1. Equipment/Software Utilized
• MakerBot Replicator2
• MakerWare
• Skeinforge
• MTS InsightTM Electromechanical 5[kN]
Universal Test Machine
• MTS Direct Contact Extensometer
• MTS Clip Gauge
• MTS TestWorks 4
Research Methodology
Specimens are printed by a MakerBot Replicator2 in batches of 9 using uniform settings corresponding to their run whereas each batch
contains 3 specimens of each of the 3 orientations. Specimens are designed and tested to ASTM testing standards D638 and D5045. These
specimens are then subjected to uniaxial loads with an MTS InsightTM Electromechanical 5kN Universal Test Machine till complete failure.
Due to the nature of thermoplastics, a method was developed to account for the extensions beyond the capabilities of the measurement
devices. The method developed utilizes a linear correlation between the extension and the displacement of the measurement devices. The
derived information is input into a spreadsheet that calculates the influence of the factors on the material characteristics.
The FDM style 3D printer has recently garnered mass popularity
which lead to their utilization in home and small businesses and
encouraged by their relative cheapness and safety. Growth
encouraged research into material properties of FDM parts.
Historically research has focused specimens manufactured out
of acrylonitrile butadiene styrene (ABS), a popular
thermoplastic. As of recently though, a newer thermoplastic
called polylactic acid (PLA) has garnered popularity.
Unfortunately, FDM manufacturing can produce tremendous
amounts of waste, of which doesn’t include specimens that
break. This creates a demand for optimizing the part material
properties to reduce both material and monetary waste. To
adequately optimize the specimen properties, the parts must be
manufactured using a variety of printer settings (factors, shown
in Table 1). The quantity of specimens manufactured can be
lowered through the utilization of a statistical method, taking an
example from related research the Taguchi Method is chosen.
Taguchi Method
The Taguchi Method is a statistical method utilized to determine
an experimental array by which multiple factors, adjustable of
popular fused deposition modeling (FDM) printer can be
evaluated simultaneously without the need for excessive
testing. In this experiment alone it drastically reduced the
quantity of specimens needed from 1152 to 144. The results are
calculated using analysis of variance (ANOVA) in order to
determine factor impact on tensile and fracture characteristics,
such yield strength (σy), Young’s modulus (E), and fracture
toughness (KIC).
Figure 2: Pictures taken of a pair of specimens on the print bed of the
MakerBot Replicator2.
To present the influences of several production variables on the
mechanical properties of specimens manufactured using fused
deposition modeling (FDM) with polylactic acid (PLA) as a
media and relate the practical and experimental implications of
these, especially as related to end-use of manufactured
products by consumers.
Optimization of Mechanical Properties of Fused Deposition
Modeling with Polylactic Acid for Consumer End-use via Design
of Experiments
Zachary DeMastry
Mechanics of Materials Research Group
University of Central Florida
Figure 3: Naming convention for the different orientations
possible on an FDM device.
Results/Conclusions
Based upon the data, it is observed that the three settings with
the greatest overall influence upon the material properties of FDM
specimens are: Density, Thickness, and Temperature. Orientation
has heavy influence on material properties too, as illustrated in
Figures 4-11. However, such information has been established in
previous research and thusly will be omitted as a result from this
research. It should be noted that the Perimeter setting has a
greater influence than Temperature in the L1-S orientation. For
certain properties, the actual numerical difference between the
factor influence coefficients produced through the Taguchi
method can be negligible though.
Table 2-4: The ranks of each factor on material properties for each
orientation. Color coded to highlight the three most influential settings
overall.
Future Work
In addition to this research conducted utilizing tensile and fracture
testing, there are follow-up specimens to be manufactured with
the purpose of verifying a combination of settings to theoretically
yield the greatest strength. This work is to be followed by similar
sets of experiments designed to find the optimal settings to
achieve the greatest shear and compressive properties.
2013-2014 EXCEL Program
Background
Objective
References
1. ASTM, 2010, “Test Methods for Tensile Properties of Plastics”, D638
2. ASTM, 2007, “Standard Test Methods for Plane-Strain Fracture Toughness
and Strain Energy Release Rate of Plastic Materials”, D5045
Acknowledgements
This research is conducted with funding provided by the National
Science Foundation, Duke Energy, and the University of Central
Florida. Also, this project is kept in motion due in part to the
efforts of :Jonathan Torres, Matthew Cole, Allen Owji, and Ali P.
Gordon.
S-L1 Ranking by Influence on Property
Material Property 1 2 3 4 5 6
Young's Modulus, E Thickness+ Density+ Temperature+ Perimeter+ Infill Direction+ Speed-
Max Stress, σmax Thickness+ Density+ Temperature+ Perimeter+/0 Speed+/0 Infill Direction0
Yield Strength, σy Thickness+ Temperature+ Density+ Speed+ Infill Direction0 Perimeter-/0
Modulus of Resilience, Ur Thickness+ Temperature+ Speed+ Density+ Infill Direction+/0 Perimeter-/0
Max Load, Pmax Density+ Thickness+ Perimeter+ Infill Direction+ Temperature+ Speed-/0
Critical Load, PQ Density+ Thickness+ Perimeter+ Infill Direction+ Temperature+/0 Speed+/0
Ultimate Strength, SUT Thickness+ Density+ Infill Direction+ Perimeter+/0 Speed+/0 Temperature+/0
Fracture Toughness, KI Density+ Thickness+ Perimeter+ Infill Direction+ Temperature+ Speed-
L1-L2 Ranking by Influence on Property
Material Property 1 2 3 4 5 6
Young's Modulus, E Density+ Temperature+ Infill Direction- Perimeter+ Thickness- Speed0
Max Stress, σmax Thickness- Infill Direction- Density+/Tempertature+ Speed- Perimeter+/0
Yield Strength, σy Temperature+ Density+ Perimeter+ Thickness-/Infill Direction- Speed+
Modulus of Resilience, Ur Temperature+ Density+ Speed+ Perimeter+ Infill Direction+ Thickness-
Max Load, Pmax Density+ Temperature+ Thickness- Infill Direction+ Perimeter+ Speed0
Critical Load, PQ Density+ Temperature+ Thickness- Infill Direction+ Perimeter- Speed+
Ultimate Strength, SUT Density+ Thickness+ Speed+ Temperature0 Perimeter0 Infill Direction0
Fracture Toughness, KI Density+ Temperature+ Thickness- Infill Direction+ Perimeter- Speed+
L1-S Ranking by Influence on Property
Material Property 1 2 3 4 5 6
Young's Modulus, E Density+ Temperature+ Perimeter+ Thickness+ Infill Direction+ Speed+
Max Stress, σmax Density+ Thickness+ Perimeter+ Temperature+ Infill Direction- Speed0
Yield Strength, σy Density+ Thickness+ Perimeter+ Temperature+ Infill Direction- Speed0
Modulus of Resilience, Ur Thickness+ Density+ Perimeter+ Infill Direction- Temperature+ Speed-/0
Max Load, Pmax Density+ Thickness+ Perimeter+ Speed- Infill Direction+/0 Temperature-/0
Critical Load, PQ Density+ Thickness+ Perimeter+ Speed- Temperature/Infill Direction0
Ultimate Strength, SUT Thickness+ Density+ Temperature- Infill Direction+ Perimeter+ Speed-
Fracture Toughness, KI Density+ Thickness+ Perimeter+ Speed- Temperature/Infill Direction0
Figure 1: Microscopy of specimen. Illustration denotes a specimen
with 100% Infill and 30% Infill on the left and the right respectively.
0
500
1000
1500
2000
2500
3000
3500
Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Run 8
Young'sModulus(MPa)
E
L1_L2
S_L1
L1_S
0
5
10
15
20
25
30
35
Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Run 8
YeildStrength(MPa)
σy
L1_L2
S_L1
L1_S
Factors
Run
Temperature
(°C)
Speed (mm/
s)
Infill Direction
(°)
Relative Density (%) Thickness (mm) Perimeter Layer
1 215 60 90/180 0.35 0.1 No
2 215 60 90/180 1 0.3 Yes
3 215 120 45/135 0.35 0.1 Yes
4 215 120 45/135 1 0.3 No
5 230 60 45/135 0.35 0.3 No
6 230 60 45/135 1 0.1 Yes
7 230 120 90/180 0.35 0.3 Yes
8 230 120 90/180 1 0.1 No
Table 1: Taguchi Test Matrix.
0
0.05
0.1
0.15
0.2
0.25
Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Run 8
ModulusofResilliance(MPa)
Ur
L1_L2
S_L1
L1_S
0
5
10
15
20
25
30
35
40
Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Run 8
MaxStress(MPa)
σmax
L1_L2
S_L1
L1_S
Figure 5-8: Shows a comparison between the tensile properties across all runs and help to
exemplify the importance of the respective orientation.
0
50
100
150
200
250
300
350
400
450
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Load(N)
Displacement (cm)
Fracture Run 1
L1L2-
1
SL1-2
0
50
100
150
200
250
300
350
400
450
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Load(N)
Displacement (cm)
Fracture Run 2
L1L2-1
SL1-1
L1S-3
Figure 8-11: Comparing orientations via fracture testing results
0
50
100
150
200
250
300
350
400
450
0 1 2 3 4 5 6
Load(N)
Displacement (cm)
Fracture Run 4
L1L2-2
SL1-2
L1S-2
0
50
100
150
200
250
300
350
400
450
0 0.5 1 1.5 2 2.5 3 3.5
Load(N)
Displacement (cm)
Fracture Run 6
L1L2-
1
SL1-3
L1S-2
Figure 4: Example of how material properties are drawn
from a typical Stress vs. Strain curve.
Experimental Setup
Specimen (Illustrated below from left to right: fracture specimen and tensile
specimen) is positioned into the MTS load frame as Illustrated below. A measuring
device (extensometer for fracture, clip gauge for tensile) is then attached to the
surface of the specimen. The load frame then applies a uniaxial tension force on the
specimen, while recording force and extension data, which continues until total
specimen failure.
Fracture Mechanisms of Specimen
Due to how FDM manufacturing builds parts, in a stacking fashion, internal
structure this process creates illustrated in Figure 1. As a consequence of this
internal structure, specimen manufactured this way have a sort of
“grain” (functioning similar to wood grain), based upon structural orientation.
This causes the components to behave in different ways dependent on the
direction of an applied force. Standard fracture mechanics indicate that a
component will fracture between two layers of material, called delamination.
Standard fractures as determined by ASTM standard D5045 should manifest
themselves in a manner similar to what is shown to the right. Figure 12
illustrates delamination along unintended planes.
Top view Inner surface view
Figure 12: Illustration of a
fracture specimen undergoing
delamination in an
unexpected direction.
Figure 13: Illustration of a fracture
specimen that failed in a non-
delamination manner.