses bits of paper or card stuck together that are then cut out using a laser.