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¡@ Last Updated 31st August, 2002
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Design Criteria According to this project, the spring and foot lever mechanism system is used to provide a non-powered system. The methodology is based on springs. Therefore, the compression springs should be used in this design project. Detailed CAD and some hand drawings will do the design. Beside the above, it is also more concerned about the accuracy, repeatability, precision, transportation, safety and quiet. Moreover, the design criteria of machine should be enhanced safety features, lightweight, compact, set up fast and easily, portable, affordable, easy to operate, elevation and angular adjustment, long life cycle, warranty, quiet and height adjustment and ball capacity or feeder and drive system. In this cricket bowling machine, the main design criteria is designed or produced a low cost non-powered system to propel the ball at different suitable adjustable speeds, rotations and directions. The material selection and manufacturing processes are also the design criteria to affect the product. ¡@ Criteria Ranking The first step in formal concept selection procedures is to rank the PDS criteria in order of relative importance. Most methods of criteria ranking involve the formation of a matrix and one method, proposed by Pugh, is perhaps the most widely used. This matrix has become known as the binary dominance matrix. The criteria listed on both the vertical and horizontal axes. A 1 or 0 is placed in each box of the matrix depending upon the relative importance of the pair of criteria. The followings are the design criteria: Criteria A: Size and weight Criteria J: Precision Criteria B: Materials Criteria K: Accuracy Criteria C: Lightweight Criteria L: Consistency Criteria D: Portable Criteria M: Easy to manufacture Criteria E: Transportation Criteria N: Easy to operate Criteria F: Costing Criteria O: Direction Criteria G: Safety Criteria P: Rotation Criteria H: Speed adjustment Criteria Q: Set-up Criteria I: Height adjustment Criteria R: Stress concentration effect 1: The most important
Table 1 Criteria ranking matrix Back to top¡@Table 1 shows the criteria ranking matrix. When all of comparisons have been made, the row totals calculate and indicate the positional importance, or rank order, of the criteria. This reordering ensures that those criteria which have the greatest influence on concept selection are considered first. This is particularly important when many criteria are involved and made decisions have to be made. The aim has to be to assist the designer in any way possible.
Table 2 To reorder the criteria by ranking The above shows reordering the criteria for the following rating and weighting method. The result in table 2 is produced from table 1. The method is adding the sum of the horizontal value. Therefore, the total is calculated. The ranking is rearrange to reorder the proper criteria. After doing the criteria-ranking matrix, the criteria are reorder and rename. For example Criteria H is speed adjustment that will change into criteria A. The speed adjustment is the main concerned in this project. The second important is height adjustment. According to the table 1 and table 2, the criteria are rearranged to produce the following weighting. Final the concept selection is done in table 3. Back to topCriteria A: Speed adjustment Criteria J: Precision Criteria B: Height adjustment Criteria K: Set-up Criteria C: Lightweight Criteria L: Consistency Criteria D: Portable Criteria M: Easy to manufacture Criteria E: Transportation Criteria N: Size and weight Criteria F: Costing Criteria O: Direction Criteria G: Safety Criteria P: Rotation Criteria H: Accuracy Criteria Q: Materials Criteria I: Easy to operate Criteria R: Stress concentration effect The rating of criteria and its existence within a solution as follows: Rating 1-5 (5 is the best, 1 is the worst) Weight 1-5 (5 is the most important) ¡@
Table 3 Criteria rating and weighing Back to top |
