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robotics Designing the Mechanisms for Automated Machinery Part 10

Tham khảo tài liệu 'robotics designing the mechanisms for automated machinery part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 8.2 Automatic Assembling 285 INSPECTION FIGURE 8.1 Flow diagram of assembly process. I and II preparation operations. The question of whether one two or no inspection operations must be included as well as that of the number and location of preparation operations is answered according to each specific case. One of the criteria taken into account is the time needed for every operation. For instance inspection for the presence of a part in the correct position takes about 0.5 second completing an assembly by driving a screw can take about 1 second assembling that is done simultaneously with feeding of the parts takes about 0.3 second etc. We illustrate this in Figure 8.2. Here screws 1 slide down along tray 2 while washers 3 slide down along tray 4. Guide 5 controls the behavior of the screw heads. The slopes of trays 2 and 4 are shaped so as to promote insertion of the FIGURE 8.ịeAM L RNs of screw-washer assembly. 286 Functional Systems and Mechanisms screws into the washers during their movement. When the screw and washer come to the end of their travel they rest against the threaded opening of detail 6 which is held at this moment in a pocket of holder 7. The presence of part 6 is checked by feeler 8. Now screwdriver 9 can complete the assembly This example helps in further explanation of typical assembly problems. To achieve high reliability during screw-washer assembly special measures can be taken as illustrated in Figure 8.3. Case a is adequate for manual assembly but is less suitable for automatic assembly because of the highly precise alignment required. Human hands fingers and eyes can provide this level of precision but automatic devices find it difficult. Humans unconsciously correct for deviations of dimensions locations forces etc. but an automatic tool is unable to. So one must look for a compromise such as in case b . Tail 1 of the screw helps the latter to find the washer s opening. Additional help is provided by facet 2 resulting in a considerable .