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Create a 2
Level Factorial/Screening Design
1. Click
SigmaXL > Design of Experiments > 2 Level Factorial/Screening
Designs.
2. The
Number of X Factors can be 2 to 19.
Using
process knowledge we will limit ourselves to 3 factors: Pull Back
Angle, Stop Pin and Pin Height.
Pull Back
will be varied from 160 to 180 degrees, Stop Pin will be positions
2 and 3 (count from the back), and Pin Height will be positions 2
and 3 (count from the bottom).
3. Select
Number of Factors = 3.
4. The
available designs are then given as: 4-Run, 2**(3-1), 1/2 Fraction,
Res III
and 8-Run, 2**3, Full-Factorial.
If we had
more than 5 factors, a Resolution III or Plackett-Burman Screening
design would typically be used. Here we will choose the 8-Run,
2**3, Full-Factorial design.
5. Next we
will review the Power Information to help us determine the number
of replicates. This design currently shows the following:
These
power calculations assume 3 center points:
Very Low
Power to detect Effect = 1*StDev (1-Beta < 0.5);
Very Low
Power to detect Effect = 2*StDev (1-Beta < 0.5);
Medium
Power to detect Effect = 3*StDev (0.8 <= 1-Beta < 0.95).
Note: the
power calculations require an estimate of experimental error, hence
an assumption of 3 center points is used.
We would
like to have a reasonable chance (medium power) to detect an Effect
= 2*StDev.
Change
the Number of Replicates to 2. The Power Information is now:
Very Low
Power to detect Effect = 1*StDev (1-Beta < 0.5);
Medium
Power to detect Effect = 2*StDev (0.8 <= 1-Beta < 0.95);
Very High
Power to detect Effect = 3*StDev (1-Beta >= 0.99).
We will
therefore choose two replicates.
The
number of replicates will always be a tradeoff between the desired
power and the cost of the experimental runs.
Specify 2
or more blocks if there are constraints such as the number of runs
per day or some other known external “nuisance” variable (like 2
different catapults or 2 operators).
Here we
will keep Blocks = 1 (i.e. no Blocking).
Center
Points are useful to provide an estimate of experimental error with
unreplicated designs, and allow detection of curvature.
Typically
3 to 5 center points are used.
Here we
will not use center points because we have replicated the design
twice and do not expect significant curvature in the distance
response.
Furthermore
center points could not be set for Pin Height and Stop Pin (without
drilling additional holes!).
6.
Complete the Factor Names, Level Settings and Response Name as
shown:
7. Click
OK. The following worksheet is produced:
8. You can
enter information about the experiment in the fields provided. If
you have access to a catapult, perform the experimental runs in the
given randomized sequence, and enter the distance values in the
Distance column.
Do not
add or delete rows, or sort the worksheet. Doing so will produce
erroneous DOE Analysis results. To
Analyze this design go to, Analyze 2
Level Factor/Screening Design.
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