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Design of Experiment (DOE)


There were certain variables which were identified to test the durability and the performance:


Design Variables:


  • Factor A: Length of the extrusion

  • Factor B: Width of extrusion


Performance Variables

  • Factor A: Time for machinability


Uncontrolled Variables:

  • Factor A: Orientation of Impact


Target Values (X%)


Length of extrusion:

In accordance to the target value, it can be predicted that the longer the extrusion on the piston head, the lesser is the travel by the connecting rod. However, due to the numerous collisions of the connecting rod with the extrusion, there may be chances of defects especially when the piston is operating at a high RPM (rotations per minute). For the purposes of this DEA, the thickness will be within a range of 0.5in and 1in.


Width/Thickness of extrusion:

With larger width of the extrusion, the product is more resistant to defects, especially through contact with the connecting rods. For the DEA the thickness will be within the range of 0.01 and 0.02in.


Time for machinability:

X is the percentage on the basis of which the target value of performance will be measured by. It is defined as the amount of time required to machine a particular piston head of a particular geometry. The time will be within the range of 60s and 300s.

Orientation during RPM:

The piston head can move about 90 degrees during the a traditional piston cycle in a four stroke engine. In this experiment the piston will be dropped from 1 ft throughout to simulate piston orientations in an engine.

The experimental matrix is shown below. A (+) represents the upper level and a (-) represents a lower level range.  

Table 1: Experimental Matrix


To calculate the times, a stopwatch will be used 

Table 2: Results based on experiments


*The data in this step has been hypothetically generated

Table 3: Variance



Effect Values

Plot 1: Probability vs Effect Values  

To predict Variance;


Based on the analysis done above, there are two major design improvements that could have been made: 

  1. Lower extrusion lengths lead to lower machining time

  2. Lower width of the extrusions also lead to lower machining times.

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