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Note for Production Design and Production Tooling - PDPT By Jitendra Pal

  • Production Design and Production Tooling - PDPT
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PRODUCT DESIGN AND PRODUCTION TOOLING Module-I 1.1 PRODUCT DESIGN Definition of Design: The process of applying the various techniques and scientific principles for the purpose of defining a device, a process or a system in sufficient detail to permit its realization. Fig 1.1: The design and manufacturing processes of a product [1] 1.2 Product Design Consideration Design is a multifaceted process. The various considerations in a good design can be grouped into three categories: (1) design requirements, (2) life-cycle issues, and (3) regulatory and social issues. Authors: Prof. R.K. Sahoo, Dr. P.K. Parida, Prof. Chimay Das

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PRODUCT DESIGN AND PRODUCTION TOOLING 1.2.1 Design requirements It is obvious that to be satisfactory the design must demonstrate the required performance. Performance measures both function and behaviour of the design, i.e., how well the device does what it is designed to do. i) Performance requirements can be divided into following two groups. • Functional Performance Requirements: They address capacity measures such as forces, strength, energy, material flows, power, deflection, and efficiency of design, its accuracy, sensitivity etc. • Complementary Performance requirements: They are concerned with the useful life of design, its robustness to factors in the service environment, its reliability, and ease, economy, and safety of maintenance. Issues such as built-in safety features, noise level in operation, all legal requirements, and design codes must be considered. ii) Physical Requirements: These pertain to such issues as size, weight, shape, and surface finish. iii) Environmental Requirements: There are two separate aspects. The first concerns the service conditions under which the product must operate. The extremes of temperature, humidity, corrosive conditions, dirt, vibration, noise, etc., must be predicted and allowed for in the design. The second aspect of environmental requirements pertains to how the product will behave with regard to maintaining a safe and clean environment, i.e., green design. Among these issues is the disposal of the product when it reaches its useful life. iv) Aesthetic Requirements: They are concerned with how the product is perceived by a customer because of its shape, colour, surface texture, and also such factors as balance, unity, and interest. v) Manufacturing Technology: This must be intimately connected with product design. There may be restrictions on the manufacturing processes that can be used, because of either selection of material or availability of equipment within the company. vi) Cost: The final major design requirement is cost. Every design has requirements of an economic nature. These include such issues as product development cost, initial product cost, life cycle product cost, tooling cost, and return on investment. 1.2.2 Total Life Cycle The total life cycle of a part starts with the conception of a need and ends with the retirement and disposal of the product. Material Selection: Material selection is a key element in the total life cycle of a product. In selecting material for a given application, the first step is evaluation of the service conditions. Next, the properties of materials that relate most directly to the service requirements must be determined. Authors: Prof. R.K. Sahoo, Dr. P.K. Parida, Prof. Chimay Das

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PRODUCT DESIGN AND PRODUCTION TOOLING Producibility: Material selection can not be separated from Producibility. There is an intimate connection between design and material selection and the production processes. The objective in this area is a trade-off between the opposing factors of minimum cost and maximum durability. Durability: It is concerned with the number of cycles of possible operation, i.e., the useful life of the product. Current societal issues of energy conservation, material conservation, and protection of environment result in new pressures in selection of materials and manufacturing processes. Energy costs, once nearly totally ignored in design, are now among the most prominent design considerations. Design of materials recycling is becoming more and more important consideration. 1.2.3 Regulatory and Social Issues Specifications and standards have an important influence on design practice. The standards produced by such societies as ASTM, ASME, CE and BIS represent voluntary agreement among many elements (users and producers) of industry. As such, they often represent minimum or least common denominator standards. When good design requires more than that, it may be necessary to develop company or agency standards. The code of ethics of all professional engineering societies requires the engineer to protect public health and safety. Increasingly, legislation has been passed to require government agencies to regulate many aspects of safety and health. The designer has to develop the design in such a way to prevent hazardous use of the product in an unintended but foreseeable manner. When unintended use cannot be prevented by functional design, then clear, complete, unambiguous warnings must be permanently attached to the product. In addition, the designer must be cognizant of all advertising materials, owner’s manuals, and operating instructions that relate to the product to ensure that the contents of the material are consistent with safe operating procedures and do not promise performance characteristics that are beyond the capability of the design. An important design consideration is adequate attention to human factors engineering, which uses the sciences of biomechanics, ergonomics, and engineering psychology to assure that the design can be operated efficiently by humans. It applies physiological and anthropometric data to such design features as visual and auditory display of instruments and control systems. It is also concerned with human muscle power and response time. 1.3 PRODUCT SPECIFICATION: The product specifications are the precise description of what the product has to do. It don’t tellhow to address the customer needs, but represent an unambiguous agreement on what the team will attempt to achieve in order to satisfy the customer needs. Example: In contrast to the customer need that “the suspension is easy to install” the corresponding specimen might be that “the average time that to assemble the fork to the frame is less than 75 seconds”. A specification consists of a metric and a value. As in earlier example “average time to assemble” is the metric and “less than 75 seconds” is the value of this metric. The values Authors: Prof. R.K. Sahoo, Dr. P.K. Parida, Prof. Chimay Das

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PRODUCT DESIGN AND PRODUCTION TOOLING are of several forms along with a specific unit. Together the metric and value form a specification. The product specifications are simply a set of the individual specifications. 1.3.1 Target Specification: The target specifications are established after the customer needs have been identified, but before product concepts have been generated. The process of establishing the target specifications contains following steps: (i) Prepare the list of metrics (ii) Collect competitive benchmarking information (iii)Set ideal and marginally acceptable target values (iv) Reflect on the results and the process. (i) Prepare the list of Metrics: The most useful metrics are those that reflect as directly as possible the degree to which the product satisfied the customer needs. A few guide lies should be followed when constructing the list of metrics. • Metric should be complete: Ideally each customer need would correspond to a single metric and the value of that metric would correlate perfectly with satisfaction of that need. In practice several metrics may be necessary to completely reflect a single customer need. • Metric should be dependent, not independent variables: Metrics specify the overall performance of a product and should there fore be the dependent variable in the design problems. • Metrics should be practical: Metrics will be directly observable or analyzable properties of the product that can be easily evaluated. • Some needs can’t easily be translated into quantifiable metrics: In these cases the need statement simply repeats as a metric in the specifications. • The metrics should include the popular criteria for comparison in the marketplace. (ii) Collect competitive benchmarking information: The benchmarking chat is conceptually very simple. For each competitive product the values of the matrices are simple entered down a column. An alternative competitive benchmarking chat can be constructed with rows corresponding to the customer needs and columns corresponds to competitive products. (iii)Set ideal and marginally acceptable target value: In this step the available information s synthesized in order to actually set the target values for the metrics. Two types of target values are useful (a) an ideal value which is the best result could hopeful (b) a marginally acceptable value which is the value of the metric that would just barely more the product commercially viable. There are different ways to express the values of metrics: → At least X: These specifications establish targets for the lower bound on a metric, but higher is still better. Example: Brake mounting stiffness. Authors: Prof. R.K. Sahoo, Dr. P.K. Parida, Prof. Chimay Das

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