Processes Capabilities (Cp, Cpk) and Techniques Efficiency (Pp, Ppk) – What is the Improvement?

P_pk

_{From the Six Sigma top quality methodology, process overall performance try claimed towards the team given that a beneficial sigma top. The better the newest sigma level, the higher the process is creating.}

_{Another way to report process capability and process performance is through the statistical measurements of Cp, Cpk, Pp, and} . This article will present definitions, interpretations and calculations for C_pk and though the use of forum quotations. Thanks to everyone below that helped contributed to this excellent reference.

A simple and quick indicator out of process possibilities

Definitions C_p= Process Capability. C_pk= Process Capability Index. Adjustment of C_p for the effect of non-centered distribution. P_p= Process Performance. A simple and straightforward indicator of process performance. = Process Performance Index. Adjustment of P_p for the effect of non-centered distribution.

Interpreting C_p, C_pk “C_pk is an index (a simple number) which measures how close a process is running to its specification limits, relative to the natural variability of the process. The larger the index, the less likely it is that any item will be outside the specs.” Neil Polhemus

“If you hunt our shoot targets with bow, darts, or gun try this analogy. If want College dating site reviews your shots are falling in the same spot forming a good group this is a high C_p, and when the sighting is adjusted so this tight group of shots is landing on the bullseye, you now have a high C_pk.” Tommy

“C_pk measures how close you are to your target and how consistent you are to around your average performance. A person may be performing with minimum variation, but he can be away from his target towards one of the specification limit, which indicates lower C_pk, whereas C_p will be high. On the other hand, a person may be on average exactly at the target, but the variation in performance is high (but still lower than the tolerance band (i.e., specification interval). In such case also C_pk will be lower, but C_p will be high. C_pk will be higher only when you r meeting the target consistently with minimum variation.” Ajit

“Consider a car and a garage. The garage defines the specification limits; the car defines the output of the process. If the car is only a little bit smaller than the garage, you had better park it right in the middle of the garage (center of the specification) if you want to get all of the car in the garage. If the car is wider than the garage, it does not matter if you have it centered; it will not fit. If the car is a lot smaller than the garage (Six Sigma process), it doesnt matter if you park it exactly in the middle; it will fit and you have plenty of room on either side. If you have a process that is in control and with little variation, you should be able to park the car easily within the garage and thus meet customer requirements. C_pk tells you the relationship between the size of the car, the size of the garage and how far away from the middle of the garage you parked the car.” Ben

“The value itself can be thought of as the amount the process (car) can widen before hitting the nearest spec limit (garage door edge).C_pk =1/2 means youve crunched nearest the door edge (ouch!)C_pk =1 means youre just touching the nearest edgeC_pk =2 means your width can grow 2 times before touchingC_pk =3 means your width can grow 3 times before touching” Larry Seibel

Interpreting Pp, Ppk “Process Abilities Index fundamentally attempts to make certain when your sample one you really have generated on processes try competent to meet Consumer CTQs (requirements). It differs from Procedure Abilities where Techniques Abilities just applies to help you a particular batch regarding topic. Examples about batch could need to getting a little highest to be associate of the type from the batch. Process Show is just utilized whenever process-control can’t be examined. A good example of this can be for an initial pre-production work at. Procedure Performance generally spends take to sigma within its computation; Techniques abilities uses the method sigma well worth calculated off often the new Moving Diversity, Variety or Sigma handle charts.” Praneet