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EST 200, Identifying Constraints
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- 2. 2 Contents • Introduction. • Theoryof Constaints. • Features of Constraints. • Constraints vs Objectives. • Combined Objectives - Constraints Tree. • Examples.
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- 5. 5 Theory of Constraints •An overall management philosophy introduced by Eliyahu M. Goldratt in his 1984 book titled The Goal. • Goldratt adapted the concept to project management with his book Critical Chain, published in 1997. • “The rate of goal achievement by a goal oriented system (i.e., the system's throughput) is limited by at least one constraint.”
- 6. 6 Theory of Constraints •“If there was nothing preventing a system from achieving higher throughput (i.e., more goal units in a unit of time), its throughput would be infinite – which is impossible in a real-life system”. • Organizations can be measured and controlled by variations on three measures : throughput, operational expense, and inventory.
- 7. 7 Constraints and Goals •Only by increasing flow through the constraint can overall throughput be increased. • Identify the system's constraint(s). • Decide how to exploit the system's constraint(s). • Subordinate everything else to exploitation decision(s). • Alleviate the system's constraint(s). • If in the previous steps a constraint has been broken, go back, but do not allow inertia to cause a system's constraint.
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- 9. 9 Misidentifying a Constraint Youthought the real constraint is upstream!
- 10. 10 Dealing with Constraints -Adding Capacity Upstream
- 11. 11 Misidentifying a Constraint Youthought the real constraint is downstream!
- 12. 12 Dealing with Constraints -Adding Downstream Capacity
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- 14. 14 Design Constraints • Alimit or restriction on the design’s behaviors or attributes. • Identifying limits that cannot be exceeded and boundaries that may not be crossed. • Are there things or circumstances you want us to avoid? • Framed as a binary yes-or-no choice. • Limit the size of a design space. • Exclusion of unacceptable alternatives.
- 15. 15 Safe Ladder Constraints Constraintsas a kind of “checklist”. Keep our list of possible designs to a reasonable length. May be expressed in terms of specific numerical values.
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- 17. 17 Constraints vs Objectives ConstraintsObjectives Limit the size of the design space. Permit to explore what remains in that design space Enable us to reject unacceptable alternatives. Enable us to select among design alternatives that are at least acceptable Designs that satisfy are accepted. Designs that satisfice may not be optimal or the best.
- 18. 18 Constraints vs Objectives •Design an affordable toy vehicle using biodegradable material alone. Objective : To design a toy vehicle, should be affordable. Constraint : Use of biodegradable material. Cost can become a constraint (say below Rs. 25/-). • Objectives are desirable attributes. • Constraints are required attributes.
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- 20. 20 Combined Objectives and ConstraintsTree - Juice Container Constraints in Italics Boxes differently shaped
- 21. 21 Combined Objectives and ConstraintsTree • Combined Tree communicates how objectives and constraints interact. • Constraints are related to but are different from objectives. • Constraints help us prune or narrow our space of designs. • Constraints help us do our screening and evaluation of designs.
- 22. 22 Constraints • Design ofa widely used product to be done in a more constrained design space than client- or user-specific devices. • Constraints lists prepared by different teams may differ rather markedly. • Different teams may identify different limiting values for the same constraint. • Constraints may sound binary or fuzzier. • There may be differences in granularity.
- 23. 23 List of Constraintsfor an Arm Support – Team A MORE GRANULAR
- 24. 24 List of Constraintsfor an Arm Support – Team B Compact
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- 26. 26 Reference • Clive LDim, Patrick Little and Elizabeth J Orwin, “Engineering Design, A Project Based Introduction”, 4th Edition, Wiley, U.S.A, 2014. • https://medium.com/praxis-blog/theory-of- constraints-106-the-five-focusing-steps- 741f1b770bf1
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