Process Layout Flashcards
Advantages of Long and thin processes
○ Controlled flow of items.
○ Simple handling
○ Lower capital requirements .
○ More efficient operation .
○higher space utilisation
advantages of short and fat
○ Higher mix flexibility
○ Higher volume flexibility .
§ long thin arrangements would need rebalancing each time the cycle time changed.
○ Higher robustness
§ If one stage breaks down, parallel stages are unaffected;
a long thin arrangement would cease operating completely.
○ Less monotonous work
○ higher ownership
what is a push system
material is moved to the next stage as soon as it has been processed
what is a pull system
material is moved to the next stage only when the next stage needs it
long and thin vs short and fat
-n.b. long and thin only works as fast as its slowest process
long and short = number of stages
thin and fat = amount of work
push vs. pull
push = greater flexibility, less efficiency
pull = more efficient, limited flexibility and must be balanced
what is layout of a process
- how its transforming resources are positioned relative to each other,
- how its various tasks are allocated to these transforming resources and
- the general appearance of the transforming resources.
What happens if a layout is wrong?
○ over-long or confused flow patterns, ○ customer queues, ○ long process times, ○ inflexible operations, ○ unpredictable flow, ○ high costs and ○a poor response for whoever is within the operation.
objectives of layout activity
Inherent safety – Security Length of flow – Minimize delays – Reduce work-in-progress – Clarity of flow – Staff conditions Communication Management co-ordination – Accessibility Use of space Use of capital – Long-term flexibility Image
What are the basic layout types?
- Fixed-position layout
- Functional layout
- Cell layout
- Line (‘product’) layout.
what is fixed position layout?
• the transformed resources do not move between the transforming resources.
• Instead of materials, flowing through an operation, the recipient of the processing is stationary and the equipment,
move as necessary.
examples of fixed-position layout
○ Motorway construction – the product is too large to move.
○ Open-heart surgery – patients are too delicate to move.
○ High-class service restaurant – customers would object to being moved to where food is prepared.
○ Shipbuilding – the product is too large to move.
○ Mainframe computer maintenance – the product is too big and probably also too delicate to move,
What is functional layout?
- In functional layout, similar resources or processes are located together.
- Flow pattern in the operation very complex.
examples of functional layout
○ Hospital –
§ some processes are required by several types of patient;
§ some processes can achieve high staff and bed utilization.
○ Machining the parts which go into aircraft engines –
○ Supermarket –
○ A library has different types of user with different traffic patterns.
What is a cell layout?
• A cell layout is one where the transformed resources entering the operation are pre-selected (or pre-select themselves) to move to one part of the operation (or cell) in which all the transforming resources, to meet their immediate processing needs, are located.
the Cell Itself arranged in either a functional or line layout.
examples of cell layout
Some computer component manufacture –
‘Lunch’ products area in a supermarket –
Maternity unit in a hospital
associated with manufacturing –
What is line (product) layout
• Line layout involves locating the transforming resources entirely for the convenience of the transformed resources.
• Each product follows a prearranged route in which the sequence of activities that are required matches the sequence in which the processes have been located.
○ The transformed resources ‘flow’ along a ‘line’ of processes according to their ‘product’ needs.
○ Flow is clear, predictable and therefore relatively easy to control.
• Usually, it is the standardized requirements of the product or service that lead to operations choosing line layouts.
examples of line layout
○ Automobile assembly –
○ Mass-immunization programme –
○ Self-service cafeteria –
what is mixed layouts
• Many operations either design themselves hybrid layouts which combine elements of some or all of the basic layout types, or use the ‘pure’ basic layout types in different parts of the operation.
example of mixed layout
a hospital would normally be arranged on functional layout principles
restaurant complex is shown with three different types of restaurant and the kitchen which serves them all.
What type of layout should an operation choose?
The importance of flow to an operation will depend on its volume and variety characteristics.
- When volume is very low and variety is relatively high, ‘flow’ is not a major issue = fixed-positon layout
- With higher volume and lower variety, flow becomes an issue. = cell layout
Advantages and disadvantages of fixed-position layout
Advantages
- very high mix and product flexibility
- product and customer not moved or disturbed
- high variety of tasks for staff
Disadvantages
- very high unit costs
- scheduling of space and activities can be difficult
- can mean much movement of equipment and staff
-used in professional/jobbing processes
Advantages and disadvantages of functional layout
Advantages
- high mix and product flexibility
- relatively robust in the case of disruptions
- relatively easy supervision of transforming resources
Disadvantages
- low facilities utilization
- can have very high work-in-progress or customer queuing
- complex flow can be difficult to control
-used in batch/ service shops/ professional and jobbing
Advantages and disadvantages of cell layout
Advantages
- gives a compromise between cost and flexibility for relatively high-variety operations
- fast throughput
- potential good staff motivation
Disadvantages
- can be costly to rearrange the existing layout
- can require more equipment
- can give lower equipment utilization
- mass process/ services and continuous
Advantages and disadvantages of line layout
Advantages
- low unit costs for high volume
- gives opportunities for specialisation of equipment
- materials or customer movement is convenient
Disadvantages
- can have low mix flexibility
- not very robust if there is disruption
- work can be very repetitive
- batch, service shops, some mass processes
Cost analysis of layout types
• Fixed costs then tend to increase as one moves from fixed-position, through process and cell, to line layout.
Variable costs per product or service tend to decrease
• The total costs for each layout type will depend on the volume of products or services produced
Characteristics of MRP (materials requirements planning)
- need to anticipate future demand
- copes with product and process complexity
What is a push strategy?
Production decisions based on long-term forecasts
Ordering decisions based on inventory & forecasts
Problems with push strategies
- Inability to meet changing demand patterns
- Obsolescence
- The bullwhip effect (disturbances at one end “travel and expand” along the supply network):
- Excessive inventory
- Excessive production variability
- Poor service levels
Characteristics of JIT
- reacts to demand (demand driven)
- requires level scheduling
what is a pull strategy
Production demand driven
- Production and distribution coordinated with true customer demand
- Firms respond to specific orders
problems with Pull strategy
Harder to leverage economies of scale
• Demand peaks are managed with capacity rather than inventory
• Requires “small” lead times
• Difficult to achieve when supply networks are complex
advantages of pull strategy
- Decrease inventory levels at retailers and manufacturers
- Stimulate reduced production lead times
- Result in better responsiveness to changing demand
What is the decoupling point?
the push-pull boundary
Push | (low uncertainty; forecast at | generic level; economic | batch quantities; maximise | efficiencies) v Strategic Inventory | | | v Pull (high uncertainty; Demand driven; localised configuration; maximise responsiveness)
Locating the push-pull boundary
The Push section Uncertainty relatively low Economies of scale important Long lead times Complex supply chain structures
The Pull section:
High uncertainty
Short lead times
Simple supply chain structure
