Computer Integrated Manufacturing (CIM): Introduction To CIM, CIMS Benefits, Basic components of NC system, Applications of NC

 Introduction To CIM

Computer Integrated Manufacturing (CIM) encompasses the entire range of product development and manufacturing activities with all the functions being carried out with the help of dedicated software packages. The data required for various functions are passedfrom one application software to another in a seamless manner. For example, the productdata is created during design. This data has to be transferred from the modeling softwareto manufacturing software without any loss of data. CIM uses a common databasewherever feasible and communication technologies to integrate design, manufacturingand associated business functions that combine the automated segments of a factory ora manufacturing facility. CIM reduces the human component of manufacturing andthereby relieves the process of its slow, expensive and error-prone component. CIM standsfor a holistic and methodological approach to the activities of the manufacturing enterprise in order to achieve vast improvement in its performance.This methodological approach is applied to all activities from the design of the productto customer support in an integrated way, using various methods, means and techniquesin order to achieve production improvement, cost reduction, fulfillment of scheduleddelivery dates, quality improvement and total flexibility in the manufacturing system.

CIM requires all those associated with a company to involve totally in the process of productdevelopment and manufacture. In such a holistic approach, economic, social and humanaspects have the same importance as technical aspects.

Manufacturing industries strive to reduce the cost of the product continuously to remaincompetitive in the face of global competition. In addition, there is the need to improve thequality and performance levels on a continuing basis. Another important requirement ison time delivery. In the context of global outsourcing and long supply chains cutting acrossseveral international borders, the task of continuously reducing delivery times is really anarduous task. CIM has several software tools to address the above needs.

Manufacturing engineers are required to achieve the following objectives to be competitive in a global context.

• Reduction in inventory

• Lower the cost of the product

• Reduce waste

• Improve quality

• Increase flexibility in manufacturing to achieve immediate and rapid response to:

• Product changes

• Production changes

• Process change

• Equipment change

• Change of personnel

CIM technology is an enabling technology to meet the above challenges to the manufacturing.

The advances in automation have enabled industries to develop islands of automation.Examples are flexible manufacturing cells, robotized work cells, flexible inspection cellsetc. One of the objectives of CIM is to achieve the consolidation and integration of theseislands of automation. This requires sharing of information among different applicationsor sections of a factory, accessing incompatible and heterogeneous data and devices. Theultimate objective is to meet the competition by improved customer satisfaction throughreduction in cost, improvement in quality and reduction in product development time.

Types Of Manufacturing

Manufacturing industries can be grouped into

i. Continuous Process Industries

In this type of industry, the production process generally follows a specificsequence. These industries can be easily automated and computers are widelyused for process monitoring, control and optimization. Oil refineries, chemicalplants, food processing industries, etc are examples of continuous processindustries.

ii. Mass Production Industries

Industries manufacturing fasteners (nuts, bolts etc.), integrated chips, automobiles,entertainment electronic products, bicycles, bearings etc. which are all massproduced can be classified as mass production industries. Production lines arespecially designed and optimized to ensure automatic and cost effective operation.Automation can be either fixed type or flexible.

iii. Batch Production (Discrete Manufacturing)

The largest percentage of manufacturing industries can be classified as batchproduction industries. The distinguishing features of this type of manufacture arethe small to medium size of the batch, and varieties of such products to be takenup in a single shop. Due to the variety of components handled, work centersshould have broader specifications. Another important fact is that small batchsize involves loss of production time associated with product changeover.

 Definition of CIM

Jack Conaway, CIM Marketing manager, DEC, defines CIM is nothing but a data managementand networking problem.

The computer and automated systems association of the society of Manufacturing Engineers(CASA/SEM) defines CIM is the integration of total manufacturing enterprise by usingintegrated systems and data communication coupled with new managerial philosophies thatimprove organizational and personnel efficiency.

CIM Wheel

CIM components

Nine major elements of a CIM system are

• Marketing

• Product Design

• Planning

• Purchase

• Manufacturing Engineering

• Factory Automation Hardware

• Warehousing

• Logistics and Supply Chain Management

• Finance

• Information Management

i. Marketing:

The need for a product is identified by the marketing division. The specifications of the product, the projection of manufacturing quantities and the strategy for marketing the product arealso decided by the marketing department. Marketing also works out the manufacturing costs to assess the economic viability of the product.

ii. Product Design:

The design department of the company establishes the initial database forproduction of a proposed product. In a CIM system this is accomplished through activities such as geometric modeling and computer aided design while considering the product requirements and concepts generated by the creativity of the design engineer.

Configuration management is an important activity in many designs. Complex designs are usually carried out by several teams working simultaneously, located often in different parts of the world. The design process is constrained by the costs that will be incurred in actual production and by the capabilities of the available production equipment and processes. The design process creates the database required to manufacture the part.

iii. Planning:

The planning department takes the database established by the design department and enriches it with production data and information to produce a plan for the production of the product. Planning involves several subsystems dealing with materials, facility, process, tools, manpower, capacity, scheduling, outsourcing, assembly, inspection, logistics etc. In a CIM system, this planning process should be constrained by the production costs and by the production equipment and process capability, in order to generate an optimized plan.

iv. Purchase:

The purchase departments is responsible for placing the purchase orders and follow up, ensure quality in the production process of the vendor, receive the items, arrange for inspection and supply the items to the stores or arrange timely delivery depending on the production schedule for eventual supply to manufacture andassembly.

v. Manufacturing Engineering:

Manufacturing Engineering is the activity of carrying out the production of the product, involving further enrichment of the database with performance data and information about the production equipment and processes. In CIM, this requires activities like CNC programming, simulation and computer aided scheduling of the production activity. This should include online dynamic scheduling and control based on the real time performance of the equipment and processes to assure continuous production activity. Often, the need to meet fluctuating market demand requires the manufacturing system flexible and agile.

vi. Factory Automation Hardware:

Factory automation equipment further enriches the database with equipment and process data, resident either in the operator or the equipment to carry out the production process. In CIM system this consists of computer controlled process machinery such as CNC machine tools, flexible manufacturing systems (FMS), Computer controlled robots, material handling systems, computer controlled assembly systems, flexibly automated inspection systems and so on.

vii. Warehousing:

 Warehousing is the function involving storage and retrieval of raw materials, components, finished goods as well as shipment of items. In today’s complex outsourcing scenario and the need for just-in-time supply of components and subsystems, logistics and supply chain management assume great importance.

viii. Finance:

Finance deals with the resources pertaining to money. Planning of investment, working capital, and cash flow control, realization of receipts, accounting and allocation of funds are the major tasks of the finance departments.

ix. Information Management:

Information Management is perhaps one of the crucial tasks in CIM. This involves master production scheduling, database management, communication, manufacturing systems integration and management information systems.

Evolution Of CIM

Computer Integrated Manufacturing (CIM) is considered a natural evolution of thetechnology of CAD/CAM which by itself evolved by the integration of CAD and CAM.Massachusetts Institute of Technology (MIT, USA) is credited with pioneering the development in both CAD and CAM. The need to meet the design and manufacturingrequirements of aerospace industries after the Second World War necessitated thedevelopment these technologies. The manufacturing technology available during late 40‟sand early 50‟s could not meet the design and manufacturing challenges arising out of theneed to develop sophisticated aircraft and satellite launch vehicles. This prompted the USAir Force to approach MIT to develop suitable control systems, drives and programmingtechniques for machine tools using electronic control.

The first major innovation in machine control is the Numerical Control (NC),demonstrated at MIT in 1952. Early Numerical Control Systems were all basically hardwiredsystems, since these were built with discrete systems or with later first generation integratedchips. Early NC machines used paper tape as an input medium. Every NC machine wasfitted with a tape reader to read paper tape and transfer the program to the memory of themachine tool block by block. Mainframe computers were used tocontrol a group of NCmachines by mid 60‟s. This arrangement was then called Direct Numerical Control (DNC)as the computer bypassed the tape reader to transfer the program data to the machinecontroller. By late 60‟s mini computers were being commonly used to control NC machines.At this stage NC became truly soft wired with the facilities of mass program storage, offlineediting and software logic control and processing. This development is called ComputerNumerical Control (CNC).

Since 70‟s, numerical controllers are being designed around microprocessors, resultingin compact CNC systems. A further development to this technology is the distributednumerical control (also called DNC) in which processing of NC program is carried out indifferent computers operating at different hierarchical levels – typically from mainframehost computers to plant computers to the machine controller. Today the CNC systems arebuilt around powerful 32 bit and 64 bit microprocessors. PC based systems are alsobecoming increasingly popular.

Manufacturing engineers also started using computers for such tasks like inventorycontrol, demand forecasting, production planning and control etc. CNC technology wasadapted in the development of co-ordinate measuring machine‟s (CMMs) which automatedinspection. Robots were introduced to automate several tasks like machine

loading,materials handling, welding, painting and assembly. All these developments led to theevolution of flexible manufacturing cells and flexible manufacturing systems in late 70‟s.

Evolution of Computer Aided Design (CAD), on the other hand was to cater to thegeometric modeling needs of automobile and aeronautical industries. The developmentsin computers, design workstations, graphic cards, display devices and graphic inputand output devices during the last ten years have been phenomenal. This coupled withthe development of operating system with graphic user interfaces and powerful interactive(user friendly) software packages for modeling, drafting, analysis and optimizationprovides the necessary tools to automate the design process.

CAD in fact owes its development to the APT language project at MIT in early 50‟s.Several clones of APT were introduced in 80‟s to automatically develop NC codes from the geometric model of the component. Now, one can model, draft, analyze, simulate,modify, optimize and create the NC code to manufacture a component and simulate themachining operation sitting at a computer workstation.

Needs of CIM

  • Computer Numerical Control (CNC)
  •  Direct Numerical Control (DNC)
  • Computer Process Control
  •  Computer Integrated Production Management
  •  Automated Inspection Methods
  •  Industrial Robots etc.

CIMS Benefits:

(i) Products quality improvement.

(ii) Shorter time in launching new product in the market.

(iii) Flow time minimized.

(iv) Inventory level reduced.

(v) Competitiveness increases.

(vi) Improved scheduling performance.

(vii) Shorter vendor lead time.

(viii) Improved customer service.

(ix) Increase in flexibility and responsiveness

(x) Total cost minimized.

(xi) Long term profitability increases.

(xii) Customers lead time minimized.

(xiii) Manufacturing productivity increases.

(xiv) Work in process inventory decreases.

Basic components of NC system

1.Input medium

2.MCU

3.Machine Tool

Basic Components of an NC System And NC system consists of three basic components: 

(1) Program of instructions:

 The detailed step-by-step commands that direct the actions of the processing equipment. In machine tool applications, the program of instructions is called a part program, and the person who prepares the program is called a part programmer. In these applications, the individual commands refer to positions of a cutting tool relative to the worktable on which the workpart is fixtured. Additional instructions are usually included, such as spindle speed, feed rate, cutting tool selection, and other functions. The program is coded on a suitable medium for submission to the machine control unit. (2) Machine control unit MCU: Consists of a microcomputer and related control hardware that stores the program of instructions and executes it by converting each command into mechanical actions of the processing equipment, one command at a time. The related hardware of the MCU includes components to interface with processing equipment and feedback control elements. The MCU also includes one or more reading devices for entering part programs into memory. The MCU also includes control system software, calculation algorithms, and translation software to convert the NC part program into a usable format for the MCU.

 NC motion control system

In order to accomplish the machining process, the cutting tool and workpiece must be moved relative to each other. In NC, there are three basic types of motion control system (Point-to-point, Straight cut and Contouring). Point-to-point systems represent the lowest level of motion control between the tool and workpiece. Contouring represents the highest level of control.

1-Point-to-point Positioning Control:

Point-to-point (PTP) is also sometimes called a positioning system. In PTP, the objective of the machine tool control system is to move the cutting tool to a predefined location. The principle function of the PTP is to position the tool form one point to another within coordinate system. The positioning may be linear in the x-y plane or linear and rotary if the machine has a rotary table. Each tool axis is controlled independently, therefore; the programmed motion always in rapid traverse. Once the tool reaches the desired location, the machining operation is performed at that position (machining can only take place after positioning is completed).

NC drill presses are a good example of PTP systems. The spindle must first be positioned at a particular location on the workpiece. This is done under PTP control. Then the drilling of the hole is performed at the location, and so forth. Since no cutting is performed between holes, there is no need for controlling the relative motion of the tool and workpiece between hole locations.

Positioning systems are the simplest machine tool control systems and are therefore the least expensive of the three types. However, for certain processes, such as drilling operations, tapping, riveting and spot welding, PTP is perfectly suited to the task and any higher level of control would be unnecessary. Example bellow illustrate path of three drilled holes.

2-Straight-cut Positioning Control: –

Straight-cut control systems are capable of moving the cutting tool parallel to one of the major axes at a controlled rate suitable for machining. It is therefore appropriate for performing milling operations to fabricate workpieces of rectangular configurations. Most of the straight-cut systems an fitted with manually adjustable feed control, this feed control is shared by all the programmable axes of the NC machine, because of this shared feed control feature; the system can also perform milling operation at 45˚ to the primary axes of the machine. An example of a straight cut operation is shown in Figure (2). An NC machine capable of straight cut movements is also capable of PTP movements.

3-Contouring (continuous) Path CNC System: –

Contouring is the most complex, the most flexible, and the most expensive type of machine tool control. It is capable of performing both PTP and straight-cut operations. In addition, the distinguishing feature of contouring NC systems is their capacity for simultaneous control of more than one axis movement of the machine tool. The path of the cutter is continuously controlled to generate the desired geometry of the workpiece. Contouring system generates a continuously controlled tool path by the capability of computing the points of the path (interpolating). For this reason, contouring systems are also called continuous-path NC systems. All NC contouring system have the ability to perform linear and circular or parabolic interpolation features which recorded in the NC computer under a (G preparatory code).

 Applications of NC

1.Machine tool applications, such as drilling, milling, turning, and other metal working.

2.Non machine tool applications, such as assembly, drafting, and inspection. The common operating feature of NC in all of these applications is control of the work head movement relative to the work part.

Also…

1-Parts are processed frequently and in small to medium lot sizes. 2- Part geometry is complex. 3- Close tolerances must be held on the workpart. 4- Many operations must be performed on the part in its processing. 5- Much metal needs to be removed (for machining applications). 6- Engineering design changes are likely. 7- It is an expensive part where mistakes in processing would be costly. 8- Parts require 100% inspection

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