By L Ramanan (www.LRamanan.com), Founder RAISE Consultancy & RICE Trust. SME in DFSS and Robust Design | Editorial Board Member RAME, IJTEEE, IJSTR & SJCAR
What is Robust Design?:
Robust design is a sub-set in the process of DFSS (Design for Six Sigma) in delivering a defect free product. It is an approach towards predicting the risks in the development of a new product by marrying cutting edge technology tools in predictive design along with cutting edge statistical tools in analysing the data from predictive design. It involves structured experiments thus predicting and mitigating risks.
Robust Design Is it Applicable to Process like Manufacturing and Transactions?:
Attributing Robust Design is applicable only to ‘Design’ (either to D&D or R&D) is a misnomer. The benefits of application of robust design extends to both ‘Robust Process’ and ‘Robust Product’. Robust process design largely helps in setting the right ‘parameters’ of the inputs by appropriately controlling their variation, thus resulting in minimising the out-put variation of the process. The robust process design can also be helpful in improving the productivity by identifying few ‘significant’ parameters.
Is there a Manufacturing Process Example?
The following two examples from RAISE’s Course on Robust Process Design are self explanatory and another example for design and R&D is also provided in explaining the usefulness.
Elimination of Shrinkage in Manufacture of Plastic Component:
Example from PROCESS QUALITY: Shrinkage or warping is one of the common product quality defect in manufacture of plastic component. The issue arises due to many factors from the process and also based on the component design – size and shape. Each problem is unique and generic drug like ‘paracetamol‘ for fever can not be prescribed for this process quality issue. However, most of the time without deeper understanding of the issue, the common approach adopted in practise is to blame “Tool & Die” design and kill the tool designer. A practical example of this nature handled in RAISE’s Course demonstrates what are the other factors that are responsible that can be controlled in avoiding defect due to ‘Shrinkage’ , without die correction, using ‘Robust Process Design’. Die corrections leads to ‘time delay’and also involves ‘money’.
Example from Manufacturing Process COST SAVINGS:
Tool Wear is one of the important aspects in mass production industry. Frequent tool grind reduces productivity, costlier investments on high end tooling is not a viable solution. Tool wear depends on many input factors and their variations like material processed, cutting speed, feed, depth of cut, coolant and the like. The question is without investing on costlier tool, can I have the same tool and what input factor settings will give me maximum tool life, hence good productivity, a practical example we deal in RAISE’s Course on Robust Design.
Example From Product RESEARCH & DESIGN for SAFETY CRITICAL Joint Design:
In a new product development, for Rail and wheel is assembled world-over by interference joint. The tolerance between the wheel bore and axle diameter is critical and the interference resulting from tolerance of design spec is a critical parameter on JOINT INTEGRITY.
As an R&D expert you have to deliver a design and allocate tolerance based on data. The material differences, surface finish, geometrical variations and similar are the factors that influence the output on Joint Integrity.
CAE simulation with variation for various factors has been considered in analysing the ‘Risk’ through ROBUST DESIGN approach in finalising the final design and allocation of tolerance, which can not be done by any other means.. Data driven decision helped in freezing the right choice.
RELIABILITY Testing Will it Not Ensure ROBUST PRODUCT?
Yes, it will ensure RELIABILITY of the product, however one has to remember smallest variation in components or subsystems will result in product quality issues and safety. Each sub-assembly and component variations cannot be addressed in reliability testing as it would be time consuming and costlier.
Read the following most recent news on TOYOTA Recalls. The issue is not because of the functional defect of the car, but defect from a sub-system.