rl networks presentation
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Reverse LogisticsTRANSCRIPT
Reverse Logistics Networks
Steven WalkerLogistic Systems: Design and
Optimization (Chapter 6)
Introduction
Definition Reverse logistics –
Handling of the return flows of product or equipment back from consumer for reuse, recovery, or recycling.
How is it different? Reverse flow of goods back from customer May require additional facilities and
transportation costs for material handling (disassembly)
Introduction
Reasons for Reverse Logistic (RL) Networks: Environmental
Green initiatives Electronic waste Hazardous metals (RoHS)
Economic Reduced raw material costs
Customer Service Customer satisfaction
Introduction
Applications Facility Location* Inventory Management* Transportation* Production Planning
*Example problem will focus on these applications.
Recovery Programs Economic interests
Reduces raw material costs Types of Recovery:
Product – recycled directly or repaired and sent back under warranty
Component – Product is dismantled and components are used in same or similar products
Material – recyclables like metal, paper, or glass Energy - Incineration
Types of Networks
Directly Reusable Easily re-used with very little added effort. Example – pallets, bottles, or containers
Remanufacturing Returned products dismantled and parts or
components used like new Example – copy machine, aircraft engine
Types of Networks (cont’d)
Repair Service Defective products returned and repaired
Recycling Recycling of raw materials
RL Network FrameworkSuppliers
Material Recycling
ProductionDistribution Customers
CollectionIntermediate Processing
Types of Decisions
Strategic Must include reverse flow recovery path in
network Must consider costs related to forward and
reverse channels that returned material travel through
Location of plants and warehouses for recovery
Ex.- collection points and remanufacturing plants.
Types of Decisions (cont’d)
Tactical Integration of return flows with forward flows.
Combining or separating return flow goods with forward flow?
Isolating forward goods from reverse goods in warehouses to prevent shipping errors?
Designated holding areas, “QA Jail” Deciding when to use new or recycled parts? Organization of labor? When should products be repaired?
Repair, Scrap, Send back to OEM
Types of Decisions (cont’d)
Operational Production Scheduling Assignment of Labor Disassembly and reassembly
Example Problem Closed-loop logistics model for remanufacturing
Closed-loop – forward flows are closely related to reverse flows
Model involves both inventory costs, facility location, and transportation
Remanufacturing is both environmentally and economically friendly in the re-use of returned products
Cores = returned used products Source: Jayaraman, V., et.al. (1999). A closed-loop logistics
model for remanufacturing. Journal of the Operational Research Society, 50:497-508.
Example Problem (cont’d) Parameters
dik
Example Problem (cont’d) Decision variables
Example Problem (cont’d) Objective Function Minimize costs
Inventory holding Facility Location Transportation
Example Problem (cont’d) Constraints
(1) Total number of remanufactured products does not exceed the demand
(2) Total number of remanufactured products is less than the total cores of the product brought into the facility.
Example Problem (cont’d)
(3) Product storage capacity constraint
(4) Core storage capacity constraint
(5) Total number of facilities is less than P
Example Problem (cont’d)
(6) Restricts the amount of cores that can be supplied from a collection zone
(7) Non-negativity
(8) Binary (yes/no) decision variable Zj
Example Problem (cont’d) How is the problem solved?
Can be solved with LP solvers (GLPK) Commercial Solvers (CPLEX)
Because these problems can get large in a hurry, commercial solvers are necessary due to the # of variables
Interfaces with C++ Uses the simplex method much like other LP
solvers Heuristics also used due to the size of these
problems.
Questions?
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