Warehouse Zoning

1
Warehouse Zoning Bucket Brigades

• (Chpt. 9 in Bartholdi Hackman
• also see
• http//www.isye.gatech.edu/jjb/bucket-brigades.ht
  ml)

2
The two main concepts of zoning in contemporary
warehousing

• Warehouse zoning The physical and/or logical
  segmentation of the warehouse / picking area,
  through
• the employment of different storage modes and
  practices due to the product differentiation
  w.r.t.
• dimensions,
• physical characteristics
• storage and material handling requirements
• throughput,
• etc.
• the parallelization of the order-picking
  activity.

3
Zone-based order picking
Progressive Zoning / Order assembly
Parallel/Simultaneous Zoning (typically organized
in pick-waves with downstream sortation)
To sorting and consolidation
Z1
Z2
Z3
Z4
Z5
Order (Batch)
4
The problem and the problems of establishing
effective logical zones in Warehouse operations

• The problem Try to achieve maximum utilization
  of the picking resources, by distributing
  equally the total (picking) workload among the
  defined zones.
• The problems
• The warehouse picking environment usually is a
  very dynamic environment workload profiles are
  constantly changing.
• Existing zoning systems seek to balance the
  average workloads across zones, based on some
  hypothetical order work-content and worker
  behavioral models.
• Furthermore, constant zone redefinition requires
  a lot of effort from, both, the warehouse
  management (who must keep track of all the
  workload changes and re-establish the zones) and
  the warehouse pickers (who must adjust to the new
  policies).
• The results Very limited scientific literature.

5
Bucket Brigades( c.f. Bartholdi Hackman, Chpt.
10)

• A dynamic self-balancing scheme for progressive
  zoning.
• The three main requirements of bucket brigades
• Carry work forward, from station to station,
  until someone takes over your work.
• If a worker catches up to his successor, he
  remains idle until the station is available
  (i.e., no overpassing is allowed)
• Workers are sequenced from slowest to fastest.

6
The self-balancing property of bucket brigades

• Theorem Letting v_i denote the working rate of
  the i-th worker,
• the line operation under the three main
  requirements of bucket
• brigades, converges to a balanced partition of
  the effort, wherein
• the fraction of work performed by the i-th
  worker is equal to
• v_i / ?_j1n v_j
• and the line production rate is equal to
• ?_j1n v_j
• items per unit time.