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Critical Parameter Design(CPD)

Clyde Creveling, the author of Design for Six Sigma presented a terrific speech on CPD in yesterday's System Engineering class. 'CPD is about all the stuff MIT does not teach us.', he proclaimed.' It can be defined as oil under the hood or Designing for Excellence.' This book is an 'autobiography' of 6 years of his work.

Here are my takeaways:


  • Phase Gate Nomenclature:The phases of product development usually include Concept,Design,Optimization and Verification
  • CPD can be defined as a bunch of tasks done by a bunch of pools to deliver work at critical points or gates and then matched with expected results.
  • If requirements are anemic you don't know what you're doing.
  • Robustness: It is the insensitivity/indifference of a system. Like the Timex ad, a good system 'takes a lickin'but keeps on tickin'. It is a measure of Engineering Control Factors (Control, constraint set as a specification) and noise (External sources of mass and energy.).
  • The third type of noise is deteriorating noise. (The entropy effect)
  • Tolerance: There are two types of tolerance, analytical and empirical (meaured by methods like Design of Experiments)
  • One must involve markeing(technology and portfolio) from the R&D phase to he post launch phase of product development.
  • CPD helps to manage complexity form development to deployment and into production and service cycles.
  • It is critically based on and tracks back to customer needs.
  • Customer Behavior Dynamics: You cannot make money on Newton's second law without understanding human dynamics.
  • CPD manages the flow of variation. It creates a system integration mindset throughout the design community.
  • CPD forces attention on system, subsystem and subassembly interfaces.
  • Interfaces:

- These are the points where functional interaction and variation are most critical

- These are the 'HotSpots' . Look at them with 'System Engineering glasses' and they'll glow.

- In almost every system the variations are hot.

-Most of the time the hot spots are in the boundaries.

-They are rarely internal. They are in the interfaces.

- They are often ignored.

- Engineers blame each other for interface problems.

-Usually, no one assumes ownership of the interface.

Customer Needs

  • Customer needs can be defined in terms of 'ranges of tolerance'.
  • Criticality breaks down into three different pockets: New(Something that is new to you) , Unique(Something that is new to you or soemthing that your competition does but is new to you.) and Difficult(Something that is difficult to deliver.), the NUDs.
  • The opposite of this is the old, common and easy. These are things you still have to do to leverage product development.

  • The NUDs give the Business financial horsepower while the old, common and easy don’t sell except at commodity prices. In a premium price market, it is essential to find the NUDs.

  • To get the voice of the customer down to engineering, one uses the House of Quality (HoQ) The HoQ translates Grandma’s words to Isaac Newton’s Language. Requirements are linked to critical functional response.

    Tasks and Tools: The following is a summary of the tasks and tools used in CPD

  • Document and Link Critical Requirements: This is where one establishes the concept and design. Tools like KJ technologies are used for this process. This is the stage of grouping, structuring, ranking and prioritizing
  • Develop, document and link function parameters and specification. It is the stage where one uses 1st principles, Design of Experiments(DoE), DFMEA and DFMA. DoE is useful as not all modeling can use empirical data and we need to trust mother nature to answer questions. DFMEA and DFMA are the tests in failure mode. They are the dark side of the force. This involves inferential statistical analysis to measure signal to noise ratio and uses simulation techniques like the Monte Carlo method.
  • Measurement of Critical Functions
  • Calculation of the capability of Critical Functions and Specifications: We try to develop and optimize parameters with low Cp and CpK Performance.
  • Calculate the capacity by growth: Transfer the CPM relational database to production, supply chain or service/support.

Most good companies start capability analysis process in R&D and then take it to design, requirements through the end of the product lifecycle. They save a lot of time by front loading the system and catching problems early.



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