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Industrial Work GroupIndustrial Work Group
Group Technology and Group Technology and
Cellular ManufacturingCellular Manufacturing
Ramiro Bonaque Rodríguez
Jose Luís Gandia Fornés
Toni Barberà Pastor
Universitat Jaume I de
Castelló
1. Introduction1. Introduction
2. Parts classification and coding2. Parts classification and coding
3. Production flow analysis3. Production flow analysis
4. Cellular manufacturing4. Cellular manufacturing
5. Application considerations in group 5. Application considerations in group
technologytechnology
6. Quantitative analysis in cellular 6. Quantitative analysis in cellular
manufacturingmanufacturing
Table of contentsTable of contentsTable of contentsTable of contents
1. Introduction1. Introduction1. Introduction1. Introduction
Processes types for batch manufacturingProcesses types for batch manufacturing
Process type plant layout Process type group technology
Turning
Milling
Assembly
Drilling
Shipping
Receiving
Machines are arranged by function.
Machines are arranged into cells
1. Introduction1. Introduction1. Introduction1. Introduction
DefinitionsDefinitions
Group technology is a philosophy in which similar parts are identified and grouped together to take advantage of their similarities in design and production.
Group technology is a philosophy in which similar parts are identified and grouped together to take advantage of their similarities in design and production.
Part familyPart family
Part family is a collection of parts that are similar either because of geometric shape and size or because similar processing steps are required in their manufacture.
Part family is a collection of parts that are similar either because of geometric shape and size or because similar processing steps are required in their manufacture.
Cellular manufacturingCellular manufacturing
Cellular manufacturing is grouping the production equipment into machine cells, where each cell specializes in the production of a particular part family.
Cellular manufacturing is grouping the production equipment into machine cells, where each cell specializes in the production of a particular part family.
Group technologyGroup technology
1. Introduction1. Introduction1. Introduction1. Introduction
ObjectiveObjective
• To make batch production more efficient and productive.
• To integrate design and manufacturing in a firm.
ObstaclesObstacles
BenefitsBenefits
• Identifying the part families.
• Rearranging production machines into machine cells.
• It promotes standardization
• It reduces material handling, setup times and work-in-process
• Workers satisfaction and quality work improve
Features of group technologyFeatures of group technology
1. Introduction1. Introduction1. Introduction1. Introduction
The changeover from a conventional The changeover from a conventional production to group technologyproduction to group technology
1) Visual inspection
2) Parts classification and coding
3) Production flow analysis
1) Visual inspection
2) Parts classification and coding
3) Production flow analysis
Three methods to group the parts into families:
It involves the classification of parts into families by looking at either the physical parts or their photographs and arranging them into groups having similar features.
It involves the classification of parts into families by looking at either the physical parts or their photographs and arranging them into groups having similar features.
1) Visual inspection
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
DefinitionDefinition
Each part family is exclusively identified by an alpha-numerical code, which represents their design attributes, manufacturing attributes or both.
Each part family is exclusively identified by an alpha-numerical code, which represents their design attributes, manufacturing attributes or both.
AdvantagesAdvantages
Methods to obtain the code from a particular partMethods to obtain the code from a particular part
• Design retrieval• Automated process planning• Machine cell design
• Looking in tables to match the subject part against the features described.
• Using a computerized classification and coding system to reply questions about the part’s features.
FeaturesFeatures
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
Parts coding systems Parts coding systems
OpitzOpitz Brisch SystemBrisch System CODECODE CUTPLANCUTPLAN
DCLASSDCLASS MultiClassMultiClass Part Analog SystemPart Analog System
Hierarchical / monocode
Types of structures of coding systemsTypes of structures of coding systems
Chain-type / polycode
Mixed-modee.g. Opitz Classification System
(by H. Opitz)
e.g. Opitz Classification System (by H. Opitz)
e.g. MultiClass (by Organization for Industrial Research)
e.g. MultiClass (by Organization for Industrial Research)
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
Opitz Coding System Opitz Coding System
12345 6789 ABCD12345 6789 ABCD12345 6789 ABCD12345 6789 ABCD
Digit sequence:Digit sequence:
Form code: design attributes
Supplementary code: manufacturing attributes
Secondary code: operation sequence and particular needs
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
Opitz Coding System Opitz Coding System
Part ClassPart Class
0
Rotational
L/D ≤ 0,5
1 0,5 < L/D < 3
2 L/D ≥ 3
3With deviation
L/D ≤ 2
4With deviation
L/D > 2
5 Special
6 Non-rotational
A/B ≤ 3
A/C ≥ 4
7 A/B > 3
8A/B ≤ 3
A/C < 4
9 Special
External Shape
Element
External Shape
Element
Main ShapeMain
Shape
Internal Shape
Element
Internal Shape
Element
Rotational MachiningRotational Machining
Main bore and
rotational machining
Main bore and
rotational machining
Main ShapeMain Shape Rotational MachiningRotational Machining
Machining of plane surface
Machining of plane surface
Plane Surface Machining
Plane Surface Machining
Machining of plane surface
Machining of plane surface
Machining of plane surface
Machining of plane surface
Other holes and
teeth
Other holes and
teeth
Additional Holes Teeth and Forming
Additional Holes Teeth and Forming
Other holes,
teeth and forming
Other holes,
teeth and forming
Other holes,
teeth and forming
Other holes,
teeth and forming
Digits
6 7 8 9
Dim
ensions
Material
Original shape of raw
materials
Accurany
Main ShapeMain
Shape
Main ShapeMain
Shape
Main ShapeMain
Shape
Digit 1 Digit 2 Digit 3 Digit 4 Digit 5
Su
pp
lemen
tary co
deForm code
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
Opitz Coding System Opitz Coding System
Part ClassPart Class
0
Rotational
L/D ≤ 0,5
1 0,5 < L/D < 3
2 L/D ≥ 3
3With deviation
L/D ≤ 2
4
5
6 Non-rotational
7
8
9
0Smooth, no shape
elements
1
Stepped to one end
No shape elements
2
Or sm
ooth
Thread
3Functional
groove
4
Stepped to both ends
No shape elements
5 Thread
6 Functional groove
7 Functional cone
8 Operating thread
9 All others
External shape, external shape
elements
External shape, external shape
elements
Digit 1 Digit 2
0No hole, no
breakthrough
1
Sm
ooth or stepped to one end
No shape elements
2 Thread
3Functional
groove
4S
tepped to both ends
No shape elements
5 Thread
6 Functional groove
7 Functional cone
8 Operating thread
9 All others
Internal shape, internal shape
elements
Internal shape, internal shape
elements
Digit 3
0 No surface machining
1Surface plane and/or
curved in one direction, external
2External plane surface related by graduation
around the circle
3 External groove and/or slot
4 External spline
5 External plane surface and/or slot, external spline
6 Internal plane surface and/or slot
7 Internal spline
8Internal and external
polygon, groove and/or slot
9 All others
Plane surface machining
Plane surface machining
Digit 4
0
No gear teeth
No auxiliary hole
1Axial, not on pitch
circle diameter
2Axial on pitch circle
diameter
3Radial, not on pitch
circle diameter
4Axial and/or radial
and/or other directions
5Axial and/or radial
on PCD and/or other directions
6 With gear teeth
Spur gear teeth
7 Bevel gear teeth
8 Other gear teeth
9 All others
Auxiliary holes and gear teethAuxiliary holes and gear teeth
Digit 5
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
Opitz Coding System Opitz Coding System
ExampleExample Given this rotational part design, determine the form code in the Opitz parts classification and coding system.
0,70,3
0,5
0,8
½ – 13 UNC
1,5
1,0
Part ClassPart Class
0
Rotational
L/D ≤ 0,5
1 0,5 < L/D < 3
2 L/D ≥ 3
3
4
5
6 Non-rotational
7
8
9
0Smooth, no shape
elements
1
Stepped to one end
No shape elements
2
Or sm
ooth
Thread
3Functional
groove
4
Stepped to both ends
No shape elements
5 Thread
6 Functional groove
7 Functional cone
8 Operating thread
9 All others
External shape, external shape
elements
External shape, external shape
elements
Digit 1 Digit 2
0No hole, no
breakthrough
1
Sm
ooth or stepped to one end
No shape elements
2 Thread
3Functional
groove
4S
tepped to both ends
No shape elements
5 Thread
6 Functional groove
7 Functional cone
8 Operating thread
9 All others
Internal shape, internal shape
elements
Internal shape, internal shape
elements
Digit 3
0 No surface machining
1Surface plane and/or
curved in one direction, external
2External plane surface related by graduation
around the circle
3 External groove and/or slot
4 External spline
5 External plane surface and/or slot, external spline
6 Internal plane surface and/or slot
7 Internal spline
8Internal and external
polygon, groove and/or slot
9 All others
Plane surface machining
Plane surface machining
Digit 4
0
No gear teeth
No auxiliary hole
1Axial, not on pitch
circle diameter
2Axial on pitch circle
diameter
3Radial, not on pitch
circle diameter
4Axial and/or radial
and/or other directions
5Axial and/or radial
on PCD and/or other directions
6 With gear teeth
Spur gear teeth
7 Bevel gear teeth
8 Other gear teeth
9 All others
Auxiliary holes and gear teeth
Auxiliary holes and gear teeth
Digit 5
Form code0,70,3
0,5
0,8
½ – 13 UNC
1,5
1,0
11 55 11 00 00
Length-to-diameter ratio
L/D = 1,5
Length-to-diameter ratio
L/D = 1,5
External shape: stepped on both ends with screw thread on one end
External shape: stepped on both ends with screw thread on one end
Internal shape: part contains a through-hole
Internal shape: part contains a through-hole
Plane surface machining: nonePlane surface machining: noneAuxiliary holes, gear teeth, etc.: noneAuxiliary holes, gear teeth, etc.: none
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
MultiClass Coding SystemMultiClass Coding System
Coding structure:Coding structure: up to 30 digits divided into 2 regions
Region 1Region 1
Digit Function
01
2, 34
· · ·18
Code system prefixMain shape categoryExternal and internal configurationMachined secondary elements· · · Etc. · · ·Machined element orientation
Region 2:Region 2: designed by the user to meet specific needs and requirements.
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
MultiClass Coding SystemMultiClass Coding System
ExampleExample Given this rotational part design, determine the form code in the MultiClass parts coding system.
2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding2. Parts classification and coding
MultiClass Coding SystemMultiClass Coding System SolutionSolution
3. Production Flow Analysis3. Production Flow Analysis3. Production Flow Analysis3. Production Flow Analysis
• Parts whose basic geometries are quite different may nevertheless require similar or even identical process routings.
• Parts whose geometry are quite similar may nevertheless require process routings that are quite different.
DefinitionDefinition
Production flow analysis (PFA) is a method for identifying part families and associated machine groupings that uses the information contained on production route sheets rather than on part drawings.
Production flow analysis (PFA) is a method for identifying part families and associated machine groupings that uses the information contained on production route sheets rather than on part drawings.
Workparts with identical or similar routings are classified into part families. Then, the families can be used to form logical machine cells in a group technology layout.
Possible anomaliesPossible anomalies
VirtueVirtueRequire less time than a complete parts classification and coding procedure.
3. Production Flow Analysis3. Production Flow Analysis3. Production Flow Analysis3. Production Flow Analysis
ProcedureProcedure
3. Sortation of process routings: Parts are arranged into groups according to the similarity of their process routings.To make this:a) All operations or machines are reduced to code numbers;b) For each part, operation codes are listed in the order they are performedc) A sortation procedure is then used to arrange parts into packs.
2. Data collection: The minimum data needed in the analysis are the part number and operation sequence.Additional data: lot size, time standards, and annual demand might be useful.
1. Scope of the analysis: The production flow analysis must begin defining the scope of the study (population of parts to be analyzed).
3. Production Flow Analysis3. Production Flow Analysis3. Production Flow Analysis3. Production Flow Analysis
ProcedureProcedure
4. PFA Chart: The processes used for each pack are then displayed in a PFA chart.PFA chart has been referred as part-machine incidence matrix.
xij = 1 Part i requires processing on machine j
xij = 0 Part i is not processed on machine j
3. Production Flow Analysis3. Production Flow Analysis3. Production Flow Analysis3. Production Flow AnalysisProcedureProcedure
5. Cluster analysis: From the pattern of data in the PFA chart, related groupings are identified an rearranged into a new pattern that brings together packs with similar machine sequences.- Different machine groupings are indicated with blocks. - The blocks might be considered as possible machine cells.
WeaknessWeaknessThe data used in the technique are derived form existing production route sheets. The routings may contain operations that are nonoptimal, illogical or unnecessary.
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
• To shorten manufacturing lead times.
DefinitionDefinition
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 limited groups of families.
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 limited groups of families.
ObjectivesObjectives
• To reduce work in process inventory.
• To improve quality.
• To simplify production scheduling.
• To reduce setup times.
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
Composite Part Concept is a hypothetical part for a given family which includes all of the design and manufacturing attributes of the family.
Composite Part Concept is a hypothetical part for a given family which includes all of the design and manufacturing attributes of the family.
4.1. Composite Part Concept4.1. Composite Part Concept
DefinitionDefinition
A production cell designed for the part family would include all the machines required to make the composite part. Such a cell would be capable of producing any member of the family, simply by omitting those operations corresponding to features not possessed by the particular part.
Production cell designProduction cell design
The cell would also be designed to allow size variations within the family as well as feature variations.
An individual part in the family will have some features that characterize the family but not all of them. The composite part possesses all of them.
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
4.2. Machine cell design4.2. Machine cell design
Types of Machine Cells and LayoutsTypes of Machine Cells and Layouts
Manufacturing cells can be classified according to the number of machines and the degree to which the material flow is mechanized between machines.
Four common GT cell configurations:
1. Single machine cell: Consists on one machine plus supporting fixtures and tooling. This type of cell can be applied to workparts whose attributes allow them to be made on one basic type of process such as turning or milling.
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
2. Group machine cell with manual handling: an arrangement of more than one machine used collectively to produce one or more part families. - There is no provision for mechanized parts movement between the machines in the cell. Instead, the human operators who run the cell perform the material handling function.- The cell is often organized into a U-shaped layout. This layout is appropriate when there is variation in the work flow and to allow the multifunctional workers in the cell to move easily between machines.
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
3. Group machine cell with semi-integrated handling: uses a mechanized handling system to move parts between machines in the cell.
4. Flexible manufacturing system (FMS): combines a fully integrated material handling system with automated processing stations.- FMS is the most highly automated of the group technology machines cell.- Variety of layouts: U-shape, in-line, loop, and rectangular.
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular ManufacturingCell designCell design
Part movementFour types of part movement:
1. Repeat operation: a consecutive operation is carried out on the same machine so the part does not actually move.
2. In-sequence move: the part moves from the current machine to an immediate neighbor in the forward direction.
3. By-passing move: the part moves forward from the current machine to another machine that is two or more machines ahead.
4. Backtracking move: the part moves from the current machine in the backward direction to another machine.
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
Additional factors
Additional factors that must be accounted for in the cell design:
• Quantity of work to be done by the cell: number of parts per year and processing time per part at each station. Determine the workload and therefore the number of machines that must be included.
• Part size, shape, weight, and other physical attributes: determine the size and type of material handling and processing equipment that must be used.
Movement Layout
Repeat operations
In-sequence move
Passing moves
Backtracking move
Multiple stations (machines)
In-line layout / U-shaped layout
U-shaped layout
Loop or rectangular layout
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
Key machine conceptKey machine concept
Key machine is a certain machine in a cell that is more expensive to operate than the other machines or that performs certain critical operations in the plant.
Key machine is a certain machine in a cell that is more expensive to operate than the other machines or that performs certain critical operations in the plant.
The other machines are referred to as supporting machines, and they should be organized in the cell to keep the key machine busy. In a sense, the cell is designed so that the key machine becomes the bottleneck of the system.
The key machine concept is sometimes used to plan the GT machine cell. The approach is to decide what parts should be processed through the key machine and then determine what supporting machines are required.
4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing4. Cellular Manufacturing
Utilization measures Utilization measures
Two measures of utilization:
1. Utilization of the key machine: using the usual definition. The utilization of each of the other machines can also be evaluated similarly.
2. Utilization of the overall cell: obtained by taking a simple arithmetic average of all the machines in the cell.
5. Application considerations in 5. Application considerations in group technologygroup technology
5. Application considerations in 5. Application considerations in group technologygroup technology
5.1. Applications of Group Technology5.1. Applications of Group Technology
5.1.1. Manufacturing Applications5.1.1. Manufacturing Applications
1. Formation of cells
Informal scheduling and routing of similar parts through selected machines
Virtual machine cells
Formal machine cells
2. Process planning of new parts
3. Family tooling
4. Parametric programming
5. Application considerations in 5. Application considerations in group technologygroup technology
5. Application considerations in 5. Application considerations in group technologygroup technology
5.1. Application of Group Technology5.1. Application of Group Technology
5.1.2. Product Design Applications5.1.2. Product Design Applications
1. Use of design retrieval systems Design savings
2. Simplification and standardization of design parameters
• Simplify design procedures
• Reduce part proliferation
• Reduce the required number of tools
• Reduce the amount of data and information that the company must deal with
5. Application considerations in 5. Application considerations in group technologygroup technology
5. Application considerations in 5. Application considerations in group technologygroup technology
5.2. Survey of Industry Practice5.2. Survey of Industry Practice
Rank Reason for installing Manufacturing Cells
1 Reduce throughput time (Manuf. Lead time)
2 Reduce work-in-process
3 Improve part and/or product quality
4 Reduce response time for customer orders
5 Reduce move distances
6 Increase manufacturing flexibility
7 Reduce unit costs
8 Simplify production planning and control
9 Facilitate employee involvement
10 Reduce setup times
11 Reduce finished goods inventory
5. Application considerations in 5. Application considerations in group technologygroup technology
5. Application considerations in 5. Application considerations in group technologygroup technology
5.2. Survey of Industry Practice5.2. Survey of Industry Practice
Rank Costs of Introducing Cellular Manufacturing
1 Relocation and installation of machines
2 Feasibility studies, planning and design
3 New equipment and duplication of equipment
4 Training
5 New tooling and fixtures
6 Programmable controllers, computers and software
7 Material handling equipment
8 Lost production time during installation
9 Higher operator wages
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
• Quantitative techniques have been developed to deal with problem areas in GT
• Two main problem areas
Grouping parts and machines into families
Rank order clusteringRank order clustering
Arranging machines in a GT cell
An heuristic approach by Hollier
An heuristic approach by Hollier
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6.1. Rank Order Clustering Technique6.1. Rank Order Clustering Technique
• Specially applicable in production flow analysis
• It works by reducing the part-machine incidence matrix to a set of diagonalized blocks that represent part families and machine cells.
• Algorithm 1. Read each row of the matrix as a binary number and reorder them in decreasing order.
2. Do the same with the columns of the matrix
3. Repeat steps 1 and 2 until no change in the matrix is needed.
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6.1. Rank Order Clustering Technique6.1. Rank Order Clustering Technique
6.1.2. Example6.1.2. Example
Parts
Machines A B C D E F
1 1 1 1
2 1 1
3 1 1 1
4 1 1
Parts
Machines A F D B E C
1 1 1 1
4 1 1
3 1 1 1
2 1 1
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6.1. Rank Order Clustering Technique6.1. Rank Order Clustering Technique
6.1.2. Example6.1.2. Example
Parts
Machines A F D B E C
1a 1 1
4 1 1
3 1 1 1
1b 1 1
2 1 1 1
Parts
Machines A F D B E C
1 1 1 1 1
4 1 1
3 1 1 1
2 1 1 1
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6.2. Hollier Method to Arrange Machines in a GT Cell6.2. Hollier Method to Arrange Machines in a GT Cell
• Uses data contained in From-To charts
• Maximizes the proportion of in-sequence moves within the cell
• Algorithm 1. Develop the From-To chart
2. Determine the From/To ratio for each machine
3. Arrange machines in order of decreasing From/To ratio
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6.2. Hollier Method to Arrange Machines in a GT Cell6.2. Hollier Method to Arrange Machines in a GT Cell
6.2.2. Example6.2.2. Example
• 50 parts processed on 4 machines.
To: 1 2 3 4 “From” Sums
From/To Ratio
From: 1 0 5 0 25 30 0.60
2 30 0 0 15 45 1.0
3 10 40 0 0 50
4 10 0 0 0 10 0.25
“To” Sums 50 45 0 40
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6. Quantitative analysis in 6. Quantitative analysis in cellular manufacturingcellular manufacturing
6.2. Hollier Method to Arrange Machines in a GT Cell6.2. Hollier Method to Arrange Machines in a GT Cell
6.2.2. Example6.2.2. Example
• Flow diagram
50 in 3 2 1 4 30 out
20 out
40 30 25
10 15
105
Percentages of in-sequence moves = 70.4%
Percentages of backtracking moves = 11.1%
QuestionsQuestionsQuestionsQuestions