Unit – 4�Computer Integrated Manufacturing (CIM)

CIM Wheel - Role of Group Technology in CAD/CAM Integration - Artificial Intelligence in CIM - Part Families - Classification and

Coding – Design and Classification Information System (D CLASS) and Metal Institute Classification (MI CLASS) and OPITZ Coding Systems.

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Manufacturing System

Production System

• A production system is a collection of people, equipment, and procedures organized to perform the manufacturing operations of a company

• Manual Work System
• Worker machine system
• Fully Automated system

Various types of plant layout:

(a) Fixed position layout,

(b) process layout,

(c) cellular layout,

(d) product layout.

Automated Manufacturing Systems

• Automated manufacturing systems operate in the factory on the physical product. They perform operations such as processing, assembly, inspection, and material handling

Examples

• Automated machine tools that process parts
• Transfer lines that perform a series of machining operations
• Automated assembly systems
• Manufacturing systems that use industrial robots to perform processing or assembly operations
• Automatic material handling and storage systems to integrate manufacturing operations
• Automatic inspection systems for quality control.

Types of automation relative�to production quantity and product variety

Computer-integrated manufacturing (CIM)

• Computer-integrated manufacturing (CIM) denotes the pervasive use of computer systems to design the products, plan the production, control the operations, and perform the various information-processing functions needed in a manufacturing firm.
• Increase labor productivity.
• Reduce labor cost.
• Mitigate the effects of labor shortages.
• Reduce or eliminate routine manual and clerical tasks.
• Improve worker safety
• Improve product quality.
• Reduce manufacturing lead time.
• Accomplish processes that cannot be done manually
• Avoid the high cost of not automating.

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Strategies for Automation and Process Improvement

• Specialization of operations.
• Combined operations
• Simultaneous operations.
• Integration of operations.
• Increased flexibility.
• Improved material handling and storage.
• On-line inspection
• Process control and optimization.
• Plant operations control.
• Computer-integrated manufacturing

Automation and control technologies�in the production system

Group Technology and Cellular Manufacturing

• Group technology is a manufacturing philosophy in which similar parts are identified and grouped together to take advantage of their similarities in design and production.
• Similar parts are arranged into part families, where each part family possesses similar design and/or manufacturing characteristics.

Advantages:

• GT promotes standardization of tooling, fixturing, and setups.

• Material handling is reduced because the distances within a machine cell are much shorter than within the entire factory.

• Process planning and production scheduling are simplified.

• Setup times are reduced, resulting in lower manufacturing lead times.

• Work-in-process is reduced.

• Worker satisfaction usually improves when workers collaborate in a GT cell.

• Higher quality work is accomplished.

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Part Families and Machine Groups

Part Family

• A part family is a collection of parts that are similar either in geometric shape and size or in the processing steps required in their manufacture. The parts within a family are different, but their similarities are close enough to merit their inclusion as members of the part family.

• A family of parts with similar manufacturing process requirements but different design attributes.
• All parts are machined from cylindrical stock by turning; some parts require drilling and/or milling.

Process-type plant layout

Group-technology layout

Part Classification

Three methods of part classification method

• Intuitive grouping,- Visual inspection methods
• Parts classification and coding,
• Production flow analysis.

Parts Classification and Coding

• In parts classification and coding, similarities among parts are identified and these similarities are related in a coding system that usually includes both a part’s design and manufacturing attributes.
• Design retrieval
• Developing a new part can use a design retrieval system to determine if a similar part already exists. Simply changing an existing part would take much less time than designing a whole new part from scratch
• Automated process planning
• The part code for a new part can be used to search for process plans for existing parts with identical or similar codes
• Machine cell design
• Part codes can be used to design machine cells capable of producing all members of a particular part family

Parts classification and coding systems�fall into one of three categories

• Systems based on part design attributes,
• Systems based on part manufacturing attributes,
• Systems based on both design and manufacturing features.

Three structures used in classification and coding schemes

• Hierarchical structure, also known as a monocode, in which the interpretation of each successive symbol depends on the values of the preceding symbols
• Chain-type structure, also known as a polycode, in which the interpretation of each symbol in the sequence is always the same; it does not depend on the values of preceding symbols
• Mixed-mode structure, a hybrid of the two previous coding schemes.

Production Flow Analysis

• It is a method for identifying part families and associated machine groupings that uses the information contained on production route sheets rather than part drawings
• Data collection
• The minimum data needed in the analysis are the part number and operation sequence, which is contained in shop documents called route sheets or operation sheets.
• Sortation of process routings
• the parts are arranged into groups according to the similarity of their process routings.
• PFA chart
• The processes used for each pack are then displayed in a PFA chart,
• Cluster analysis

Cellular manufacturing

• Cellular manufacturing is an application of group technology in which dissimilar machines or processes have been aggregated into cells, each of which is dedicated to the production of a part or product family, or a limited group of families.

• To shorten manufacturing lead times by reducing setup, work-part handling, waiting times, and batch sizes.
• To reduce work-in-process inventory. Smaller batch sizes and shorter lead times reduce work-in-process.
• To improve quality.
• To simplify production scheduling.
• To reduce setup times.

• Two aspects of cellular manufacturing are considered in this section:
• Composite part concept and
• Machine cell design.
• The composite part for a given family is a hypothetical part that includes

all of the design and manufacturing attributes of the family

Machine Cell Design

• Single-machine cell
• consists of one machine plus supporting fixtures and tooling
• Group-machine cell with manual handling
• arrangement of more than one machine used collectively to produce one or more part families, and there is no provision for mechanized parts movement between machines in the cell
• Group-machine cell with semi-integrated handling
• mechanized handling system, such as a conveyor, to move parts between machines in the cell
• Flexible manufacturing cell or flexible manufacturing system
• fully integrated material handling system with automated processing stations

Machine Cell Layouts.

• Four types of part movement can be distinguished in a mixed-model part production system
• Repeat operation
• In-sequence move,
• Bypassing move
• Backtracking move,

Opitz system

• It is intended for machined parts. The Opitz coding scheme uses the following digit sequence

12345 6789 ABCD

• First nine are intended to convey both design and manufacturing data
• The first five digits, 12345, are called the form code.
• The next four digits, 6789, constitute the supplementary code, which indicates some of the attributes that would be useful in manufacturing.
• The extra four digits, ABCD, are referred to as the secondary code and are intended to identify the production operation type and sequence.

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Given the rotational part design in Figure , determine the form code in the Opitz classification and coding system.

• With reference to Figure 18A.2, the five-digit code is developed as follows:
• Length-to-diameter ratio, L>D = 1.5 Digit 1 = 1
• External shape: stepped on both ends with screw thread on one end Digit 2 = 5
• Internal shape: part contains a through-hole Digit 3 = 1
• Plane surface machining: none Digit 4 = 0
• Auxiliary holes, gear teeth, etc.: none Digit 5 = 0
• The form code in the Opitz system is 15100.

DCLASS (Design and Classification Information System)

• A part may be best characterized by its basic shape, usually its most apparent attribute.
• Each basic shape may have several features, such as holes, slots, threads, and grooves.
• A part can be completely characterized by basic shape; features; size; precision; and material type, form, and condition.
• Several short code segments can be linked to form a part classification code that is human recognizable and adequate for human monitoring.
• Each of these code segments can point to more detailed information

MICLASS System (Metal Institute Classification System)

• Standardization of engineering drawings
• Retrieval of drawings according to classification
• Standardization of process routing
• Automated process planning
• Selection of parts processing on particular group of machine tools