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When Theory Crashed into Reality. Yossi Rissin Chief Executive Officer, Visopt B.V Roman Barták Chief Scientist, Visopt B.V. What is the talk about?. Theory. Practice. Planning vs. scheduling. Planners from Venus Researchers from Mars. A theoretical factory. M machines N jobs - PowerPoint PPT Presentation
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When Theory CrashedWhen Theory Crashedinto Realityinto Reality
Yossi RissinYossi RissinChief Executive Officer, Visopt B.VChief Executive Officer, Visopt B.V
Roman BartákRoman BartákChief Scientist, Visopt B.V.Chief Scientist, Visopt B.V.
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What is the talk about?
Planningvs.scheduling
PracticeTheory
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Planners from VenusPlanners from VenusResearchers from MarsResearchers from Mars
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A theoretical factory
O M machinesO N jobs
- each job consists of Oi operations with the precedence relation (dedicated machines for operations)
O Job Shop Scheduling (JCC)- Flow Shop Scheduling
- Open Shop Scheduling
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JSS in Practice?
„I have never seen a Job Shop Scheduling Problem in practice“
Wim Nuiten, ILOG
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The Human Factor
(Planners & plant personnel are motivated by:)O Pride. No disclosure of mistakes, problems
and weaknesses.O Position in the organisation. Position is
protected by being nice to superiors, serving many masters at once, gaining professional respect.
O Future security. No disclosure of knowledge, development of organisation dependency.
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The Human Factor
(Planners & plant personnel are characterised by:)O Politics. Internal politics and power plays
are key factor in decision taking.O Inconsistency. A human being is tend to
inconsistency and easily affected by mood, environment and psychology pressure.
O Unexpected. Human behaviour can be determined and can be foreseen just by statistical methods (big numbers, long periods, distributions, etc.)
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The Ideal Scheduling Projects
O Fully automatic factory based on robots and AGV’s- Engineering oriented- No one to argue with- No one knows better- More visibility, less surprises and fluctuations
O New factory, not operating yet- Very stable, no fluctuations- No previous “know-how”- No old rules and procedures- No bad habits- No day-to-day-reality to confront the theory
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Points Of View
O Planners- The planner’s world consists of products and their
flow- “how can I produce this product now, and this one and that
one…”- “How can I satisfy Mr. X from sales and Mr. Y from the plant
and the customer at the same time, without getting into new troubles…”
O Academy- The engineer/researcher world consists of resources
and their usage- “How can I use the resources to get max X and min Y…”- “How can I get, using objective metrics, a plan that for the
long term, will improve the plant efficiency…”
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Not Invented Here
O “We are different…”- Means, what you know is useless here
O “Outsiders cannot understand it, it takes a lot of time…”- Means, you have to listen to us or to spend part of
your life here
O “Methods that suite others cannot implemented here…”- Means, your experience and knowledge are
impressive, but you have to start from scratch
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Visopt View
O Visual Modelling Language
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Inside Visopt
O Complex resources loadload
heatheat unloadunload
cleanclean
coolcool
O General item flow
N-to-N relationsAlternative recipes Recycling
clean load heat unload load heat unload cool clean
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Quality IssuesQuality Issues
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Theoretical Objectives
O Minimise makespan
O Minimise lateness (tardiness)
O Minimise earliness
O Minimise the number of set-ups
O Maximise resource utilisation
O ...
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Quality Definition
O Quality metrics by the user/planner - “It should looks like the schedules I am doing…”- “Good plan should resemble those I use to make
manually…”- “In order to produce good plan you have to follow my
rules, know-how, procedures…”- Good plan is a one that can be ‘sold’ to production
people easily
O Most of times there are no history records of the manual plans to analyse their efficiency!
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Visopt View
O Understand the reason by asking Why!
minimise makespan
minimise lateness
minimise earliness
minimise number of set-ups
maximise resource utilisation
...
minimise makespan
minimise lateness
minimise earliness
minimise number of set-ups
maximise resource utilisation
...
more satisfied demands
penalty for delays
storing cost
expensive set-ups
fix expenses
So what is the common objective?
M O N E YM O N E Y
In Visopt we minimise costminimise cost (= maximise profitmaximise profit).
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Bridging the GapBridging the Gap
Lessons learned
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The Common Language
O The planner tells a “story” – how to produce a given product or product family, but cannot follow what was understood- Tables and fields say nothing to the planner
and not resemble his world
O Visual modelling is the key – same, simple language for the user and the computer – the ability to draw the user story
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Best Is Worse
O “The Worst Enemy Of The Good Is The Best”- A very good plan (based on objective metrics)
delivered after three hours is not relevant anymore – the factory is not the one it was few hours ago
O The art of real-life scheduling is to deliver a plan which is good enough and fast enough:- Good enough – the user cannot improve it in
reasonable time- Fast enough – depends on the plant dynamics. One
hour can be too late for one plant and very fast to another
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The Cure Is The Pain
O Most manual planning methods that are considered as “know-how” are not relevant to automated scheduling…
O What is considered as the “solid true” (Cure), is many times simplifications of reality to enable the manual scheduling (The pain)
O Extract the real knowledge from the overall know-how with the help of plant experts- Always ask Why, for everything, and never accept an
answer such as “this is the way to do it”- If there is no solid reason behind the “fact” – ignore it
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Scheduling Is Knowledge Handling
O Scheduling is not mathematics, but first of all a knowledge handling process- Capturing the real knowledge- Mapping the knowledge so the user can verify
and update it- Process it concerning its elusive nature- Understand and overcome the accurate
mathematical metrics when dealing with knowledge
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What is the real difference?
O 2 slides per hour talkO only three words are
different on these slides
O 78 slides per hour talk
Based on „real-life“ data (PACT 96)!
PractitionerPractitioner ResearcherResearcher
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Thank you!Thank you!Yossi RissinYossi [email protected]@visopt.com
Roman BartákRoman Bartá[email protected]@visopt.com
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