Fractional Factorial Designs

Experimental Objective

A quality engineer observes that too many units manufactured by an injection molding process exhibit excessive shrinkage. He designs a fractional factorial screening design to determine the causes of shrinkage with variables as shown in Table 4.1.

Table 4.1: Variables in the Injection Molding Experiment

Type	Variable	Factor Name	Low	High
Factors	MTEMP	Mold temperature	-1
	SSPD	Screw speed	-1
	HTIME	Holding time	-1
	CTIME	Cycle time	-1
	GSIZE	Gate size	-1
	HPRESS	Holding pressure	-1
Response	SHRINK	Observed shrinkage ( 10)

The goal is to minimize shrinkage.

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Task List