Seminar Presentations

Design Validation Using Rapid Prototyping.
S. J. Bakshi, Protosys Technologies Pvt. Ltd., Mumbai, India.

As presented at "Competitive Design Management" module on "Achieving Competitive Excellence" management programme conducted by Warwick Manufacturing Group (U.K.) & Confederation of Indian Industry (CII) Mumbai.

Objective

To highlight the use of Rapid Prototyping techniques in the Design Validation process for mechanical products.

Introduction

In the modern times when technology developments are the key to success and survival of any business, design is gaining more emphasis than ever before. It has been a traditionally known fact that "a product can only be as good as its design". It is also worth noting, "a design can only be as good as its specifications".

Design Validation is a process that enables us to confirm that the design is in accordance with its specifications. As the specifications vary from product-to-product and application-to-application, processes too vary vastly e.g. Validation process for Mechanical, Civil, Electrical, Electronic or software product will differ from each other; similarly, the specifications of a building in Mumbai will differ from that in the Gulf or the Arctic region. Thus Design Validation is a very generic term used to ensure the conformance of the design for its end purpose.

Mechanical Product Design Validation

The validation of designs of mechanical products can be broadly classified into the Form, Fit & Function categories. These have to be applied to each individual component that goes into the product and also to the product as a whole. As these processes have to be undertaken before the production stage, they need a model. Traditionally, the models were physical, sketched or mathematical.

Then, the early 1980's saw the evolution of Information Technology (IT) era and thus computational intensive techniques like Finite Elements, Kinematics and Tolerance Charting became easy to implement. Further advancements in the IT arena saw development of Computer-Aided-Design softwares. These evolved from simple 2D drafting to 3D modeling to assembly modeling to parametric & feature based modeling. These eased out many of the validation processes e.g. visualization, interference checking, dimensional inter-relations etc.

All these digital methods of validation enabled more alternatives to be tried for the same concept and thus have proven their worth. However, the physical world still has its own advantages in terms of the feel-of-the design. If a picture is worth a thousand words, then a prototype is worth a thousand sketches. Hence, the importance of physical model was always maintained.

Rapid Prototyping

Cost incurred on a product development project increase drastically once the prototype stage is completed and the product is taken for production. The cost involved in implementing a change at a stage thereafter is also goes on increasing steeply. A study conducted by Mckinsey & Co shows that the cost overrun by 50% only affects the profitability by 3.5% whereas a delay in the launch of the product affects it by nearly 33%.

Thus it is important that the product development has to be fast and at the same time ensuring it is in conformance with the original specifications. It may be worth spending more during this stage than having to spend many folds higher later.

Until early 1980s, the IT developments had already speeded up most of the other stages of the product development cycle. However, the conventional methods of making a physical prototype were either manual or by machining. These are either not accurate or take a long time.

In 1982, the technology of Rapid Prototyping (RP) was first established in the US and process for speeding up the prototype making was patented and commercialized in 1985. It was called Stereo-lithography. The basic concept of this technology is to build the part layer-by-layer. Over the next decade, many other processes got patented all over the world e.g. Fused Deposition Modeling, Laminated Object Manufacturing, Selective Laser Sintering etc.

Growth in RP also saw the use of RP parts being used as patterns for various casting applications which give fully solid parts in materials that are equivalent various engineering plastics or at times, even metals. Any tooling process that uses RP at any of its stages is known as Rapid Tooling process and similarly Rapid Manufacturing.

With a physical prototype in hand visual validation becomes extremely easy. It also facilitates the fitment checking in many cases and limited functional trials can also be conducted with most of the parts that are made using Rapid Prototyping, Tooling and Manufacturing processes.

These techniques are extremely fast and the equipment is so versatile that it has almost zero setup time for change of parts. Smaller parts having high complexity in terms of shape and orientation of features are very economical by these processes when compared to conventional machining methods.

The enclosed literature and case studies highlight the benefits of Rapid Prototyped parts for validating various aspects of mechanical product design.