View
217
Download
4
Tags:
Embed Size (px)
Citation preview
MMM256/1
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Manufacturing Systems II
Chris [email protected]
http://www.staff.ncl.ac.uk/chris.hicks
MMM256/2
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Topics
• Group Technology (Cellular Manufacture)
• Inventory Management• Material Requirements Planning• Just-in-Time Manufacture
MMM256/4
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
References
• Apple J.M. (1977) Plant Layout and Material Handling, Wiley, New York.
• Askin G.G & Standridge C.R. (1993) Modelling and Analysis of Manufacturing Systems, John Wiley
ISBN 0-471-57369-8 • Black J.T. (1991) “The Design of a
Factory with a Future”, McGraw-Hill, New York, ISBN 0-07-005550-5
MMM256/5
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
References (cont.)• Burbidge J.L. (1978)
Principles of Production Control
MacDonald and Evans, England
ISBN 0-7121-1676 • Gallagher C.C. and Knight W.A. (1986)
Group Technology Production Methods in Manufacture
E. Horwood, England ISBN 0-471-08755-6
• Hyde W.F. (1981)
Data Analysis for Database Design
Marcel Dekker Inc
ISBN 8247-1407-0
MMM256/6
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Manufacturing Layout
• Process (functional) layout, like resources placed together.
• Group (cellular) layout, resources to produce like products placed together.
MMM256/8
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Scientific Management• F.W.Taylor 1907• Division of labour - functional
specialism• Separation of “doing” and “thinking”• Workers should have exact instructions• Working methods should be
standardised• Specialisation led to functional layouts
MMM256/9
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Process Layout
• Like machines placed together• Labour demarcation / common skills• Robust wrt machine breakdown• Common jigs / fixtures etc.• Sometimes high utilisation• Components travel large distances• High work in progress• Long lead times• Poor throughput efficiency• Often hard to control
MMM256/10
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Group Technology (Cellular Manufacturing)
• Group Technology is a manufacturing philosophy with far reaching implications.
• The basic concept is to identify and bring together similar parts and processes to take advantage of all the similarities which exist during all stages of design and manufacture.
• A cellular manufacturing system is a manufacturing system based upon groups of processes, people and machines to produce a specific family of products with similar manufacturing characteristics (Apple 1977).
MMM256/11
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Cellular Manufacturing• Can be viewed as an attempt to obtain the
advantages of flow line systems in previously process based, job shop environments.
• First developed in the Soviet Union in 1930s by Mitrofanov.
• Early examples referred to as Group Technology.• Promoted by government in 1960s, but very little
take up.• In 1978, Burbidge asked “What happened to
Group Technology?”• Involves the standardisation of design and
process plans.
MMM256/12
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Group (Cellular) Layout
• Product focused layout.• Components travel small distances.• Prospect of low work in progress.• Prospect of shorter lead times.• Reduced set-up times.• Design - variety reduction, increased
standardisation, easier drawing retrieval.
• Control simplified and easier to delegate.
• Local storage of tooling.
MMM256/13
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Group (Cellular) Layout
• Flexible labour required.• Sometimes lower resource utilisation
due to resource duplication.• Organisation should be focused upon
the group e.g. planning, control, labour reporting, accounting, performance incentives etc.
• Often implemented as a component of JIT with team working, SPC, Quality, TPM etc.
• Worker empowerment is important - need people to be dedicated to team success. Cell members should assist decision making.
MMM256/14
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Characteristics of Successful Groups
Characteristic Description
Team Specified team of workers
Products Specified set of products
& no others
Facilities Dedicated machines / equipment
Group layout Dedicated space
Target Common group goal for period
Independence Groups can reach goals
independently
Size Typically 6-15 workers
MMM256/15
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
1 10 100 1,000 10,000Part Variety
(Number of different parts per hour)
1
10
100
1,000
Volume
FRED
High
Low
Job Shop
Transfer lines
Dedicated flow lines
Cells
FMS
Adapted from Black (1991)
MMM256/16
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Implementation of Cellular Manufacturing
• Grouping - identifying which machines to put into each cell.
• Cell / layout design - identifying where to put to place machines.
• Justification• Human issues
MMM256/17
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Types of Problem
• Brown field problem - existing layout, transport, building and infrastructure should be taken into account.
• Green field problem - designers are free to select processes, machines, transport, layout, building and infrastructure.
• Brown field problems are more constrained, whilst green field problems offer more design choice.
MMM256/18
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Grouping Methods
• “Eyeballing”• Classification of parts• Product Flow Analysis• Cluster Analysis
– Matrix methods (e.g. King 1980)– Similarity Coefficient methods
• Layout generation without grouping
Beware:• Different methods can give different
answers• There may not be clear clusters• Cellular manufacturing not always
appropriate
MMM256/19
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Classification of Parts
• Based upon coding.• Many schemes available.• Basic idea is to classify according to
geometry, similar shapes require similar processes.
• Grouping codes together is synonymous with grouping together like parts.
• Very prevalent in 1960s and 70s.• Many schemes aimed at particular
sectors.
MMM256/20
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Coding issues• Part / component population
– inclusive should cover all parts.– flexible should deal with future parts
/ modifications.– should discriminate between parts
with different values for key attributes.
• Code detail - too much and the code becomes cumbersome - too little and it becomes useless.
• Code structure - hierarchical (monocode), chain (polycode) or hybrid.
• Digital representation - numeric, alphabetical, combined.
MMM256/22
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Product Flow Analysis
• Developed by Jack Burbidge (1979).• Uses process routings.• Components with similar routings
identified.
Three stages• Factory flow analysis.• Group analysis• Line analysis
(See Askin and Standridge p177-179)
MMM256/23
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Factory Flow Analysis
• Link together processes (e.g. machining, welding, pressing) and subprocesses (turning, milling, boring) used by a significant number of parts.
• Large departments are formed by combining all related processes.
• These are essentially independent plants that manufacture dissimilar products.
MMM256/24
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Group Analysis
• Breaks down departments into smaller units that are easier to administer and control.
• The objective is to assign machines to groups so as to minimise the amount of material flow between the groups.
• Small inexpensive machines are ignored, since they can be replicated if necessary.
MMM256/25
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Group Analysis• Construct a list of parts that require
each machine. The machine with fewest part types is the key machine.
• A subgroup is formed from all the parts that need this machine plus all the other machines required to make the parts.
• A check is then made to see if the subgroup can be subdivided.
• If any machine is used by just one part it can be termed “exceptional” and may be removed.
MMM256/26
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Group Analysis
• Subgroups with the greatest number of common machine types may be combined to get groups of the desired size.
• The combination rule reduces the number of extra machines required and makes it easier to balance machine loads.
• Each group must be assigned sufficient machines and staff to produce its assigned parts.
MMM256/27
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Process Plan Example
PartsMachine 1 2 3 4 5 6 7 8A 1 1 1B 1 1 1C 1 1 1 1D 1 1 1 1E 1 1F 1 1
(Askin and Standridge 1993)
MMM256/28
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Applying Grouping
Steps
1. Identify a key machine. Either E or F.
Create a subgroup to D,E and F.
2. Check for subgroup division. All parts visit F and so subgroup cannot be subdivided. Only part 7 visits machine D so it is exceptional and is removed.
1. Identify an new key machine for remaining 6 parts. A is the new key machine with subgroup A,B,C producing parts 1,2 & 3.
2. Subgroup division - C only used for part 3, therefore exceptional and can be removed.
MMM256/29
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Applying Grouping
1. Identify next key machine. Only parts 4,5, & 6 remain as well as machines C and D.
2. All parts use all machines - no subdivision possible.
3. Cell designer can now recombine the three subgroups into a set of workable groups of desired size.
4. The final solution must provide adequate machine resources in each group for the assigned parts. If exceptional parts exist, or if groups are not self contained, then plans must be made for transport.
MMM256/30
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Rank Order Clustering
PartsM/C 1 3 4 7 2 5 6 8 ValueA 1 1 1 200E 1 1 17C 1 1 1 1 102F 1 1 17D 1 1 1 1 54B 1 1 1 200
2N-k 128 64 32 16 8 4 2 1
1. Evaluate binary value of each row.2. Swap rows over to get them in rank order.
MMM256/31
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Rank Order Clustering
PartsM/C 1 3 4 7 2 5 6 8 ValueA 1 1 1 200B 1 1 1 200C 1 1 1 1 102D 1 1 1 1 54E 1 1 17F 1 1 17
2N-k 128 64 32 16 8 4 2 1
Next apply same method to the columns
MMM256/32
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Rank Order Clustering
Parts
M/C 1 3 4 7 2 5 6 8 2M-k
A 1 1 1 32B 1 1 1 16C 1 1 1 1 8D 1 1 1 1 4E 1 1 2F 1 1 1Tot 48 56 12 7 48 12 12 3
M = number of machines, k number of rows
Next swap over columns to get in rank order.
MMM256/33
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Rank Order Clustering
Parts
M/C 3 1 2 4 5 6 7 8 2M-k
A 1 1 1 32B 1 1 1 16C 1 1 1 1 8D 1 1 1 1 4E 1 1 2F 1 1 1Tot 56 48 48 12 12 12 7 3
ROC has got a solution close to a block diagonal structure. The process can be repeated iteratively until a stable solution isfound.
MMM256/35
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Consider a pair of machines I,j,
ni = number of parts visiting machine i
nj = number of parts visiting machine j
nij = number of parts visiting i and j.
Define similarity coefficient as:
sij = max(nij/ni,nij/nj)
Values near 1 denote high levels of interaction.
Values near 0 denote little or no interaction.
Similarity Coefficients
MMM256/36
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Similarity Coefficients
1
654
32
S ij = m ax(n ij/n i, n ij/n j)
S 2,5 = m ax(2 /3 , 2 /2)
S 2,5 = 1
Machine 1 2 3 4 5 6 7 8A 1 1 1B 1 1 1C 1 1 1 1D 1 1 1 1E 1 1F 1 1
M/Cs A B C D E FA ---- 1 0.33 0 0 0B 1 ---- 0.33 0 0 0C 0.33 0.33 ---- 0.75 0 0D 0 0 0.75 ---- 0.5 0.5E 0 0 0 0.5 ---- 1F 0 0 0 0.5 1 ----
Initial similarity coefficient Sij
(Askin and Standridge 1993)
MMM256/38
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Clustering• We start with 6 clusters, one for each
machine.• With a threshold of T = 1 machines A
and B can be grouped. Likewise E and F.
• There are several methods for updating similarity coefficients between newly formed clusters and existing clusters.
• The single linkage approach uses the maximum Sij for any machine i in the first cluster and any machine j in the second cluster. Therefore any single pair of machines can cause groups to be combined
MMM256/39
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Updating Similarity Coefficients (Using Single Linkage)
MachinesM/CsAB C D EFAB ------ 0.33 0 0C 0.33 ------ 0.75 0D 0 0.75 ------ 0.5EF 0 0 0.5 ------
Updated similarity coefficient Sij
Next consider the highest value of Tpossible. This gives the cluster CD atT = 0.75.The coefficients then need to be updatedagain.
MMM256/40
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Dendogram
1
0.75
0.5
0.25
0
A B C D E F
M A C H IN E S
4 G roups
3 G roups
2 G roups
1 G roups
Sim
ilar it
y C
oe
ffic
ien
t T
hr e
sho
ld
MMM256/42
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Variety Reduction
Basic principle: always use common designs and components wherever possible.
• Modular design.• Standardisation.• Redundant features.• Can base upon geometric series.• Imperial / metric series.• Reduced estimated & work planning.• Simplified stock control.• Less problems with spares.
MMM256/43
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Variety Reduction
• May use slightly more expensive parts than necessary.
• Increases the volume of production of items.
• Reduced planning / jigs and fixtures etc.
• Reduced lead times.
MMM256/44
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Product Family Analysis
There are a number of different ways of identifying part families. The following factors should always be considered:
• How wide is the range of components?• How static is workload?• What changes are anticipated?• Is Group Technology aimed purely at
manufacturing or is standardisation and modularisation of design a major issue?
MMM256/45
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Manufacturing Layout
• Concerned with the relative location of major physical manufacturing resources.
• A resource may be a machine, department, assembly line etc.
• A block plan can be produced that shows the relative positioning of resources.
• Evaluation criteria are required such as minimising transport costs, distance travelled etc.
MMM256/46
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Approaches• Many methods are based upon a static
deterministic modelling approach.• Dynamic effects may be “guessed” by
trying out a variety of scenarios.• Dynamic and stochastic effects may be
evaluated by simulation.• A premium may be placed upon
favourable attributes– Flexibility dealing with changes in
design, demand etc.– Modularity the ability to change the
system by adding or removing component parts to meet major changes in demand.
– Reliability– Maintainability
MMM256/47
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Line Layout
D D D
Departments
Material Flow
Single Line, single row layout
D D D
Departments
D D D
Single line, double row layout
MMM256/48
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Spine Layout
Materials Products
• Spine is central core for traffic.• Secondary aisles for traffic into departments• Each department has input /output storage areas along the spine.• Point of use storage reduces material flow.
MMM256/49
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Material
Loop Structure
Circular Structure
MMM256/50
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Layout Configurations
• Eli Goldratt I, V, U, W• I layouts have linear flow with no
direction changes, empty pallets may go in reverse direction.
• V and U lines have more direction changes but may help with empty pallets.
• Rectilinear layouts may restrict operators from working multiple machines.
• Circular layouts may enable operators to work multiple machines.
MMM256/51
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Analysing Flow• Sting diagrams provide a very quick
way to identify the pattern of flow.• Look at performance measures:
– Distance travelled per component;– Material handling costs %;– Material handling time %;– Load / unload times;– Number of direction changes;– Number of moves per day;– Many, many more.
• Looking at performance measures enables alternative layouts to be evaluated.
MMM256/52
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Measures of Performance
• Resource Measures:– Resource utilisation;– Productivity.
• Inventory:– work in progress;– queues.
• Product:– lead times;– delivery performance;– Quality.
• Financial, overhead recovery v.s. ABC costing.
MMM256/53
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Creating Layouts
• If there is a dominant flow, such as all parts going from department 1-> 2 -> 3 then the layout should reflect this.
• At the other extreme, if the flow between departments is uniformly distributed, then any arrangement may be equally good.
• However, most problems will lie between the extremes of dominant and equal flow.
MMM256/54
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Systematic Layout Planning
1. Data collection.
2. Flow analysis.
3 Qualitative considerations.
4. Relationship diagram.
5. Space requirements.
6. Space availability.
7. Space relationship diagram.
8. Modifying considerations and limitations.
9. Evaluation.
(Muther 1973)
MMM256/55
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
1. Data Collection• Products to be produced & volumes.• Routing, Bill of Materials, parts lists.• Resources for production, layout &
geometrical information.• Timing information - set-up, processing
& transfer durations.• Data determines loads & resource
utilisation.• Quantity & variety determine
appropriate layout type.• A Product-Quantity chart, which is a
Pareto analysis of product importance can be used to determine items that justify their own lines or families of parts that justify a cell.
MMM256/56
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Product-Quantity Chart
1 2 3 4 ... NProduct
Quantity
MMM256/57
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
2. Flow Analysis
• Operation process charts determine movement showing major operations, inspections, moves and storage.
• Process charts, similar to operation process charts, but more detail.
• Flow diagrams.• Flow data can be summarised in From-
To charts (like mileage charts in maps)– Volumes– Distance travelled*– Costs*
• String diagrams.
MMM256/58
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Operation Process Chart
1010Thread,cut-off &chamfer
Face bottom
20 20
3030
40 40
SSA1 50
60SA1
A1
BaseHandle
Deburr
Inspect
Degrease
Knob
Rod
Face top
Drill 3 boltholes
Drill pinhole
Ream pinhole
Inspect
60 Inspect
MMM256/59
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Process Chart Symbols
D
Operation
Transportation
Inspection
Delay
Storage
Combined activity
MMM256/61
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Flow Diagram
Process chartsymbols
Material flow
Facility layout
MMM256/62
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
3. Qualitative Considerations
1. Offices
2. Foreman
3. Q/C
4. Store
5. Tool rm
A
5
Rating
Reason
Code Reason
1 Material flow2 Convenience
3
4
Rating
A Absolutely essential
E Especially important
I Important
O Ordinary closeness
U Unimportant
X undesireable
REL Chart
MMM256/63
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
4. Relationship Diagram
• Combines quantitative and qualitative relationship data.
• Provides a mechanism for visualising relationships.
MMM256/64
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
5. Space Requirements
• Departmental space requirements need to be estimated.
• May have standards that define space requirement for each machine type.
• Can work from current space needs.• Can determine space requirement by
considering tasks performed, tooling, access, flow of materials etc.
MMM256/65
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
6. Space Availability
• Need to accommodate machines, material handling equipment, people, energy transmission, drainage, air lines, communications etc.
• If an existing facility is to be used, the available space and constraints need to be accurately defined.
• In the case of new facilities there are financial and often planning constraints.Need to consider possibility of future changes in demand or use.
MMM256/66
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
7. Space Relationship Diagram
• Represents departments with templates that are proportional in size to space requirements.
• Templates can be rearranged to find improved solutions.
MMM256/67
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
(a)
(b)
a) Relationship Diagramb) Space Relationship Diagram
MMM256/68
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
8. Modifying Considerations and Limitations
• Steps 1-7 have not taken into account implementation details.
• Site specific or operations specific conditions may require adjustments to the layout.
• Need to consider:– Utilities, power, heating, light,
drainage compressed air etc.– Structural limitations, load-bearing
capacity of floors, ceiling heights, columns.
– Location of external connections e.g. roads.
MMM256/69
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
9. Evaluation
• Several alternatives should be considered.
• Drawings, flow diagrams etc form the basis of assessment of advantages and disadvantages of each.
• Costs / benefits can be attributed to each alternative.
• Quality of flow can be evaluated.• Flexibility, maintainability, expandability
safety and ease of operations should be reviewed.
MMM256/70
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Computerised Layout Planning
• Improvement algorithms are based upon an initial layout. They generate improvements by rearrangement. Suitable for brown field sites. Examples CRAFT (Armour & Buffa 1963)
• Construction algorithms start with a blank shop floor and add machines to it. Suitable for green field sites. Example: ALDEP (Seehof & Evans 1967), CORELP (Parsaei et al 1987), SHAPE (Hassan et al 1986).
• Hybrid algorithms include both construction and improvement algorithms.
MMM256/71
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Computerised Relative Allocation of Facilities (CRAFT)
• Creates layouts by exchanging machine pairs and then evaluating the layout.
• When all pairs of exchanges have been completed, the exchange with the best evaluation is chosen and a new layout in generated.
• This process is repeated until no improvement can be made through exchanges.
MMM256/72
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Automated Layout Design Program (ALDEP)
• A machine is randomly selected and added to the layout.
• The closeness of all the remaining machines to it is calculated. The “closest” machine is added. This is repeated until all machines have been placed.
• Once a machine has been placed, it is fixed. This makes it difficult to find good solutions.
• Often use an improvement algorithm to improve layout produced.
MMM256/73
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Construction Algorithm Differences
• Method for election of next machine and its placement.
• Evaluation of the relationship between machines already located and the selected machine (e.g. by using different definitions of similarity coefficient).
• How the layout is represented.
MMM256/74
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Synthetic Machine Concept
• A group of machines form a synthetic machine.
• Resource hierarchy flattened.• Framework to assist delegated
responsibility.• Local planning, control and work
organisation.• Concerned only with cell inputs and
outputs.
MMM256/75
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Types of Cell• Highly automated - conveyers, robot
handling, Flexible Manufacturing Systems (FMS).
• Semi-automated - some automated material handling.
• Simple cells without automated material handling.
• Work grouped on a single machine using a multi-functional machine tool.
NOTE: Need to find an appropriate mix for given production volumes. Increasing automation normally increases overheads and reduces flexibility.
MMM256/76
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Supporting Techniques
• Statistical process control.• Quality Circles.• Team working.• Empowerment.• Visible performance measures.• Total preventative maintenance.• Single minute exchange of dies.• Simple machine concept.
MMM256/77
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Case Study 1
• World class automotive components supplier.
• Adopted lean manufacturing practices yet productivity still 50% of Japanese sister plant.
WHY?
MMM256/78
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Findings
• Layout - rectilinear v.s clusters.• Supervision of resources.• Smallest machine concept.• Flexible resource variable.• Cost of capital and accounting
philosophies.
MMM256/79
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Case Study 2
• SME supplier of orthotics (surgical appliances).
• Very long delivery.• High work in progress.
How can situation be improved?
MMM256/80
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Solution
• Business process analysis:– Non physical processes;– Physical processes .
• Target queuing by streamlining processes or increasing capacity.
Result:• Lead time 14 weeks to 4;• Cash flow improved by £300k on £2M
turnover.
MMM256/81
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Other Key Issues
Batch sizes• Set-up• Machining• Transfer
Effect on other measures of performance.
MMM256/85
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Hints
• Look at the material flow
• Try to simplify
• Think about removing in-process inventory
• Think about the operators
• Consider other layout constraints
MMM256/90
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Inventory
• Money invested in materials
3 Types of inventory• Raw materials• Work in progress• Finished goods
MMM256/91
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Advantages of Inventory
• Raw materials offset lead time• Work in progress offsets disturbances
in the production system and may help keep resource utilisation high
• Finished goods stocks enable fast delivery
• Economic order quantity methods claim to claim
• People feel busy• Process “decoupling”
MMM256/92
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Inventory: Disadvantages
• Expensive to keep– Interest on capital– Storage costs
• Adverse effect on cash flow and liquidity
• Risk of obsolescence• Lack of flexibility• Masks problems with manufacturing
system• Difficult to control
MMM256/93
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Types of Demand
• Independent– Demand for an item is independent
of the demand for another item• Dependant
– Demand for an item is linked to the demand for another item
– Product structure defines dependencies
MMM256/94
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Inventory Control
“The activities and techniques of maintaining stock items at desired levels, whether they are raw materials, work in progress or finished products”
MMM256/95
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Inventory Control Decisions
• How many?
– (lot size or order quantity
• When
– timing or order point
MMM256/96
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Independent Demand• Fixed order quantity (FOQ) systems
order a predetermined quantity of items when stock levels drop below a predetermined level e.g. 2 bin system
• Economic order quantity systems aim to minimise the combination of ordering and carrying costs. They make a number of assumptions:– annual demand can be estimated– demand is uniform– no quantity discounts
• Ignores the costs associated with stock outs
MMM256/97
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Dependent Demand
• Demand for one item linked to the demand for another
• Producing an assembly causes dependent demand for all the components that go into the assembly
• Assembling a car requires one windscreen, 5 wheels, one engine etc.
• One engine requires one crankshaft, one cylinder head etc.
• One cylinder head requires ….
MMM256/98
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Product Structure
A
B C
Simple Product Structure
MMM256/99
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Product StructureA
B Dc
E F
G H
MMM256/100
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Material Requirements Planning
• Method for planning dependent demand
• Requirement for subassemblies and components based upon requirements for end items and product structure
• Takes into account current stocks of each item to calculate net requirements
MMM256/101
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Material Requirements Planning
MRPStocksProduct Structure
End Item Requirements
Net Requirements
MMM256/102
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
ABC Classification
Break items into 3 groups:• A - the items that represent 75% of
value and 20% volume• B - the items that represent 20% value
and 30% volume• C - the items that represent 5% value
and 50% volume
This approach is based upon
Parieto analysis
MMM256/104
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Just-in-Time
• Approach to achieve excellence in manufacturing
• Minimise waste: anything that adds cost but not value
• Just the correct quantity• at just the right quality• at just the right time• in the right place
MMM256/105
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Push Scheduling
Manufacturing Systems
Inventory
“PUSH”
MMM256/106
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Kanban
• Japanese word for card• One card• Two card
MMM256/107
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
One Card Kanban
MC1 MC2
Machine 1 operatesat a constant rate
StockArea
Kanban
Item + Kanban
MMM256/108
© Dr. C.Hicks, MMM EngineeringUniversity of Newcastle upon Tyne
Two Card Kanban
MC1 MC2
StockArea
“C” Kanban
Item + Kanban
“P” Kanban
Item
“P” Production Kanban“C” Conveyance Kanban