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DFSS is a flexible process in that it can be selectively equipped from the large array of tools available in the master toolbox based upon the needs of the specific task at hand.

The ultimate purpose of tools is to help in the development and delivery of Six Sigma products and services, on-time, at the lowest possible cost. No process can replace competent engineering.

Detailed DFSS training is required to expand the knowledge base of the tools and their applicability and selection criteria. However, phase and process appropriate tool trays are typically prepared that can address most needs.


QFD - Quality Function Deployment

QFD is a visual, connective process that helps teams focus on the needs of the customers throughout the product development and process engineering.

Due to its disciplined, systematic approach it ensures you remain faithful to the voice of the customer. It is a more thorough version of the CT Matrix.

QFD translates customer requirements into company requirements at each stage – from marketing, research and product development, to engineering and manufacturing to marketing/sales and distribution. Connections are ensured, as the actual columns of one phase become the rows of the next – throughout the process.

On the down side, as you may have heard, it can get tedious if applied to every design case. The key to its successful utilization is being ' "selective' " in its use.

quality function deployment

QFD is a systematic process to understand and integrate customer’s needs into the design of a product, process or service and is very effective in translating customer attributes into engineering characteristics.

For example, if customers indicate that they want a fast car, translating to a specific MPH number, to achieve this performance, several parameters are involved. These parameters are further deployed into other specific engineering characteristics and so on.

Eventually these specific engineering characteristics form part of the specification for the vehicle and engines which are in turn flowed down to the detail part level through the use of Key Characteristics and Critical Characteristics.

Robust Design

Robust Design means different things to different people – so what does it mean to us?

If DFSS were to have a "heart" through which all essential elements must pass it would be Robust Design. It can be broken down into two inter-playing foundations as seen below:

1. Design for Producibility, which matches designs to manufacturing capabilities in order to have a Six Sigma production (product and process are "optimal" relative to each other).

2. Design for Reliability which matches designs with the operating environment in order to have a Six Sigma product (product and operating environment are "optimal" relative to each other).

While clearing the above "basic" requirements, there are additional underlying considerations which are operating either in parallel or serial (with the above), depending on the complexity of the problem at hand.

These are design to cost targets, design to weight targets, design to customer ergonomics and performance requirements, etc. While these additional considerations are not "strictly speaking" part of Robust Design, they must play together.

robust design

The goal in a robust design is to identify a near-optimal design point such that if the design variables vary by some prescribed amount (i.e. as experienced under operating conditions), the solution will still be a practical optimal solution. There is minimal sensitivity to process variation.

Design for Manufacturability and Assembly

Design for Manufacturability and Assembly (DFMA). Is an effective design tool for simplifying products and reducing cost. It is a core tool of the DFSS process.

In designing for manufacturability and assembly, initially suggestions are generated for simplifying the product structure. Then, early manufacturing cost estimates are obtained for a benchmark and the new design. During this process, the best materials and manufacturing processes to be used for the individual parts are considered.

Once the materials and processes have been finally selected, a more thorough analysis for manufacturability can be carried out for the detail design of the parts.

design for manufacturability and assembly

DFMA provides a systematic procedure helping to eliminate excess parts and make designs as easy as possible to assemble, resulting in simpler and more reliable products which are less expensive to manufacture.

Not only are reductions in recurring cost achieved, but also tooling costs are generally reduced. In addition, there are further cost reductions because of the drawings that are no longer needed, the number of vendors that are reduced, and the inventory that is eliminated.

By reducing part and fastener count and the number of manufacturing operations and processes, DFMA helps to reduce the number of opportunities for defects which also improves product quality.

DFMA Guidelines

-Minimize the number of parts.

-Standardize and use as many common parts as possible.

-Design parts for ease of fabrication (use castings without machining and stampings without bend).

-Minimize the number of assembly planes (Z-axis).

-Use standard cutters, drills, tools.

-Avoid small holes (chips, straightness, debris).

-Use common datum’s for tooling fixtures.

-Minimize assembly directions.

-Maximize compliance; design for assembly themselves.

-Minimize handling.

-Eliminate adjustments.

-Use repeatable, well understood processes.

-Design parts for efficient testing.

-Avoid hidden features.

-Use Guide features.

-Incorporate symmetry in both axis.

-Avoid designs that will tangle.

-Design parts that orient.

The DFSS master toolbox consists of many tools. QFD, Robust design, and DFMA are aligned with the core principles of DFSS.

From DFSS Tools to Design for Six Sigma.

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