Most distribution centres today
utilize wave-based order processing whereby many orders are simultaneously
released to pickers in a single “wave.” In theory, all of the orders will be
completed simultaneously as well. However, unexpected events routinely impact
the efficiency of wave-based processing. From personnel working at a slower
pace than anticipated, to equipment breakage and stockouts — every event has a
negative impact on the efficiency of wave-based processes.
Waveless processing is a proven means
for optimizing order selection by dynamically controlling tasks and handling
unexpected events as new current conditions of the system. Rather than
assigning work in a single wave, tasks are dynamically released to orders in
real-time. Using a revolving batch instead of a wave batch allows pickers to
work continuously, regardless of unexpected events that may slow down one
worker vs. another, and allows individuals to receive assignments at a more
even pace.
Waveless processing also allows work to
be dynamically re-assigned from one pick zone to another. If one area falls
behind another, workers from a zone that is further ahead can be dynamically
reassigned to the other area. This dynamic re-assignment allows a more even
finish to order fulfillment tasks and enhances overall labour productivity.
Your Bottom Line
Even those companies with
well-designed wave-based processes have experienced immediate benefits from
implementing waveless processing. For example:
1.
Picking
productivity increases by up to 20%
2.
Throughput
capacity increases by up to 35%
Additionally, designing a new facility
based on waveless processing substantially reduces the initial investment when
compared to a wave-based design. Examples exist to validate that facility
utilization is higher in waveless systems. The same throughput can be achieved
with smaller facilities.
The Past — Justifying
Wave-Based Processes
The advantages of batch picking have
been clear to distribution professional for many years. Picking multiple orders
simultaneously greatly reduces travel time among the pickers.
When the first batch picking systems
were implemented, they operated on paper. Pickers travelled first to a printing
location to pick up a batch of orders, then they travelled throughout their
zone to complete the batch transactions. Upon completion, they travelled back
to the printer to pick up the next batch.
As shipping sorters and unit sortation
devices were introduced to support batch picking, the approach remained the
same. A batch (now called a “wave”) was released to all the pickers
simultaneously. All pickers would work in that wave until it was completed.
Some finished much sooner than others who may have faced an unexpected event
such as a stock-out along the way. Workers completing their assignments ahead
of others were then “idle.” When all stragglers had completed the wave, it was considered
“closed” and a new wave was released.
Wave-Based Issues
Soon the shortcomings of wave-based
processing became evident. At the beginning and middle of waves, the operation
was very efficient. However, once the tail of the wave was reached, there was a
severe drop in productivity.
Complex algorithms were developed to
minimize the negative effects of wave-based transitions. Stragglers became the
bad guys in this process because pickers who completed their portion of a wave ahead
of others had to wait for the stragglers before continuing in the next wave.
Massive and expensive buffers were added to wave-based designs to reduce idle
times of pickers waiting for stragglers. Sophisticated pre-planning tools were
developed to balance work across pick zones for them to complete waves in
synch. Regardless of all these efforts, low-productivity wave transitions did
not go away.
Wave-based Picking
has its Advantages, but…
The advantages of picking orders in
batches are undeniable: Pickers spend less time walking and more time picking
when multiple orders are grouped and picked together. On the other hand,
wave-based systems self-impose the constraint that a batch must be completed
before a new batch can be started. In reality, unexpected events cause a wide
range of batch completion times, resulting in low productivity for workers who
finish early.
How Does Waveless
Processing Result in Higher Worker Productivity?
Waveless Picking Can
Optimize Your People & Assets
Waveless processing is batch picking
without the artificial self-imposed constraints of wave picking. Instead of
releasing orders in static batches that must be completed before a new one is
released, waveless processing dynamically adds individual orders to a revolving
batch. Every time that an order in the batch is completed, a new order is added
to replace the one just completed. In real-time, the waveless system adds the
picking transactions for the new order to the existing picking transactions of all
the required pickers.
There is no lost productivity from
wave transitions while waiting for the stragglers. Work flow is evenly paced
through dynamic assignment, allowing and planning for the variations in task
completion time. Further, workers can be re-assigned to zones that fall behind,
allowing a more even completion time between zones. Thus, the high efficiency
achieved in the middle of a traditional “wave” is maintained continuously in
waveless processing.
Picking productivity is higher with
waveless processing for two primary reasons:
1.
Waveless
processing eliminates work starvation periods for the pickers created by wave transitions
— pickers are not working faster, they are working consistently
2.
Waveless
processing reduces pickers’ walking
In wave-based systems, pickers go
around their entire picking loop in every wave. Their loops have a start point
and an end point. In waveless processing, an order starts as soon as the
previous order for the same destination finishes. In a direct-to-consumer
operation based on a unit sorter, if the order profile has an average of 3
lines per order, orders would expect to complete in three quarters of the loop.
In picking walking, this translates to 25% less walking. Adding further
intelligence to dynamic task assignment based on current picker location can
reduce walking time even further.
What Benefits Can I
Expect by Implementing Waveless Processing?
1- Higher Throughput Capacity
Reclaim the wasted capacity between
waves by eliminating the low-productivity wave transition periods. Actual
applications that have switched from wave-based processing to waveless
processing have seen throughput capacity increases of up to 35%.
2 - Lower Initial Investment in New
Projects
Distribution centres designed for
waveless operation require less initial investment than
those designed to operate with waves
for 3 primary reasons:
·
Without
the low-productivity wave transitions, facility utilization is higher in
waveless systems. The same actual throughput can be achieved with smaller
facilities.
·
With
waveless processing the need for buffers required by wave-based processes is eliminated
or greatly reduced.
·
In
unit sortation-based designs working with waves, most orders seize chutes at
the beginning of a wave, while most orders do not complete until the tail of
the wave. The requirement of chutes for incomplete orders is not leveled
through the wave, resulting in a large requirement peak mid-wave. Waveless
processing levels the requirements for chutes holding incomplete orders,
allowing equivalent waveless designs with much fewer chutes than wave-based
designs.
3 - Lesser Straggler Impact
In wave-based processes stragglers
affect entire waves, creating low productivity periods at wave tails and
potentially bringing operations to a full stop. In waveless processes, stragglers
affect only the order they belong to and all other destinations can continue working
without any delay.
4 - Better Handling of Last Minute
Orders
In wave-based processes, emergency
orders are often held to be assigned to a forthcoming wave where they will have
a minimal impact on productivity. With waveless processing, the emergency order
can be the next released order (as the highest priority order to process)
without any impact on the productivity of the operation.
5 - Enhanced Customer Service through
Better Shipping Deadline Management
The real-time nature of waveless
processing allows the distribution centre to better manage shipping deadlines.
If a retail distribution centre is currently processing 50 stores and realizes
that the next 30 stores to complete are at risk of missing their deadline, management
can place a hold on the other stores to speed up the processing of the at risk stores.
This hold can be cancelled when the situation is rectified. This is an option
that wave-based systems do not offer. In a wave-based system, once a wave
starts, that wave must complete before the next can begin.
Where Do I Start to
Create a Waveless Processing Program?
The principles of waveless processing
are easy to understand and the risks of implementing waveless processing are
low. Its implementation, on the other hand, is not trivial. Issues like labour balancing
pick zone synchronization, real-time replenishment, and label requirements need
to be fully analysed and resolved during the design phase. Fortunately,
technologies are now available to address these issues.
Additional investment in equipment is
minimal in most cases, if any. The bulk of the change revolves around software
systems. Highly configurable Warehouse Control System (WCS) or Warehouse
Management Systems (WMS) tools that are compatible with most existing software
packages make the transition easier.
Switching to real-time waveless
processing requires software and process change. A proven path for a smooth and
risk-minimized implementation utilizes WCS / WMS modules that can progressively
add the required features in several steps.
In Conclusion…
Waveless processing offers multiple
financial and operational advantages over traditional wave-based systems. It is
a proven means for optimizing order selection by dynamically controlling tasks
and anticipating unexpected events. Pickers work at a more even pace, and the
system is able to manage and resolve unexpected events in real-time. Tools and
expertise exist today to analyse and create an effective waveless system for
you. Waveless processing will positively impact your bottom line by providing
higher throughput, increased overall labour optimization, and enhanced customer
service.
Contributed by Dewald Geldenhuys, Manager Operations Design, Fortna EMEA (Pty) Ltd
