Design for six sigma
The Six Sigma movement pushed these concepts to the extreme of targeting 6σ quality levels in the short-term that would achieve 4.5σ quality levels in the long-term. Defect rates at this quality level fall at about 3.4 defects per million opportunities. The variability of a 6σ process relative to its specification limits is illustrated in.
The quality movement toward Six Sigma effectively decoupled the definition of defects from defectives. At Six Sigma, defectives are still any observation outside of the customer’s specification limits, although such observations become exceedingly rare. Defects remain however, as roughly 3-7% of all observations will continue to fall outside of the control limits. With the control limits at 3σ, and the specification limits at 6σ, the vast majority of defects do not rise to a level close to resulting in a customer defective. Each defect, though, remains an opportunity to continue to improve the process and bring the expected process shift under control. By managing these defects effectively, the process continuously improves without ever producing a defective for the customer. That distinction – the 3σ to 6σ gap – is the essence and opportunity of Six Sigma Math.
(E. Biehl, Data-Oriented Quality Solutions, 2005, p. 6.)
Knowledge-based engineering
Knowledge based engineering originated from a combination of computer aided design (CAD) and knowledge based systems but has several roles depending upon the context. In a design process, computer aided design is considered as the basis of the generative design with many expectations for hands-off performance along with the knowledge based engineering which would result in a limited human involvement in the design process. Today, the application of knowledge based engineering includes design (CAD), analysis (FEA), simulation (CAS), optimization, manufacturing, and support (CAPP) where CAD is the foundation for the rest of the cycle. In this paper, the authors start with discussing the traditional process, its pros and cons, how knowledge based engineering is revolutionizing today’s design capability, and finally, the role played by CAD in synergizing knowledge based engineering.
(Kulon, J., Broomhead, P., & Mynors, D.J. (2006). Applying knowledge-based engineering to traditional manufacturing design. International Journal of Advanced Manufacturing Technology. 30,p. 945-951.)
Design freeze
The conducted industrial case studies have shown that freeze can apply to different parts of the design process. At least in theory the specifications are frozen before conceptual design begins, which in turn is frozen before detailed design starts. Before manufacturing can start the entire design needs to be frozen. However, reality is often far more fluid and processes can iterate across different stages. Freezes of the complete design or its details play a vital role throughout the entire design process, arising from within the company or coming from outside. Four freeze categories result that either address the product concept as a whole or part details in particular:
• external conceptual freezes arise from customer requirements or tooling constraints;
• external detailed freezes include detailed customer specifications, lead times and the use of pre-defined parts like platform parts, legacy parts or standard components that need to be incorporated into the design;
• internal conceptual freezes reflect the fundamental decisions made about the concept of the design throughout the iterative refinement of the product; 3
• internal detailed freezes occur when components, features or parameters of parts are frozen at any time throughout the design process; this typically occurs as a means of structuring the design process.
(Eger T., Eckert C., Clarkson P. J., The Role of Desing Freeze in Product Development, August 2005, p.2.)
Continuous Improvement
Continuous Improvement is a culture of sustained improvement targeting the elimination of waste in all systems and processes of an organization. It involves everyone working together to make improvements without necessarily making huge capital investments. CI can occur through evolutionary improvement, in which case improvements are incremental, or though radical changes that take place as a result of an innovative idea or new technology. Often, major improvements take place over time as a result of numerous incremental improvements. On any scale, improvement is achieved through the use of a number of tools and techniques dedicated to searching for sources of problems, waste, and variation, and finding ways to minimize them.
(Bhuiya N., Baghel A.,Management Decision, Vol. 43 No. 5, 2005,pp. 761-771.)
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