Hi, welcome to lecture 34 for an interesting and important concept as well. This lecture is about understanding the process capability distinguish between natural process limits and specification limits. Let us learn what is a process capability. process capability is the ability of a process to meet its customer specifications and important tool for choosing the best out of a set of Competing processes predict the extent of variation for any process, evaluation of new equipment, process audit, etc. Two key variables to study the process capability of our processes our specification limit control limit that does exist examine these two factors in detail. We have started measure phase with a definition of a process.

A process is a set of interrelated activities that transfer input into output. Every process has its own inherent ability to produce a product or services. And this inherent ability depends upon the men involved in the processes, their experience, skill training, etc. The machine involved in the process if it is manual or automated, etc. The material supplied to this process like quality of inputs, the methods used in production processes, standard operating procedures, etc. These inherent abilities determine the control limits of a process or the whys of processes.

Similarly, outputs are delivered to customers the output should meet the specification requirement of customers the requirements specified by the customer for an output is it specification limits. specification limits has nothing to do with control limits. These specification limits are called the voice of customers. Now, what is process capability capability of a process is its ability to meet the customer's specification requirements. Let us learn further about control limits and specification limits more as we just discussed, the control limits are inherent to the process. control limit is a function of natural variability of a process.

What does it mean? It means the control limit of a process is a function of the standard deviation of a process. So, in order to find the control limit of processes, we need to know population mean of the process and standard deviation. If standard deviation is not known, it can also be estimated from sample standard deviation. The control limits for a process is equals two mil plus minus three sigma. Let me repeat again the control limit of a process is expressed as mean plus minus three standard deviation.

Examples of control limit We have a process that produces shafts we know the mean and standard deviation of the processes as 200 mm and 10 mm respectively. What will be the control limits of this processes the control limit are 200 plus minus three into 10 mm the lower control limit LCL and upper control limit UCL, r 170 and 230 respectively now, let us learn What is specification limit? For every product or processes, there is desired level of performances commonly called as target and limits this desired level is stipulated by customers target value examples might be curing temperature is equals to 90 degrees centigrade. Korea delivery time is equals to 10 M, etc. But is it possible to maintain the curing time exactly at 90 degrees centigrade or is it possible to deliver the courier exactly At 10am know, there will always be a variation. Hence, we need to allow a permissible limit of variation.

This permissible limit of radiation is called as tolerance. For example, 90 plus minus four degrees centigrade it's 10 m plus minus one hour etc. Examples for local specification limit LSL target and upper specification limit USL are as shown on screen look at the last column specification with it has got a significant role and process capability. The specification width is calculated as opposed specification limit minus lower specification limit us l minus ls l. Let us have more insight of process capability and operation manager of a manufacturing company need an efficient supplier for his input components. The specification of this product is 40 plus minus five mm he has to select among the four suppliers namely a B See Andy. Now, what can he do to select the best?

He had his team visited the supplier premises, carried out some audit collected random samples of 20 components and conducted a study to analyze the processes of the profitable suppliers. Let us see their results to analyze who is more capable. The measurements of the entire suppliers are what you see on the screen. You can see that the average of all suppliers are 40. Is this information enough To select the supplier No. Then what makes the difference between the supplier?

Yes, that is the standard deviation sigma that differentiates the suppliers we have already learned to calculate the standard deviation. The standard deviation of all suppliers are calculated as 3.76 1.68 1.06 and 0.08 respectively. Now tell me which is the best supplier remember since the beginning of the lecture we have been discussing that lesser the variation better that process is. Hence, we can say that process of supplier D is best as it has the least standard deviation. Let us have a graphical analysis of their processes similar to our shooting test. The customers specification limit is 35 to 45 mm that means, the specification width is equal to 45 minus 35 equals to 10 mm this will be the same for all the suppliers Now, let us analyze the process of supplier a supplier a as standard deviation of 3.76 the control limits are mean plus minus three standard deviations and process where is equal to three sigma minus minus three sigma which comes to six standard deviation.

This is equal to six into 3.76 equals true 22.58. Let us see the curve anything that crosses The upper and lower specification limits our defects. In the similar way, we analyze the process of supply of b we can see that the specification limits are almost equal to the process width. Now, the process of suppliers see with the standard deviation as 1.06 we can see that the process with of supplier C is lesser than the specification with Finally, the process of supplier D the process with offset player is much lesser almost half of the specification with required by the customer. Now let us analyze the process of entire suppliers in one slide. In first case of supplier a the process with was less than the specification with we see the process is not capable the process with of supplier B is just same as that of the specification with in this case the process is just capable but we cannot see the process is good any slight variation further will lead to generation of defects.

Suppliers see as less process with than the specification limit we can say this process is capable our capability index CP is more than one at last process with of supplier D it is almost half of the specification with capability index CP is equals to two or we can say this process is operating at Six Sigma capability Don't be confused by hearing new terminologies. I will clarify them in my next lecture. That's all for this lecture. We will continue the concepts and next lecture on process capability studies based on V okay. Three, f three. Thank you