Why Not Pick
The scene was the trial of a
new pass-along roller conveyor pick line in a operation that had used individual picker
carts for many years.
Conventional wisdom says that pass along picking is a good choice
(when the pick area is not too big), especially when picking bulky or heavy products. We
were working to switch over to conveyor line picking so a light directed picking system
could be installed, and the presence of a fixed order sequence was absolutely necessary.
We installed un-powered roller conveyor along both sides of an
existing powered take-away conveyor. The problems started when the pickers were assigned
to equal sized zones and cartons began to flow down the line.
The first problem was the delay while cartons gradually worked
down the conveyor to "charge" the line. Company policy required that all orders
be completed and shipped in the same day, it became apparent there would always be this
delay at the start and end of each day.
Skill differences begin to show
Soon, the pickers began to experience the pressure or boredom of
having a high or low demand pick zone. There had always been differences in skill and
resulting pick rate between the "high achiever" and "average" pickers.
When trapped in a pass-along pick line, these differences became unavoidably obvious,
bottle necks soon developed.
Trying to cope with differences
The workers tried to solve the zone variation pressures by
helping each other, or by exchanging zones between faster and slower workers. However,
each worker was expected to take his share of the "hard" and "easy"
zones. When a slow worker was in a heavy zone, the entire line eventually slowed to a
crawl. The group anxiety elevated to the point where the experiment was stopped!
This experiment has led me to reexamine "conventional
wisdom" on the efficacy of the "pass-along" roller conveyor pick method.
This would be especially true in a union work environment where workers may be assigned or
"bumped" into order picking based more on seniority than skill or desire.
The following guidelines should be helpful as
you consider pass along picking for your specific situation.
When orderliness of pass-along picking could be
- The presence of a short pick line with few pickers.
- Small orders of under 2 totes.
- The ability to set up approximately equal pick zones (workload and
- The desire to closely supervise workers for high security reasons.
- Long distances between pick and ship areas.
- Knowledge of product required in each individual zone.
Situations where cart or pallet picking should be given
- Large pick area where conveyors are impractical and expensive and
batch picking could reduce most picker walking.
- Presence of large, full case orders that should be picked directly
onto a pallet.
- Wide range of order sizes makes zone balancing difficult.
- Wide variation of pick slots.
- Bulky product that makes picking to a pallet desirable.
- Desire to hold one picker responsible for an entire order's
- Desire to ensure that orders stay together without staging.
- Wide variation in picker skill and motivational levels.
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