Summarizing our current results
with respect to the warehouse
design and control problem
Based on:
Yoon, C. S. and Sharp, G., “A structured procedure for
analysis and design of order pick systems”, IIE Trans.,
Vol. 28, pgs 379-389, 1996
The warehouse processes and the
underlying material flow
Replenishment
Case
Picking
Reserve Storage
and
Pallet Picking
Replenishment
Broken
Case
Picking
Accumulation, Sortation & Packing
Direct
putaway
to reserve
Direct
putaway
to primary
Receiving
Shipping
Cross-docking
…or in Yoon and Sharp’s representation...
RECEIVING
pallets
PALLET RESERVE
Breakdown
function
pallets
pallets
(items
cases)
pallets
(items
totes)
cases
cases
overpacks
mul
pallets
CASE PICK
cases
cases
cases
ITEM PICK
totes
(cases)
items
(items
cases)
totes
SORTING A
totes
totes
SORTING B
totes
cases
overpacks
UNITIZING
totes
mul
cases
pallets
overpacks
SHIPPING
(items
cases)
totes
Consolidation
Function
Defining Department and Subsystem
structure
Department B
Department A
Subsystem A1
Transport Equipment 1
Subsystem B1
Subsystem A2
Transport Equipment 2
Subsystem B2
Subsystem An
Transport Equipment k
Subsystem Bn
Storage structure (e.g., Gravity Flow Rack)
Transport
Equipment
(e.g., forklift)
Transfer
Device
Storage
Equipment
Retrieval
Equipment
(e.g., pick to
light)
Transfer
Device
Transport
Equipment
(e.g., Belt
Conveyor)
Yoon & Sharp’s design procedure
MANAGERIAL CONSIDERATIONS
PRODUCT DATA
DATA ANALYSIS
ORDER DATA
DATA ANALYSIS
INPUT
STAGE
SPECIFICATION OF ORDER
PICK SYSTEM STRUCTURE
SPECIFICATION
OF EQUIPMENT
SPECIFICATION
OP. STRATEGIES
MATERIAL
FLOW
SUBSYSTEM
I
SELECTION
STAGE
INFORMATION
FLOW
SUBSYSTEM
II
SUBSYSTEM
N
SUBSYSTEM RECONCILIATION
EVALUATION & SELECTION
OVERALL PERFORMANCE ANALYSIS
EVALUATION
STAGE
Determining the
basic system structure
Product data:
•Activity level
•requested quantities
•product properties
•vendor types
Order data:
•number of line items
•number of items
•cubic volume
•shipping priorities
•product correlation
Managerial requirements /
company strategy
• Definition of major functional
areas / departments
• Definition of departmental subsystems
• Storage and material handling
modes
• Operational policies
• storage policies
• replenishment policies
• order picking policies
• batching
• sorting
• zoning
• routing
• receiving & shipping
policies
Topics Covered
• Equipment types, features and efficiencies
• Warehouse Activity Profiling: Product and Order data
analysis
• Configuration of (departmental) storage:
– space allocation
– storage sizing
– storage mode selection (pallet rack vs. floor storage) and
configuration
• Optimal sizing and space allocation of the case-pick and
item-pick areas; determination of the associated
replenishment lots
Topics to be addressed next
• Warehouse Layout: Spatial Arrangement of the Warehouse
departments
• Order picking policies:
– Routing / sequencing
– Batching
– Zoning
• (Sub-system) Performance Evaluation
• Cross-docking
Determining the overall
Warehouse Layout
Based on:
• E. Frazelle, “World-Class Warehousing”, Logistics
Resources International, Inc., 1996
• Francis, McGinnis and White, Chpt. 2 and 3
Most Typical Warehouse Layouts
(according to Frazelle)
• U-shaped
• Straight-thru
• Modular
U-shaped Layout
Replenishment
Case
Picking
Reserve Storage
and
Pallet Picking
Replenishment
Broken
Case
Picking
Accumulation, Sortation & Packing
Direct
putaway
to reserve
Direct
putaway
to primary
Receiving
Shipping
Cross-docking
Some key advantages of
the U-shaped layout
• Excellent utilization of dock resources since the receiving
and shipping processes can share dock doors.
• Facilitates cross-docking since the receiving and shipping
docks are adjacent to each other and may be co-mingled.
• Excellent lift-truck utilization since
– put-away and retrieval trips are easily combined
– storage locations closest to shipping and receiving docks are
natural locations to house fast-moving items.
=> U-shaped layout/flow is the benchmark upon which all
other layouts/flows should be compared.
Straight-thru Layout
(Primarily for cross-docking facilities)
SHIPPING
SHIPMENT STAGING
SORTING AND
ASSEMBLY
AREA
TEMPORARY
HOLDING
AREA
RECEIVING CHECK-IN
RECEIVING
Modular Layout
• Appropriate for large-scale operations in which the
individual processes are so large that they merit standalone and uniquely designed buildings
• E.g.,
– a rack-supported building for unit-load AS/RS;
– an air-conditioned low-bay building for customizing operations
such as monogramming, pricing and marking;
– a low-bay shipping building equipped with high-speed sortation
equipment.
Systematic Layout Planning (SLP)
(R. Muther, 1961)
Input Data and Activities
Material
Flow
Activity
Relationships
Analysis
Relationship
Diagram
Space
Requirements
Modifying
Considerations
Space
Relationship
Diagram
Develop
Layout
Alternatives
Evaluation
Space
Availability
Practical
Limitations
Search
Selection
Computerized Layout Generation
• Input: Activities, Space Requirements, Material Flows,
Adjacency Requirements
• Output: A “block” layout
• Procedures:
– Construction Algorithms: Iteratively, add one more activity to a partial
layout until all activities have been placed.
– Improvement Algorithms: Starting with a “block” layout, try to
improve it, by going through a series of location exchanges for
facility pairs or triplets.
– Scoring model: An evaluation mechanism that assesses the efficiency
of each block layout or insertion step, in the case of construction
algorithms, based on the resulting material handling effort or the
extent to which the layout satisfies the adjacency requirements
expressed in the REL chart.
• Example Software: CRAFT, CORELAP, ALDEP, SPIRAL,
(AUTOCAD)