Batch
picking is a process where multiple orders are filled simultaneously,
and it is used
to
reduce transit time. With a “man to goods” system where
an order selector travels to
the
product to fill orders, batch picking can drastically reduce the
travel time. In a
“goods
to man” system where product is delivered to the selector,
batch picking can
reduce
delivery traffic.
This
paper addresses batch picking in a “man to goods” system.
With modern
technology,
the transition to a batch pick system can be very inexpensive and un-
complex
both in implementation and operation. This paper provides the basis
for
determining
the benefit of transitioning a “pick ticket” based order
fulfillment system into
a batch
picking system.
remonter
To
analyze the benefits of a proposed transition to a batch fulfillment
system, the order
fulfillment
process is divided into three time categories.
Pick
Time – (PT) the time to retrieve an item from its storage
location and place
the
item in the “order” container.
Transit
Time – (TT) the time to travel to an item
Setup
and Close Time – (CT) the time to prepare or setup the “order
container”
prior
to putting any items into it and the time to complete the order
container once
the
required items have been collected.
To
analyze the potential benefits of a system, the values for each of
the above items
must be
known. Obtaining these numbers is a very easy process; do not believe
those
that
would tell you that it is complex. Just follow the following five steps:
remonter
1.
Obtain the normal or average overall picking productivity for a
worker Base
Fulfillment
Rate (BFR) in units per hour. For an existing system, this is easily
obtained
by dividing the total number of units picked, packed and shipped over
some
period of time by the number of workers that preformed that work.
Normalize
the value into the number of units per hour. Insure that the time
used
does
not include “non-productive time”. The result is an
average BFR units per
hour
that a worker can pick, pack and make ready for shipping. . If there
are no
existing
metrics, this number will need to be estimated. There are many
existing
installations
that should be similar enough to get an estimate. Additionally, if
necessary,
there are several simple techniques to refine such estimates.
2.
Obtain the average units per order container (i.e. carton) (UC) by
either reported
metrics
or estimation.
remonter
3.
Obtain the order container (carton) Setup and Close Time (CT) in
seconds
through
direct measurement. This time does NOT include any pick time or
travel
time.
It only includes preparation time prior to picking and completion
time
following
picking. This measurement is always done through observation with a
stop watch. If there is no existing system to measure, set up and measure
the
remonter
time of
a simulated operation with real goods, cartons, simulated labels, tapers,
staplers,
etc. Take many measurements and calculate an average.
4.
Determine the Pick Time (PT) in seconds also through direct
measurement using
a stopwatch. The pick time should not include any walk time but should
include
any
required location or SKU verification, the picking of the product and
the
placement
or packing in the order container. Make many measurements and
take an average.
remonter
5. Once
the above values are obtained the average Transit Time (TT) in
seconds is
calculated.
This calculation yields a TRUE representation of the REAL
AVERAGE
TRAVEL TIME, for there are no other “productive time”
operations
that
the worker may be doing other than prepare, travel, pick, pack and
close.
The
formula is:
TT = (3600/BFR) – ( PT +
(CT / UC))
For a
system that has a base fulfillment rate (BFR) of 120 units per hour,
10 units per
carton (UC), a pick time of 6 seconds and a carton setup and close time of
60 seconds,
the
transit time is:
TT =
(3600/120) – ( 6 + (60/10))
TT =
(30) – (6 + 6)
TT = 18
seconds
remonter
To
batch-pick with a pick cart is one of the most popular ways of
reducing transit time
per
transaction. Picking several orders at the same time will reduce the
transit time by
nearly
the number of orders picked simultaneously – the size of the
batch (SB). There is
a small
increase in handling time of each item due to the need to select
which order
container
to put the item into – the selection time (ST). There are means
to nearly
eliminate
the additional selection time (ST) through lights and automatic
pushers. ST is
almost
never greater than 2 seconds and in many cases can be less than .5
seconds.
The
calculated transit time for the new batch fulfillment system (TTN) is
based on the
calculation
of transit time (TT) for filling single orders (see above). The
formula for
calculation
is:
TTN =
(TT / SB) + ST
remonter
Converting
from a paper based single order fulfillment system as described above
to a
batch
picking system with carts holding nine orders (SB) would yield a
travel time of
TTN =
(TT / SB) + ST
TTN =
(18 / 9 ) + 2
TTN = 4
; or a travel time reduction of TT – TTN = 18 – 4 = 14
seconds
The
fulfillment rate of the new batch system (NFR) is calculated as follows:
NFR =
3600 / ( TTN + PT + ( CT / UC ) )
NRF =
3600 / ( 4 + 6 + ( 60 / 10 ) )
NFR =
3600 / 16
NFR =
225
The
single order fulfillment rate (FR) in the example above was 120. With
the new
fulfillment
rate of 225, the productivity increase is a whopping 187% (225 / 120)
remonter
Why
batch pick?
Because
you are not running a gym!
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2002-2003 ADS Specialists, Inc.
www.ads-specialists.com
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