1. Optimizing quality characteristics
of 3D printer using six sigma
methodology
Submitted by
Shiva Teja Sepuri
Abbas Sayed
Advisor- Dr. Joseph Chen
Department of IMET
2. Introduction:
3D printing or additive manufacturing is
a process of making three dimensional
solid objects from a digital file.
The creation of a 3D printed object is
achieved using additive processes.
In an additive process an object is
created by laying down successive
layers of material until the entire object
is created.
Each of these layers can be seen as a
thinly sliced horizontal cross-section of
the eventual object.
Key Parameters:
• Infill Percentage
• Extruder Speed
• Build Platform Temperature
• Extruder Temperature
• Filament-Maker bot PLA
• No of layers
• No of Shells
3. Working:
This virtual design is made in a CAD file using a 3D
modeling program.
A 3D scanner makes a 3D digital copy of an object.
Not all 3D printers use the same technology. There are several ways to
print and all those available are additive, differing mainly in the way
layers are build to create the final object.
Some methods use melting or softening material to produce the layers.
Selective laser sintering (SLS) and fused deposition modeling (FDM)
are the most common technologies using this way of printing.
Another method of printing is when we talk about curing a photo-
reactive resin with a UV laser or another similar power source one layer
at a time. The most common technology using this method is called
stereolithography (SLA).
4. Company Overview:
Shape ways is a 3D printing company, located in Chicago, IL.
It servers its ever growing customer base from 60,000 units
production capacity facility, and focuses on complex industrial
and plastic components
6. Goal statement:
Improve the part Tensile strength to meet the customer’s requirement
Y=F(x1,x2,x3,x4,x5,x6…)
Y=Yield Strength
X1=Material Infill percentage %
X2=Number of shells
X3=Build Platform Temperature °C
X4=Extruder Temperature °C
X5=Raw material type
X6=Layer height mm
7. Oppurtunity statement:
Shape ways products are currently experiencing significant quality issues,
which is negatively impacting customer satisfaction. For the year of 2016,
the cost of poor quality is $135,000. The Plastic Rod failed because of the
low strength. So improving the strength of the rod represents a large
opportunity to increase customer satisfaction and reduce the cost
• Cp = 0.73
• Cpk = 0.49
• USL= 5300psi
• LSL = 4500psi
8. CTQ & CTP- Based on customer needs
Need (VOC) Drivers CTQs/CTCs CTPs
Part with required
specifications
Type of material
Product Quality surface roughness
Layer height (mm)
Infill rate (%)
Number of shells (°C)
Dimensions
Temperature of
extruder(°C)
Tensile Strength Level of plate(°)
Delivery Average order delivery time
Order process time(s)
Order handling time(s)
Order delivery time(s)
Cycle time nozzle speed (mm/sec)
Cost Selling Price
Material Cost($)
Process Cost($)
Packaging Cost ($)
Shipping Cost ($)
12. Equipment Variation (EV)=
0.00092
EV = ( R Avg) (K1)
Appraiser Variation
(AV)=8.726*E^-5
AV = SQRT[ (Diff Max-Min)(K2)]²
-[(EV)² / (n x r)]
R & R = 0.00093
R&R = SQR((EV) ²+ (AV)²)
Part Variation (PV) =0.00020
PV = (Rp)*(K3)
Total Variation (TV)=0.001
Calculations:
% 100[(EV)/(Total Variation)]
% EV= 97.23
% AV = 100 [ (AV) / (Total Variation)]
% AV=9.18
% R&R= SQRT( ( % EV) ²+ (% AV) ²)
% R&R=97.659
13. Collected data:
The collected data for the base samples is as follows
Baseline Input Parameters:
• Infill % - 20%
• Extruder Speed -150mm/S
• Build Platform Temperature - 110°C
• Extruder Temperature - 240°C
• No. of shells -2
• Filament - Maker bot PLA in Red
• Fan power - 50% max power
Part 1 2 3 4 5 6 7 8 9 10 Mean St.dev
Tensile strength
(psi) 4777.084 4527.499 4724.934 4854.003 4493.467 4543.354 4501.850 4441.447 4509.883 4607.335 4598.086 139.128
Tensile Strength= (Max load) (psi)
Cross sectional Area
Cross sectional Area = Width*Thickness
(square inch)
14. Process capabilities:
Cp = (USL-LSL)/6σ
Cpk = Min{(usl-x.bar);(x.bar-lsl)}/3σ
Cp = 0.73
Cpk =0.49
On calculating,
USL= 5015.47 =5300psi
LSL = 4389.39 =4500psi
Nominal value =4900psi
19. Analysis & results:
• Understand what can cause Modulus go wrong by Fishbone Study for six
categories
• Identify the key process input variables and key process output variables by
C & E Matrix Study
• Use process FMEA to prioritize the tasks
Target KPIV for improve stage:
• Infill%
• Number of Shells
• Extruder temperature deg.F
• Layer height mm
24. Taguchi method- response variables
From collected data:
(Optima value)
A1B2C2D3 - 4067 psi
From S/N ratio:
(Optima value)
A1B3C2D1 - 5213 psi
Tensile Strength
Level A (IR) B (NS) C (LH) D (ET)
1 4939.0 5066.7 5096.2 5193.1
2 4981.2 4780.4 4928.4 5386.9
3 5529.1 5602.2 5424.7 4869.3
optima: 4067.732167
S/N Ratio
Level A (IR) B (NS) C (LH) D (ET)
1 35.18 29.68 26.41 35.25
2 27.34 28.94 37.27 26.56
3 32.87 36.76 31.71 33.59
optima: 5213.382833
Nominal Value: 4900psi
As, S/N ratio’s value is nearer to nominal value the respective parameters are
selected
25. Mean and s/n response figure:
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
4600.0
4700.0
4800.0
4900.0
5000.0
5100.0
5200.0
5300.0
5400.0
5500.0
5600.0
1 2 3
Tensilestrength(psi)
Mean and S/N ratio based on Factor A (Infill rate)
Tensile
Strength
S/N ratio
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
4200.0
4400.0
4600.0
4800.0
5000.0
5200.0
5400.0
5600.0
5800.0
1 2 3
TensileStrength(psi)
Mean and S/N ratio based on Factor B (Number of
shells)
Tensile
Strength
S/N ratio
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
4600.0
4700.0
4800.0
4900.0
5000.0
5100.0
5200.0
5300.0
5400.0
5500.0
1 2 3
TensileStrength(psi)
Mean and S/N ratio based on Factor C (Layer
Height)
Tensile
Strengt
h
S/N
ratio 0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
4600.0
4700.0
4800.0
4900.0
5000.0
5100.0
5200.0
5300.0
5400.0
5500.0
1 2 3
TensileStrength(psi)
Mean and S/N ratio based on Factor D (Extruded
Temperature)
Tensile
Strength
S/N ratio
Infill rate (1=20%, 2=30%, 3=30%) Number of shells (1=1, 2=2, 3=3)
Layer Height (1=0.1mm, 2=0.2mm, 3=0.3mm) Extruded Temperature (1=230°F, 2=240°F, 3=250°F)
26. T test – Non-controllable factor analysis
Average (high temperature) = 5239.051psi
Average (low temperature) = 5060.507 psi
Std.dev (high temperature) = 547.7732 psi
Std.dev (low temperature) = 583.9924 psi
T-stat = 0.9461 T (alpha=0.0.1, d.f=34) =2.75
Hypothesis for noise factor:
Conclusion:
H0: μAT (65-75) = μAT (76-85)
H1: μAT (65-75) ≠ μAT (76-85)
since t-stat=0.946 which is smaller
than the t(alpha=0.01, two tails)=2.75
we fail to reject H0 and this means no
significant difference between high
temperature and low temperature.
27. Optima results for input parameters:
A ( Infill rate ) 20%
B ( Number of shells) 3
C ( Layer height ) 0.2mm
D ( Extruded Temperature) 230 °F
Ambient Temperature: (65-75) °F
28. Confirmation run:
Part 1 2 3 4 5 6 7 8 9 10 Mean Std.dev
Tensile Strength
(psi) 4953.255025.2564878.4534998.6394834.0774923.857 4896.945089.3414987.5114947.2494953.457 75.1345
A ( Infill rate ) 20%
B ( Number of
shells)
3
C ( Layer height ) 0.2mm
D ( Extruded
Temperature)
230 °F
Cp 1.73
Cpk 1.5
31. Takt Time of Shapeways:
Annual demand for products per annum: 60,000 pieces
Number of working days in a year: 250 days
Daily Demand: 240 pieces
Time available per working shift : 480 (8 hours)-30 mins(break time)= 450 minutes/ shift
One shift working hours : 450 minutes/day
Efficiency: 91%
Total daily operating time: 450*0.91= 409 minutes/day
Takt Time:
Total daily operating time
Total daily 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 requirement
= 409/240= 1.70 minutes per piece
Number of machines needed : Cycle time / Takt Time
34. Cost estimation:
Product unit price = $3.
Cost of poor quality per part =$9.
Annual demand =60,000 pieces
Annual defect rate =13,500 pieces
Annual cost of poor quality =$121,500.
Money saved on each machine = $5,000.
Money saved on 2 machines = $10,000.
Miscellaneous savings (power, maintenance, etc.) =$3,500.
Total savings =$135,000.
35. Performance improvement -Overall
Baseline Process
Production Capacity=60,000 Units
Cycle Time= 23 Minutes
D.p.M.O=226,627 (2.25 Sigma Level)
Defects per year=13,500
Number of machines used : Cycle Time/ Takt Time = 23 mins/ 1.70 mins = 14
Improved Process(Using Taguchi)
Production Capacity=60,000 Units
Cycle Time=19 Minutes
D.P.M.O=72 (5.30 Sigma Level)
Defects Per year= 5.4 units
Number of machines used : Cycle Time/ Takt Time = 19 mins/ 1.70 mins = 12
Estimated annual savings = $ 135,000
