Computer Aided design and Manufacturing pdf

principles of computer-aided design and manufacturing methods and tools what is the difference between computer aided design and computer aided manufacturing pdf
Dr.BenjaminClark Profile Pic
Dr.BenjaminClark,United States,Teacher
Published Date:21-07-2017
Your Website URL(Optional)
MCE 511 COMPUTER AIDED DESIGN AND MANUFACTURING E – NOTE 3 Units Course Lecturer – Engr. Prof. Sam. B. ADEJUYIGBE INTRODUCTION The technology that has the greatest impact on the production system over the last decades is computer technology. For any meaningful technological, or industrial design, or manufacturing breakthrough in developing countries like Nigeria, it is time to abandon the old traditional ways of manual preparation in favour of more consistent and faster tool as Computer-Aided Design/Drafting/Manufacturing/Process Planning/Computer Aided Engineering (CAD/CADD/CAM/CAPP/CAE), so that fast accurate data drawings and manufactured products can be correctly obtained in good time. The basic concepts, challenges and motivation of Computer-Aided Engineering (CAE) in developing countries like Nigerian is looked at in this paper using twenty six (26) Industries scattered in the Southern part of Nigeria. National and International competition in manufacturing is causing industrial leaders to look at new strategies for remaining competitive and improving quality in their products. Developments in the computer industry are having profound impact on the manufacturing industries from design to machine processing as well as the management and marketing components. Governments of all industrialized countries place great emphasis on the development of their manufacturing sectors. It is great importance, not only as a means of supporting sustainable growth, but also because of the nature of the technological developments that have taken place particularly over the last decade. Industrialization has a particular significant role to play in the amelioration of power and unemployment. Acceleration of industrial development of any nation depends on maximum utilization of Industrial Automation and Computer Aided Engineering (CAE). Therefore, the Nigerian Industries will have to imbibe the Computer Aided Engineering and its entire facet for improved productivity and rapid product development The trend in manufacturing call for the development of the following modern day manufacturing systems. There are: - Global competition in the manufacturing market; - Customers now demanded high-quality goods, with low production cost and timely delivery of manufacturing products. - Increase in the variety of products produced, thereby choosing the product life cycles to be shorter. Therefore, the modern day technology that manufacturing systems make use of are discussed in this write up.. Manufacturing system entails a large number of interdependent activities consisting of distinct entities such as materials, tools, machine, power, and human beings. It is a complex system because it is comprised of many diverse physical and, human elements. The choice are many, so the manufacturing engineers should be able to select correct which one to choose, that will profit the whole manufacturing system. BASIC CONCEPTS Computers are widely used throughout manufacturing industry. Hence in this paper introduction is made to all the relevant basic concepts of the computer applications to COMPUTER Computer is a machine that handles information with amazing speed. It works with such information as names and address hook titles, lists of item sold in stores, mathematical problems and weather forecasts. It handles information in the form of numbers. It solves problems dealing numbers. The fattest computers can do millions of problems in a few seconds (4,5,6). A computer by definition simply adds, subtracts, compares and store data. Computers are universally recognized as the most powerful and effective tool for improving productivity in industry, which is the single, most important concern of every manufacturing manager. Computers excel in three areas of manufacture namely: - Collecting information: - Reaching a decision; and - Issuing and order. COMPUTER – AIDED ENGINEERING (CAE) CAE systems can provide support to businesses. This is achieved by the use of reference architectures and their ability to place information views on the business process. Reference architecture is the basis from which information model, especially product and manufacturing models. Computers are used throughout as an aid in the manufacturing process. Some of the engineering application of computer is manufacturing fall mainly into the following areas of Computer Aided Engineering (CAE) which comprises all area of: • Computer Aided Design CAD; • Computer Design and Drafting (CADD) ; • Computer Aided Manufacturing CAM; • NC, CNC, AND DNC Machines; • Computer Material Handling System (Robotics) ; • Computer Aided Plant Layout (CAPL); • Computer Aided Design/Manufacturing (CAD/CAM) ; • Computer Integrated Manufacturing CIM; • Computer Aided Process Planning and Control CAPPC • Computer Aided Material Handling (CAPM); • Computer Aided Quality Assurance (CAQA); • Computer Aided Maintenance Management (CAMM); • Computer Aided Costing (CAC); • Computer Aided Quality Management (CAQM); • Computer Aided Production Control and Management (CAPCM); • Computer Aided Software Engineering (CASE); • Knowledge Based Expert System; • Artificial Intelligence (CAAI); • Virtual Reality (CAVR); • Mechatronics; and • Automation. The CAD system is the most important initial source of the product data that is used subsequent CAE operations. CAD, CAQA, CAPM and CM systems create and/or collect data, which is used to control or monitor other aspects of the manufacturing process. The need to re- program at each of manufacturing is avoided by the use of standard form of data already stored in the computer by CAD. This method eliminates human error, and save a lot of time. The ability to link all the various activities/operations together, through common database, is known as Computer-Integrated Manufacturing (CIM). CAE fields and phases CAE areas covered include: • Stress analysis on components and assemblies using FEA (Finite Element Analysis); • Thermal and fluid flow analysis Computational Fluid Dynamics (CFD); • Kinematics; • Mechanical Event Simulation (MES). • Analysis tools for process simulation for operations such as casting, moulding, and die press forming. • Optimization of the product or process. In general, there are three phases in any Computer-Aided Engineering task: • Pre-processing – defining the model and environmental factors to be applied to it. (typically a finite element model, but facet, voxel and thin sheet methods are also used) • Analysis solver (usually performed on high powered computers) • Post-processing of results (using visualization tools) This cycle is iterated, often many times, either manually or with the use of commercial optimization software. CAE in the automotive industry CAE tools are very widely used in the automotive industry. In fact, their use has enabled the automakers to reduce product development cost and time while improving the safety, comfort, and durability of the vehicles they produce. The predictive capability of CAE tools has progressed to the point where much of the design verification is now done using computer simulations rather than physical prototype testing. CAE dependability is based upon all proper assumptions as inputs and must identify critical inputs (BJ). Even though there have been many advances in CAE and it is widely used in the engineering field. Physical testing is still used as a final confirmation for subsystems due to the fact that CAE cannot predict all variables in complex assemblies (i.e. metal stretch, thinn COMPUTER – AIDED DESIGN (CAD) Computer Aided Design (CAD) is defined as the use of computer system to assist in creation, modification analysis or optimization of design (8). Computer – based systems are used for creating, modifying and communicating a plan or product design (9) Activities performed by CAD include: - Engineering design: - Design analysis: and - Design presentation. CAD systems have become more intelligent. Many potential customers are focusing less on geometry creation and more on integration (10) The CAD software consists of the computer programs to implement computer graphics on the system plus application program to facilitate the engineering functions of the user company. The process design is charascterized by an iterative procedure which consists of identifiable steps or phase thus. - Recognition of need – that a problem exists - Definition of problem – specification - Synthesis – conceptualized the component - Analysis and optimization - Evaluation – measuring the design against specification - Presentation – documentation for example, drawing etc. The above mentioned related design tasks can be performed by the use of modern Computer – Aided Design System. The CAD hardware typically includes. - The Computer - One or more graphics display terminal - Keyboard; and - Other peripheral equipment A typically commercially available CAD system consists of the following components. - One or more design workstations - Processor; - Plotter and or other input devices The benefits derived from the use of CAD system are numerous some are enumerated below thus; - Improved quality - Designers can monitor the progress of a problem solution and terminate the run or modify the input data as required. - Reduction of rafting labour: - Reduction of turn around time: - The designer can make subjective decisions at critical branch points, which guide the computer in continuing the problem solution: - Reduction in the number of drawings required: - Direct cost savings; - High accuracy (to-one-millionth of a unit): - Improvement in the general flow of information through a company: - Provision of more reliability in design work by having relevant information’s: - The drawing speed increased up to three times faster drafters using traditional tool: - Evaluation of alternative design - Use of standard libraries “copy repeats” - Modification of the CAD is quick and easy; - Generation of rotations, bills of materials, and materials and symbols be placed on drawing savings valuable time: and - Designers can immediately see and correct any gross errors in their drawings or input statements. COMPUTER – AIDED DESIGN AND DRAFTING (CADD) The engineering drawing has been an integral part of industry for many years. It is the link between engineering design and manufacturing. Design information is quickly communicated to manufacturing in the form of drawings prepared according to prescribed drafting standards. Drawing can be classified into two categories (12, 13) thus: • Logic drawing: Electric circuit diagrams; process sheets, etc. • Geometric drawings: Mechanical drawing: Architectural drawing, maps, and printed circuit tools. Traditionally drafting instrument has been, used to apply lead or ink or vellum or mayler or the use of pencil, scale and T-square. The popular alternative now is to prepare the drawing with the aid of a computer. A CAD system is a tool of the drafter. The combination of equipment to operate a CAD system is referred to as the workstation. It includes a computer, CAD software, display screen, input devices and copy devices Other names for CADD are: - Computer – Assisted Drafting - Computer – Augmented Drafting; and - Computer – Automated Drafting. A CAD drawing is in fact, a database of graphic and textual information. The computer can be directed to develop a three – dimensional drawing, or picture of the object. It can be rotated through any desired angle. In addition, it can be sectioned at any point. This section can be rotated to expose the inside of the object under consideration. If changes are to be made, they are made and the section portion rotated and joined with its mating part. The next step is to direct the computer to make blue print (hard copy) of the object that has been designed. A CADD programs contains hundreds of functions that enable you to accomplish specific drawing tasks. A task may involve drawing an object editing and existing drawing, displaying a view of the drawing, printing and savings it, or controlling other operation of the computer. The CADD modules include: - Draw, edit, data output, system control, data storage and management and specific features The software requirements for CADD depend on a matter of choice after careful study of the various options. These are various software option available such as: • Micro station, Autocad, Turbocad, Archicad, Drafix window Scad, Floor plan plus, 3D Home Architect, etc. There are also enhancement programs such as • Corel Draw, 3D studio, Auto Desk, Animator and Adobe Illustrator. What is important here is to analyze your interest and needs and look for the software are that meet them. COMPUTER-AIDED MANUFACTURING (CAM) Computer Aided Manufacturing (CAM) is a natural extension of the technology of Computer Aided Design (CAD). CAM is the use of computers and computer technology to assist in all phases of manufacturing a product, including process and production planning, machining, scheduling, management, and quality control Computer-Aided Manufacturing (CAM) has attracted so many definitions, some of them are reviewed below thus: - As the use of computer systems to plan, manage and control the operations of manufacturing plant through either direct of indirect computer interface with the plant’s production resources. - The Computer-Aided Manufacturing (CAM) facility is a natural extension of the technology of CAD, CAM can be defined as a plan for utilizing numerically controlled machines such as mills, lathes, drills, punches, and other programmable production equipment controlled by computers. Computers are also used in a CAM facility to control production scheduling and quality control, as well as the business functions of manufacturing such as purchasing, financial planning and marketing. - CAM is the effective use of computer technology in the planning, management, and control of manufacturing function. The planning, management and control of the manufacturing systems involved in CAM are linked together at the shop floor. - CAM include the use of a digital computer to enhance the shop floor manufacturing process, including monitoring an control of machining equipment shop floor information systems with automatic data gathering are part of a CAM system. CAM is the use of computers and computer technology to assist in all phases of manufacturing a product, including process and production planning, machining, scheduling, management, and quality control THE APPLICATION OF CAM The ultimate application of CAM occurs when the various operations and routings needed to allow production of the product are automatically from the CAD data, a process commonly referred to as Computer Aided Process Planning (CAPP). The application of CAM can be divided into two broad categories: Manufacturing Planning (Monitoring) In manufacturing planning or monitoring, the computer is used indirectly to support the production function, but there is no direct connection of interface between the computer and the manufacturing process. The computer is used “of-line” to provide information for the effective of production activities. The application of CAM in this category includes; (i) Cost Estimating; (ii) Computer –Aided Process Planning (CAPP) (iii) Computerized Machinability Data Systems; (iv) Computer-Assisted NC Part programming; (v) Development of Work Standards; (vi) Computer-Aided Line Balancing; and (vii) Production and Inventory Planning. Manufacturing Control This is the second application of CAM and it is concerned with developing computer system for implementing the manufacturing control functions. Manufacturing control is concerned with managing and controlling the physical operations in the factory. Process control, quality control, shop floor control, and process monitoring are all included within the scope of this function. Computer process control includes; - Transfer line; - Assembly system; - Numerical control; - Robotics; - Material handling; and - Flexible manufacturing system. Also, shop floor control reverse to production management techniques for collecting data form factory operations and using the data to help control production and inventory in the factory. This is shown in Fig, 13.2 below, Another classification of application of CAM centers around four main area; (i) Numerical control (NC); (ii) Process planning; (iii) Robotics; and (iv) Factory management Process Computer Process Data (planning) (a) Process Data Computer Process (b) Control Signal Fig. 13.2 Computer Monitoring (Planning) versus Computer Control (a) Computer Monitoring (Planning) (b) Computer control. The use of computer is seen throughout the manufacturing process. Mechanical CADD is part of the much broader concept of Computer-Aided Manufacturing (CAM). At first, Computer- Aided Design (CAD) systems are used to define the geometry of the object. This geometry is then converted to Numerical Code (NC) by an NC processor. The code is read by a controller, connected to a milling machine or lathe, to direct the speed and direction of the machine tool. CAM speeds up the manufacturing process since the same information used to create the design is used by machinery to machine the part before being sent to a machine, the numerical code can be used for machine to simulate using this type of program, the computer displays the tool path on the screen. Errors in tool movement can be detected before part is machines. If the tool moves too fast or too deep, the designer can edit the tool path. AN INTEGRATED CAD/CAM CAD/CAM is a term which means Computer-Aided Design and Computer-Aided Manufacturing. It is the technology that concerned with the use of digital computers to perform certain functions in design and production process to improve productivity. This technology is moving in the direction of greater integration of design and manufacturing, two activities which have traditionally been treated as distinct and separate function in production form. Ultimately, CAD/CAM will provide the technology base for the computer-integrated factory of the future. The scope of CAD/CAM in the operations of a manufacturing firm and the product cycle is presented in Fig. 13.3. Except for engineering changes which typically follow the product in all of the different activities in the product cycle. Product Design Drafting Concept Engineering Order New Customers Process Equipment and Market Planning and Tooling Production Quality Production Scheduling Control Fig. 13.3. Product Cycle (Design and Manufacturing) ADVANTAGES OF USING CAM Some advantages for using CAM includes; (i) Communications are improves by the direct transfer of documentation from design to manufacturing. (ii) Production is increased and more efficient (iii) Errors are reduces with the same data base used by design an manufacturing. (iv) Material handling and machine processing are more efficient; (v) Quality control is improves (vi) Leads items are reduced, improving market responses and (vii) Work environment is safer and more humans CAD SOFTWARE DESIGN Software is defined as the set of written instruction, procedure and rules that direct the operation of the computer. Software is another name for programs. The names are interchangeably used until ROM (Read-Only Memory) chips were introduced. A computer software include the instructions which enable the computer hardware to carry out specific task. It is the instructions that tell the computer how to process data. The set of instructions that a computer follow to solve a problem is called a computer program. Program stored in ROM are termed firmware, since they cannot be altered, while the programs on files are software. The two kinds of software are: (i) Application software; and (ii) System software. Application software is known as “end users” software. It is used for useful work and general purpose tasks, for example work processing. While system software is the background software that helps the software and the computer, for example running (“executing”) programs. Storing data, programs, and processing data. Software tools that have been developed to support these activities are considered CAE tools. CAE tools are being used, for example, to analyze the robustness and performance of components and assemblies. The term encompasses simulation, validation, and optimization of products and manufacturing tools. In the future, CAE systems will be major providers of information to help support design teams in decision making. CHARACTERISTICS OF GOOD SOFTWARE The characteristics of good software are enumerated below thus: i. Efficiency: The program must result in the effective use of the Central Processing Unit (CPU) in terms of both time and storage. It may be costly to develop, and it is also related to the size or complexity. A well designed small program may be more efficient than a large complex one. ii. Simplicity: Must be very easy to use or user-friendly. iii. Flexibility: This is the measure of degree of difficulty involved in modifying software to conform to a new specification. - Properly designed software will easily be amenable to future modifications ore changes. - Flexible software requires little maintenance. iv. Readability: This is a measure of how easily user can comprehend the logic behind the software. - Requires proper documentation of the programming process within the program - Style and aesthetics are important: helpful to less much space as possible between various parts of the program. v. Portability: Deals with transfer of a program from one system to another; very desirable in CAD. - Most applications programs so far in CAD are machine dependent. vi. Reliability: Measure of the functionality of the software with respect to desired specifications. - Very important aspect of software design, especially many processes/operations that are software dependent deal with human life. vii. Recoverability: Must not crash owing to an error made by user. Entry data error must have some way of warning the user and continue to function. This is recoverability of software. Recovery from error. SOFTWARE COMPONENTS The software components are divided into three parts: i. Data; ii. Algorithm; and iii. Structure. Data: are raw, unprocessed facts that are input to a computer system. It can also be set whose members or elements are numerical values, names symbol and codes. Algorithm: show how a set of data should be manipulated Structure: is the organisation of software Good software provides a good organisation of data algorithm. Algorithm Structuring Increases Data Structuring Decreases Fig. 5.1: Shows that properly structured data-less structuring of algorithm and vice-versa DATA STRUCTURE Organisation of data elements such as to both maintain the logical assembly and relationship between them and provide access from one data element to another. Each data element may be one of 3 types: integer, real or logical. Integer data: elements have integer numerical values: data elements of the real type consist of numerical value that includes decimal parts. Logical type data elements have logical values of “TRUE” and “FALSE”. Classification: There are fixed or constant and variable structure in fixed structures, relationship between data element in invariant whereas in variable structures, the relationship between data elements is subject to change. Fixed Data Structures There are four types of fixed data structure, (a) Vectors: Vector is a data structure with the same type of data elements e.g. the data elements are either all real numbers or all logical values. The size of a vector is determined by the number of elements it contains. The elements can be accessed through an index usually a positive integer associated with it. This is shown in fig. 5.2 below thus: Index Elements 1 5 2 210 3 1000 4 355 5 628 Fig. 5.2: Identification of Vector Elements. For example, the number 1000 can be accessed through the index number 3. If the programming language is FORTRAN, this number can easily be called or assigned to another entity as shown in Fig. 5.3 below thus; C THE VARIABLE A REPRESENTS THE ELEMENTS OF FIGURE 5.2 INTEGER A (20) C X TAKES ON THE VALUE OF INDEX NUMBER 3 X = A (3) FIG. 5.3Assignment of array – element to another variable (b) Array: An array is a set consisting of a fixed number of the same type of data elements. If an array is I-D then there is no difference between an array between a vector. Vector is a 10 array. An n-D array can be brought of as a collection of vectors. The elements of an array are referenced by an ordered set of indexes. The index used depends on the dimension of the array, e.g. a 2D array requires a set of 2-index values. The limit to the dimensions of an array is set by specifically the compiler of the computer system, some systems permits arrays of more than 3 dimensions. A 2D array can be viewed as row and column vectors or as a table, for example, suppose that during the design of a shift, various materials are to be considered and the computer is required to output the diameter in a tabular form. Suppose the final output appears as follows: _____________________________________________________________ Design No Materials _____________________________________________________ 1 2 3 4 _______________________________________________________________________ 1 1.0250 1.0000 1.5000 1.3750 2 1.5600 1.2500 1.8750 1.7000 3 2.7500 1.6250 2.0000 1.9000 4 3.2500 2.5650 2.1750 2.1250 _______________________________________________________________________ The portion of the computer program that will result in such an output may appear as follows” X DESIGN OF SHAFTS USING VARIOUS MATERIALS X DIA = DIAMETER REAL DIA (4,4) WRITE (6, 20) 20 FORMAT (40X, ‘MATERIAL/5X, ‘DESIGN ”, 10X, ‘1’, 30X , 2, 10X, ‘3’, 10X, ‘4’) DO 120 I = 1, 4 DO 120 J = 1, 4 WRITE (6, 140 1, DIA (I, J) 120 CONTINUE 140 FORMAT (3X, 12, 17X (4 (F 5.4) The order in which the elements of an array c ≥ 1 are stored in the computer memory must st always be remembered during programming. The elements are stored with the 1 subscripts varied most rapidly and the last subscript least rapidly, for example, in a 20 array, P (2, 3), the storage of the elements is as follows; P (1, 1) P (1, 2) P (1, 3) P (2, 1) P (2, 2) P (2, 3) - Size of array remains in variant although the element may change. - Useful feature in storing computer data for graphic applications for example, if one is dealing with rotation all that is required is to enter the rotation matrix in an array form and then change the angles, when necessary. Rotation can be accomplished using the matrix given by The rotation matrix is a 2D array, and if all the 9 elements, only 4 of them will actually change as the rotation is performed through various angle. (c) Strings: A string is a sequence of characters (alphabetical of numeric) or symbols. In FORTRAN, a string is characterized by single quotes- for example “CHEM” pr “4234’- but some FORTRAN compilers requires the use of double quotation marks. . The use of strings is the processing of nonnumerical data. It is particularly useful in the development of interactive programs, for example, in BASIC, if you want a response in order to decide what course of action to take, a string such as the following may be used. 100 INPUT A 900 IF A = “YES” THEN 910 ELSE 2000 (d) Record: It is an ordered set of different data elements. Organizing and collection of arrays by using a record. It allows data to be represented as a tree, such as: Student Name ID Grade Test 1 Test 2 Final Exam FORTRAN provides for the use of arrays but does not directly provide for the use of records. The programmer must construct records for simple data array structures by defining the individual components of the record. For example, suppose a record of student is to be kept, using an ID number as shown. ID No Grade % _________________________________________________ 1 83 2 60 3 75 N 90 __________________________________________________________ A record data structure may be created in FORTRAN using the program given as: C A RECORD OF GRADES FOR STUDENTS IN A CLASS C C CLASS SIZE 15 35 REAL GRADE (35) DO 2 1 = 1, 35 READ, GRADE (I) 2 CONTINUE Variables Structures There four different types of variable structures are: - List; - Stock; - Queue; and - File Enumerate it one by one gives; (a) List: A 10 data structure consisting of an assemblage by elements; it is one of two forms: (i) Linear; or (ii) Linked (i) A Linear List: is made of element whose adjacent members are contiguous (Fig 5.4). It is similar to a vector, except that a linear list allows addition or deletion of elements and it need not be homogenous. (ii) A Linked List: is a list in which each list element has a pointer to its successor. Usually, a special pointer are used to mark the head of the list and the end of the list is marked by a pointer whose value is a null (empty, Fig. 5.5) The link in a linked list may be useful to establish and desired logical order for the data elements without changing the physical order of the elements (Fig. 5.5). For example, suppose an array A contains some data and the contents are not to be printed sequentially, the order of points is to be dictated. The linked list structure to perform the job is shown in Fig. 5.5 and a sample program follows. Cube Cylinder Sphere Cone Fig. 5.4: A linear list of geometric primitives. Index Printed order The program: • Portion of program illustrating the use of linked list, • Assuming that array A and link exist ORDER = 1 30 CONTINUE IF (ORDER, NE O) THEN WRITE (6, 40) A (ORDER) 40 FORMAT (20 X 1 4) ORDER = LINK (ORDER) GO TO 30 ELSE GO TO 100 END IF 100 CONTINUE (b) Stack: A stack is a linear list accessible only at one end with addition/election taking place at the accessible end. Alternate name for stack list is LIFO (acronym for last-in-first-out), st for example, warehouse where plywood boards are placed in stacks, the 1 to be removed is the last board placed. There are two main types of manipulation of stack: - Pushing and popping Pushing – is the process of adding an element to the stack. Popping – is the process of deleting element from stack. Stack data structure is useful for processes where there is an interruption of main task for a sub stack and consequent return to the maim: this is called a subroutine. Stacks are also used for arithmetic operations. (c) Queue: A queue is a linear list that can be accessible at two locations. Insertion can be performed only on one end (rear), while deletion is carried out on the other end (font). And another name for queue is FIFO (acronym for first-in-first-out). It is useful for operation where information is processed in the order in which it is received; it has many applications in operating systems where jobs are queue until an execution slot can be found for the queued jobs. (d) Files: A file is a list (or an array) of records. It may involve 100’s or over 1000’s of storage units require large storage space; hence stored in secondary (external) storage devices such as magnetic tapes and disk. It is called to main memory when processing. It needs to access files since they are in external memory in FORTRAN, two access methods are possible sequential and direct. Sequential: Permits only orderly retrievals of records in a file. Direct: allows random access of records in a file. They are stored in magnetic disks where the records are arranged in an arbitrary order. READ and WRITE FORTRAN struts are used to transfer data from external memory to the main memory of the computer and vice versa. NC, CNC, DNC, AUTOMATION, ROBOTICS, CIM, ARTIFICIAL INTELLIGENCE AND EXPERT SYSTEMS This topic focuses on the following new technologies of manufacturing systems: - Numerical Control Machine Tools (NC); - Computer Numerical Control Machine Tools (CNC); - Direct Numerical Control Machine Tools (DNC); - Robotics; - Computer Integrated Manufacturing (CIM); - Artificial Intelligence; and - Expert Systems. The trend in manufacturing call for the development of the following modern day manufacturing systems. There are: - Global competition in the manufacturing market; - Customers now demanded high-quality goods, with low production cost and timely delivery of manufacturing products. - Increase in the variety of products produced, thereby choosing the product life cycles to be shorter. Therefore, the modern day technology that manufacturing systems make use of are discussed in this chapter. Manufacturing system entails a large number of interdependent activities consisting of distinct entities such as materials,. Tools machines, power, and human beings. It is a complex system because it is comprised of many diverse physical and, human elements. The choice are many, so the manufacturing engineers should be able to select correct which one to choose, that will profit the whole manufacturing system. MANUFACTURING CYCLE Manufacturing is a dominant activity in an individual organization. Before areas of computer needs are established, the need to understand the manufacturing process it self. Like design, there is no unique process for manufacturing. It all depend on products to be manufactured. For example, we have manufacturing industry, tyre, fuel/chemical products, machines tools, heavy vehicles such as earth moving equipment for farming and road construction, food processing, canning/bottling plants such as breweries, foundries, etc. each has its manufacturing process with diversification within each group as in the case of processed adopted by different company’s in the same industry. Nevertheless, there are some general processes that would need manufacturing as an activity that shares an interface with engineering design. It is an engineering activity in Fig. 13.1. shows a typical manufacturing cycle. As in design, the manufacturing process begins with a set of objectives which are set by management. Such objectives may be; (i) To develop and fabricate product; (ii) To produce parts or products designated by the customer/client (iii) To reproduce items that has been manufactured in the plant. Manufacturing environment can differ with respect to; (i) Size of the plant; (ii) Type of industry; and (iii) Type of production. Regardless of manufacturing environment, the fundamental principles are the same for all manufacturing concerns, hence a general cycle can be formulated in Fig. 13.1 Process Method Palnning Time and Engineering Manegment Engineering Motion Forecasting and Drawing Design study Customers Orders Routing Master Production Scheduling Requirement Planning Capacity Planning Dispatching Expediting Job Recording Auxillary Shop Services Floor Fig. 13.1. Manufacturing Cycle Emphasis varies with respect to mode of manufacturer’s specific problems, for example, mass production; emphasis would be on process planning and methods. Auxiliary production aids such as special tools and machinery, jigs and fixtures are automatic inspection services should be designed, produced and used. Material Requirements Planning and Scheduling need not to be sophisticated; therefore, rate of production is limited as fixed by initial design. For production of the large-scale job-shop type, where several orders are to be produced in small quantities and only once, emphasis would be on scheduling. In small-size jobs specializing in producing parts designed by customers, the engineering phase may not be required at all (except for customer consultation and advice). In goods type industry. Emphasis is on engineering design phase. Fig. 13. 1 shows the different types of phases of activities involved in a manufacturing cycle. Each phase consists of a continuous chain of activities. Notice that engineering design and engineering drafting are processes in the manufacturing cycle. CAD is involved in these processes. Similarly, computer aids are required in all the other phases. All amount to CAM. The challenge of CAM is the interface programs to link all the processes in the cycle computer software are available for most of the processes and they are independent of one another. To integrate all the processes constitutes the Integrated manufacturing System (IMS). . Numerical Control (NC), Computer Numerical Control (CNC), Direct Numerical Control (DNC), Automation and Robotics The introduction of NC, CNC, DNC, Automation and robotics is the beginning of CAD/CAM. The automation witnessed in manufacturing is a result of the development is a result of the development of the following machines which will be discussed in this section. Numerical Control (NC) Machines Numerical Control (NC) can be defined as a form of programmable automation in which the process is controlled by numbers, letters and symbols. In NC, the numbers form programme of instructions designed for a particular work part or job. When the job changes the programme of instruction also changes. Numerical Control (NC) is an automated method used to operate general purpose machines from instructions stored on a roll of tape for future as well as present use. The method can be used with or without a computer. Numerical Control (NC) is just what the term implies- control by the numbers. The two words “control” and “numbers” have brought about a revolution in manufacturing. NC technology has been applied to a wide variety of operations, including drafting, assembly, inspections, sheet metal press working and spot welding. However, NC found it principal applications in metal machining process. Fig. 13.4 Three basic components of a NC system (a) Program of instruction (b) Controller Unit (c) Machine Tool An operational NC system consists of three basic components. Thus, • Program of instruction; • Controller unit of machine control unit; • Machine tool or other controlled process. How an NC System Operates NC system falls into two categories thus; • Open Loop; and • Closed Loop. Fig. 13.5 Open and Closed Loops NC System Open- loop Fig. 13.5 above shows an open- loop NC system when a signal or command is given to the machine tool in order to carry out specific operation, and the tool more to its ordered

Advise: Why You Wasting Money in Costly SEO Tools, Use World's Best Free SEO Tool Ubersuggest.