A Beginners Guide to 3D Printing

In recent years 3D printing has received much attention, promising
to revolutionise manufacturing, and completely overturning the way we
produce items. As with many emerging disruptive technologies, a lot of
the coverage in the popular press is exaggerated, more like a Star
Trek replicator than the actual processes.

However, whether some of the
wilder claims pan out or not, for designers 3D printing does offer a
tantalising prospect: the capability to produce objects without the
constraints of traditional manufacturing, the capability even to
fabricate objects on your desk without traditional making or
engineering skills.

By the end of this article you will have been introduced to the
terminology of 3D printing and have an idea which method is best for
you. First we will discuss the three most common technologies, and then
some options in designing a model.

3D PrintingTechnologies

It would be incorrect to think of 3D printing as a single
technology. Instead it is a set of technologies following a
shared idea of additive manufacturing driven by software.

So what is
additive manufacturing? Many manufacturing techniques start with a
block of material and selectively remove it until we are left with
the desired object. Additive manufacturing turns this on its head, starting with a blank canvas and adding only what is required for the
final object.

In itself this additive manufacturing is nothing
special—a child building sand castles on the beach is using additive
manufacturing. It is the addition of using digital technology for a
reliable and accurate result that makes 3D printing special.

Typically this works by slicing an object we wish to create into
thin sections and building these slices one at a time, stacked on top
of each other. Think of building a pyramid as a series of square
buildings, 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 Depositional
Modelling, or FFF, Fused Filament Fabrication if we want to avoid
trademarked terms. It relies on “extruding” a filament of
material, i.e. heating it to a point at which it can be squeezed through a
nozzle, producing an even thinner filament. This nozzle is moved over
a surface, drawing the outline of the slice we want to create, then
filling this outline with a pattern of material.

Because the material
is hot as it is extruded, it bonds to any filament already laid down,
forming a solid slice of material. Once complete, the nozzle moves up
a small amount and starts extruding the next layer.

This is
the technique you will find in most hobbyist 3D printers, typically
with the material being ABS or PLA plastic. The technique
produces a “wood grain”-like surface with slight grooves between
each layer (although this can be removed by sanding, polishing or
acetone vapour). Imperfect calibration of a machine can result in
strands of filament protruding in places or blobs of molten material.

The technique can struggle with overhanging shapes. Since it is
building on top of the layer below, anything overhanging is extruded
onto 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 extruded
from a second head, built as a scaffold to support any overhangs
which can be snapped or dissolved off afterwards. There are some
hobbyist attempts to replicate this, but they tend to be less
reliable.

SLA: Setting Resins

The next technique,
Stereolithography or SLA, relies on photo-sensitive resins,
photopolymers, materials which change from liquid to solid when
exposed to (usually ultra violet) light. By exposing each slice of
the object on the surface of a thin layer of the liquid with
ultra-violet (UV) light, we can harden just the parts we want. This
hardened resin is repeatedly flooded with another thin layer of
liquid and then exposed with UV light in the shape of the next slice
of model, to leave a hardened 3D structure once we drain off the
fluid.

The method of UV exposure differs: some SLA printers use a
laser, steering it over the surface to draw the slice, while others use a
DLP projector to expose an entire layer at once.

SLA more easily produces a smoother, higher resolution print, but
tends to be more expensive. It has the same issue of overhangs, and
parts tend to be built on a scaffold made of the same resin as the
built object, necessitating quite a bit of clean-up sanding.

A lot of
“model making” type prints in the professional world of 3D
printing tend to use this technique, and there are a lot of
photo-polymers now available mimicking different materials. Until
recently patents limited this technique to professional machines,
but machinesaccessible to hobbyists haveappeared over recent years, and with this, cheaper resins have also
appeared. That being said, the technique uses gloopy chemicals with
limited life, so I don't think it'll completely replace FDM in the
hobbyist sphere.

SLS: Melting With Lasers

The
very best 3D printers again use a laser, but this time at a higher
power, either melting or sintering powders together (sintering is
when you heat a material enough to fuse it together, but not quite
enough to fully melt it into a liquid).

These powders can be
engineering grade plastics such as Nylon, or even metals, allowing 3D
printing of parts suitable for machinery. If you see a news articleabout
Formula 1 racing teams or rocket manufacturers using 3D printing, this
will be the type they mean. Very high resolution and very strong, but
typically rather expensive.

These types of machines are usually used
as an alternative to traditional engineering techniques and, although
expensive, can be cheaper than traditional techniques for one-off
parts or small production runs.

Other 3D PrintingTechnologies

These
three technologies are in no way exhaustive. You can get printers
that deposit drops of wax, producing a model that can be cast into a
mold for metals (often used for jewellery). You can use technology
similar to an inkjet printer over a vat of powder, to deposit a binder and pigments, making full colour models. Or a very similar technology
followed by glazing to make ceramics (plates, cups, etc.). Even more
specialist 3D printers can lay down bio-compatible materials to print
living tissues for implantation, nanoscale objects to make tiny
machines, 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 rangeof 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

There
are two big approaches to 3D modelling: surface modelling and solid
modelling.

• 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. Solid
  modelling is typically harder for the programmer to write and more
  limiting to the designer to model in, and for this reason most modellers
  aiming just to render images from a 3D model will use a surface
  modelling package.

For
3D modelling, either can be used, although there are caveats to that.
Remember that the software will aim to slice the model into sections
and must know which is the inside and outside of those sections.
Obviously a modelling package which represents objects as solids will
be unambiguous which is which, but surface modelling can produce
files where it isn't so obvious.

There is a very strict approach you
must take to produce valid files with such software, quite unlike the
usual approach for making a model to render. In brief the file has to
be “manifold”, i.e. no intersecting faces, no internal faces, no
holes, and all vertices welded not just very very close. The model
would have to be water tight if you made it from plastic sheets. Try
following this guide for more details.

So unless you're already skilled with surface modelling, I'd suggest
having a go with a solid modelling package. Although they are less
expressive, there is less to go wrong for your first attempt!

I tend
to use Solidworks, but it is rather expensive. Thankfully with
the rise of 3D printing comes a matching proliferation of free solid
modelling 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 extensionto 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 Your3D Print

So
you 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 it
printed already! There are a few ways you can go here: you can invest
in a machine, you can use a 3D printing service, or you can find
somewhere to use a 3D printer. Each has pros and cons.

Buying
your own machine can be quite an investment, although a lot less than
in the past. You'll be limited to the one technology your machine
uses, 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 a
professional machine, you may have to delve into the techy side of
your machine if anything needs to be replaced or recalibrated, although
many hobbyist machines have excellent online communities to support
this.

However, having said all that, you'll have the cheapest option
per part you want to make, so if you get hooked you can churn out
parts to your heart's content. And you'll be able to rapidly
iterate parts—if you're anything like me and you're making multiple
parts to join together, you'll get something wrong the first time you
make it!

Another option is 3D printing services, either online or your local 3D
printing company. This has the benefit of no upfront cost (although
it is considerably more expensive per part), and a range of
technologies and materials available. The other main downside beside
the cost is time, because you'll have to wait for them to make it and ship it
to you. There are a few big services out there, such as Shapewaysor iMaterialise, but shop around and find the solution that has the best
balance of price and speed for you.

The third option is a halfway house between these, but is dependent
on finding a 3D printer you can use locally. The maker movement has
resulted in lots of local maker spaces, which may have machines
available at the cost of entry and material, or even just someone
who's willing to trade time on a machine for 3D modelling skills for
their projects. Look into it!

Or
you can do what I do, and do all of these! Quickly test models on your
own machines, send files off for alternative materials, and get involved
with 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!

Preview image credit: Seth Woodworth via Flickr