When Theory Crashed into Reality

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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 Rissinyossi.rissin@visopt.comyossi.rissin@visopt.com

Roman BartákRoman Bartákbartak@visopt.combartak@visopt.com