In recent years 3D printing has received much attention, promisingto revolutionise manufacturing, and completely overturning the way weproduce items. As with many emerging disruptive technologies, a lot ofthe coverage in the popular press is exaggerated, more like a StarTrek replicator than the actual processes.
However, whether some of thewilder claims pan out or not, for designers 3D printing does offer atantalising prospect: the capability to produce objects without theconstraints of traditional manufacturing, the capability even tofabricate objects on your desk without traditional making orengineering skills.
By the end of this article you will have been introduced to theterminology of 3D printing and have an idea which method is best foryou. First we will discuss the three most common technologies, and thensome options in designing a model.
3D Printing Technologies
It would be incorrect to think of 3D printing as a singletechnology. Instead it is a set of technologies following ashared idea of additive manufacturing driven by software.
So what isadditive manufacturing? Many manufacturing techniques start with ablock of material and selectively remove it until we are left withthe desired object. Additive manufacturing turns this on its head, starting with a blank canvas and adding only what is required for thefinal object.
In itself this additive manufacturing is nothingspecial—a child building sand castles on the beach is using additivemanufacturing. It is the addition of using digital technology for areliable and accurate result that makes 3D printing special.
Typically this works by slicing an object we wish to create intothin sections and building these slices one at a time, stacked on topof each other. Think of building a pyramid as a series of squarebuildings, each smaller than the last, stacked up to make a 3D shape.
FDM: Extruding Filaments
The first technique we will look at is FDM, Fused DepositionalModelling, or FFF, Fused Filament Fabrication if we want to avoidtrademarked terms. It relies on “extruding” a filament ofmaterial, i.e. heating it to a point at which it can be squeezed through anozzle, producing an even thinner filament. This nozzle is moved overa surface, drawing the outline of the slice we want to create, thenfilling this outline with a pattern of material.
Because the materialis hot as it is extruded, it bonds to any filament already laid down,forming a solid slice of material. Once complete, the nozzle moves upa small amount and starts extruding the next layer.
This isthe technique you will find in most hobbyist 3D printers, typicallywith the material being ABS or PLA plastic. The techniqueproduces a “wood grain”-like surface with slight grooves betweeneach layer (although this can be removed by sanding, polishing oracetone vapour). Imperfect calibration of a machine can result instrands of filament protruding in places or blobs of molten material.
The technique can struggle with overhanging shapes. Since it isbuilding on top of the layer below, anything overhanging is extrudedonto nothing but air! As long as we don't need to overhang too far, the material will support itself and not sag too much. However, commercial machines tackle this with a support material that is extrudedfrom a second head, built as a scaffold to support any overhangswhich can be snapped or dissolved off afterwards. There are somehobbyist attempts to replicate this, but they tend to be lessreliable.
SLA: Setting Resins
The next technique,Stereolithography or SLA, relies on photo-sensitive resins,photopolymers, materials which change from liquid to solid whenexposed to (usually ultra violet) light. By exposing each slice ofthe object on the surface of a thin layer of the liquid withultra-violet (UV) light, we can harden just the parts we want. Thishardened resin is repeatedly flooded with another thin layer ofliquid and then exposed with UV light in the shape of the next sliceof model, to leave a hardened 3D structure once we drain off thefluid.
The method of UV exposure differs: some SLA printers use alaser, steering it over the surface to draw the slice, while others use aDLP projector to expose an entire layer at once.
SLA more easily produces a smoother, higher resolution print, buttends to be more expensive. It has the same issue of overhangs, andparts tend to be built on a scaffold made of the same resin as thebuilt object, necessitating quite a bit of clean-up sanding.
A lot of“model making” type prints in the professional world of 3Dprinting tend to use this technique, and there are a lot ofphoto-polymers now available mimicking different materials. Untilrecently patents limited this technique to professional machines,but machines accessible to hobbyists have appeared over recent years, and with this, cheaper resins have alsoappeared. That being said, the technique uses gloopy chemicals withlimited life, so I don't think it'll completely replace FDM in thehobbyist sphere.
SLS: Melting With Lasers
Thevery best 3D printers again use a laser, but this time at a higherpower, either melting or sintering powders together (sintering iswhen you heat a material enough to fuse it together, but not quiteenough to fully melt it into a liquid).
These powders can beengineering grade plastics such as Nylon, or even metals, allowing 3Dprinting of parts suitable for machinery. If you see a news article aboutFormula 1 racing teams or rocket manufacturers using 3D printing, thiswill be the type they mean. Very high resolution and very strong, buttypically rather expensive.
These types of machines are usually usedas an alternative to traditional engineering techniques and, althoughexpensive, can be cheaper than traditional techniques for one-offparts or small production runs.
Other 3D Printing Technologies
Thesethree technologies are in no way exhaustive. You can get printersthat deposit drops of wax, producing a model that can be cast into amold for metals (often used for jewellery). You can use technologysimilar to an inkjet printer over a vat of powder, to deposit a binder and pigments, making full colour models. Or a very similar technologyfollowed by glazing to make ceramics (plates, cups, etc.). Even morespecialist 3D printers can lay down bio-compatible materials to printliving tissues for implantation, nanoscale objects to make tinymachines, and giant machines building sections for architecture.
3D Printing Materials
For the widest range of materials, look to a 3D printing service with a range of machines, for instance Shapeway's offering. You're looking at a number of plastics, metals and ceramics with different properties to suit what you're trying to make.
Excellent, you may think—I don't need to care how it works, as long as it works! But there's the catch: look at each material they offer and you'll see they all have different requirements, minimum wall thicknesses, minimum surface detail sizes, minimum clearances, etc. You might find you need to tweak your design to work with the material you're using.
If you go the other direction, getting a hobbyist 3D printer, you are a bit more limited, but not as much as you might expect. There's a range of filaments out there now that'll work on this kind of machine. There are flexible filaments, wood-like filaments, translucent materials, and plastics with all sorts of differing characteristics.
Beware, however: these materials will usually need a bit of tinkering with temperatures and possibly even alternative parts in the printer. Most people with these sorts of machines like to tinker with such things, however.
Modelling for 3D Printing
Thereare two big approaches to 3D modelling: surface modelling and solidmodelling.
- Surface modelling typically represents an object as points,edges and faces.
- Solid modelling instead, as the name suggests,maintains a representation of the inside of the object. Solidmodelling is typically harder for the programmer to write and morelimiting to the designer to model in, and for this reason most modellersaiming just to render images from a 3D model will use a surfacemodelling package.
For3D modelling, either can be used, although there are caveats to that.Remember that the software will aim to slice the model into sectionsand must know which is the inside and outside of those sections.Obviously a modelling package which represents objects as solids willbe unambiguous which is which, but surface modelling can producefiles where it isn't so obvious.
There is a very strict approach youmust take to produce valid files with such software, quite unlike theusual approach for making a model to render. In brief the file has tobe “manifold”, i.e. no intersecting faces, no internal faces, noholes, and all vertices welded not just very very close. The modelwould have to be water tight if you made it from plastic sheets. Tryfollowing this guide for more details.
So unless you're already skilled with surface modelling, I'd suggesthaving a go with a solid modelling package. Although they are lessexpressive, there is less to go wrong for your first attempt!
I tendto use Solidworks, but it is rather expensive. Thankfully withthe rise of 3D printing comes a matching proliferation of free solidmodelling packages. The company that produces AutoCAD, another expensive but very powerful 3D package, offers a few packages. Of these, some of most useful for this purpose are Tinkercad, a basic browser-based CAD package, and 123D Design, an offline tool with similar capabilities.
My free go-to tool is usually Trimble Sketchup, which is free for non-commercial use, but you will need an extension to get the right kind of file.
Whichever tool you use, you'll typically need to end up with one or more stl files. This is a very basic file format, but what most 3D printing tools will accept.
Producing Your 3D Print
Soyou know some of the technologies, you know some of the software,perhaps you've even made a file, and you just want to know how to get itprinted already! There are a few ways you can go here: you can investin a machine, you can use a 3D printing service, or you can findsomewhere to use a 3D printer. Each has pros and cons.
Buyingyour own machine can be quite an investment, although a lot less thanin the past. You'll be limited to the one technology your machineuses, and hence the one (or a few) materials used in that technology.Assuming you're not made of money and have been able to get aprofessional machine, you may have to delve into the techy side ofyour machine if anything needs to be replaced or recalibrated, althoughmany hobbyist machines have excellent online communities to supportthis.
However, having said all that, you'll have the cheapest optionper part you want to make, so if you get hooked you can churn outparts to your heart's content. And you'll be able to rapidlyiterate parts—if you're anything like me and you're making multipleparts to join together, you'll get something wrong the first time youmake it!
Another option is 3D printing services, either online or your local 3Dprinting company. This has the benefit of no upfront cost (althoughit is considerably more expensive per part), and a range oftechnologies and materials available. The other main downside besidethe cost is time, because you'll have to wait for them to make it and ship itto you. There are a few big services out there, such as Shapeways or iMaterialise, but shop around and find the solution that has the bestbalance of price and speed for you.
The third option is a halfway house between these, but is dependenton finding a 3D printer you can use locally. The maker movement hasresulted in lots of local maker spaces, which may have machinesavailable at the cost of entry and material, or even just someonewho's willing to trade time on a machine for 3D modelling skills fortheir projects. Look into it!
Oryou can do what I do, and do all of these! Quickly test models on yourown machines, send files off for alternative materials, and get involvedwith local makers and students to make things.
Conclusion
So you now know a bit of the terminology, some of the options, and the pros and cons of each. Go forth and 3D print something interesting. Also be sure to keep your eyes open for future tutorials delving into some of the details more closely. If you have any questions, post them in the comments!
For your first step into 3D printing, why not try using a 3D printing service. Try out our tutorial on creating a 3D printed mobile phone case.
Preview image credit: Seth Woodworth via Flickr
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