KI7TU's Reference Page - 3-D Printing: An overview and introduction
I'm certainly not a "guru" on 3-D printing,
but I do have a 3-D printer and have printed quite a few objects on it.
(I first got it in early 2015.)
I've also published a few designs.
This page is based on the contents of a presentation that I've put
together to give to various clubs.
It assumes that you have a "technical bent", but likely
little to no background on 3-D printing beyond what you've seen
on TV or the like.
It's also subject to change, reorganization, and general improvements
based on audience comments at the presentations.
The one sentence summary:
3-D printing is the process of making a physical object
by building up thin layers of material under computer
It sounds a lot more complicated than it is
When you first read through the stuff below, it sounds really
But in reality, once you've done it a few times, it
becomes pretty easy.
Actually printing an object breaks down into four basic steps:
(Just remember that virtually anything you do, if you
start breaking it down into the steps that a
"complete newbie" will understand will
make the whole sound horribly complex, even if it's
just driving over to get a cup of coffee, especially
when you have to throw in the background info like
"if the traffic light is red, stop and wait for
it to turn green".)
- Getting and preparing the model
- Preparing the printer
- Actually printing (mostly "hurry up and wait")
- Clean up the printer
Classes of making things
You can break down all processes of actually making things into two
general classes (though some ways fall into both classes):
additive and subtractive.
An "additive" process is one where material is added to
the object being created.
One example that you've probably done is making something with
modelling clay, where you shape a basic head, then make ears
that you stick onto it and so on.
A "subtractive" process is where you start with a big
chunk of raw material and start removing parts of it until
you have what you want.
The classic example of this is a sculptor starting with a
piece of stone and "removing everything that doesn't look
like an elephant", in order to create an elephant.
Some examples of subtractive techiques would include:
Some examples of additive techniques would include:
- Milling, drilling, lathe work
It's worth noting that many, if not most, actual items
are produced by a combination of subtractive and additive
For instance, a craftsman making a cabinet will use
some subractive techniques, such as sawing, planing,
and drilling, to prepare the pieces, then
use additive techniques such as gluing parts
together and connecting the hinges to the wooden parts
- Building a brick wall
- Assembling a model airplane
- Welding two pieces of metal together
It's also worth noting that some techniques, such as
molding or casting, can be seen as either additive
or subtractive, depending on your view point.
3-D printers are about as additive a process as it gets.
They start with an empty build platform, and start adding
material one thin layer at a time.
Types of 3-D printers
There are basically 3 types of 3-D printers, though there
are also some other more exotic ones.
(There may be others that I'm not aware of!)
- Sintered metal
- Liquid immersion
- Fused filament
Sintered metal printers
These printers take a powdered metal,
and use a high powered laser to melt it a bit
so that it sticks together.
(This process is called sintering.)
The process of sintering has been around, as far as I know, since
the late 19th century, and is used to produce bronze bearings for
motors and engines.
One of the advantages to it is that it does not produce a solid
part, the way casting does, as the metal isn't fully melted.
For bearings, this porosity of the part is good for getting
lubrication (e.g., oil) to the contact points.
The sintered metal 3-D printers have added computer control,
using lasers to do the melting.
Typically the part will be lowered in the powder as it is
Sintered metal 3-D printers are well beyond the average hobyist,
with costs on the order of $50,000 and up. (Mostly up!)
Liquid immersion printers
There are materials (mostly plastic emulsions) that are liquid, but when struck
by light of a certain wavelength, become solid.
Often a laser is used to provide the light.
This property is put to use by having a computer-controlled laser,
and an arrangement to lower a print bed into a bath of the liquid.
This method of 3-D printing has some advantages, but it also has
One of the major drawbacks is that you have to have enough of
the liquid on hand to fill the print chamber to at least the
height of the object to be printed.
Another is that, being a liquid, unwanted raw material can
pose a disposal problem.
There are a few "hobbyist" grade liquid immersion printers
around, starting at around $1,000.
The liquid for them is not as readily available as for the fused
There are also commercial grade liquid immersion printers, and
the ones I've seen start at around $30,000.
Fused filament printers
These 3-D printers take a filament, which looks vaguely like a very
heavy fishing line or the "string" for a string trimmer
(also known as a "weed whacker").
The printer melts the filament, and moves the tip and/or the print
bed around, depositing the molten plastic directly onto the bed or
the layer of plastic
(If you're not aware of it, one of the meanings of the word
"fused" is "melted".)
The newly deposited layer melts the top of the layer beneath it,
causng them to weld together.
Once all of the plastic in one layer is deposited, then either the
print bed is lowered, or the print head is raised, and the process
repeated for the next layer.
The motions of the print bed and/or the print head can be controlled
to a small fraction of an inch.
However, it's usually possible to see the layering in a printed
object, unless other steps have been taken to smooth the surface.
The vast majority of "hobbyist" 3-D printers, as well
as most of the commercial-grade printers, are fused filament
They can range in price for a few hundred dollars for small
hobbyist printers, up to $50,000 (or more) for commercial-grade
The raw materials, the filaments, are readily available in most
larger cities, as well as from many on-line suppliers.
They are available in a wide variety of both colors and types of
Other types of printers
I should mention that there are other, more specialized printers.
They can use a variety of techniques to deposit the layers.
I've heard about 3-D printers that print wax objects for use
in lost-wax metal casting.
I've also heard about ones that print in a fine plaster
used by archaeologists to make copies of fossilized bones,
or to produce replicas for missing bones in a skeleton.
The rest of this section is going to concern itself with
fused filament printers.
As I mentioned above, the filaments resemble very heavy fishing
line or the "string" for yard string trimmers.
Older printers use filament that is 3mm in diameter, but newer
printers have gone to 1.75mm diameter filament.
Filament is generally sold by weight, usually in kilogram or
half kilogram rolls, though others are sometimes available.
There is really quite a variety of filaments available.
Naming a few:
Most of these come in a variety of colors.
Some are also with a "filler", such as wood chips or powdered
There's at least one that's electrically conductive (although
it has fairly high resistivity).
- ABS (this is used for Lego® blocks, as well as drain pipes)
- PLA (made from cornstarch, it's biodegradable)
- Ninja Flex® (a rubbery sort of plastic)
- Nylon (can be finicky to print, from what I've heard)
Each of them has their own special requirements, advantages,
For instance, ABS tends to give off a bad smell while it's being
PLA can start to get soft around 50°C (122°F), which can
be a problem if left in a car in Phoenix.
Most of the filaments can absorb moisture from the air, causing
problems when it gets heated well over the boiling point of water.
In general, it's wise to take steps to protect one's supply of
filament from humidity, especially when it's not actually being
Some, such as ABS or PLA, can be had for $20 to $30 a kilo.
Others, such as Ninja Flex® can cost as much as $50 for a
3-D Computer models
Before a computer can build a 3-D object,
it has to have a "picture in its mind"
of what it is going to build.
We call this picture a "model".
(Note that it actually has to be a 3-D picture, not just a
This picture, or model, can take several different forms.
It can be a surface, usually represented by a mesh of
small triangles or other shapes, of the object.
One way to think about this is to have a mental image
of what the object would look like if a pantyhose leg
were slipped over it and stretched tight.
This can be done for any arbitrary three dimensional
Another form for a model is to have one or more (usually
many more) basic shapes, such as cubes, cylinders, pyramids,
and so on, that are assembled to make a larger object.
The shapes can also be what is referred to by the fancy
term "negative space" which just means describing
a hole where ever it intersects with another basic shape which
is not negative space.
(Thus we might have a cube with a cylindrical hole through it.)
This type of model is sometimes referred to as a parametric
model, because it is fully described by the parameters of the
various basic shapes that
make it up.
Getting a 3-D model
One way to get a model into a computer is to use a 3-D scanner and
scan an existing object.
This can work well when you already have an existing object and
want to use a 3-D printer to make a copy of it.
The downsides include the cost of the 3-D scanner
(which sometimes is more expensive than the 3-D printer),
and the fact that you have to actually have the original of
There are a number of CAD (Computer Aided Design) programs around
that can be used for designing 3 dimensional objects.
Some of these are intended mainly for use by artists, and often
times include features for animation.
Some of these programs are more intended for doing things like
designing parts for small machines, or designing playing pieces
In many of them you create drawings, and by actions such as
extrusion or rotation, you create a three dimensional object.
There is at least one of them (OpenSCAD) that you actually write a
"program" that parametrically details the final object.
Once you have designed a solid model in any of these,
you export a mesh file (usually with the file type ".STL")
for use in the next step in the process.
The prices range from free (for open source programs such as
tens of thousands of dollars per year of license.
Some of the commercial programs do have a "free hobbyist"
version that is limited in what it can do.
Also, there are some "on-line" design programs available.
Many people (myself included) are willing to share their designs
by posting them to one of the many repositories.
The one I like best is Thingiverse.
That's where I post mine.
As far as I know, they don't let people charge for downloading their designs
(though the person posting it may prohibit you from selling objects made
from their design).
Every day there are dozens of new designs posted on Thingiverse (go to Explore and select Things to see the newest first).
There are some other repositories that allow people to charge for their
Slicing the model
Having a 3-D "picture" of what you want to print, in the form
of a mesh file (usually a ".STL" file) is nice, but 3-D printers
can't directly make it from that.
For one thing, the mesh file very well may start at the top, when the
3-D printer needs to start at the bottom.
Also, the mesh file only includes information about what the
surface of the object is like,
and it (usually) does not include information about what's
"inside the solid parts".
There is a process to convert the model to something that the
3-D printer can actually use.
It's called a "slicer", or
The name comes from the idea that the 3-D printer builds up
the object using fine slices,
sort of the way a cook might build a sandwich.
There are a number of slicing programs available.
To name a few:
There are several others.
For what it's worth, I normally use Cura.
The slicer programs prepare what is called a "gcode" file.
The gcode is an extension of an older standard for controlling things
like milling machines.
It includes things like setting the temperatures that the 3-D printer
uses, moving the printhead around (usually after calibrating it to
the print bed), and when and how fast to feed the filament.
The slicer program also deals with the "infill" for
"solid" portions of the object.
To conserve both materials and time, the slicer program is capable
of doing a sort of "honeycomb" structure within the
The user can specify a percentage infill, from 0% (empty) to 100%
Parts that have higher mechanical stress, and thus need more
strength, can be printed at higher fill levels.
Printing the model
Once the "gcode" has been generated, you need to actually
get it to the printer, and have it print it.
There are also some steps that (sometimes) need to be taken to
prepare the printer, but I'll mention those later.
There are basically three ways that you can do this,
depending on which printer you actually have:
- Use your main computer
- Controller built into printer
- Separate Single Board Computer as controller
Using your main computer
Although this is the least expensive (at least at the start),
it does tie up your computer and you may have problems doing
other tasks while running the 3-D printer.
Since large prints can take several hours, that can be a problem.
Also note that the 3-D printer can introduce large amounds of
vibrations and shocks into the table that it's on,
and if you try to use the typical general purpose computer
and have it on the same table, you may soon have problems
induced by the vibrations and physical shocks.
Some slicing programs, such as Cura, can actually send the
gcode to the printer while it's being generated, rather than
sending it to a file.
Controller built into printer
Some (many) higher-end 3-D printers include a controller computer
that has a nice LCD display screen,
and some user-interface controls.
You download the gcode file to the printer, via a USB connection,
a memory card or stick, or possibly a WiFi connection.
You use the controls to select which file you want to print,
as well as some other possible prarameters to control (such as
adjusting the temperatures the printer will use).
Separate Single Board Computer as controller
You can use a Single Board Computer, such as a Raspberry Pi,
to control your 3-D printer.
One good program to do this is called OctoPrint.
You can then talk to the Raspberry Pi via either ethernet
or WiFi, and it controls the printer.
Once it's set up, you can use any device that has a web browser (that can
get into your local network)
to actually control the printer.
If you have an older "Model B" Raspberry Pi sitting around,
this is a good use for it, as OctoPrint will run quite happily on it.
(By the way, this is the setup that I use, as I happened to have a spare
Model B that was not doing anything.)
Common problems in printing the model
There are many things that can go wrong when actually
doing a 3-D print.
However, there are generally things that can be done about every
(Lots of folks are making lots of 3-D prints,
so it's just a matter of fixing what's wrong.)
To name a few things that can go wrong:
Going into the solutions is beyond the scope of the overview,
but I will say that the most common problem I've seen are
adhesion problems, that is, getting the object being printed
to stick to the print bed.
The main things to do about this are to make sure the
actual print surface is clean, and that the plastic
being printed has a good chance of adhering to it.
(For some plastics, this may mean putting a layer of blue
painters' tape down, while for others this may mean putting
a coating of adhesive down.)
- Adhesion problems
- Printer alignment problems (especially vertical)
- Filament feed issues
- Delamination between layers
- Clogged extruders
Limitations of 3-D printing
There are several limitations to what can be 3-D printed,
though there are also some things that can only be produced
by 3-D printing.
Some of the limitations and drawbacks of 3-D printing
Some of these limitations do have work-arounds.
- Time it takes
- Size limits
- Need for physical support
- Smoothness of surfaces
- Multi-color is difficult
Time it takes
The time to print an object will often be in the hours,
depending on the complexity of the object and how big it
It also depends somewhat on exactly what type (and even
color) of plastic is being printed.
(The colorants used in the plastic can affect it's
properties, and sometimes this means printing more
It's also a bad idea to leave the printer alone for
very long, as there are many things that can go wrong.
At best, they cause a print to be ruined, and may
make a horrible mess.
At worst, they can cause a fire.
(Once you've got it set up correctly, you don't
have to watch it every moment, but checking on it
every few minutes is a very good idea.)
Due to how long it takes to produce an object,
if many copies of the same object are needed, it may
be less expensive to make a mold and injection mold
It should be noted that making even a simple mold
costs several thousand dollars,
so this is only economically viable when the number
of objects exactly the same design to be made is
Injection molding machines can generally make several,
to even hundreds, of objects per hour
(again, depending on both the size and complexity of
While comparing injection molding and 3-D printing,
it should be noted that injection molding generally
uses pelletized plastic, while 3-D printers generally
use an extruded filament (which itself is made from the
This means that the cost of the actual plastic for
3-D printers is
several times that of what's used for injection molding.
Also, it's easier to "reuse" plastic (e.g.,
from objects that didn't come out quite right) for injection
(One can get an extruder that accepts the pellets, or
ground up bad prints, and makes "new" filament
out of them, but the cost of the extruder will exceed
what most folks will spend on filament in several years.)
About the smallest 3-D printer on the market has a
"print space" of 100mm X 100mm X 100mm
(about 4 inches on a side).
Many printers can do 300mm on a side, and a few
can do more than that,
though going much beyond
that introduces its own problems.
It should be noted that there is some
"unusable" space on every side of the object
Although this is, to some extent, controlled by the
software, it's typically about 5mm to 6mm (roughly
1/4 inch), on each side, or about 10mm to 12mm (a
half inch) in every direction that can't be
By comparison, there are injection molding machines
that can deal with objects several meters on a side
(think large truck parts), though ones this big are
few and far between.
Much more typical are ones that can do 500mm or so
on a side.
Need for physical support
Because the prints are made of layers, every layer (after the first
one) needs to have something underneath it.
It will work to have an object that expands with height,
though as a general rule of thumb the overhang should not
exceed 45° of angle.
The one exception to this is that it is possible to
"span" short distances, usually a very few
millimeters, as long as there is support on each end.
Most of the slicer programs are capable of including
small support structures in the print,
thus allowing it to be printed with a single plastic.
After the object is printed, the support sturctures
are then either broken off or removed with a knife.
Many professional grade machines,
and some hobbyist grade machines,
are able to print using
two different plastics, intermingling them.
One of the plastics is usually selected to be soluable in
some solvent (e.g., water) that does not effect the
Once the printing is completed, the object is immersed
in the solvent to dissolve the supports.
Smoothness of surfaces
Given the fact that the printers work by putting down a
series of layers of "threads" of plastic,
it's no surprise that the printed surfaces aren't
However, depending on which plastic you're printing,
it is possible to do some "post processing"
to make the surface smoother.
For instance, if you are using ABS, it is possible to
use acetone as a solvent to smooth out the surface.
Multi-color is difficult
Today we're used to having 2-D printers (that print on paper)
that can print in "full color".
(Actually, this is a bit of an illusion, as they really
only print in 3 colors, though they usually also have black
ink as much of what gets printed is black.)
They work by printing a series of fine dots, and adjusting
the amount of the three "primary" colors to
get the desired color.
Part of the trick is that the dots are so fine that they
appear to the eye as a single dot of the resultant color
Today (2015), a 300 dots per inch (DPI) printer is considered
to be not all that good.
For a 3-D printer, it's not unusual to lay down the layers
at a rate of about 70 or so per inch, or less than a quarter
the resolution of even a cheap paper printer.
Furthermore, most consumer grade 3-D printers have only
a single extruder, though some have two extruders.
This means that they can only build a print with one color
(or two colors for a dual extruder).
While it is theoretically possible to build a printer with
three extruders, it would be much more expensive using
Also, the results would likely be disappointing given the
Although most 3-D printers are capable of higher resolution,
the time to actually print the object goes up dramatically.
To achieve higher resolution, a tip with a smaller opening
needs to be used, meaning many more passes per layer, and
many more layers.
Another issue with multiple extruders is that the stepper
motor that drives the extruder needs to be actually at the
Most designs for 3-D printers have a movable printhead,
meaning that the extruder moves.
Having multiple extruders means more mechanical load on
the moving mechanism, which creates more demands for a
rigid structure, further increasing cost.
I probably should also mention that it is a bit of a hassle to
change filaments with today's technology.
The extruder has to be brought up to temperature (this
can take 10 or so minutes), then the old filament has to be
removed, and the new filament fed through the extruder.
Steps then need to be taken to clear the old filament
from the extruder.
The easiest way to do this is to print a small object,
like a calibration block (which also verifies some of the
other settings of the printer).
This screen last updated: 08-Oct-2015
Copyright © 2015 by Clark Jones