How Stuff Works
Ashley McKinnon is not an acronym or initialism
software will take your 3d object model and mathematically slice it up into layers
One of the “hot” topics at the moment is 3D printing. The idea that you can quickly and easily print out plastic parts, sculptures and pretty much anything your mind can imagine has lit the creative fires under many people. Even though they may be outside the price range of most users, the technology is becoming more accepted and prices are coming down (you can get a DIY kit now for around the $500 mark). But just what is a 3D printer. What components go together to make it up and how does it work. Let’s take a look.
There are several competing technologies that power 3D Printers, which wildly affect the price. 3D Printers can range from home use DIY kits for several hundred dollars all the way up to commercial quality several hundred thousand dollar units which print parts for the likes of NASA. They all work on pretty much the same principle, which is to add material layer upon layer to build up the shape of the item. This is called Additive Manufacturing. Here we’ll take a look at some of the 3D print technologies and how they work.
At the high end of the scale we have Stereolithography, or SLA for short. In this process the printing tray is suspended in a liquid called photopolymer. The tray is held just below the surface of the photopolymer (we’re talking a fraction of a millimetre here) and a laser traces out the shape of the first layer to be printed. As the laser hits the photopolymer it hardens leaving a solid path forming the layer. The printing tray then descends just enough for another layer of photopolymer to cover the already printed layer and once again the laser traces out the shape and creates another layer. This process repeats until the entire product has been printed.
Next we have Selective Laser Sintering (SLA). This process involves releasing a tiny squirt of powdered building material (can be plastic, metal, ceramic or glass) over the printing area which is then targeted by a laser which fuses the material back to solid. The process is repeated over and over to finally form the shape you are wanting to print.
The final method is the one we will concentrate on – called Fused Deposition Modelling (FDM). This is by far the most popular method – and cheapest. It is the technology found in nearly all of the 3D printers available to retail customers. You may also here FDM referred to by other names. These include Fused Filament Fabrication (FFF) and also Plastic Jet Printing (PJP)
With FDM, a material is fed into print head which melts it into liquid form and deposits this onto a printing surface. Think of the way that you use a hot glue gun and you’ve pretty much got it figured out. Let’s take a closer look at how it works.
Typically the material that is used in FDM is plastic which comes in a long strand on a spool. The plastic can be either ABS (Acrylonitrile Butadiene Styrene) or PLA (Polyactic Acid). Other materials can be used as well such as rubber and some metals.
In a standard FDM 3D printer, the strand of material (filament) is fed into the print head which then heats it up until it becomes a liquid. The actual temperature that the print head achieves will vary depending on the material being used.
The molten material is then passed from the print head out an extrusion nozzle onto the printing surface (some 3D printers have dual extrusion nozzles so can print faster).
The extrusion nozzle moves around on the X and Y axis tracing out the shape that needs to be printed for that layer. The extruded material will rapidly cool and solidify thereby leaving the hardened printed layer. The 3D printer will now reposition the print head and begin printing the next layer of the object. Once again the molten material is extruded, but this time onto the previously printed layer, tracing out the shape to be printed. And so the process continues over and over until all layers of the object have been printed.
The thickness of the layers being printed determines the quality of the final product. The thinner the layers, the less the pancaking effect (the ability to see the individual layers of the print process in the final product).
Of course, this technology needs to be told what to do and this is where the software comes into it. The 3D objects you want to print have to be interpreted into a form that the 3D printer will understand. Most 3D printers will come with their own software to do this but there are freeware and paid alternatives available.
The software will take your 3d object model and mathematically slice it up into layers and orientation points. The software will also put in any support structures needed as part of the print. For example, if you were printing a 3D model of a human figure with outstretched arms, a 3D printer can’t just start printing the arms on layer with nothing underneath it to act as support. This is where support structures are needed. This can typically be snapped off or cut away once the final product has been printed.
Once the 3D print file has been generated it can be sent to the printer either over USB or written to an SD Card and directly loaded from the 3D Printer itself. Print times for 3D printers vary greatly but because we are talking about printing layers that are a fraction of a millimetre thick at a time, you can understand why several hours, even days to print are not unheard of.
That’s 3D printing in a nutshell. To get an idea of what can be achieved with a 3D printer checkout shapeways.com. This is a website for people to share 3D print designs and ideas, as well as sell items they have printed (such as phone cases and drone parts).