Automation Technologies For Manufacturing Systems PDF

AUTOMATION TECHNOLOGIES FOR MANUFACTURING SYSTEMS 1. 2. 3. 4. Automation Fundamentals Hardware for Automation Computer Numerical Control Industrial Robotics ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manufacturing Systems  A manufacturing system can be defined...

AUTOMATION TECHNOLOGIES FOR MANUFACTURING SYSTEMS 1. 2. 3. 4. Automation Fundamentals Hardware for Automation Computer Numerical Control Industrial Robotics ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manufacturing Systems  A manufacturing system can be defined as a collection of integrated equipment and human resources that performs one or more processing and/or assembly operations on a starting work material, part, or set of parts  The integrated equipment consists of production machines, material handling and positioning devices, and computer systems  The manufacturing systems accomplish the valueadded work on the part or product ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manufacturing Systems in the Larger Production System ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Automation Fundamentals  Automation can be defined as the technology by which a process or procedure is performed without human assistance  Humans may be present, but the process itself operates under its own self-direction  Three components of an automated system: 1. Power 2. A program of instructions 3. A control system to carry out the instructions ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Three Components of an Automated System  Power is required to drive the process and the control system  The program of instructions may also require power  The form of the power is usually electrical ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Two Types of Control System  (a) Closed loop and (b) open loop ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Three Basic Types of Automation  Fixed automation - the processing or assembly steps and their sequence are fixed by the equipment configuration  Programmable automation - equipment is designed with the capability to change the program of instructions to allow production of different parts or products  Flexible automation - an extension of programmable automation in which there is virtually no lost production time for setup changes or reprogramming ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Features of Fixed Automation  High initial investment for specialized equipment  High production rates  The program of instructions cannot be easily changed because it is fixed by the equipment configuration  Thus, little or no flexibility to accommodate product variety ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Features of Programmable Automation  High investment in general purpose equipment that can be reprogrammed  Ability to cope with product variety by reprogramming the equipment  Suited to batch production of different product and part styles  Lost production time to reprogram and change the physical setup  Lower production rates than fixed automation ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Features of Flexible Automation  High investment cost for custom-engineered equipment  Capable of producing a mixture of different parts or products without lost production time for changeovers and reprogramming  Thus, continuous production of different part or product styles  Medium production rates  Between fixed and programmable automation types ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Hardware Components for Automation     Sensors Actuators Interface devices Process controllers - usually computer-based devices such as a programmable logic controller ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Sensors  A sensor is a device that converts a physical stimulus or variable of interest (e.g., force, temperature) into a more convenient physical form (e.g., electrical voltage) for purpose of measuring the variable  Two types:  An analog sensor measures a continuous analog variable and converts it into a continuous signal  A discrete sensor produces a signal that can have only a limited number of values ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Actuators  An actuator is a device that converts a control signal into a physical action, usually a change in a process input parameter  The action is typically mechanical, e.g., change in position of a worktable or speed of a motor  The control signal is usually low level, and an amplifier may be required to increase the power of the signal to drive the actuator  Amplifiers are electrical, hydraulic, or pneumatic ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Interface Devices  Interface devices allow the process to be connected to the controller and vice versa  Sensor signals from the process are fed into the controller  Command signals from the controller are sent to the process ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Types of Interface Devices  Analog-to-digital converters - periodically samples continuous signals from process and converts the sampled data into encoded values for the controller  Digital-to-analog converters - Converts the digital output of the controller into quasi-continuous signals to drive analog actuators or other analog devices  Contact input/output interfaces - communicates binary data between process and controller  Pulse counters and pulse generators ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Process Controllers  Most process control systems use some type of digital computer as the controller  Requirements for real-time computer control:  Respond to incoming signals from process  Transmit commands to the process  Execute certain actions at specific points in time  Communicate with other computers that may be connected to the process  Accept inputs from operating personnel ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Programmable Logic Controller (PLC)  A PLC is a microcomputer-based controller that uses stored instructions in programmable memory to implement logic, sequencing, timing, counting, and arithmetic control functions, through digital or analog input/output modules, for controlling machines and processes  PLCs are widely used process controllers that satisfy the preceding real-time controller requirements ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Major Components of a Programmable Logic Controller ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Computer Numerical Control (CNC)  A form of programmable automation in which the mechanical actions of a piece of equipment are controlled by a program containing coded alphanumeric data  The data represent relative positions between a workhead (e.g., a cutting tool) and a workpart  NC operating principle is to control the motion of the workhead relative to the workpart and to control the sequence of motions ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Components of a CNC System 1. Part program - detailed set of commands to be followed by the processing equipment 2. Machine control unit (MCU) - microcomputer that stores and executes the program by converting each command into actions by the processing equipment, one command at a time 3. Processing equipment - accomplishes the sequence of processing steps to transform the starting workpart into completed part ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e NC Coordinate System  Consists of three linear axes (x, y, z) of Cartesian coordinate system, plus three rotational axes (a, b, c)  Rotational axes are used to orient workpart or workhead to access different surfaces for machining  Most NC systems do not require all six axes ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e NC Coordinate Systems  Coordinate systems used in numerical control: (a) for flat and prismatic work and (b) for rotational work ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e NC Motion Control Systems  Two types: 1. Point-to-point 2. Continuous path ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Point-to-Point (PTP) System  Workhead (or workpiece) is moved to a programmed location with no regard for the path taken to get to that location  When the move is completed, some processing action is performed by the workhead  Example: drilling a hole  Thus, the part program consists of a series of point locations at which operations are performed  Also called positioning systems ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Continuous Path (CP) System  Continuous simultaneous control of more than one axis, thus controlling path followed by tool relative to part  Permits tool to perform a process while axes are moving, enabling system to generate angular surfaces, two-dimensional curves, or 3-D contours in a workpart  Examples: many milling and turning operations, flame cutting, laser cutting etc.  Also called contouring in machining operations ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Two Types of Positioning  Absolute positioning  Locations are always defined with respect to origin of axis system  Incremental positioning  Next location is defined relative to present location ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e NC Positioning System  Motor and leadscrew arrangement in a numerical control positioning system ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e NC Positioning System  Converts the coordinates specified in the NC part program into relative positions and velocities between tool and workpart  Leadscrew pitch p - table is moved a distance equal to the pitch for each revolution  Table velocity (e.g., feed rate in machining) is set by the RPM of leadscrew  To provide x-y capability, a single-axis system is piggybacked on top of a second perpendicular axis ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Two Basic Types of Control in Numerical Control  Open loop system  Operates without verifying that the actual position is equal to the specified position  Closed loop control system  Uses feedback measurement to verify that the actual position is equal to the specified location ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Two Basic Types of Control in Numerical Control ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e How a stepper motor works https://www.youtube.com/watch?v=eyqwLiowZiU Operation of an Optical Encoder ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Precision in Positioning  Three critical measures of precision in positioning: 1. Control resolution 2. Accuracy 3. Repeatability ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Control Resolution (CR)  Defined as the distance between two adjacent control points in the axis movement  Control points are locations along the axis to which the worktable can be directed to go  CR depends on:  Electromechanical components of positioning system  Number of bits used by controller to define axis coordinate location ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Control Points along Linear Axis  A portion of a linear positioning system axis, indicating control resolution, accuracy, and repeatability ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Statistical Distribution of Mechanical Errors  When a positioning system is directed to move to a given control point, the movement to that point is limited by mechanical errors  Errors are due to various inaccuracies and imperfections, such as gear backlash, play between lead-screw and worktable, and machine deflection  Errors are assumed to form a normal distribution with mean = 0 and constant standard deviation over axis range ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Accuracy in a Positioning System  Maximum possible error that can occur between desired target point and actual position taken by system  For one axis: Accuracy = 0.5 CR + 3 where CR = control resolution; and  = standard deviation of the error distribution ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Repeatability  Capability of a positioning system to return to a given control point that has been previously programmed  Repeatability of any given axis of a positioning system can be defined as the range of mechanical errors associated with the axis Repeatability = 3 ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e CNC Part Programming Techniques 1. 2. 3. 4.  Manual part programming Computer-assisted part programming CAD/CAM-assisted part programming Manual data input Common features:  Points, lines, and surfaces of workpart must be defined relative to NC axis system  Movement of cutting tool must be defined relative to these part features (accounting for tool geometry as well) ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manual Part Programming  Uses basic numerical data and special alphanumeric codes to define the steps in the process  Suited to simple point-to-point machining jobs, such as drilling operations ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manual Part Programming: Example  Example command for drilling operation: n010 x70.0 y85.5 f175 s500 where n-word (n010) = a sequence number; x- and y-words = x and y coordinate positions (x = 70.0 mm and y = 85.5 mm), and f-word and s-word = feed rate and spindle speed (feed rate = 175 mm/min, spindle speed = 500 rev/min)  Complete part program consists of a sequence of commands ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Computer-Assisted Part Programming  Uses high-level programming language  Suited to programming of more complex parts  First NC part programming language was APT = Automatically Programmed Tooling  In APT, part programming is divided into two basic steps: 1. Definition of part geometry 2. Specification of tool path and operation sequence ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e APT Geometry Statements (Automatically Programmed Tooling)  Part programmer defines geometry of workpart by constructing it of basic geometric elements such as points, lines, planes, and circles  Examples: P1 = POINT/25.0, 150.0 L1 = LINE/P1, P2 where P1 is a point located at x = 25 and y = 150, and L1 is a line through points P1 and P2  Similar statements are used to define circles, cylinders, and other geometry elements ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e APT Motion Statements: Point-To-Point  Specification of tool path accomplished with APT motion statements  Example for point-to-point operation: GOTO/P1  Moves from current location to location P1  P1 has been defined by a previous APT geometry statement ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e APT Motion Statements: Continuous Path  Previously defined geometry elements such as lines, circles, and planes are used to direct tool  Example for contouring operation: GORGT/L3, PAST, L4  Directs tool to go right (GORGT) along line L3 until it is positioned just past line L4  L4 must be a line that intersects L3 ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e CAD/CAM-Assisted Part Programming  In computer-assisted part programming, the part program is entered into the computer for processing  Programming errors may not be detected until computer processing  Using CAD/CAM, programmer receives visual verification as each statement entered  If part design is prepared on CAD, then the CAD model can be used in part programming, so that geometric definition is unnecessary ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manual Data Input (MDI)  Machine operator enters part program at machine  Involves use of a CRT display with graphics capability at machine tool controls  NC part programming statements are entered using a menu-driven procedure  MDI does not require a staff of NC part programmers  MDI makes it feasible for small machine shops to implement NC ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Applications of Computer Numerical Control   Operating principle of NC applies to many processes  Many industrial operations require the position of a workhead to be controlled relative to the part or product being processed Two categories of NC applications: 1. Machine tool applications 2. Non-machine tool applications ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Machine Tool Applications  NC widely used for machining operations such as turning, drilling, and milling  NC has motivated development of machining centers, which change their own cutting tools to perform a variety of machining operations  Other NC machine tools:  Grinding machines  Sheet metal press-working machines  Thermal cutting processes ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e CNC Horizontal Machining Center  Worker loading and unloading parts onto indexing table (courtesy of Cincinnati Milacron) ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Beginners guide to manual and CNC milling https://www.youtube.com/watch?v=TecC9_nwpUw Ultra High Precision CNC Demo https://www.youtube.com/watch?v=1F4-plhdnj0 Non-Machine Tool Applications  Tape laying machines and filament winding machines for composites  Welding machines, both arc welding and resistance welding  Component insertion machines in electronics assembly  Drafting machines (x-y plotters)  Coordinate measuring machines for inspection ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Benefits of CNC  Reduced non-productive time  Results in shorter cycle times  Lower manufacturing lead times  Simpler fixtures  Greater manufacturing flexibility  Improved accuracy  Reduced human error ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Industrial Robotics  An industrial robot is a general purpose programmable machine that possesses certain anthropomorphic features  The most apparent anthropomorphic feature is the robot’s mechanical arm, or manipulator  Robots can perform a variety of tasks such as loading and unloading machine tools, spot welding automobile bodies, and spray painting  Robots are typically used as substitutes for human workers in these tasks ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Robot Anatomy  An industrial robot consists of  Mechanical manipulator  A set of joints and links to position and orient the end of the manipulator relative to its base  Controller  Operates the joints in a coordinated fashion to execute a programmed work cycle ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e  Manipulator of an industrial robot (photo courtesy of Adept) ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manipulator Joints and Links  A robot joint is similar to a human body joint  It provides relative movement between two parts of the body  Typical industrial robots have five or six joints  Manipulator joints - classified as linear or rotating  Each joint moves its output link relative to its input link  Coordinated movement of joints enables robot to move, position, and orient objects ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manipulator Design  Robot manipulators can usually be divided into two sections:  Arm-and-body assembly - function is to position an object or tool  Three joints are typical for arm-and-body  Wrist assembly - function is to properly orient the object or tool  Two or three joints are associated with wrist ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Five Basic Arm-and-Body Configurations 1. 2. 3. 4. 5. Polar Cylindrical Cartesian coordinate Jointed-arm SCARA (Selectively Compliant Assembly Robot Arm) ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Basic Arm-and-Body Configurations  (a) Polar, (b) cylindrical, and (c) Cartesian coordinate ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Basic Arm-and-Body Configurations  (d) Jointed-arm and (e) SCARA (Selectively Compliant Assembly Robot Arm) ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Manipulator Wrist  The wrist is assembled to the last link of the arm-and-body  The SCARA is sometimes an exception because it is almost always used for simple handling and assembly tasks involving vertical motions  A wrist is not usually present at the end of its manipulator  Substituting for the wrist on the SCARA is usually a gripper to grasp components for movement and/or assembly ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e End Effectors  Special tooling that connects to the robot's wrist to perform the specific task 1. Tools - used for a processing operation  Applications: spot welding guns, spray painting nozzles, rotating spindles, heating torches, assembly tools 2. Grippers - designed to grasp and move objects (usually parts)  Applications: part placement, machine loading and unloading, and palletizing ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Gripper End Effector  Robot gripper: (a) open and (b) closed to grasp a work part ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Robot Programming  Robots execute a stored program of instructions that define the sequence of motions and positions in the work cycle  Much like a part program in NC  In addition to motion instructions, the program may include commands for other functions:  Interacting with external equipment  Responding to sensors  Processing data ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Two Basic Robot Programming Methods 1. Leadthrough programming  Teaching-by-showing - manipulator is moved through sequence of positions in the work cycle and the controller records each position in memory for subsequent playback 2. Computer programming languages  Robot program is prepared at least partially offline for subsequent downloading to robot controller ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Where Should Robots be Used?        Work environment is hazardous for humans Work cycle is repetitive The work is performed at a stationary location Part or tool handling is difficult for humans Multi-shift operation Long production runs and infrequent changeovers Part positioning and orientation are established at the beginning of work cycle, since most robots cannot see ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e Applications of Industrial Robots  Three basic categories: 1. Material handling  Moving materials or parts (e.g., machine loading and unloading) 2. Processing operations  Manipulating a tool (e.g., spot welding, spray painting) 3. Assembly and inspection  May involve moving parts or tools ©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e FANUC Industrial robots at AUDI Hungary https://www.youtube.com/watch?v=rbki4HR41-4