Process capability Premiered by EDOUARD GATETE of The Pennsylvania State University. Overview Definition Measurements of process capability control How can Process Capability be used in an organization Overview A real world example Exercise Summary Definition Process capability is defined as a how likely a product is going to meet the design specification. – It has been argued whether the specifications are actually set by customers or design engineers. Measurements of process capability Most of the times, conventional process capability work quite well, but we have to keep in minds that they will be times when the usual formulas don’t work. – An index that measure potential process capability is used in unusual situation. Measurements of Process Capability The formula C sub P is the tolerance divided by six standard deviations (also known as sigma) » C sub P = tolerance/6-sigma Reveals how many six-sigma fits within a specified tolerance In order for a product to meet specifications, at least 99.773% of productions should confirm anticipated operation condition. Measurement of process capability Population : a collection of all observation of interest to a decision maker. Sample: a portion of population population distribution: a distributions of the entire population sampling distribution: distributions of sample means. How to use process capability in an organization The control chart • bell-shaped curve: as long as all inputs to a process remain constant, the output will always vary The difference between Stable and capability A process is capable if a given product meets specifications. A process is stable if there is a common variation present in the process The disadvantage of using process capability Over-correcting: the most common reducing variation Factors influencing the tolerance allocation Statistical aspects of the dimensions and manufacturing processes involved Assembly requirements and conditions the cost-tolerance relationship International Standards Organization's practices for fits. A real world example Taking an example of a car manufacture company. The process capability will be used if out of 1000000 cars produced, only 3.4 cars come out defective Exercise A certain manufacturing process is producing metal washers that have diameters that are known to be normally distributed with mean 1 inch and standard deviation .006 inch. The process is known to be stable and in control. The specifications for these washers are 1 inch +/- .01. What percentage are within specification limits? Summary We have just reviewed process capability. This process is used in production to determine whether a product meets specification on a consistent basis. Even though they are a lot of complex ways to to figured out process capability, it’s more important to understand the basics before we can get in more details. summary This presentation has definitely focused on the basics of process capability. It is very important to minimize defects in production if you want to optimize the profit. summary A bibliography used to come up with these slides is as follow; Hart, M. Quality Tools for Decreasing Variation and Defining Process Capability. V33 n2. Second Quarter 1992, p.6-11. summary Raouf, A. On developing optimal process capability index. International Journal of Quality & Reliability Management. V9 n7. 1992. P. 17-22 Bothe, D. R. Measure process capability when Cp won’t work. Quality. V34 n8. Aug 1995. P. 20-22 Summary Foster, T. S. An integrative approach. Managing Quality 2001. P. 374-376.