The waiting period might be due to the robot being

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Unformatted text preview: d on any one of the machine. The waiting period might be due to the robot being occupied elsewhere, etc… Therefore the period actually utilized in transforming the part into another form is the effective work utilization. Robot task functional utilization. This refers to robotic movements involved in doing work or intending to do work (i.e. transferring parts). It does not include wait periods at the neutral position and any tool changes. In addition the time taken to reach the neutral position after working is idle time. Therefore, idle time is; - waiting at neutral position - period to reach position - tool changes It is not common to find that in some cases the average robot cycle time might be less that a human’s. However, the robot’s higher productivity, measured in terms of increased parts per day, represents an economic gain, in addition, improved quality and reduction in waste. Productivity = output/hour ; is a better measure of the performance of a robotic cell. Can compare the productivity of manned and robot station: For the machining operation described above; S. Venkannah October 2006 MECH 4041 Item Available cutting time System at rest or otherwise Efficiency Total utilization Part cycle time Load/unload Cut time Total Fatigue factor (loss of efficiency with time) Throughput = [(Total utilization) /(Fatigue factor*total)] S. Venkannah Robotics Technology Manned Robot October 2006 MECH 4041 Robotics Technology GRIPPER: It is common for assembly robots to have to make provision for gripper changes for all but simple assemblies, in order to meet different picking requirement and to handle different shaped parts. Of the various methods of gripping – mechanical, electromagnetic, pneumatic, etc.- each is generally suitable for a small range of part sizes. Since gripper changes are non productive, they should be minimized and this can be achieved by: 1. Mount two grippers on the robot arm and make use of the wrist roll feature to select the appropriate one. This is an excellent solution on occasion, but its application is probable suited to only a very small proportion of robotic assembly problems. 2. Develop a “universal programmable” gripper which can cope with a much wider range of part sizes and geometries. Much effort is currently going into such development and grippers much more versatile than those currently in use will become available but this will be at the cost...
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