Effectiveness of computer controlled robotic precision manipulator

A robotic precision manipulator has been designed and interfaced with a micro-computer for the manipulation of a workpiece in such a way that 2-D/3-D complex shaped surfaces may be produced using a wire EDM machine in which the cutting forces are relatively negligible. The manipulator is operated by four AC servo motors, two of them are for the linear manipulation along the X and Y axes and the other two motors are used for the manipulation of the rotary motions, alpha and beta around the X and Y axes respectively. The maximum X and Y axes linear travel for the manipulator is 100 mm and 120 mm respectively, and the angular cutting facility for alpha and beta is 70° and 65° respectively. For carrying out the tests on model material (polystyrene) for the simulated WEDM process a wire cutting unit was also designed, and commissioned on which the cutting wire and a micro-switch is housed. The interfacing system used for this manipulator has two PC23 indexers and four KS-drives. One PC23 indexer controls three motors and the other controls the fourth motor. There are approximately 80 PC23 commands which can be used for setting the process operating modes and motion parameters. There are approximately 40 KS-dnve commands for setting the servo conditions on the KS-dnve for system optimisation and to match the operating conditions described for the PC23 indexer. Other additional facilities offered by the interface system were also utilized by designing the programmable voltage regulator (PVR) circuit to change the voltage in the cutting wire through the micro-computer based software during the generation of the shape. The micro-switch on the cutting wire unit is installed and connected with the PC23 indexer to check if the wire cutting rate is less than the workpiece feedrate so that a signal can be sent to the computer for retracing the workpiece cutting path. A number of programs were developed to generate different 2-D/3-D complex shapes using the model material. The software developed, describes the shape geometry sizes, workpiece feedrate and voltage allowed to the cutting wire on user’s choice. The effectiveness of the manipulator, interfacing system and software was studied qualitatively and quantitatively and was found to be very satisfactory- For carrying out the tests on a real WEDM machine, the hardware and software will need to be modified. The commercially available WEDM machines cost over one hundred thousand pounds with angular cutting facility of ±30° only at 12 mm thick workpiece. The present robotic precision manipulator offers greater angular cutting flexibility of up to ±70° at 50 mm thick workpiece with around 25% cost of these commercially available WEDM machines. The components which are not possible to be manufactured using these costly WEDM machines can easily be manufactured by using this robotic precision manipulator