Manufacturing Systems III. Chris Hicks MMM Engineering Email: [email protected] Assessment. End of year examination 2.5 hours duration Answer 4 questions from 6. Manufacturing Systems III. Manufacturing Strategy JIT Manufacturing Manufacturing Planning and control
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Manufacturing Systems III
Chris Hicks MMM Engineering
Email: [email protected]
“In the broad sense, an approach to achieving excellence in a manufacturing company based upon the continuing elimination of waste (waste being considered as those things which do not add value to the product). In the narrow sense, JIT refers to the movement of material at the necessary time. The implication is that each operation is closely synchronised with subsequent ones to make that possible”
APICS Dictionary 1987
JIT links four fundamental areas
Vollmann et al 1992
1.Separate internal set-up from external set-up. Internal set-up must have machine turned off.
2.Convert as many tasks as possible from being internal to external
3.Eliminate adjustment processes within set-up
4.Abolish set-up where feasible
Shingo, S. (1985),”A Revolution in Manufacturing: the SMED System”, The Productivity Press, USA.
1.Preparation, after process adjustments, checking of materials and tools (30%).
2. Mounting and removing blades, tools and parts (5%) Generally internal.
3. Measurements, settings and calibration (15%) includes activities such as centring, dimensioning, measuring temperature or pressure etc.
4. Trial runs and adjustments (50%) - SMED
Typical proportion of set-up time given in parenthesis.
1.Separating internal and external set-up
doing obvious things like preparation and transport while the machine is running can save 30-50%.
2.Converting internal set-up to external set-up
3.Streamlining all aspects of the set-up operation
A board which shows if any operator on the line has difficulties
1.Lower inventory levels
4.Improve use of resources
5.Go back to step 1
Design - focus
Computer Aided Production Management Systems (CAPM)
(Earlier editions just as good!)
“All computer aids supplied to the manager”
Information systems responsible for:
“Material requirements plannning originated in the 1960s as a computerised approach for planning of materials acquisition for production. These early applications were based upon a bill of materials processor which converted demand for parent items into demand for component parts. This demand was compared with available inventory and scheduled receipts to plan order releases” Browne et al (1986)
“The function of establishing, measuring and adjusting limits or levels of capacity.
Capacity planning in this context is the process of determining how much labour and machine resources are required to accomplish the tasks of production.
Open shop orders and planned orders in the MRP system are input to CRP which “translates” these into hours of work, by work centre, by time period”
APICS Dictionary 1987
“A prerequisite to having an effective capacity planning system is to have an effective priority planning system.
If the due dates, or lead times are incorrect, the schedule, the priorities and the projection of when the load will hit the resources will be fiction. The system will not work”
Plossl & Wight 1973
General company classification
Classification of manufacturing
Five classification areas:
Relationship between cumulative lead time and delivery lead time e.g. make to stock or
make to order
Continuum from pure ETO - pure MTS
effects co-ordination of assembly processes (phasing), uncertainties, lead times etc.
Modelling & Simulation
(last two points relate to simulation modelling)
“Descriptive models offer some symbolic representation of some problem space without any guidance on how to search it. The use of descriptive models is an inductive, experimental technique for exploring possible worlds”
“The term simulation is used to describe the exploration of a descriptive model under a chosen experimental frame”
“Simulation is partly art, partly science. The art is that of programming: a simulation should do what is intended. One should also know how to answer questions about the system being simulated”
“A system is defined as a collection of objects, their relationships and behaviour relevant to a set of purposes, characterising some relevant part of reality”
“Symbolic images of objects, relationships and behaviour patterns are bound into structures as part of some larger framework of beliefs, background assumptions and theories of the problem solver”
“A model is an appropriate representation of some mini-world. Models can very quickly grow to form very complicated structures. Control and the constraint of complexity lie at the heart of any modelling activity. Care must be exercised to preserve only those chracteristics that are essential. This depends upon the purpose of the model”
“It is necessary to abstract from the real system all those components (and their interactions that are considered to be important”
“This stage exists when computers are being used as the modelling medium. This stage seeks a formal representation of symbolic structures and their transformations into data structures and computational procedures in some programming language”
“Dynamic simulation. The clock is sequenced by a clock in uniform fixed length intervals. The size of the increment determines the resolution of the model”