Industrial Robotics. Training Objective

Transcription

1 Training Objective After watching the program and reviewing this printed material, the viewer will learn the basics of industrial robot technology and how robots are used in a variety of manufacturing and assembly operations. An overview of robot technology is provided The primary types of industrial robots are shown Programming methods are demonstrated Robot tooling and sensors are detailed Robotics Overview Industrial robots are defined as 'multi-functional manipulators designed to move materials, parts, tools, or specialized devices through various programmed motions'. As such, robots provides consistent reliable performance, repetitive accuracy and are able to handle heavy work loads and perform in harsh environments. Additionally, robots can be quickly reprogrammed to reflect changes in production needs and cycles. All of the above result in vastly improved productivity and quality. However, this technology has certain disadvantages, which can include: The need for skilled programmers The high cost of robotic systems Constant maintenance procedures Unique worker safety precautions Robots can have either hydraulic, electric, or pneumatic power sources. Movement configurations can range from simple arm extension and retraction movements to very complex movements involving body, upper arm, lower arm, and wrist movement. These various configurations are differentiated by the number of 'degrees of freedom' or 'axes of motion'. The number of axes determines the overall dexterity of the robot. Robots may have up to seven axes of motion which include four arm motions and three wrist motions. The axes, or joints, can be either linear or rotary in motion. Another defining aspect is the robot s work envelope which is its maximum reach in all directions. Robots are broadly classified by their arm s geometry. The primary types are: Rectangular Arm Robots - also called Cartesian Robots, or Gantry Robots, move in the standard Cartesian coordinate axes 'X', 'Y', and 'Z'. This type is usually used for handling small parts in pick and place operations and is easily integrated into assembly operations. Selective Compliant Articulated Robot for Assembly (SCARA) Robots - these SCARA robots have two parallel rotary axes that enable vertical axis insertion from the end of the wrist. SCARA robots are especially well suited for assembly work. Articulated Robots - also call jointed arm robots, they have three axes of rotary arm motion but do not have any corresponding coordinate system. Being able to move simultaneously along its three axes, the articulated robot is used for very complex tasks. Robots are typically fixtured in place and thus have a clearly defined but finite work envelope. In some instances the robot may be mounted on a slide, transporter, or gantry. This arrangement allows the robot to service multiple work stations or machines. Fundamental Manufacturing Processes Study Guide, DV04PUB11-1 -

2 Robot Wrist & End of Arm Tools The wrist provides one, two, or three axes of motion relative to the arm itself. The motions are: Pitch - motion in the vertical plane Yaw - motion in the horizontal plane Roll - a rotary motion Additionally, the wrist serves as the mounting point for a variety of devices. These 'end effectors' are either hand, or gripping devices, or job specific tools. Gripping devices can include: Suction cups Multiple jaw grippers that grip internal or external surfaces A system of interchangeable grippers Tools can include welding guns, paint spraying nozzles, and a wide variety of machining tools: Welding - both arc and spot welding can be effectively done with robots while providing fast, high quality assembly line production capability Part coatings - robots facilitate the accurate and consistently stable application of paints, adhesives, and powder coating to flat, curved, and hard to reach surfaces Machining - wrist mounted drills, mills, boring, and deburring tools are typical of a wide variety of tools used in manufacturing operations Robot Programming Programming gives the robot system specific instructions governing the movement of the arm and its end effector. These include: Direction Path Distances to move Sequences Tool selections These programs may be created either on-line or off-line with each method having distinct advantages or disadvantages. On-line Programming - uses a 'teach pendant' to direct the robot s movement. Taught data is stored in the pendant s memory then transferred to the robot s controller. This is a convenient and easy method of programming when tasks are simple and revisions or adjustments can be made on the spot. However, the production line must be stopped during the programming and there are safety issues to consider as the programmer must work within the robot s work envelope. Off-line Programming - this method is accomplished on computers located away from the robot station. Using simulation software, data is generated then sent to the robot s controller where it is translated into instructions. Additionally, the software contains modeling data which assists selection of the best robot configuration for a particular application. A primary advantage of off-line programming is that production need not be interrupted in order to create an initial or revised program. Fundamental Manufacturing Processes Study Guide, DV04PUB11-2 -

3 Robot Sensors Sensors are used to monitor part location and orientation during the production cycle. In so doing, the sensors can allow the robot to compensate for any variation in the parts or other aspects of the process. The sensors may either be contact or non-contact in function. Contact sensors include force gages and compliance devices which compensate for part positioning errors. Non-contact sensors include: Pneumatic sensors which detect part presence by air flow disturbance Ultrasonic sensors that analyze sound waves reflected from a part Proximity sensors that register the approach, arrival, or removal of parts Optical sensors utilizing interrupted light beams across the path of an incoming part Machine Vision Systems that use visual sensors, usually video cameras, to provide data that allows the robot to make intelligent decisions regarding parts Fundamental Manufacturing Processes Study Guide, DV04PUB11-3 -

4 Review Questions 1. 'Degrees of Freedom' refer to: a. a robot being stationary or movable b. the number of axes of motion c. the robots reach d. the size of the work envelope 2. Robot dexterity is determined by: a. its programming b. its end effectors c. the number of axes of motion d. its size 3. The number of robot wrist motions possible is: a. 1 b. 4 c. 7 d Another name for Rectangular Arm Robots is: a. Coordinate Robot b. SCARA Robot c. Cartesian Robot d. Jointed Arm Robot 5. SCARA Robots are well suited for: a. assembly work b. welding c. paint spraying d. machining 6. 'Pitch and Yaw' refer to: a. upper arm movements b. robot column movements c. forearm movements d. wrist movements 7. The primary advantage of off-line programming is: a. programmer safety b. ability to do complex programming c. little or no production downtime d. all of the above 8. Simulation software is used for: a. teach pendants b. for on-line programming c. for off-line programming d. optical sensors Fundamental Manufacturing Processes Study Guide, DV04PUB11-4 -

5 Answers 1. b 2. c 3. d 4. c 5. a 6. d 7. d 8. c Fundamental Manufacturing Processes Study Guide, DV04PUB11-5 -