Power control and scheduling with minimum rate constraints in
Lean Scheduling and Theory of Constraints
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Transcript of Lean Scheduling and Theory of Constraints
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VISUAL User Conference 2009VISUAL User Conference 2009
October 25 – 28, 2009Marriott Downtown Providence, RI
VISUALize the Rebound – Graphicast’s Path Through the Dark Recession Forest
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Graphicast, Inc.
• Founded in 1978• Located in Jaffrey, NH• Contract manufacturer of machined, zinc alloy
castings In-house design, mold making, casting, machining
capabilitiesProprietary, graphite mold casting process creates high
density castings with exceptional surface finish Most applications are high valued added machine
components
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A Long Time VISUAL User
• Implemented VISUAL in July 1999• The impetus for selecting VISUAL was the scheduling
capability• VISUAL consolidated all operational and financial
activity• We developed numerous Crystal reports running off
the VISUAL database Provide detailed analysis of sales, financial, and
operational information for fine tuning the business
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Some Scheduling Problems Persisted
• The machine shop was booked solid 8 weeks in advance• Normal shop floor issues wreaked havoc with the schedule• The schedule wasn’t pulling jobs in if previous jobs finished
early• Rush orders were very disruptive to the schedule and caused
late shipments • The schedule tried to break into jobs to improve lead times • Ultimately, the schedule was not able to efficiently reflect the
nature of our business. We needed a different scheduling solution. Fortunately, we found the solution just before the economy collapsed.
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What’s behind Lean Scheduling
• Lean scheduling is based on Goldratt’s Theory of Constraints (TOC) introduced in the business novel, “The Goal”
• Utilizing TOC in production Identify the constraint that limits the throughput of the
systemRelieve or eliminate the constraint to free the system to
operate at its peak level• If you have a production constraint, add extra shifts, add a second
machine or use unconstrained machines to produce the same part• If you have a “between the ears” constraint, change restrictive
policies and procedures • If you have a market constraint, increase throughput (sales
revenue)
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What’s behind Lean Scheduling - continued
• TOC scheduling relies on three components “Drum” – The pace of the “constraint” “Buffer” – Some amount of WIP or time that protects the
constrained component “Rope” – A signal to upstream operations to release work
into the system
• TOC thinking is consistent with Lean and Six SigmaUse TOC to focus on constraintsUse Lean or Six Sigma techniques to improve and stabilize
operations
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System With an External Constraint
Market too small for your capacity – the constraint
DRUM
ROPE
Work Order Release
SHIPPING BUFFER - TIME
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The Impact of Lean Scheduling
• Lead times dropped to four weeks from sixteen weeks
• Practically eliminated overtimeSavings of about $100,000 per year
• Went to four day work weekBonus to employees for losing overtimeReduced electric bill by 15%
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The Impact of Lean Scheduling - continued
• Reduced Inventory by 30%Freed up about $100,000 of cash
• Effectively doubled plant capacityOverall plant utilization is about 50%Plenty of capacity to handle rush orders without
impacting on-time deliveriesNo increase in equipment or employees needed to
grow• Major issue is now increasing throughput
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A minimal amount of oversight day to day
• Simple reportsVISUAL Planned LoadVISUAL Resource Operations Buffer StatusPlant Wide Buffer Status - Crystal
• Simple schedulingFloor supervisors decide where to run jobsMinimal management involvement
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A minimal amount of oversight day to day - continued
• Lean Scheduling efficiently reflects our day to day operationsRapid changesRush ordersCapacity planning
• Very quick “what-if” analysis Increasing or decreasing bookings Impact of overtime, personnel levels, vacations or
absences• We do not have a scheduling person
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“Driving Business Innovation to Improve Business Performance”
• Savings From day one of the Lean Scheduling transformation
• Payback 2 ½ months for the entire investment in Lean Scheduling
• Fingertip Information Lean Scheduling gave us a rapid and efficient response tool to the
current economic crisis• Recognition
Graphicast received a 2009 PM100 award from Managing Automation Media for the Lean Scheduling project
• “Progressive Manufacturing” awards were bestowed on the 100 companies deemed to have most effectively used innovative methods to improve business performance.