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Knowing the amount of time it takes to pick an order is essential when designing a warehouse or Distribution Center (DC). When operating a warehouse or DC, it is useful
for staff planning, employee performance evaluation, scheduling and general benchmarking.
In warehousing, time standards are often difficult to develop for reasons discussed below. In the following pages we show tables for estimating pick times
under various situations. These tables are overall averages based on a typical warehouse situation and operation. They are suitable for some purposes and
unsuitable for others. Their primary advantage is ready availability and ease of use.
The Uses of Time Standards
Time standards have many uses. The accuracy and sources of those standards will affect their appropriate use. For example, overall average times for picking
are not appropriate for measuring individual picker performance on a daily basis. Or, detailed time study may be unnecessary for initial warehouse design.
Warehouse Design
When the overall design and layout of a warehouse requires some reasonable estimate of picking volume and pick times to estimate the number of people
required. This, in turn, affects aisles, restroom locations and other aspects of the design.
Equipment Selection
Equipment selection depends on many factors and the time required for picking is one of the more important. Equipment selection then affects staff planning and
operating cost estimates.
Estimating Operating Cost
Operating cost estimates are usually part of the initial design of a warehouse or part of an equipment selection process.
Staff Planning
Staff planning is usually an issue in the initial design but a high level of accuracy or detail is unnecessary. Staff planning
may also be the sort of short-range planning that merges with scheduling. For example, "will we need to work overtime on Saturday?"
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Employee Performance Evaluation
Overall average pick times may not be suitable for evaluating employees, especially on a daily or weekly basis. This is because
of the large variation in pick lists.
Daily/Weekly Performance Evaluation
This sort of management review is quite common. Normally, it compares recent performance to past time periods. It shows
improvement or degradation but does not establish an external, independent benchmark.
Benchmarking
Benchmarking compares warehouse performance to outside standards, rather than just comparing to previous performance.
Scheduling
Scheduling ensures that orders will be picked and filled in a timely manner and people and equipment will be available. Most
warehouse operations do little formal scheduling. Highly accurate standards are not usually necessary.
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Sources of Time Standards
There are several ways to establish time standards for equipment and people. Among these are:
Historical Data
Historical data is normally easy to find or develop. If one knows the number of orders or line items picked or shipped in a given week and the number of
pickers or picking hours, the efficiency for that week is easily calculated. The result may be useful for evaluating performance in subsequent weeks or in
design modifications.
Stopwatch/Video Observation
Real-time stopwatch observations are the traditional way of setting time standards. Video studies are the modernized version. Both have limited application
in warehousing because of the wide variation in pick lists and the resulting travel times. They are sometimes useful to establish specific elements such as
the actual pick operation for a class of items once the operator has arrived at a pick face. These elements can than be placed in formulae to set a standard
for a specific pick list.
Pre-determined Time Systems
These systems use historical data for each movement or micro-element of a motion. These small elements are then built up into larger elements and,
eventually, into a standard for a complete pick list. MTM is an example of a pre-determined time system.
Warehouse Management Systems (WMS)
The more sophisticated Warehouse Management Systems generate a standard time for each pick list. The use location codes and elemental times, mostly from
pre-determined time systems. These types of system are excellent for daily management and employee evaluation. They do require considerable input data for
the location information.
NS 529 Standards
The following pages offer picking standards for several types of storage and warehouse situations. They are taken from the
Warehouse Modernization & Planning Guide (NS 529) published by the U.S. Navy. They are available as a
free download in xls format.
There are many factors that make up a truly accurate
standard. For our purposes here, a more or less typical warehouse is assumed. These pick times are adequate for design, planning and overall benchmarking.
They are not accurate enough for evaluating individual performance and, particularly, they do not apply to a specific pick list.
The three major categories of storage are Pallets, Rackables and Binnables as shown below. The time values are then further subdivided by transport
method and, in some cases, shown for different sizes of warehouse or storage module.
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