Chapter 39 Numerical Control and Industrial Robotics Numerical Control-form of programmable automation in which the mechanical actions of a piece of equipemt are controlled by a program containing coded alphanumeric data. What is Numerical Control History-John Parsons and Frank Stulen at Parsons Co. in Michigan in 1940?s Components of an NC system-1)part program2)machine control unit3)processing equipment Coordinate Systems and Motion Control 1 Point-to-point vs. 2 continuous path systems-1-move workhead to a programmed location with no regard for path taken to get to location. 2-provides continuous simultaneous control of more than one axis, thus controlling the path followed by the tool relative to the part. 1 Absolute vs. 2incremental positioning 1-workhead locations are always defined with respect to origin. 2-next workhead position is defined relative to present location NC Positioning Systems Motion hardware components-workstations, material handlilng system, central control computer. 1 Open vs. 2 closed loop systems; feedback-1uses a stepping motor to rotate the leadscrew. 2-uses servomotors and feedback measurements to ensure desired position. Programming-Manual part programming, computer assisted part programming, CAD/CAM assisted part programming, manual data input Non-machining applications-1)tape laying machines and filament winding machines for composites 2)welding machines 3)component insertion machines in electronics assembly 4)drafting machines 5)coordinate measuring machines for inspection. Benefits of numerical control- reduce nonproductive time, lower manufacturing lead times, simpler fixturing, greater manufacturing flexibility, improved accuracy, and reduced human power. Industrial robotics Definition of industrial robot-general purpose programmable machine peossessing certain anthropomorphic features. Robot anatomy Joints and links-provides relative movement between two parts of the body. Arm & body functions-moves to cover all axis Wrist functions- simple handling and assembly tasks involving vertical motions. Not always at the end of the arm. End effectors-special tooling that connects to the robots wrist end to perform a specific task. Robotic motion control categories (limited sequence, etc.)-limited sequence, playback with point to point, playback with continuous path, intelligent control. Programming ? leadthrough- involves ?teach by showing? in which the manipulator is moved by the programmer through the sequence of positions in the work cycle. Work situations that indicate potential beneficial use of robot in place of human worker ? know several-1)work environment too hazardous for humans 2)work cycle is repetitive, 3)work is performed at a stationary loc. 4)part or tool handling would be difficult for haunts, 5)it is multishift operational. Accuracy/Precision of motion Chapter 40 Group Technology and Flexible Manufacturing Systems Group technology Definition and reason for use-an approach to manufacturing in which similar parts are indentified and grouped together in order to take advantage of their similarities in design and production. Approach-in production, group similar parts together to be made. Classification and coding Part families- a group that possess similarities in geometric shape and size, or in the processing steps used in their manufacture What is classification and coding?-most are one of the following: systems based on part design attributes, systems based on part manufacturing attributes, systems based on both design and manufacturing attributes. Benefits of a well-designed system-facilitates formation of part families, permits quick retrieval of part design drawings, reduces design duplication, promotes design standardization, improves cost estimate and cost accounting. Cellular manufacturing What is it?- to fully exploit the similarities among parts in a family, production is organized using machine cells designed to specialize in making particular parts. Benefits and problems + promotes standardization of tooling, fixturing, and setups, material handling is reduced, production scheduling is simpler, manufacturing lead time is reduced, work in progress is reduced, process planning is simplified. Problems: rearranging production machines, identifying part families Composite part of a part family- a hypothetical part that includes all of the design and manufacturing attributes of the family. Flexible manufacturing systems What are they and what are their components; functions of central control computer- a highly automated group technology machine cell, consisting of a group of processing stations, interconnected by an automated material handling and storage system, and controlled by an integrated computer system. NC part programming - development of NC programs for new parts introduced into the system Production control - product mix, machine scheduling, and other planning functions NC program download - part program commands must be downloaded to individual stations Machine control - individual workstations require controls, usually CNC Layout Applications: machining, assembly, inspection, sheet metal processing, forging Benefits:higher machine utilization, reduce work in process, lower manufacturing lead times, and greater flexability in production scheduling Chapter 41 Production Lines Production lines Product variations- can be designed to cope with variations in product models 3 types: single model line, batch model line, mixed model line. Forms of material transfer manual and mechanized: continuous transfer sys., synchronous transfer sys., asynchronous transfer sys. (moves independently.) Manual assembly lines- human workers at workstations 1problem =line balancing Line balancing (general terms, not calculated times)- workers must have equal amount of work. Automated production lines Transfer lines- lines that perform processing operations. Automated assembly systems- one or more workstations that perform assembly operations, such as adding components and or fixing them to the work unit. Chapter 42 Manufacturing Engineering Introductory/functions- technical staff concerned with planning the manufacturing processes for the economic production of high quality products. Overall goal=optimize manufacturing within a particular org. Process planning-determining the most appropriate manufacturing processes and the sequence in which they should be performed to produce a given part or product specified by design engineering. Part plans; route sheets; assembly plans; Make/buy decisions- wether a part should be purchased from an outside vendor or made internally Computer-aided process planning - what is it- automating the process planning by a computer system Problem solving/continuous improvement-problems arise in manufacturing that require technical staff support beyond what is normally available in the line organization of the production departments. Constantly searching for and implementing ways to reduce cost, improve quality, and increase productivity in manufacturing. Design for Manufacturability- much of process planning is pre-empted by decisions made in product design. The manufacturing engineer must act as an advisor to the design engineer in matters of manufacturability because manufacturability matters, not only to the production departments but to the design engineer Concurrent Engineering - what is it and why is it important-An approach to product design in which companies attempt to reduce elapsed time required to bring a product to market by integrating design engineering, manufacturing engineering, and other functions Chapter 44 ? Quality Control What is quality? Aspects of quality-Quality is the degree of excellence which a thing possesses. Product features - the characteristics of the product that result from design Freedom from deficiencies ? the product is absent of defects and out of tolerance conditions Random vs. Assignable Cause Variation- Random-Caused by factors such as human variability, variations in raw materials, machine vibration, and so on. Assignable Cause-An exception from normal operating conditions due to operator mistakes, defective raw materials, tool failures, machine malfunctions, and so on Process Capability and PC Index What are they? Process Capability- Defined as ( 3 standard deviations about the mean output value (a total of 6 standard deviations) Why is it desirable to have PCI ? 1? Taguchi Loss Function- Taguchi defines quality as "the loss a product costs society from the time the product is released for shipment" Robust Design ? what is it?- A basic purpose of quality control is to minimize variations. Taguchi calls these ?noise factors?. (A design in which the product's function and performance are relatively insensitive to variations in design and manufacturing parameters) Off-line/on-line quality control-Off line quality control - concerned with design issues, both product design and process design . It precedes on line control . On line quality control - concerned with production operations and customer relations after shipment Statistical process control-The use of various statistical methods to assess and analyze variations in a process Control charts for variables- A process that is out of statistical control manifests this condition in the form of significant changes in: Process mean, and/or Process variability Corresponding to these possibilities, there are two principal types of control charts for variables: x chart (?x-bar? chart) - indicates how the process mean changes over time R chart ? monitors the range of each sample In/out of statistical control Two methods for detecting out of control situations (the second not specifically described in text, but described in class) A point outside control limits 8 or more consecutive points on same side of centerline
Want to see the other 2 page(s) in Test 4 Study Guide Manufacturing?JOIN TODAY FOR FREE!