SCS186: Name: ___________________ ID: _____________ Group: _____ Date: ______
Lab Introduction to 3D printing: 3D modeling, slicing & g-code.
Notes:
During this session, we will mainly work on the computer to prepare models for 3D printing.
It would be great if each group could bring at least one additional laptop with the following
software installed.
Some questions/research can be done before coming to the lab.
3D modeling software: FreeCAD, link: https://www.freecad.org
Slicing software: Ultimaker Cura, link: https://ultimaker.com/software/ultimaker-cura/
We will use the profile AnyCubic Kobra.
Take time to watch all the videos presented in this sheet.
Introduction
The development of 3D printing technology enables the fast prototyping of complex
models. It revolutionized the industry by enabling a new way to produce complex shapes.
Various types of printers exist (resin, extrusion, and powder-binding), but today, we will only
focus on extrusion-based 3D printing technology.
The most known application of 3D printing is a home 3D printer such as the one we will use
in this lab. It enables the creation of small objects made of various plastic materials.
Video: 3D printed Eiffel Tower time-lapse, link: https://youtu.be/FqQAjkZOBeY?si=ODFm_v8bhjUyjAp
Figure 1: 3D printing of Eiffel Tower.
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Question: Find the common materials used by home 3D printers (3 materials). Discuss their
different properties. – Note – You can prepare this question before coming to the lab!
In addition to the 3D printing of plastic material, the 3D printing technology enables printing
a wide range of different materials depending on the application. Let’s discover some.
On a large scale, 3D printing can form objects such as houses and/or bridges using materials
such as metals or concrete. Recently, SIIT collaborated with SCG on a project related to the 3D
printing of concrete. At the end of the project, SCG would print a building at SIIT.
Video: How Concrete Homes Are Built With A 3D printer, Insider Art, link:
https://youtu.be/vL2KoMNzGTo?si=SQ_yzwA1P0OZ1_cM
Figure 2: 3D printed home.
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Currently, researchers are working on using 3D printing technology to enable the development
of new foods.
Videos: 3D Printed Vegan Steak That Tastes like Real Meat, link:
https://youtu.be/238yRdb0niw?si=qdr0cEEDkp75scWw
Videos:7 layers printed cheesecake, link:
https://youtu.be/ECCLUIe3Lus?si=j-VuvLqh1mIpaEaZ
Figure 3: 3D printed cheesecake.
Question: Discuss 2 more fields/applications not presented here where the 3D printing
technology can be used. Give some examples. – Note – You can prepare this question before
coming to the lab!
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Preparation of 3D objects.
Today, we aim to prepare 3D objects from scratch. As we currently have one 3D printer, you
must create 3D objects and make the necessary adjustments before printing. The objects will
be printed later, and you will use them for the material testing lab.
The first step consists of modeling 3D objects. To do so, we will use the software FreeCAD.
There is other software available, but today, we will introduce this one as it is free and has a
user-friendly interface.
1. Open FreeCAD and select “Create new”.
Figure 4. FreeCAD opening interface.
2. We land on an empty workspace. Observe the UI (User Interface).
3. Select the workspace dropdown list. We will mainly use the Part Design and Sketcher
workspaces.
Figure 5. Workspace dropdown list.
4. Select the “Part Design” workspace.
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5. Before starting, save your file as GroupA_SecB_cube where A and B are your group
and section number. The file's name should appear in the “Model” section of “Combo
View” on the left.
Figure 6. Combo view.
6. Before starting, save your file as GroupA_SecB_cube where A and B are your group
and section number. The file's name should appear in the “Model” section of “Combo
View” on the left.
7. Now, we must indicate the software that we will create a new object. To do so, click
“Create a new body” or “Create part” on the upper ribbon. The part appears under the
previous model’s name.
Figure 7. Create part.
8. Now let’s click on “Create a sketch”.
Figure 8. Create sketch.
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9. We first need to select the axis plane we want to use. Move the mouse over the x-y
plane, select the “XY_Plane,” then click “Ok”.
10. We now arrive in the Sketcher workplace.
Figure 9. Sketcher workplace.
11. The upper ribbon is separated into 4 lines. The first is for general options, the second is
for viewing, and the last two are related to the sketch of the 3D objects.
We will focus on these. The third line draws items such as squares, circles, lines… The
next line is related to the constraints submitted to the drawn items.
Figure 10. Drawing tools list.
12. The objective here is to prepare a square WITHOUT using the square tool. To do so,
let’s start by drawing 4 lines separated from each other. Avoid drawing parallel lines.
Figure 11. Lines drawn randomly.
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13. Now, we will look at how to turn these lines into a square using different constraints.
Figure 12. Constraints lists.
14. Find the “Constraint Coincidence” tool. Click on it, then select two points.
Question: What does this constraint do?
15. Repeat this action to connect all the lines together and to form a 4-sided polygon.
Question: Select one point or one line in the polygon. Move it, observe, and note what happens.
16. Find the “Constrain Parallel” tool. Click on it, then select two lines. Repeat until you
obtain a square.
Question: What does this constraint do? What other constraints can we use to form a square?
Select one point or line and move it. What happens?
17. Now we have a square. Before forming a cube, it’s important to fix its dimensions and
to fix its position in the 2D/3D space.
Note: You can zoom in/ zoom out in the space by scrolling with your mouse.
18. Find the constraints “Constrain horizontal distance” and “Constrain vertical distance”
and set both distances to 30 mm.
Note: The lines indicating the length can easily be moved out of the design by selecting and
dragging it outside.
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Figure 13. Square prepared.
19. Close the Sketcher workspace by clicking on “leave” the Sketcher. We are now back in
the Part Design workspace. Now, let’s form our 3D object.
20. Select the “Pad” tool. Set the length accordingly to obtain a cube.
21. On the combo view, select the object by clicking on “Body,” then click on “File” and
export your file as GroupA_SecB_cube.stl (you need to look for the correct extensions),
where A and B are your group and section numbers on the computer desktop.
Figure 14. Pad tool.
Question: Put a screenshot of your cube below.
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If you want to print your cube during this lab, move to the next session “Slicer” and
prepare the file accordingly. Once the file is ready, inform your TA to check it and start
the printing.
It’s time for you to create your 3D object that will be tested during the material testing lab.
You are asked to create two objects respecting the given dimensions.
Izod specimen
An Izod specimen is presented in the following figure (2D sketch).
The dimensions are:
- Length = 64 mm
- Height = 13 mm
- Width = 3.2 mm
̂). Length AC = 32 mm, Height AC = 3 mm,
- Triangular notch with an angle of 45°(BCD
̂ =?
angle ABC
A
B
D
E
C
G
F
Figure 15. Izod 2D sketch.
Prepare it with FreeCAD.
Note: You may need to use constraints not used before to set the angle.
Export your file as GroupA_SecB_Izod.stl.
̂ ? What tool did you use? Place a screenshot of your object.
Question: What is the value of 𝐴𝐵𝐶
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Tensile test specimen
We are now interested in designing a specimen for tensile testing, as presented in the following
figure. Can you design it?
Figure 16. ASTM D638 Specimen Type I.
If you can’t design it, go to the following website: https://www.thingiverse.com
- Search for ASTM D638 Specimen Type I.
- Download the correct object, “Tensile_Test_Type_I.stl”.
- Open it with FreeCAD.
Question: Place a capture of your object below.
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Slicer.
After preparing the 3D object, it is important to slice it. Slicing is an operation that transforms
a given object file (.stl) into a set of instructions that will be followed by the printer to form the
physical object. There is many slicing software available, but we will use Ultimaker Cura. Most
of the software operates in the same manner.
The printing available in this lab is the Anycubic Kobra 2. This printer is quite popular because
it can print at a speed up to 300 mm.s-1. However, today, we will not use this high printing
speed.
(https://www.anycubic.com/products/kobra-2)
Figure 17. Printer used in this lab.
One material will be used to carry out printing. The material is PLA.
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A 3D printer can easily be represented in the following figure.
Each part has its importance.
Question: Name all the different parts. Discuss their role.
Object, heated extruder, filament, support, heated bed.
Figure 18. Schematic of a 3D printer.
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Table 1. Printer settings according to the selected material.
Printing Temperature
Printing Speed
Bed Temperature
PLA
200 – 220 °C
30 - 50 mm.s-1
70 °C
PETG
225 – 245 C
30 - 50 mm.s-1
85 °C
1. Open the software Ultimaker Cura
2. Check that the printer AnyCubic Kobra is correctly selected.
3. Open your ATSM D638 tensile specimen file. You arrive on the following screen.
Figure 19. Cura view.
On this view, we have XX areas of interest.
- The area circled in yellow corresponds to the object list and different views available.
It is important to note that the camera can be rotated by pressing the left button on the
mouse and moving.
- The area circled in blue directly concerns the object. By looking at the different options,
it is possible to reshape the object, move its original position, or even rotate it.
- The area circled in red corresponds to the tool to open the file, select the printer, and
select the printing material. Make sure to select the Anycubic Kobra and your
assigned material.
- The area circled in green concerns the printing settings. We will look more at it in the
following pages.
- Lastly, the area circled in orange is the slicer button. When pressed, the software will
prepare a g-code, a series of code lines used by the 3D printer according to the
parameters and shape previously designed.
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4. Select the objects individually to ensure their dimensions are correct, Table 2.
Table 2. Object dimensions.
X (mm)
Y (mm)
Z (mm)
ATSM D638
165
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3.2
5. Move the ATSM specimen at Y = 35 mm.
6. Now, let’s work on the printing settings (green area). Click on it and verify that the
profile selected corresponds to your material. Change it if not by selecting “Kobra 2 –
Cura – material suggested parameters”.
Note: This last selection corresponds to the printer supplier's predefined setting. Every printing
parameter here can and must be modified according to your needs.
7.
-
Modify the parameters related to the print quality as follows:
Layer Height = 0.2 mm
Initial layer height = 0.2 mm
Line width = nozzle diameter = 0.4 mm
8. In the walls category, set the number of walls to 1 or 2.
9. In the top/bottom category, set the number of top and bottom layers to 0.
10. Vary the infill category as you wish. Select the infill type you prefer. The infill density
must not be above 60%. Fill out the following table.
Note: To observe the different infill patterns, click the slice button. There, you can observe how
the infill will be printed, the duration of your print, and the quantity of material required, figure
20. Changing any parameters in the setting will require clicking on slice one more time.
Number of walls
Infill type
Infill density
Number of layers
Filament required (g)
Print duration
Do not exceed 10 g of filaments and 0.5 hours of printing time.
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Figure 20. Infill observation.
11. The last part concerns the material properties and, more precisely, the printing
temperature. Select a temperature according to table 1.
12. Change the printing bed adhesion to “Skirt”.
Question: Select an appropriate temperature for your material. What temperature did you
choose? Why is it important to set the extrusion temperature ideally?
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13. Press Slice, save your file as GroupA_SecB_print1.gcode, then send it by email to your
TA at the end of the lab.
14. Repeat the same operation with the same object. This time, you must change the infill
type, and the infill percentage must be lower than the first one by a factor of 2.
Complete the following table and submit the stl file to your TA as
GroupA_SecB_print2.gcode.
Number of walls
Infill type
Infill density
Number of layers
Filament required (g)
Print duration
Do not exceed 10 g of filaments and 0.5 hours of printing time.
Now, do the same with the Izod specimen. Start creating a new project by clicking “File”, “New
project”. You must open the Izod specimen .stl file twice as we will print this object two times.
Follow the same instructions to slice your file, but we will initiate a group competition
here. In the next session, you will be asked to conduct material testing. To do so, we will
carry out some measurements of the material’s fracture.
You are limited to a maximum infill density of 80%, 20 min of printing, and 12 g of
materials.
Question: How can you make your material more resistant to fracture? Which printing
parameters can you modify? Place a capture of all your settings on the next page.
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G-code.
After slicing, the software generates a g-code. A g-code is a computing language that some
machines, such as a 3D printer, can read. It gives the machine a precise set of instructions to
follow.
Figure 21. Part of a printing g-code.
Go to the website: https://gcode.ws
Import one of your g-codes and visualize it.
Question: Place a capture of the presented object and look at the tab g-code. Place a capture.
What do you observe?
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Question: Find the meaning of the following instructions. You can search online.
G1
Z1.6
X40
Y60
M109 S210
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Brief summary of what you’ve learned during this session.
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Topics
Score
from
lab
book
(10)
2
-
Models
Examples
-
Accuracy of the drawn models
Respect of the printing constraints
Relevant printing conditions
-
1
-
Photos/
Capture
-
Note down important details in the lab book.
Make simple sketches, simple yet important
details! E.g., for some experiments, if
ambiguity could occur about where you
make measurements, can just take a photo
for later investigation / or to be attached in
the lab book.
Do not be overcomplicated.
-
2
Neat work
-
Basically, neat means traceable later. Not
necessarily a beautiful look, but tidiness helps.
Good Observation and noting down in the lab
book/ the extra interesting points noted in the lab
book.
- Sufficient writing of what is going on, even when
things do not work out, scientifically.
-
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Discussion
-
Note down observation, e.g., the temperature
continues rising a bit. The current max out at 3A
flat – cannot go higher, there was smoke, etc.... Or show some calculations/ derived quantity
Extra resources you obtained from the
internet/TA/instructor
can
be
included/added to enhance your
understanding too.
-
1
Accuracy
-
Most results/records are sufficiently accurate,
sensible within the range of the instruments, e.g.
can measure at most 0.1mm, not stating anything
like 0.0001mm in the record.
Missing results, or make-up results has 1 pt off.
Badly-off results, or results that do not make sense
should be discussed, or given indication, and
possibly repeated.
-
1
At the end:
Reflection
Student
score
-
Summary of key points,
What have been learned.
What could be fun ideas to do further / opportunity/
innovation?
(Can submit right away after class, or no later than midnight).
Late submission results in the 0.8 factor.
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Additional information
SLT objects library: Free STL file available.
https://www.thingiverse.com/
FreeCAD wiki: https://wiki.freecad.org/Main_Page
Scientific Journals:
- Additive Manufacturing → current development in 3D printing for various application
https://www.sciencedirect.com/journal/additive-manufacturing
- Bioprinting → 3D printing applied to biological applications
https://www.sciencedirect.com/journal/bioprinting
- Journal of Food Engineering → large collection of food printing articles
https://www.sciencedirect.com/journal/journal-of-food-engineering
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