Little’s Law
Mathematical relationship between throughput time, work in progress and cycle time
Tells us how long it will take for a given unit to work its way through the process
Throughput time = WIP x Cycle time
Throughput efficiency
Ratio between the actual work done by the resources and the amount of resources (time) invested to process one unit
% throughput efficiency = work content/throughput time x100
Cycle time = time producing/numbers produced
Process design
Must think about the best way of designing the operation to produce the product/service
Process design is about establishing the look, arrangement, resources required and workings of the operation before it is created
Need to think about the performance objectives and the volume/variety characteristics
Manufacturing processes
- Project : construction site
- Jobbing: photolithography materials on a jobbing basis
- Batch: Batch process in a restaurant kitchen
- Mass: Packing factory
- Continuous: Oil, chemical and gas
Service Processes
- Professional service: consultancy
- Service shop: gym, hair salon
- Mass service: supermarket, airport
Layout of the process
It’s the positioning of the transforming resources and the allocation of production tasks to these
A good layout will have;
- inherent safety
- Length of flow
- clarity of flow
- management coordination
- accessibility
- use of space
- certain degree of long-term flexibility
Fixed Position layout
Transformed resource stationary
Why?
- product too large
- patients to delicate
- customers object to being moved
Key Points?
- Adequate space required
- All contractors have access to their part of the project
- minimal movement
E.g
- motorway building
- ship construction
+
- very high variety and flexibility
- high variety of tasks for staff
-
- high unit costs
- scheduling of space and tasks very complex
- coordination issues
Functional/Process Layout
Needs and convenience of the transforming resource functions dominate the layout decision
Convenient to group together resources performing the same/similar functions
Key Points;
- similar transforming processes/products are located together
- products, customers or information flow through the op taking the route from process to process according to their needs
- flow pattern can be complex
E.g
- library
- machine component construction
+
- High variety
- High mix flexibility
- robust to disruption
- easy to supervise
-
- low utilisation
- complex flow
- queuing
- high WIP
Product layout
Transforming resources located entirely for the convenience - prearranged route through fixed series of activities
Sequence of the activities matches the order in which the processes have been located
Key points;
- transformed resource flow along the line of processes
- line layout
- flow is clear
- used for standardised product
E.g
- car assembly
- most mass production
+
- process is stable
- ease of movement
- high degree of specialisation
- easy to supervise
- low unit costs
-
- Low mix flexibility
- work is repetitive
- might not be robust
Cell layout
Transformed resource are pre-slected to move to one part of an operation where they are transformed by a set or resources before moving to another cell
Anticipated process order
Key points;
- cell itself may be functional or product
- attempts to bring some order to the complexity of the process
E.g
- buffet
- business school services
- shop within a shop
+
- good variety and mix compromise
- overall comprise of product and functional layouts
-
- Low utilisation
- costly to rearrange
Mixed layout
Restaurant complex
Kitchen-functional
Seating-fixed
Flow
Long and thin
- high degree of specialism
- quicker
- cheaper labour costs
- few decisions
Short and Fat
- more autonomy
- more flexibility
- higher job satisfaction