Lecture 3- Material extrusion Flashcards
• To introduce Material Extrusion (ME) • To explore the ME process and technologies • To investigate print parameters
Is Material extrusion (ME) solid/powder/Liquid based
Solid
5 Basic steps in ME process(past exam)
CAD – model the required CAD geometry using a 3D CAD
program such as NX or SolidWorks.
STL – convert the 3D CAD model to a .stl file by tessellating the surface of the
CAD model with an airtight mesh.
Setup Build – load the .stl file into the AM machines operating software and set
the part orientation, number of parts, process parameters, and support structures for the
build
Manufacture the component – when the setup is correct the machine is initialised
and the build process begins in an autonomous fashion
Post Process – when the manufacture of the component is complete it must be
post-processed for the particular AM process. This may include but is not limited to excess
powder removal, support structure removal, UV curing, infiltrating parts.
How to design for ME?
Only 3d solids
Avoid thin walls
Allow sufficient clearance between moving parts
Applications of part
Single spool tech VS Dual (EXAM)
Single and Dual spool
Example answer: Most me printers at the low cost end are single spool, meaning that they
run one reel of filament at a time and have one extruder, hot end and nozzle. Low cost is a
key advantage a key disadvantage is that they can only print in one material meaning
support structures can be more difficult to remove. Duel spool machines have two
extruders, hot ends and nozzles and can run two reels within a single print. The two
materials are printed separately in succession for each layer of the print. In addition to cost
this extra complexity increases the print time, however its advantages include easy
removal of support structure for example, if a water soluble materials is used.
What is an integrated extruder
Extruder is situated by the print head thus increasing its mass
Lowers print speed and acceleration
Remote extruders
Situated away from the print head
Can distort the filament
The 2 XYZ Print head technologies.
Cartesian
Delta
ME beds can be heated or ambient
Why?
Prevents warping and cracking
How to calculate extrusion rate?
ER=nozzle diamlayer heightprint speed
Infill structures can be useful for applied forces in fixed trajectories as….
The can offer directional performance
Integrated VS remote extruder (EXAM)
Provide pic from lecture notes
Example answer: Filament driver generally consists of a toothed or grooved bolt attached
to a stepper motor and an adjacent opposing wheel. Filament is squeezed between the
wheel and bolt and this resistance provides the torque to feed or retract the filament.
There are two main types of filament feeding systems or extruders– integrated and remote.
Integrated extruders are built into the print head feeding directly into the melt chamber/hot
end. They are simpler in design but increase the weight at the print head.
The advantages
of the integrated extruder
- easy changeover of filamen
-less chance of feeding
problems and ability to handle softer, flexible materials.
disadvantages is the extra
mass in the print head creates greater inertia and so the print may have to run slower to
limit shaking caused by acceleration and deceleration of the greater mass.
The remote
extruder is sited away from the print head, usually outside the print chamber. They use a
Bowden cable to transmit mechanical force to the hot end. Tend to be faster – less mass in
the print head, but can suffer from friction feeding issues and distortion of the filament by
the filament driver.
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Cartesian VS Delta?
(Exam)
Provide pic from lecture notes
) Cartesian and Delta coordinate systems
There are two main types of XYZ movement that the printers employ to print in 3d space,
Cartesian and Delta. The most commonly used is the Cartesian coordinate system that can
map any point in 3d space to the x,y,z coordinate. Virtually all ME printers using this
system move in straight lines – linear robots. Movement along these linear axes is usually
achieved using fixed rods, timing belts, pulleys and stepper motors. This allows very
precise movements to be made – fractions of a millimetre. Good quality stepper motors are
critical to achieving high quality prints. One of the problem associated with this is this
system is increased vibration caused by rapid acceleration and deceleration in the x and y
axis. The Delta system, as shown in the diagram, moves the print head in 3d space through
a z axis only movement of the three carriages. Movement of one carriage in one direction
(z) will move the nozzle in all 3 (x,y & z). To move the nozzle in one direction may
require movement in all 3 carriages. Requires the application of simple trigonometry to
control the movement of the print head. Because the movement of the carriages is limited
to z axis movement only and the print head is more fluid in movement there is less
vibration and shaking of the printer.
Heated vs non heated chamber
Heated and Non-Heated platform and chamber
The build platform is the base upon which the print is built. These platforms can be fixed
or move depending upon the printer type and movement system employed. The chamber is
the enclosure that contains the part being built, effectively the outside walls of the printer.
Non heated m/c’s are simpler and usually cheaper, however they are limited to the
materials they can run – usually PLA. Heated chambers and platforms are mainly required
for running conventional thermopolymers such as ABS, Nylon etc. that have higher
extrusion/melt temperatures and greater dimensional change when cooling that can cause
warping and cracking of the part. A heated platform can also make part removal easier and
improve initial material to plate adhesion.
(3 marks are given to the description of the
