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Cliff Holste

Supply Chain Digest
Material Handling Editor

Logistics News - Sorting It Out

Cliff Holste is Supply Chain Digest's Material Handling Editor. With more than 30 years experience in designing and implementing material handling and order picking systems in distribution, Holste has worked with dozens of large and smaller companies to improve distribution performance.

March 29, 2017

Sorting It Out : Work Rate Verses System Productivity

Properly Interpreting and Analyzing Work Related Data is Key to Optimizing System Performance


In today’s digital environment businesses run on data. However, ever since analysts have been crunching numbers there’s been this old adage – “Garbage In = Garbage Out”. What they’re saying is that data is only as good as the methods used to measure it. If an operation is being measured the “wrong way”, the results can be misinterpreted and misapplied. As obvious as this may be, the proper way to measure is not always so obvious.

For instance, many shippers have issues with low picking rates. Often, the pick rate is being measured base on a 420 minute work period (8 hrs minus lunch and break periods). But, if due to system generated accumulative idle times the pickers are actually picking between 240 and 360 minutes per period that would then translate into low rate on a spreadsheet and would therefore be a miss leading measurement of pick rate. However, it is a measurement of system productivity. By comparing the true pick rate capability against system productivity, opportunities for improvement can be exposed. 

The following examples show how basic data can easily be misinterpreted:

Holste Says... is only as good as the methods used to measure it.

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Inconsistent Flow of Work:

Many picking and shipping operations are unable to provide workers with a steady flow of work, which can be a serious problem for batch picking systems. The lack of constant work could be the result of IT issues, a lack of orders in process, or even a deficient routing system for passing orders. Pickers cannot consistently pick at high rates if they don’t have enough orders. This drought in orders creates lost picking time, which can be incorrectly interpreted as a low pick rate.

One way to track workflow is to measure the number of orders present in each picking zone throughout the day in short time increments (5-minute intervals). Although it sounds tedious, this is an exceptionally important measurement because it directly verifies the effectiveness of the order routing operation. If full batches are not available on a constant basis, pick rates will not reach their maximum. In this case, changes should be made to move more orders into the zones.

Organization of Operations:

Typically, picking and shipping systems operate in sporadic bursts of work with time left over in between. It’s a kind of hurry up and wait situation. This is most common in wave picking operations and is referred to as the bell curve effect. Sometimes this can be corrected by overlapping waves. However, you can’t fill that time appropriately if you don’t know when and how long it is. So the first step is to measure this over for a period of multiple days so you can see those busy versus slack time windows.

If wave overlapping is not an option – try filling the gaps with other tasks, which may mean combining different tasks in the same time frame (picking and replenishment, for example).

Not Accounting For Peak Periods:

It is not uncommon for a large percentage of the day’s work to get compressed into a few hours at the end of the day due to customer order shipping requirements. This creates a wave of work that leads to over or under stating rates for both the day and peak times.

To avoid this error measure the rate for that peak time period and the number of people working concurrently. This will then provide a measurement of the peak rate per person. You can then use that rate for labor assignments during peak and slack times.

An effective way to determine the capacity of your picking and shipping operation is by doing a Performance Audit. A performance audit can help you zero in on productivity drains, evaluating such areas as picking, conveying, and sorting rates. Whether you utilize internal resources or hire an industry expert, a comprehensive audit will analyze systems from both an operational and functional standpoint, including a final report detailing recommended adjustments. Thus, you will be able to pinpoint and fix inefficiencies, realizing cost savings from improved work rates and productivity.

Final Thoughts

Work rate and productivity are two very different measurements. Properly interpreting and analyzing work related data is key to optimizing system performance.

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