Sunday, 10 April 2016

A common approach to the design of material handling systems is to consider material handling as a cost to be minimized. This approach may be the most appropriate in many situations because, while material handling can add real value to a product, it is usually difficult to identify and quantify the benefits associated with material handling; it is much easier to identify and quantify the costs of material handling (e.g., the cost of material handling equipment, the cost of indirect material handling labor, etc.). Once the design of a production process (exclusive of material handling considerations) is completed, alternate material handling designs are generated, each of which satisfies the material handling requirements of the production process. The least cost material handling design is then selected.
The appropriateness of the use of material handling cost as the sole criterion to select a material handling design depends on the degree to which the other aspects of the production process are able to be changed. If a completely new facility and production process is being designed, then the total cost of production is the most appropriate criterion to use in selecting a material handling—the lowest cost material handling may not result in the lowest total cost of production. If it is too costly to even consider changing the basic layout of a facility and the production process, then material handling cost is the only criterion that need be considered. In practice, it is difficult to consider all of the components of total production cost simultaneously, even if a new facility and production process is being designed. Aspects of the design that have the largest impact on total cost are at some point fixed and become constraints with respect to the remaining aspects of the design

Sunday, 3 April 2016

Analysis of a Plate with Critical Point of Max. and Min

Any device or object that is designed and manufactured is expected to operate as advertised over a stated length of time. If the product does not function as expected then it is considered a failure. Failure can have many reasons. Failure is usually associated with reliability - the expression of confidence that the product will deliver on its expectation. Failure also has a practical side effect which is best attributed to Taguchi :”When a product fails, you must replace it or fix it. In either case, you must track it, transport it, and apologize for it. Losses will be much greater than the costs of manufacture, and none of this expense will necessarily recoup the loss to your reputation”. Failure is serious business and designing for actual failure is impossible because of so many variables. Instead we try and ensure that the design meets the Failure Criteria. There is no unique criteria and the designer usually satisfies the failure criteria that is appropriate for the type of the product and its underlying design. Many failure criteria are based on principal stresses rather than the standard engineering stress and strain. Since we can calculate the principal stress form the value of the engineering stress and strain at every point, we examine some of the popular failure criteria. Prior to application of such criteria we should also consider the fact that if the design is stretched beyond the elastic domain then the residual strain on the structure changes the design forever. If the bridge does not return back to its original state it is likely to cause additional problems in many ways