MT437 Unit 7 Labor Productivity Study Example

Lines per Which Hour: An MT437 Unit 7 Labor Productivity Study of Fourteen Night Pickers

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Purdue University Global

MT437: Strategic Warehouse Management

Unit 7 Labor Productivity Study

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[Date]

Lookout Parts Supply, its pickers and ten nights of data are composite; the work-sampling observations were drawn at random moments, and the sources cited are real.

Defining the Hours

Fourteen pickers worked 1,120 paid hours over ten nights. Not all of those hours were available for picking. Breaks took 70 hours. A nightly start-up meeting, about ten minutes for each picker, took 23.3. Assigned replenishment and housekeeping, which supervisors gave to pickers on slow nights, took 58. That leaves 968.7 direct hours, time on the pick floor with a pick list.

Over the ten nights the pickers picked 62,384 lines. Divided by paid hours, that is 55.7 lines an hour; divided by direct hours, 64.4. Both are reported, because they answer different questions. Lines per paid hour measures what the building gets for its payroll and belongs in a budget. Lines per direct hour measures how efficiently picking itself is done and belongs in a comparison of methods or people. Mixing them would make a picker who spent two hours on assigned replenishment look slow at picking.

Work Sampling

To see how direct time is spent, an observer recorded what each picker was doing at 2,400 random moments over the ten nights, choosing the moments from a random-number table so that pickers could not anticipate them. Freivalds and Niebel (2013) describe work sampling as the standard way to estimate how time divides among activities without timing every action. With 2,400 observations, a share near 47 percent is estimated within about two percentage points at 95 percent confidence.

Travel took 47 percent of direct time, about 455 hours. Picking itself, reaching, taking and placing parts, took 21 percent. Searching for locations and scanning took 11 percent, about 107 hours. Handling totes and carts took 9 percent. Waiting, mostly for replenishment of an empty location or for the conveyor to clear, took 7 percent, about 68 hours. Other tasks took 5 percent.

Pickers spend more than twice as long walking to parts as they spend picking them.

Productivity by Zone

Lines per direct hour differ sharply by zone. In the forward zone, where fast-moving parts sit on shelves close together, pickers averaged about 104 lines an hour. In general shelving, about 61.4. In the battery and rotor rack, where each line is a heavy item moved by pallet jack, about 33.

These differences come from the work, not the workers. A picker assigned to the battery rack for a week will always look slower than one assigned to the forward zone, however hard either works. Ranking pickers by a single building-wide rate would therefore penalize whoever drew the heavy zone. Comparisons should be made within a zone, or against a standard for each zone that reflects its work content. Richards (2018) warns that productivity measures in warehouses must be adjusted for differences in the work itself before being used to judge people.

What the Study Points To

Each share of direct time points to a different improvement. Travel, at 47 percent, is the largest, and the slotting in Unit 4 and the layout redesign in Unit 10 attack it directly. Searching and scanning, at 11 percent, often reflects locations whose stock does not match the system, which the cycle count plan in Unit 8 addresses. Waiting, at 7 percent, comes mostly from empty pick locations; better replenishment timing would recover much of the 68 hours. Picking itself, at 21 percent, offers the least room, since reaching and placing a part takes the time it takes.

How the Results Should Be Used With Pickers

The study will be shared with the pickers before any target is set. Their own explanations of waiting, for example, may point to causes the observer missed, such as replenishment workers starting their runs at the same time the pick waves begin. Productivity data used only to rank people tends to make them guard their numbers; used to find delays they did not cause, it tends to make them point out more.

Limits

Ten nights is a short window, and the mix of parts changes with the season; battery season would raise the share of heavy lines and lower building-wide rates. The observer's presence may have changed behavior on the first nights, which is why the first night's observations were checked against the rest and found similar. Frazelle (2016) recommends repeating such studies at different seasons before setting standards.

What a Better Target Would Look Like

A useful target for each zone starts from its own work content: the walking distance a typical line requires, the time to pick it and an allowance for waiting the picker cannot control. For the forward zone, that points to about 110 lines a direct hour once the Unit 4 slotting is in place; for the battery and rotor rack, about 35. Targets set this way can be met by a typical picker working steadily, which is what makes them credible.

Recommendation

Report lines per paid hour for budgeting and lines per direct hour by zone for managing picking, set zone standards rather than a single building target, and repeat the work sampling during battery season.

References

Frazelle, E. H. (2016). World-class warehousing and material handling (2nd ed.). McGraw-Hill Education.

Freivalds, A., & Niebel, B. W. (2013). Niebel's methods, standards, and work design (13th ed.). McGraw-Hill.

Richards, G. (2018). Warehouse management: A complete guide to improving efficiency and minimizing costs in the modern warehouse (3rd ed.). Kogan Page.