Abstract Automation started out as an assembly line of workers doing the same repetitive task all day long. Some of the jobs were very boring, dirty, unpleasant, and possibly dangerous. After the introduction of the first robot in 1961, automation began to advance in ways people could only imagine. Each of the six basic styles of robot used in industry today were designed with different applications in mind. Some of the robots were designed for assembly, others are more suited for simple pick and place applications, while a select few are capable of carrying heavy loads over a large area. The operations of the robots have also advanced from simple hard-stop, one-function, hydraulic actuated robots to the more sophisticated, high-precision, servo controlled robots that can be reprogrammed to do many different jobs.
Robots have greatly increased production, the quality of the parts, and the safety of workers. The main reason for the use of robots is to make a company profitable while producing a high quality part at competitive prices. The number of robots used in industry increases every year as more companies realize their many benefits. Robots are the future of the manufacturing industry. As the performance and flexibility of robots increases and their prices continue to drop, many companies will uses these added incentives to invest in the future. Soon every company that has an application for a robot will be forced to invest in one, to stay competitive in the world market.
1 Introduction The Robotics Industry Association defines a robot as "a reprogrammable, multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks" (Zalda 8). In short, a robot is a machine that is programmed to perform a variety of tasks in place of humans. The first industrial robot, built in 1961, was a mechanical arm used to load presses. After the development of the computer and the CNC (Computer Numerical Control) in the 1970's, the world saw great advances in the development of robotic control and the quality of robot manufacturing.
As a result, there has been acceptance of the industrial robot world wide, improving the productivity and quality standards of industry (Hodges 3-5). Robots accomplish a wide variety of tasks in both fabrication and assembly production. As workers, they have several advantages: they never get tired, they never get board, or distracted, and they are less sensitive to their surroundings. In short, for any job that is unpleasant, boring, or dangerous the ideal worker is a robot (Williams 192). Automobile assembly lines account for 40% of the robots found in the world. The robots are used to stamp out and machine car parts, weld the parts together, and paint them.
Robots are what enable automakers to produce cars faster and at a lower cost (Time 100). The total number of industrial robots operating in the United States today is around 116,000 (Weimer 25). This report will describe the six basic types of robot, how they operate, and why they are so valuable to the manufacturing industry. 2 Collected Data Types of robots used in IndustryCartesianThe Cartesian Robot system consists of three linear axes that move at right angles to each other on a rigid structure capable of handling heavy loads.
These robots are commonly used for pick and place applications including tool loading, part stacking and part assembly (Hodges 18-29). An example of a Cartesian Robot is shown in Appendix A, Figure 1. Gantry The Gantry Robot system is very similar to the Cartesian Robot. Both have the same axes arrangement, but the Gantry Robot has an additional support for more rigidity. Gantry Robots are capable of transferring loads, up to 1000 lb over a large work area very quickly (Hodges 18-20). An example of a Gantry Robot is shown in Appendix A, Figure 2.
Cylindrical The Cylindrical Robot system has three axes. The first axis is a rigid structure that is able to rotate 300^0 about its base. The other two axes are linear travel joints, one in the vertical plane and one in the horizontal. These robots are capable of lifting heavy loads and are useful for simple material transfer and assembly, but are restricted to areas close to their base (Hodges 13-30). An example of a Cylindrical Robot is shown in Appendix A, Figure 3. Polar The Polar Robot system has three axes that are used to cover a large work area.
The first two axes are rotary joints and third is linear. Unfortunately, these robots cannot reach near there base and can only be used when there is a limited amount of vertical movement 3 required. The Polar Robot is very popular in the automotive industry and has been used since the 1960's for spot welding and loading machines (Hodges 13-30). An example of a Polar Robot is shown in Appendix A, Figure 4. Articulated Arm The Articulated Arm system is a robot that is made up of all rotary joints. This robot is the one that most resembles a human arm.
The Articulated Arm is the most widely used robot because of its ability to reach every part of the work area. This robot is also a good candidate for use in harsh environments and in clean rooms. The rotary joints are completely sealed from the environment, preventing them from becoming contaminated or the joints contaminating the environment (Hodges 13-31). An example of an Articulated Arm is shown in Appendix A, Figure 5. SCARA The Selective Compliance Assembly Robot Arm (SCARA) is an extension of the Articulated Arm idea. The SCARA robot has rotary motion about its base, two smaller rotaries for the first and second joints on the arm, and a linear vertical travel.
These robots are very fast and accurate to one thousandth of an inch. These robots were originally designed for assembly work, but can be used for welding, drilling, soldering, or any light to medium load that does not require high vertical movement (Hodges 21-31). An example of a SCARA robot is shown in Appendix A, Figure 6.4 Robot ControlActuatorsActuators are what make the robot move. Actuators typically consist of electric or hydraulic motors. The motors can drive the joints directly or use a linkage such as a shaft, belt, cable, or gear to transmit motion from the motor to the joint.
Pneumatic or hydraulic cylinders can also be used to actuate linear movement in robots, as well as operate different styles of robot tooling used to grip objects (Robotics). Nonservo The Nonservo robot is the simplest kind of robot. Nonservo means there is no feedback from the robot to the sequence controller indicating the position of each joint. The operation of this robot is simple. Each joint has two extreme limits set by mechanical stops. Each mechanical stop is set at the end of the desired joint travel to prevent further movement that direction.
The sequence controller then commands each of the individual joints of the robot to move in a desired direction. The arm will move as instructed until each of its joints hits a mechanical stop. This kind of motion is fast, but neither flexible nor precise. Nonservo robots are only suitable for simple pick and place material handling jobs where accuracy is not critical (Williams 191). Servo The Servo type robot is designed for speed and accuracy.
The robots joints are always under computer control. The servomechanism on each joint of the robot has a position transducer of some type, usually an optical encoder, that monitors the position of that joint. The actual position of the joint is continuously being compared to the desired position commanded by the computer controller. If the desired position and the actual position differ, the control will send a signal to the joint actuator to correct the 5 misalignment. Servo systems enable the robot to move to any position without the need for mechanical stops. Servo controlled robots have very precise movements most with the ability to position within one thousandth of an inch.
The majority of the robots used today are servo controlled because of there accuracy and flexibility (Robotics). Programming Programming is the process in which every movement of the robot is stored, so an operator can later run the robot through the same motion endlessly. Robots cannot run on there own, every step of there operation must be programmed in advance on the computers that control them. There are several different ways to program a robot.
The early robots were programmed by manually inserting pegs into a drum to trip switches in a desired sequence. Modern robots can be programmed using a general-purpose computer language (Asfahl 156). The majority of today's robots use a hand held controller called a teach pendant to program the robot. The teach pendant is used to move the robot through the desired motion while memorizing points along the path. The pendant is also used to set timers to synchronize operations and command the sensing of external inputs.
The process of programming the robots operation is done at a very slow speed to enable the programmer to position the robot accurately. After the robot is trained, the speed is increased for production (Asfahl 156). Other robots can be taught the desired motion by simply setting the ro bot in teach mode, then pushing the end of the robot arm through the operation in a dry run of the actual process. The robot will remember the path and then be able to repeat the process indefinitely. This type of programming is especially good for welding and spray-painting applications because the operators can teach the robot their skills while simulating the 6 actual manual performance. The robot then mimics the actions of its teacher (Asfahl p 156).
The key feature of robots is their ability to be easily reprogrammed. This feature is what enables one robot to do many different functions just by changing its program. How Robots have improved manufacturingProductionThe fact that a robot should provide a minimum of 100% increase in productivity over manual methods is a good reason to invest in robot automation alone (Woodman 78). There are several reasons why robots can out produce humans.
First, they can work faster. Second, they can work 24 hours a day 365 days a year. Robots never need to take a brake and they never get sick or need time off. Robots may break down, but on average the down time for a robot in need of repair is not more than 1% or 2% of the time.
Some robots have run 48 months between repairs (Robotics 66). Robots can be used to meet production goals when a company is unable to find enough skilled workers to fill the positions. Take the welding industry for example, because there are not enough young welders coming into the industry to replace the ones retiring a company in Ontario, Canada was finding it hard to meet production goals. The company was faced with a large contract to produce pallet truck handles, but was unable to maintain the skilled work force of welders needed to produce the necessary parts. To remedy the problem the company decided to purchase an automated welding robot system. As a result, the company is now able to meet production goals without trying to find employees willing to work overtime (Small 42).
A California welding manufacturer in a 7 similar situation determined, that after buying a robotic welding system one operator could produce what once took four skilled welders (Woodman 78). Quality Using robots as much as possible is one way of ensuring high and consistent quality of manufactured products. A workers performance is never consistent because they may get tired during the shift, or their attention may wander. A robot never gets tired and always provides the same performance throughout the day.
Robots produce high quality parts because every move is programmed with great accuracy. If for some reason, the robot is not producing high quality parts the operating program can be altered until the robot produces a perfect part every time. Take for instance a company in Marne, MI that was contracted to build hydraulic reservoirs. Their current means of production was causing an excess amount of weld splatter on the tanks. To meet quality standards, the excess splatter needed to be ground off. As a result of the grinding process, the pump on the reservoir would become contaminated with dust and debris.
To remedy the problem, the company purchased several welding robots to perform precision welding on the reservoirs. The new robots were able to weld the reservoirs with less splatter, which meant significantly less grinding and no contamination to the pump. The owner of the new robots was quoted as saying, "We prefer to use the robots whenever possible. With robots, there is no human factor, which means we always get consistently good quality welds. Also, the robots can weld twice as fast as manual methods" (Automation 37). Safety The health and safety of employees is an increasing consideration for all companies.
Fortunately, the increased use of robots in repetitive jobs eliminates the risk of employees 8 contracting Carpel Tunnel Disease while robots that perform heavy lifting jobs eliminate the risk of back injuries. Hazardous environments are another area where companies should limit workers exposure. Even when workers are supposed to wear protective gear there is still a risk of exposure. Any exposure to a hazardous environment carries the potential risk of health problems to the worker, which means the potential for liability by the company.
Take painting for example, a paint booth is a hazardous environment. When a robot does the painting, workers are not needed in the booth, eliminating the chance of workers being exposed to the hazardous paint fumes (Robotics 66). Profit All the topics previously discussed can easily be linked together by one main goal, to increase profit. Robots can increase profits in many ways. Do to the fact that robots repeat the same process with great accuracy, they reduce the number of scraped parts. Workers typically scrap parts do to their lack of knowledge or carelessness, which causes companies to throw away thousands of dollars in useless parts.
The use of one robot typically reduces the number of scraped parts by 10% to 15% (Robotics 66). A robot will also save money on production materials. A robot is programmed to uses only the exact amount of material necessary to do the job, while a worker tends to waste material. Take welding companies for instance, a skilled welder builds a margin of safety into each weld, first by using more filler than necessary, and second making beads longer than necessary. A robot is programmed to use only as much filler as needed, resulting in less splatter and wasted filler (Woodman 78).
9 Conclusion As stated by Cheney "Increasing labor costs, labor shortages, ergonomic issues, product quality, and changes in OSHA standards are all causes of increased use of robotics in the manufacturing facility" (20). There are other reasons why every year more companies are investing in robots. First, robots of today are more affordable than a decade ago. A complete automated welding cell starts at $60,000. Second, the robots are faster, more accurate, reliable, and flexible than ever before. The main reason companies are going to robots is that the global market is more competitive now than ever.
The only way to stay competitive is to produce a consistently high quality part at the cheapest possible cost. The only answer is robotics (Woodman 78). With the increasing cost to run a business and the ever-increasing national and international competition for cheap quality parts, companies are going to have to invest in automation. Unions should be fighting to protect their jobs by getting companies who have not yet invested in robots to do so. If they do not, there is a good chance the company will be history in a few short years (Robotics 66). 10 Glossary Axis: A direction in which a part of a robot can move in a linear or rotary mode.
The number of axis is normally the number of guided and mutually driven links. Base: a platform or structure to which is attached the origin of the first member of the articulated structure. Computer controller: a system that uses a computer to regulate the motions of the robot mechanism. Cylinder: a device when pressurized by a fluid or gas will extend in length. Hydraulic: to operate by, or moved by a pressurized liquid.
Joint: an assembly between two rigid members to permit motion. Linear Joint: an assembly between two rigid members enabling one to move parallel in relation while in contact with the other. Optical Encoder: The light source, encoder disk, and photo diode that measure the speed of a rotating shaft. Pneumatic: to operate by, or moved by a pressurized gas.
Reprogrammable: Whose programmed motions or auxiliary functions may be changed without physical alteration. Rotary Joint: an assembly between two rigid members, which enables one to rotate in relation to the other, about a fixed axis. Sequence Controller: a system that regulates the motions of the robot mechanism. Teach Pendant: A hand-held unit linked to the control system with which a robot can be programmed or moved.
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