Published on Mar 13, 2020
Modern industrial robots are true marvels of engineering. A robot the size of a person can easily carry a load over one hundred pounds and move it very quickly with a repeatability of +/-0.006 inches. Furthermore these robots can do that 24 hours a day for years on end with no failures whatsoever. Though they are reprogrammable, in many applications (particularly those in the auto industry) they are programmed once and then repeat that exact same task for years.
The concept of how robots and other automated equipment should be used in industry has changed radically since the 1970s and 1980s when robots were first introduced into U.S. industry on a large scale. In the early 1980s most U.S. companies thought robots would be the answer to high labor cost and low production. Many companies had visions of replacing large numbers of workers with a robot that would be paid for in a few years and then work for free. What occurred nearly ended the "high-tech" automation revolution before it got started.
The first robots that were installed did not match the application they were designed for, they broke down frequently, and they were difficult to program. This meant that three to five extra skilled workers (electronic technicians, electricians, machinists, programmers) were needed to keep each robot running. Since robots broke down frequently, large amounts of downtime occurred and production schedules became unpredictable. Most robots were selected on the basis of return on investment (ROI) instead of what application they were to perform.
This meant robots were being specified and purchased by the accounting department rather than by the people who understood the technology. In the middle of the 1980s nearly 100 companies were manufacturing and selling robots. At this time robots were sold like used cars and they were shipped to the industrial site with no programs installed, no end effectors, and no integration to other technology. This meant that the factory that purchased the robot needed to supply this technology or the new robot would sit in the corner.
Today robots are selected for the application they perform, the type of interface they provide to other systems, and the type of programming they use. If a robot can do a job, but it's difficult to change its program, it won't survive in a small company where an outside programmer is required each time a programming change is needed. If a robot can do the job, but it cannot be interfaced with existing machines or other automation, it won't be useful. Most robots today perform jobs that are unsafe for humans such as lifting heavy parts, spot welding, loading and unloading presses where moving parts can injure a person, welding or painting where fumes cause long-term health problems to humans, and jobs that require a high degree of speed or accuracy such as inserting parts in a printed circuit board, continuous welding, and painting.
Fig. 1 shows examples of several types of modern robotic applications.Four basic types of robot configurations are in use today. Some robots are hybrids of one or more configurations. The configurations are called cylindrical, rectilinear, spherical, and jointed spherical, which is also called articulated arm. These robots are so named because their work envelope looks like the shape that describes them. For instance, the work envelope of the cylindrical robot looks like a cylinder, and the work envelope of the rectilinear robot looks like a rectangle.
These robots can be powered by electric motors, electric actuators, hydraulic motors, hydraulic cylinders, or pneumatic cylinders. In some cases the electric motors rotate ball-screw mechanisms or rack and pinion systems to provide linear motion from the rotary motion of the motor. Sometimes linear stepper motors are also used to provide linear motion. In other applications motors are used with gears, belts, chains, and pulleys to provide a variety of linear and rotational motion.
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