wcm - group technology & cellular manufacturing
DESCRIPTION
cellular manufacturingTRANSCRIPT
Mayuresh Unde
1st Feb, 2011
Group Technology & Cellular Manufacturing
Types of Manufacturing Layouts
Process Layout
Product Layout
Cellular Layout
Process Layouts
PROCESS-TYPE LAYOUT
Lathe Milling Drilling
Grinding
Assembly
Receiving andShipping
L
L L
L
L
L
L
L M
MM
M M
M
A A
A A
D
D D
D
G
G
G
G G
G
Process layout Characteristics
• Advantages– Deep knowledge of the process
– Common tooling and fixtures
– Most Flexible -- can produce many different part types
• Disadvantages– Spaghetti flow -- everything gets all tangled up
– Lots of in-process materials
– Hard to control inter-department activities
– Can be difficult to automate
Product Layout
PRODUCT LAYOUT
Shipping
L L M D
L M D
G
L M GG
A A
Receiving
Part #1
Part #3
Part #2
Product Layout Characteristics
• Advantages– Easy to control -- input control– Minimum material handling -- frequently linked to the
next process– Minimal in-process materials– Can be more easily automated
• Disadvantages– Inflexible -- can only produce one or two parts– Large setup – heavy capital investment– Duplicate tooling is required for all cells– Difficult to alter flow rates / introduce new products as
line re-balancing would be required
Cellular Manufacturing
A manufacturing cell is a cluster of machines or processes located in close proximity and dedicated to the manufacture of a family of parts.
The parts are similar in their processing requirements, such as operations, tolerances, and machine tool capacities
Cellular Layout
Cell #2
Cell #3
Cell #1
D D M I
D ML L I
D
M
L
M
I
CELLULAR LAYOUT
Volume Vs Variety
TRANSFERLINE
SPECIAL SYSTEM
FLEXIBLEMANUFACTURING
SYSTEM
MANUFACTURINGCells
STD. AND GEN.MACHINERY
VO
LUM
E
HIGH
VARIETYLOW HIGH
Cellular Layout Characteristics
• Advantages
– Control is simplified
– Common tooling and fixtures
– Flexible -- can produce many different part types –(part families)
– Reduced cycle times
– Reduced inter-cellular movements
– Multi-skilled workers
Design of cellular manufacturing system is a complex exercise with broad implications for an organization.
The cell design process involves issues related to both system structure and system operation
11
Cell Design
Structural issues include:
• Selection of part families and grouping of parts into families
• Selection of machine and grouping of these into cells
• Selection of tools, fixtures, and pallets
• Selection of material-handling equipment
• Choice of equipment layout
12
Issues related to procedures include:
• Organization of supervisory and support personnel around the cellular structure
• Formulation of maintenance and inspection policies
• Design of procedures for production planning, scheduling, control, and acquisition of related software and hardware
• Modification of reward & incentive systems
• Outline of procedures for interfacing with the remaining manufacturing system (in terms of work flow and information, whether computer controlled or not)
Cell Design
Cell Cycle Time & Capacity
In an assembly cell, the actual cycle time is entirely a function of the cell Manual Time, which is the time required for the workers to perform their tasks and move between workstations. Thus, if only one person operates the assembly cell then,
Cell Cycle Time = Ʃ Operation Times + Ʃ Walk Times
Cell Capacity = Time Available Cell CT
Part Families & Groups
The word ‘Family’ is used as a name for any list of similar parts. The families used with group layout are lists of parts which are similar because they are all made on the same group of machines. This type of family is called a ‘Production Family’.
The other important features that is important choosing the families;Manufacturing tolerancesRequired quantities / volumesMaterialsSpecial features, which will require the use of different machines
A ‘Machine Group or Machine Cell’ is a list of machines, selected for layout together in one place, because it contains all necessary facilities to complete the processing of a given family of parts. A family of parts can only be defined by relating it to a particular group of machines, and a group by relating it to a family. Groups vary greatly in type and size, widely in the number of machines and different machines types.
Typical Part Families
Items that are made with the same equipment
Items that look alike –Physical characteristics, dimensions, geometric shapes etc.
Family 1
Family 2
Group Technology
Group technology begun by grouping parts into families, based on their attributes.
There are three methods that can be used to form part families:
Manual visual inspection: Uses Judgment
Classification and coding: Most widely used in the industry, time consuming and complicated at times
Production flow analysis: Production Flow / Route sheets are studied from a manufacturing process perspective
Group Technology or GT is a manufacturing philosophy in which the parts having similarities (Geometry, manufacturing process and/or function) are grouped together to achieve higher level of integration between the design and manufacturing functions of a firm. The aim is to reduce work-in-progress and improve delivery performance by reducing lead times.
Classification & Coding
FUNCTIONAL CLASSIFICATION
• coding based on part design attributes
• coding based on part manufacturing attributes
• coding based on a combination of design & manufacturing attributes
STRUCTURAL CLASSIFICATION
• Hierarchical Structure
• Chain Type Structure
Functional ClassificationEX
AM
PLE
The Optiz Classification System
Form Code:describes the primary design attributes
Supplementary Code:manufacturing attributes –dimensions, work material, accuracy, starting work piece shape
Secondary Code:Identifies production operation type and sequence
12345 6789 ABCD
Mono-code – Hierarchical Code
• The structure of mono-code is like a tree in which each symbol amplifies the information provided in the previous digit.
• A monocode (hierarchical code) provides a large amount of information in a relatively small number of digits. Useful for storage and retrieval of design-related information such as part geometry, material, size, etc.
Production Flow Analysis
A technique for forming part families based on Operation Routing Summaries
Let’s consider 5 parts (n) and 6 machines (m):
n = {101, 102, 103, 104, 105}
m = {Drill1, Drill2, Mill1, Mill2, Vbore1, Vbore2}= {D1, D2, M1, M2, V1, V2}
Part No. Routing Times (min) Ave. Dem.
101 D1 -M1 - V1 9 - 12 - 14 100
102 D2 -M2- V1 5 - 11 - 14 250
103 D1 -M1 7 - 9 700
104 M2 - V2 - D2 8 - 12 - 5 100
105 V1 - M1 - D1 7 - 10 - 12 200
Operation Routing Summary
PFA Matrix
M =
Mac
hin
es
Parts
101 102 103 104 105
Drill 1 1 0 1 0 1Drill 2 0 1 0 1 0Mill 1 1 0 1 0 1Mill 2 0 1 0 1 0VB 1 1 1 0 0 1VB 2 0 0 0 1 0
King’s Algorithm (Rank Order Clustering)
Step#1Calculate the total column width for each column
Part# (j) 101 102 103 104 105
D1 1 0 1 0 1 2D2 0 1 0 1 0 4M1 1 0 1 0 1 8M2 0 1 0 1 0 16V 1 1 1 0 0 1 32V 2 0 0 0 1 0 64
42 52 10 84 42
1
Machine# (i)
23456
2 i
Generate 2i
=i
ij mw ij2
Sum: mi,j * 2i
for each column (wj)
(wj)
King’s Algorithm (Rank Order Clustering)
#2. If Wj is in ascending order, go to step #3; otherwise, rearrange the columns to make Wj fall in an ascending order.
103 101 105 102 104
D 1 1 1 1 0 0D 2 0 0 0 1 1M1 1 1 1 0 0M2 0 0 0 1 1V 1 0 1 1 1 1V 2 0 0 0 0 0
10 42 42 52 84wj
101 105
104
102
103
King’s Algorithm (Rank Order Clustering)
#3. calculate the total row weight, wi
=j
ijj
i m2w
103 101 105 102 104
D 1 1 1 1 0 0 14D 2 0 0 0 1 1 48M1 1 1 1 0 0 14M2 0 0 0 1 1 48V 1 0 1 1 1 1 28V 2 0 0 0 0 1 32
2 4 8 16 322j
wi
Sum: mi,j * 2j
for each row (wi)
Generate 2j
1
King’s Algorithm (Rank Order Clustering)
#4. If wi is in ascending order, stop. Otherwise, arrange rows to make Wi
ascend.
103 101 105 102 104110000
111000
111000
001011
000111
D 1
M1
V 1
V 2
D 2
M2
D2 V2
V1
M1
V2
King’s Algorithm (Rank Order Clustering)
103 101 105 102 104110000
111000
111000
001011
000111
D 1
M1
V 1
V 2
D 2
M2
#5 Stop and make Cells and Part families
Production Flow Analysis
Assumptions
• Each component is equally important in terms of cost
• Lot size & its associated cost are not directly related to grouping procedure
• Routing is assumed to be optimal
Weakness:
PFA is suitable mostly for small sized applications, but it has difficulties coping with some large cell formation problems when the Machine-Part Matrix becomes more complex
Advantages
• Reduces flow distances
• Better suited to JIT and “pull” manufacturing as the overall flow is much straighter
• Simple and Easy to implement
• Experience: Lots of Research and Background and support software
Benefits of Group Technology/ Cellular Mfg
1. Engineering design
• Reduction in new parts design
• Reduction in the number of drawings through standardization
• Reduction of drafting effort in new shop drawings
• Reduction of number of similar parts, easy retrieval of similar functional parts, and identification of substitute parts
2. Layout planning
• Reduction in production floor space required
• Reduced material-handling effort
Benefits of Group Technology
3. Specification of equipment, tools, jigs, and fixtures
• Standardization of equipment due to implementation of cellular manufacturing systems
• Significant reduction in up-front costs incurred in the release of new parts for manufacture
4. Manufacturing: process planning
• Reduction in setup time and production time
• Reduction in wait times, transfer times etc.
Benefits of Group Technology
5. Manufacturing: production control
• Reduced work-in-process inventory
• Improved material flow and reduced warehousing costs (Semi-finished)
• Increased Inventory turns
• Improved through-put
6. Manufacturing: quality control
• Reduction in number of defects leading to reduced inspection effort
• Reduced scrap generation
• Better output quality
• Increased accountability of operators and supervisors responsible for quality production, making it easier to implement total quality control concepts.
Benefits of Group Technology
7. Purchasing
• Coding of purchased part leading to standardized rules for purchasing leading to less supplier quality issues
• Economies in purchasing possible because of accurate knowledge of raw material requirements
• Reduced number of part and raw materials
• Simplified vendor evaluation procedures leading to just-in-time purchasing
8. Customer service
• Accurate and faster cost & time estimates
• More reliable operations leading to accurately meeting delivery deadlines – leads to improved customer satisfaction