The company
BAX has contracted with a major cosmetics company to
distribute its product. The customers to which this particular DC
ships are hair-care and beauty salons in the southeast US. (BAX
runs additional DC's for this customer elsewhere in the US.)
Orders are generated by the cosmetics company's salespeople.
Many submit orders electronically as soon as they have visited a
customer. Others may accumulate orders and send them once or
twice a day. All orders received by 3PM each weekday will ship
that evening via UPS, either overnight or 2-day service, as
requested by the customer. But all orders are handled identically
within the DC.
There is little month-to-month seasonality but pronounced
day-to-day seasonality. Wednesday is the busiest, Friday the
least busy; but there is a lot of variance and this is
problematic.
BAX is paid based on the numbers of lines it picks and so
wants to match workforce to workload; but variance in workload
makes it hard to do this. BAX employs temporary workers and can
call them in or can send them home; but, if called in, they must
get at least 4 hours work.
BAX runs two shifts, 7AM-1PM and 1PM-6PM. The second shift
picks orders that arrive after 3PM to get a start on next day's
work. The second shift leaves work-in-process on the line so that
next day's first shift can resume work immediately, without
having to prime the assembly line.
Picking
Picking is from flow-rack instrumented with a pick-to-light
system. After an order picker scans a shipping carton, the
warehouse management system lights up the locations of skus to be
picked into that carton and displays the number of items to be
picked.
The overall flow of material is up one side of the first
aisle, back down the other side, and then the same through the
second aisle.
The current organization of order-picking is not very
flexible: There are 8 fixed zones of 5 bays each, so it is not
possible to use more than 8 order-pickers, even during surges in
demand. If fewer than 8 are used, some worker must pick from a
double-sized zone and therefore has twice the workload and
produces at half the rate. Therefore management can set the
throughput rate at only two speeds: regular (8 workers) and
half-speed (between 4 and 7 workers).
During a recent visit 4 of 8 pickers were temps. One worker
thought that the best pickers were 1.5 times as productive as the
slowest. But this differential is not reflected in the pick rate
data, which seems to show everyone working at about the same
rate. The similar pick rates may be an artifact of restricting
workers to zones: Each zone has about the same total work and so
all workers will tend to perform alike. This means the zones
prevent the best workers from performing up to their
capabilities.
Currently, all the boxes of an order have to be kept together,
but for reasons that do not seem compelling: convenience of the
shipping station, which would otherwise have multiple mouse
clicks to print appropriate shipping labels. Orders that do not
require picks from zones 1-4 or 5-8 can be pushed to the other
side of the conveyor and so jump ahead; but this might not be
physically possible because of the glut of work-in-process
filling all available conveyor space through the first four
zones.
Restocking
The 8 pickers are supported by a single restocker, who seems
constantly busy. Apparently there is no off-line restocking. Skus
are restocked one at a time when the restocker gets a signal on
his RF gun to instructing him to fetch a specified number of
cartons from a specified location.
The restocker simply loads the cartons into the back of the
flow rack. He does not “prep” cartons (cut the boxes
open to make it easier to withdraw the items). There are about
7,000 lines picked each day and 3-4 eaches per line and so nearly
30,000 grabs. Many of these grabs are impeded by boxes that have
not been prepped and this may slow the pickers.
Currently, each picker has a box cutter and preps their own
cartons as they see fit. If the restocker could cut the boxes
then the workers could pick more easily. But there are some
advantages in asking the pickers to prep their own cartons as
needed. First, it makes it easier to pick full cartons. Also,
because less work is required to restock, fewer restockers are
needed and this reduces congestion in the restocking aisle.
Building shipping cartons for new orders
As orders are received, boxes are built and labeled for them
and then put on the conveyor. |
Cartons flow down one side, back the other
Boxes flow down one side and return along the other side,
keeping their position in the stream. |
The conveyor is kept full
The conveyor is kept full. |
Pickers scan the box
A picker scans the next box to enter her zone, which lights
up required picks in her zone. |
Pick-to-light
Lights indicate where and how much to pick. |
Work in process
Inner packs protect fragile items during shipping. |
A typical box requires few picks
Many of the boxes on the conveyor are empty because they do
not require picks until they reach the later zones. But all
the boxes of an order are kept together. |
One person restocks the flow rack
A restocker loads cartons into the back of the flow
rack. |
The restocker brings a sku
The restocker fetches cartons of a single sku on each
trip. |
Forward pick area and reserve
Each sku has an active pick area in the flow rack that is
restocked from bulk storage, visible in the background. |
A fast-moving sku is picked from a pallet
This fast-moving sku is picked from a pallet at the top of
the conveyor. |
Filled orders flow to shipping.
Boxes heading toward check/pack/ship stations |
Check-pack-ship
Checking, packing, shipping stations. A certain percentage of
the boxes are audited for accuracy. |
Completed orders
Boxes are stacked on pallets, which will be
shrink-wrapped. |
Loading the trailer
Loading a “drop trailer”, which will be retrieved
by UPS at a scheduled time and replaced by another, empty
trailer. |