UNDERSTANDING
FDM PRINTERS
4
CHAPTER
PART II: HARDWARE AND
PRINTING CHOICES
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Consumer 3D printers are described by the material and process they use to create physical objects. There
are two main descriptors of consumer 3D printers: those that use filament, and those that use liquid resin.
The filament-based 3D printers are called “Fused Deposition Modeling” (FDM) machines, and the 3D print-
ers which use light-hardened liquid resin are generically called “Resin Printers.” In this chapter, we will
focus on the FDM technology, which is the most commonly used consumer-level 3D printer. In the following
chapter, we will focus on resin printers.
A fun fact: Many (if not all) of the consumer 3D printers being used today originated from a community-
driven project called the “RepRap Project.” This project started in 2005 in England and is open-sourced
which means any future software development made must be available to all to use. This grass-roots
FIGURE 41: Anatomy of an FDM 3D printer (infographic by HoneyPoint3D™)
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community advanced FDM printing in the years to follow and the concept of keeping the advancements
available to all was contested in the years to follow with some companies wanting to “close-source” their
developments.
RepRap stands for “Replicating Rapid Prototyper.” You can learn more about it at http://RepRap.org. This
“Project” is a global community of tech-savvy people that came together to work on 3D printer hardware
and software in an effort to create and refine freely available 3D printer designs, democratizing user access
to this world-changing technology.
The first RepRap Project focused on the FDM printer, as FDM printing is more simple and straightforward
than resin printing. In 2009, patents on FDM printing expired, allowing the world to delve into custom printer
creation. They donated their time and work to the world, and to you.
Today, you can purchase a 3D printer kit you can assemble yourself by following detailed instructions, or you
can buy a fully assembled unit that is designed to be usable right out of the box...the choice is up to you!
ALL FDM 3D PRINTERS WILL HAVE THE FOLLOWING COMPONENTS SHOWN IN FIGURE 41:
Filament
Extruder or extruder assembly
Build plate/build area
Linear movement components
Frame / chassis
Controller unit
Stepper motor for the extruder assembly, to allow the build plate to move in one or more direc-
tions, and a motor to raise/lower the build plate
HERE’S A BASIC DESCRIPTION OF WHAT THE PARTS OF AN FDM 3D PRINTER DO:
• The BUILD PLATE (or PRINT BED) is a level, flat area where the 3D print starts.
• A FILAMENT SPOOL holds the plastic that will be melted.
• THIN FILAMENT (usually a type of thermoplastic) is wrapped around a filament spool and is the
raw material the 3D printer uses to make objects. Consumer printers print with a filament that is
one of two diameters: 1.75mm or 3mm. Diameters are not interchangeable, so be sure to research
what your printer uses.
• The EXTRUDER is the name for the assembly that grabs the filament and pushes it down through
the hot end (described below).
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• STEPPER MOTORS control the belts to create the movement of the build plate and extruder.
• The CHASSIS is the frame of the 3D printer, which could be made from metal, plywood, plastic, etc.
• The HOT END is the part of the extruder that heats the filament to just the right temperature based
on that material, and has a nozzle at the bottom to allow the molten filament to flow through.
• A FAN blows air over the in-process part, helping to remove excess heat from the physical model,
making the depositing and bonding of the layers more successful.
TAKE NOTE: There are many consumer 3D printers on the market, with a variety of features and functions.
For instance, some have print beds that do all the moving, while others rely on the extruder assembly to do
all the movement. All are valid designs and particular choices come down to personal preference.
RESOLUTION LEVELS
Let’s take a moment to talk about how 3D print quality is defined. In the more prevalent 2D printing world
you will see printers that claim “600 dpi” or “1200 dpi” resolution. Those metrics refer to “dots per inch” of
ink deposited on the paper. The more little dots of ink per inch, the higher the resolution. It’s similar in 3D
printing, but the process is about layer height and nozzle size!
ALL 3D PRINTERS (FDM AND RESIN) HAVE TWO DIFFERENT TYPES OF RESOLUTIONS:
• Z is the height resolution (in the up/down, or Z plane)
• XY is the positional resolution (in the left-right, forward-back, XY planes)
The Z-height resolution is the most common metric you will see in FDM printers. As you can see in Figure
4-2, these three cubes are all the same size, but they are 3D printed at different layer resolutions. All of the
measurements given here are in “microns,” which are fractions of a millimeter. 1,000 microns equal 1 mil-
FIGURE 42: A close-up image of three-layer heights printed at (left to right) 100 microns, 200 microns, and 300 microns
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limeter, so we are talking about resolutions that
are typically around 1/5th of a millimeter (or 200
microns).
In the three example prints in Figure 4-2, the
individual layers are more densely packed on
the left than on the middle or right. If you want a
higher-quality surface finish, then you will choose
a layer height that is smaller, which packs more
layers into your end object. The lower the micron
level, the less you can see the print lines on the
object. 3D printing comes under scrutiny when
people expect plastic 3D prints to look like an
injection molded part, but they are different tech-
nologies with advantages and disadvantages.
When we discuss resin 3D printing in the next
chapter, you will see that the surface finish will
look more like the plastic parts you would see at a store. This is something to consider when choosing
between the two technologies.
The other metric for resolution is the XY accuracy—how accurate each individual layer (if viewed by itself
from the top) can be “drawn” by the printer. Because most FDM printers use a .4 nozzle diameter (400
microns) the size of the “path” of deposited material coming out of the nozzle is around .48 (480 microns).
This “path width” needs to precisely overlap adjacent paths to create the detail on a print. Therefore, at
sharp points, some detail can be lost as you can see in Figure 4-3. While this still results in acceptable print
quality, you will see in the resin printing chapter (Chapter 6), there are other more accurate technologies
available if you need extreme detail.
• STEPPER MOTORS control the belts to create the movement of the build plate and extruder.
• The CHASSIS is the frame of the 3D printer, which could be made from metal, plywood, plastic, etc.
• The HOT END is the part of the extruder that heats the filament to just the right temperature based
on that material, and has a nozzle at the bottom to allow the molten filament to flow through.
• A FAN blows air over the in-process part, helping to remove excess heat from the physical model,
making the depositing and bonding of the layers more successful.
TAKE NOTE: There are many consumer 3D printers on the market, with a variety of features and functions.
For instance, some have print beds that do all the moving, while others rely on the extruder assembly to do
all the movement. All are valid designs and particular choices come down to personal preference.
RESOLUTION LEVELS
Let’s take a moment to talk about how 3D print quality is defined. In the more prevalent 2D printing world
you will see printers that claim “600 dpi” or “1200 dpi” resolution. Those metrics refer to “dots per inch” of
ink deposited on the paper. The more little dots of ink per inch, the higher the resolution. It’s similar in 3D
printing, but the process is about layer height and nozzle size!
ALL 3D PRINTERS (FDM AND RESIN) HAVE TWO DIFFERENT TYPES OF RESOLUTIONS:
• Z is the height resolution (in the up/down, or Z plane)
• XY is the positional resolution (in the left-right, forward-back, XY planes)
The Z-height resolution is the most common metric you will see in FDM printers. As you can see in Figure
4-2, these three cubes are all the same size, but they are 3D printed at different layer resolutions. All of the
measurements given here are in “microns,” which are fractions of a millimeter. 1,000 microns equal 1 mil-
FIGURE 43: XY positional accuracy between layers created
using FDM (left) and resin (right). Notice the sporadic blue
lines of the extruder trying to fill in space on the FDM printer
at the sharp areas, while the SLA print shines crisply,
creating perfectly pointed shapes.
35 Chapter 3: How 3D Printing Is Being Used Today Getting Started with 3D Printing 36
Resolution Versus Speed
An object that prints with a layer height of 100
microns will take at least twice as long to print
as the same object with 200-micron layers. That
is because the printer has to print double the
number of layers for the same object. The lower
the microns, the longer to print, but the higher the
print quality. Additionally, more layers mean more
passes of the extruder, which means more heat
gets put into the model. The model layers might
need a slightly slower print time to cool off to
prevent deformations.
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