What are the differences between process control limits and product control limits?

Product control limits is related to the specification limits, this is the customer requirements, and equal (Average Value ± deviation accepted by customer, standard or specification).

While process control limits is the characteristic of the process (Average Value ±3σ, while σ is the standard deviation), and based on past performance of the process. They are telling you what the process variability HAS produced in the past. It is possible for a process to be incapable of meeting a specification.

Example: If we need to Produce a product with pH =4 ±0.1 (This is the product control limits)

And we can Produce this product on3 different machines (This means3 different processes)

- The first machine has process control limit (average =4 & σ =0.02, Then the process control limit =4 ±3σ =4 ± 0.06  (Will then this process produce100% accepted product

- The second machine has process control limit (average =4 & σ =0.05, Then the process control limit =4 ±3σ =4 ±0.15 (then this process Will Produce some product (around5%) out of specification

- The Third Machine has process control limit (average =4 & σ =0.1, Then the process control limit =4 ±3σ =4 ±  0.3 (then this process Will Produce some product (around36%) out of specification 

i think that process control limits indicate the range of variability of process we expect ( in control or not )  ( input processes)..... but product control limits its no that give us explanation about e.g new product sales or expected profits losses  , unit price etc ... forcasting about these factors ( after producing product ) / output

انا رديت رد دا عن اقتناعى بالفرق فى كلمتى العمليات المعالجية والمنتج يعتى المعالجة بتنتج عن المدخلات لتنتج المخرجات وهى المنتج النهائى واللى عنده راى تانى يقول للاستفادة