material handling systems to boost productivity
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8/6/2019 Material Handling Systems to Boost Productivity
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Working Smarter with What You Have
In today’s credit-strapped economy, squeezing greater perormance out o existing
inrastructure and equipment is a key DC management strategy. By optimizing the
eciency and utility o buildings, equipment and systems that have already been paid
or, companies can realize bottom line-enhancing productivity gains without major
capital expenditures.
Repurposing existing technology can also enable eciency gains and increases in
capacity that allow older DCs to accommodate SKU growth, increases in store count,
or adapt to changes in the order prole without major expansions or greeneld
construction. Eciency improvements also make companies more nimble, giving them
the fexibility they need to more rapidly adapt to ongoing market and business changes.
Handling more throughput with existing “maxed out” systems
The traditional response to dealing with the demands o growth has been to apply
additional labor. Although this tactic can provide immediate incremental increases in
a DC’s capacity, there is a limit to how eective it can be in the long term. Eventually,
other constraints such as insucient sorter speed, or too ew pick aces or loading doors,
will make additional increases to the labor orce an inadequate solution. At this point,
the traditional “Plan B” was typically to purchase additional equipment, ex¬pand square
ootage, or both.
However, the current state o the global economy is causing the usual paradigm to
change. Today, when labor increases are no longer the answer, and large capitalexpenditures are out o the question, it is time to examine the DC’s operation and
identiy opportunities or reconguring material handling systems, adopting new
sotware and/or altering processes to increase eciency and overall productivity.
Productivity = Efciency x Utilization
Productivity is a unction o both eciency and utilization. For example, the most
ecient way to get product rom one side o the DC to the other is to cross-dock. The
process o unloading goods at receiving and moving them across the building, directly
onto another trailer is 100 percent ecient. But eciency is only one part o the
productivity equation. Even though it is the most ecient process you can perorm,
i you can cross-dock or only ve percent o the time, it is actually only ve percent
productive (100% eciency x 5% utilization = 5% productivity).
The goal o 100 percent productivity via cross-docking can be achieved only in a true
“store per door” environment, in which there is a 1:1 ratio o stores serviced by the DC to
actual ‘live’ shipping doors with constant availability (100% eciency x 100% utilization
= 100% productivity). In the real world, ew companies have the resources required to
ully implement such a system, but utilizing the principles o cross-docking in all other
operations will increase productivity. It is important to note that these principles can be
applied or order ulllment, manuacturing and shipping to achieve higher productivity
and lower costs. While 100 percent productivity remains the goal, the rst step toward
this ideal practice is a hybrid solution known as the two-stage cross-dock.
Boost productivity o existing distribution systems with our
cost-eective solutionsBy John Naylor, Intelligrated
Whether your goal is
to stay out in ront o
business growth or to
scale back operational
costs to conserve capital
in a shrinking economy,
the good news or
DCs is that eciency,
productivity and capacitycan oten be increased
without a signicant
investment in additional
labor, foor space or
equipment.
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Solution #1: Two-Stage Cross-Dock to Cut Picking Labor in HalOutbound positions staged in waves reduce labor, rolling stock and space requirements
It is possible to markedly boost a DC’s order ulllment productivity by implementing
a two-stage cross-dock process that capitalizes on the eciency o the cross-dock,signicantly increasing utilization without large capital expense. The two-stage cross-
dock leverages existing assets to increase order ulllment eciency. When allocated
products, those that are already part o an existing order to be lled, arrive without
a corresponding outbound trailer waiting at a shipping door, additional outbound
positions are necessary. These are created by combining products into waves as they
are received. Waves are then staged in a buer consisting o a foor position, a pallet
position, AS/RS, or a trailer. When a shipping door becomes available, the waves that
comprise the order are pulled rom the staging area and loaded onto the appropriate
outbound trailer. This process can also be used or other operations; or example,
allocated ull cases destined or a split case order ulllment system can be staged by
wave and introduced into the tilt-tray, cross-belt or put-to-light system when the wave
becomes active. This eectively eliminates the putaway and discrete picking o cartons
by wave.
The two-stage cross-dock can reduce re-picking labor by more than 50 percent.
Although more labor intensive than a single-stage cross-dock, it is an attainable solution
that requires ewer shipping doors and uses signicantly less labor than the typical
material handling process (see Figure 1). The two-stage cross-dock example illustrated
in Figure 1 reduces rolling stock requirements by eight units and associated battery
requirements, and saves 127,000 additional square eet o foor space by eliminating the
need or a pick conveyor, a pick module and associated racking.
Figure 1 - Process and Rates Comparison
Current Process and Rates (3,280 per hour)
Projected Process and Rates (3,280 per hour)
ReceivingHand Palletizing
400 cph17 People
Storage36 Pal/HR6 People
Mod Replenishment36 Pal/HR6 People
Wave Sort/Load
600 chp11 People
Trailer Pull2 Person
Module Pick400 chp
17 People
Direct Unloads
800 cph8 People
Direct Unload900 cph8 People
Shipping
Receiving
Shipping
“...i you can cross-dock
or only ve percent o
the time, it is actually
only ve percent
productive.”
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Solution #2: Minimizing Product Gap to Increase Sorter ThroughputDecreased product spacing yields 40 percent increase
For many DCs, sorter throughput is a pinch point that negatively aects order
ulllment eciency. While modern sliding shoe sorters have reached the 600-650 t / min milestone in recent years, many existing sorter systems are limited to speeds equal
to or in some case signicantly less than this benchmark. The physics o the divert angle
limit these existing systems, making it impossible to speed up the sorter without a major
rebuild o the shipping system. Fortunately, speed is not the only parameter aecting
sorter throughput. By simply reducing the gap between cartons rom the traditional
12 inch average to our inches, sorter throughput can be increased by up to 40 percent.
Intelligent sotware, available rom suppliers o material handling systems, puts these
throughput increases within reach o DC operators without the need to invest in
additional capital equipment. In many cases, a 40 percent increase in throughput can
eliminate an entire shit o operations.
Solution #3: Balancing Merging or Maximum EfciencyReal-time balancing o induction lines by the merge can reduce gaps and eliminate fow
stops — producing a higher system yield.
Most distribution centers that operate within a ‘wave’ environment or have a strict
cuto time in a “store per door” setup suer rom a lack o balance in the operation.
It is natural or resources in various areas o picking, rom modules to cross-dock and
pallet strip lines, to operate at dierent rates rom each other and also vary individually
throughout the day. A contributing actor to imbalance is simple math in terms o the
workload. As a result o slotting, a pick module may be tasked with 50 percent more
case volume or a given wave than all other modules.
A typical induction system does not take into consideration the real-time wave
progression o the in-eed lines. Instead, it simply releases lines based on a simple set o
algorithms – round robin, “rst come rst served,” etc. The eect o this is elt towardthe end o the wave/batch. As areas are completed and the wave totes arrive at the
merge, the line is disabled until all lanes have successully completed. To provide some
temporary relie, some systems are equipped with wave overlap lanes; this does not
directly combat the issue, however. When the quantity o active lanes cannot sustain
the maximum capacity (100 percent eciency) o the sorter, it becomes a major drain
on productivity. The longer the system operates (utilization) in this state, the lower the
overall yield (productivity).
As an example: A sorter and an 8:1 merge have a total capacity o 200 cartons per
minute (cpm). Each induction line is capable o releasing 50 cpm and our lines are
needed to sustain 200 cpm. Due to imbalance, the last our lanes nish at varying times.
During the time that lanes 1 through 4 are completing, there are our lanes let and
the sorter is running at 100 percent eciency. Anything less is a major loss o systemeciency as shown below. As the duration increases, productivity is lost. With three
lanes x 50 cpm = 150 cpm (75% ecient) With two lanes x 50 cpm = 100 cpm (50%
ecient) With one lane x 50 cpm = 50 cpm (25% ecient) It is typical or a traditional
batching system to yield about 75 percent o mechanical capacity.
Traditional combiners, which “zipper” cartons at the merge point, produce relatively
larger gaps between product and are typically limited to a maximum o our incoming
lines. They are also more susceptible to productivity loss because o a lack o balanced
workloads.
“Due to slotting, a pickmodule may be tasked
with 50 percent more
case volume or a given
wave than all other
modules”
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Wedge merges are becoming an increasingly popular alternative to combiners as a result
o their ability to help maximize sorter utilization. With better batch fow control and up
to or over 16:1 merge capability, wedge merges oer more fexibility and less exposure
to productivity loss. Sotware and intelligent systems controls are available to enhance
these merge/induction setups and can make an existing DC more productive. By setting
the merge release logic priorities based on the orecasted volumes or each induction
line (case ootage in lieu o carton count is more precise), the system can better marshal
the workload through the system. To maintain better balance, unbalanced lines are
released based on percentage and real-time status and updates. Figure 2 illustrates the
dierent release times associated with an unbalanced ve-line merge o a 10,000 carton
wave.
Figure 2 - Wedge: Workload Balancing
Real-time progress should be measured through the merge while making “on the fy”
adjustments based on current wave status. Typically, there are higher-velocity picking
areas in a system: cross-dock vs. module. Although these areas have the same quantity
o cartons assigned or a wave, one may nish in hal o the time even with the same
quantity o resources applied due to the nature o the pick operation. It is not unusual
to see a higher-velocity pick area have more volume because o slotting o higher SKU
velocity movers. As they progress at dierent rates, each would require dierent merge
release priorities at dierent times in the wave. Converting or enabling the merge and
system controls and sotware to monitor progress allows or precisely balanced picking,providing much higher system yield (productivity).
Solution #4: Oset Wave Plan to Balance Loads and OptimizeStafng LevelsPredictability ensures that loads are completed within minutes o each other
The stop/load model, a traditional retail door plan in which order waves are assembled
at a series o stops throughout the acility, allows DCs to load more store orders through
a limited number o doors. This method is highly sensitive to imbalance — a slowdown
Lane 1 - 20% of Release Time
Lane 2 - 10% of Release Time
Lane 3 - 20% of Release Time
Lane 4 - 20% of Release Time
Lane 5 - 30% of Release Time
Lane 1 - 2,000 Cartons Lane 4 - 2,000 Cartons
Lane 2 - 1,000 Cartons Lane 5 - 3,000 Cartons
Lane 3 - 2,000 Cartons
10,000 Carton Wave
Unbalanced Lines
Released by Percentage
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at a single pick module or shipping trailer can disrupt the entire fow and severely
reduce overall productivity by delaying wave completion. These unpredictable variances
in wave times and volumes inherent in the stop/load plan create gaps between waves
that reduce eciency. By shiting the wave paradigm slightly, an oset wave plan (seeFigure 3) improves upon the stop/load model by eliminating its unpredictability. The
oset wave plan not only increases the number o active doors compared to a standard
(odd – even) stop/load dock plan, but also removes the randomness that makes it
impossible to predict how many doors will be pulled. In a 44-door example, 40 doors are
active, o which our are being pulled at any one time. This model’s predictability makes
it easier to deploy optimum stang levels and provides better control over minimum/
maximum load per door per wave.
Figure 3 - Oset Wave Plan
Each section o every trailer gets an almost equal amount o product at the same time.
Although the oset wave plan may add a ew more waves to the day compared to the
stop/load model, balancing loads ensures that all loads are completed within just a ew
minutes o one another.
This wave plan eectively balances the entire shipping operation. The workload is
distributed across all doors and personnel evenly, allowing or predictable stang
levels and movement o resources. This helps to eliminate the scenario where shipping is
waiting or a small number o doors to be completed so that the merge can release the
next wave. This also ensures that the amount o doors active in a wave are great enough
to prevent overfow o product to re-circulation — imagine 200 cartons per minute
being distributed to our doors as a result o wave planning — and shutting down the
merge. See Solution 3 or examples illustrating the eect o merge ineciency. In either
event, the utilization o the system greatly suers. The oset wave plan ensures that the
merge and sorter are producing higher throughput or a greater percentage o the time.
Conclusion
By taking advantage o a good warehouse control system, good processes and your
existing space and equipment, you can increase productivity without great expense
while scaling back your operations to meet your changing needs. System integrators,
sotware providers or material handling equipment suppliers can help discuss which
options make the most sense or your operation.
For more inormation, contact Intelligrated by e-mail at [email protected] or by
phone at 866.936.7300, or visit www.Intelligrated.com.
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