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News from PDSS Inc.
"Leading the Future in Product Development" 
July 2012- Vol 5, Issue 7
In This Issue
Noise Diagrams and Concept FMEA: 2 Tools in Concept Development
Greetings!   
This month, Skip discusses two important tools to use during Concept Development that will get your products on the path to success: the Concept Noise Diagram and the Concept FMEA.

Enjoy the rest of summer!
-Carol

Noise Diagrams and Concept FMEA: 2 Tools in Concept Development

PDSS has had a flurry of consulting activity in the past few months in the area of Concept Development. Concept Development comprises the following major tasks: 
  • Gather and process the Voice of the Customer (VOC) culminating in the ability to discriminate between what is New, Unique and Difficult (NUD) vs. what is easy common and old (ECO).
  • Conduct External Benchmarking and Internal Assessments culminating in technical requirements often called "The Voice of Technology" (VOT) that establishes a base-line of information that can be used to set targets and ranges of performance that must be met or surpassed in order to develop a superior product.
  • Translate both the NUD VOC and VOT statements or data into measurable technical product requirements culminating in clear and stable requirements that can be allocated down through the system's hierarchy and acted upon during subsequent product development tasks.
  • Define and document ECO product requirements and constraints culminating in the main body of "normal and necessary" product requirements that are not critical but certainly important to fulfill as the new product is developed. These include legacy requirements commonly transferred from one product to the next when a successive product line is being rolled out over long periods of time, as for example, Apple's iPad and iPhone series. Constraints are very important because they state the limits or boundary conditions set by several key stakeholders: Business/Financial Leaders, Health/Safety/Legal and Regulatory Agencies, as well as Systems Engineering for size, weight, spatial relations, power and other domains where control over magnitudes of design elements must be in balance.

 

You know you are done with initial requirements development when you can demonstrate that needs, benchmarks and constraints have been converted into measurable technical requirements that are clearly ready to drive innovation.

 

  • Concept Generation, Evaluation & Selection: Once the requirements are developed and ready for iterative improvement, refinement and change control, the fun part of early product development kicks in - generating actual concepts! It is here when the product development team gets to convert ideas into technically feasible concepts. This article will provide guidance on a portion of concept development where Robust Design is first applied to the various candidate product concepts.

 

For every candidate concept, the team needs to develop two documents: the first is a Concept Noise Diagram and the second is the Concept Failure Modes and Effects Analysis (FMEA).

 

During the Pugh Concept Evaluation and Selection Process, the team must define numerous Evaluation Criteria derived from the NUD and ECO product requirements. The questions to ask that lead to the criteria for Robust Design and Reliability Development of a candidate concept include...

 

How many Noises is this concept susceptible to? How severe are the effects of the types of Noises on the functional performance of the concept? Is this concept highly affected by Noises that are going to be very difficult or impossible to induce during its modeling, simulation and physical proto type development and optimization?

 

And...

 

How many of the Functions of the candidate concept are at high risk for outright failure? How do the Risk Priority Numbers (RPN's) for this concept compare to the datum? Is this concept readily able to have Design Controls applied to it so that it is "improvable" from a reliability development perspective?

 

The Concept Noise Diagram

 

The Noise Diagram is a simple block diagram that illustrates the 3 types of Noise that can impact the functions of a candidate concept.

Noise Diagram
Noise Diagram

Note: CFR is "Critical Functional Response"

 

 

Unit-to-Unit Noise represents the variation in proto types, their materials, parts and their geometric fits and finishes as well as bulk material properties and shape factors. These are fore-runners to actual production variation.

 

External Noise represents any form or mass (material), energy or information (signal) that can get into the functions of the concept and disrupt them.

 

Deterioration Noise represents wear out phenomena, corrosion and all forms of degradation that can occur over time to deteriorate the functions of the concept.

 

List each type of noise that each concept is susceptible to.

 

The Concept FMEA

 

The Concept FMEA is a preliminary form of a Design FMEA Table.

 

Here we list the main functions of the concept and follow the normal procedure for a Design FMEA. The Concept FMEA is a "quick and dirty" version of a more formal Design FMEA. The goal is to assess the risk of failure for how each of the concepts seeks to fulfill the functional requirements that are NUD!

 

Design Controls come in 5 forms and are the building blocks to develop reliability into the functions of our concepts as they are modeled, simulated and converted into functioning proto types.

 

The 5 Design Controls include:

  1. Computer Aided Engineering (CAE) - Functional Modeling and Simulation.
  2. Computer Aided Design and Drafting (CADD) - Spatial and Geometrical Modeling and Simulation
  3. Base-line Functional Characterization - Math modeling using Regression Analysis using physical proto types to understand nominal relationships under idealized lab conditions.
  4. Designed Experiments (DOE) - Empirical knowledge building and model building using adjustable proto types under nominal and stressful (induced noises) conditions.
  5. Tests - Various tests designed to prove or disprove that the design can meet requirements under nominal or stressful conditions.

The key is to assess each candidate concept for its ease and amenability to having the 5 Design Controls applied to it. If it is difficult to forecast how the concept will be brought through the rigor of having these tools applied to it, then it is weak and vulnerable. Think of this as a check on how easy it will be for the team to learn about the design's performance, parametrics and sensitivities (if they exist!).

 

Noise Diagramming and Concept FMEA will help you illustrate and discuss how "robust" your concepts are relative to the datum. These are your first actions that are part of reliability development. If they are not done, you will probably proceed into detailed design of a concept that may turn out to be a ticking time bomb. Think of these two criteria as a filter and leading indicator of future design sensitivity and difficulty to develop efficiently (the "difficult" in NUD). 

 

 

 

 

 

Is there a topic you'd like us to write about? Have a question? We appreciate your feedback and suggestions! Simply "reply-to" this email. Thank you!
 
Sincerely,
Carol Biesemeyer
Business Manager and Newsletter Editor
Product Development Systems & Solutions Inc.
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About PDSS Inc.
Product Development Systems & Solutions (PDSS) Inc.  is a professional services firm dedicated to assisting companies that design and manufacture complex products.  We help our clients accelerate their organic growth and achieve sustainable competitive advantage through functional excellence in product development and product line management.

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