II. Reading

Read the text and be ready to find in the text the answers to the following questions:

• What are the two basic types of industrial robots?

• What tasks can industrial robots perform at enterprises?

Classification of Robots

The number of types of electromechanical robots is continually increasing. The typical features of each type of an industrial robot are as follows: the type of drive and control system, the type of coordinate configuration system in which the manipulator works, the number of degrees of freedom, load capacity, repeatability, the number of manipulators, etc.

From the control standpoint there are two basic types of industrial robots: point-to-point (PTP) and continuous-path (CP). The simplest case of PTP robots is the "two-point" or cycle robot, where each axis of this robot can generally move to only two positions. The "multi-point" PTP robot permits the control to stop each axis or manipulator at any point within its total range, rather that at only two, or a few, points. CP robots operate, in theory, in an infinite number of points in space, than, when jointed, describe a smooth compound curve. "Multi-point" PTP robots and CP robots are also called "servo-controlled" robots.

Drive is a typical feature of robots. Robots can be driven by pneumatic, hydraulic and electro-mechanical drives. The simplest of the above mentioned robots are those operated by pneumatics with fixed cycle control. Most of them have electrical control systems but there are also examples of complete pneumatically controlled models.

Hydraulic robots occupy second place in industrial application. As a rule, these are universal robots with one manipulator, covering the load capacity of 20-40 kg and point-to-point or continuous-path control of operation. The number of types of electromechanical robots is increasing quickly. Some robots work in angular coordinate system. There are also robots working in the cylindrical, spherical and cartesian systems.

Industrial robots are being used for a wide variety of tasks in factories, shops and foundries around the world. Robots unload parts from die casting machines and plastic injection moulding machines. They load and unload parts at machine tools and stamping presses; transfer parts from die to die or from press to press. In die casting and plastic injection moulding operations, robot may unload a single machine or as many as three machines. In machine tool loading and unloading, the robot may also tend more than one machine - loading and unloading each in turn, or on demand and transferring parts from machine to machine, as well as placing parts in gages for dimensional checking.

In forging operations, robots are used to transfer hot billets from furnaces to forging presses to transfer parts from die to die in successive forming operations and to handle hot and cold parts in trimming operations. Robots are also used in casting clean-up operations, handling cutting torches or abrasive cut-off wheels to remote gates and risers and for grinding flash from parting lines.

Continuous path servo-controlled robots are used for spraying a wide variety of parts and materials; for spot and arc welding. Robots are used for drilling and grinding, handling either the parts or a power tool.

In assembly operations, the microprocessor-controlled robot with sensory feedback capability performs the complex part and tool-handling tasks.