Industrial Engineering

The Ergonomic Dividends of Cellular Production

The ergonomic dividends of cellular production

ISE Magazine July 2020 Volume: 52 Number: 7

By Richard J. Schonberger

https://www.iise.org/iemagazine/2020-07/html/schonberger/schonberger.html

When productive resources are arranged into a small cluster dedicated to a narrow family of products, services or customers, we call it a cell. The concept, originating as cellular manufacturing, may also be called cellular production, cellular operations, cellular organization, cellular layout or cellular management. Whatever the name, if done reasonably well it is beneficial in most ways in which we measure effective operational performance, including:

  • Flow time, flow distance, floor space, quality, flexibility and cost.
  • Use of/requirements for containers, handling equipment and tools.
  • Simplicity in scheduling, operational transactions and cost determination.
  • Employee skills and capabilities, engagement and work life.
  • Ergonomics, an aspect seldom recognized but foremost in this article.

Cellular configurations are often seen in layout terms – groupings into small product-focused clusters rather than by its commonplace but problematic “opposites”: (a) geographically separable processes/shops, each doing only a segment or component of a whole product or service; or (b) processes arranged along a complex multi product production line or assembly line. Cellular configurations may be largely or wholly manual; partly manual and partly automated (human operation of equipment); or entirely automated, in which ergonomics issues are not relevant.

Among those workaday configurations of people, workspace and equipment, some of the ergo/human factor impacts are in the nature of bodily and physical avoidance. Other impacts are bodily and physically enhancing. Still others are cognitive, such as mental and work-life factors, displeasure vs. enjoyment. Specific to the theme of this article, well designed and functioning cells provide the following:

The avoidance of – lifting; heavy lifting; long reaches; repetitive motions; long standing or sitting in place; and long standing or sitting in place with repetitive motions, long reaches or heavy lifting.

The enhancement of – task variety in place; task variety in association with multi body movements; task variety in association with low-strain multi body movements; task variety including steps between adjacent workstations; task variety encompassing steps among multiple workstations in a single cell; and task variety among multiple workstations extending to adjacent cells

Cognitive, work life and mental factors – feelings of comfort and safety; closely linked work teams with commensurate social-interaction benefits; all cell team members recording job frustrations and safety issues – primary data for process improvement efforts; cell members tracking their team performance, for key improvement criteria, on visually prominent trend charts; cell stations and job rotations geared to expertise, experience, interests, aspirations of each member, captured and visually displayed as versatility charts.

All these are characteristics of best practices in cellular management. Moreover, they are neatly encompassed in a single sentence from leading ergonomics literature: “Ergonomics promotes a holistic approach to work systems design and management that considers the physical, cognitive, social, organizational, environmental and other relevant factors” (International Encyclopedia of Ergonomics and Human Factors, Waldemar Karwowski editor, 2001). The following discussion brings out ways in which cells encompass those factors.

Cell design and interlaced ergonomics

Ergonomic issues are plentiful in connection with the batch-and-queue system, assembly lines and one-off production for an operator of a lone process. Those issues tend to be singular in form, generally meaning applicable to a sole operator and a limited set of motions. In contrast, the cellular mode is less about attenuated ergo issues and more about intertwined ergo solutions. The following explications apply to cells operating in a large range of modes, from high-mix job-order to low-mix repetitive operations.

Mobility. Much of the ergo benefits of cells has to do with avoiding the numbing effects of being stuck in limited-motion jobs. Being brought together in a cell makes it easy for team members to learn each other’s jobs and rotate among them, necessitating that the cell population is not overly large (e.g., single-digit numbers). Done right, cross-training with frequent job rotation becomes the norm, through natural inclinations of the cell team and/or management policies. A versatility matrix, prominently displayed at the cell, lists each member across the horizontal and the various tasks or responsibilities each is qualified for along the vertical.

Cross-training with job rotation is, in itself, ergonomically valued in that it avoids spatial rigidity. The mode often entails stand up work and the elimination of chairs. Further ergonomic benefits accrue in the common cell configuration in which a member tends two, sometimes more, adjacent stations, thus requiring a step or two forward and back in each cycle. In special cases where sitting is required – such as intensive work looking down through a microscope – extended job rotation becomes an ergonomic necessity; for example, a daily cycle of two hours on task and two hours off (that “off ” time entailing rotation preferably into a stand up operation).

Owed to short flow distances, the cellular configuration forestalls potential bodily aches and strains attendant to lifting and moving materials. Gravity-feed devices, perhaps as simple as wooden ramps seen in one plant, send the product to the next stations. Where lifting and carrying is required, good cell/ergo design calls for small containers and weight-limited carry-loads.

Coordination and aspiration. Aside from physical ergo aspects, the cross-trained, job-rotating cell member gains whole-process experience, including broadened awareness of which jobs and operations are difficult, tiring and body-straining. In such an environment cell associates are likely to recognize and become favorable to process improvement, especially aimed at worst jobs and prominently including ergonomic is-sues. Among better ways to tap such engagement proclivities is for the cell team to establish its own “rule” of every member recording at least one frustration every day. Those frustrations accumulate into a targeted improvement agenda that gets at deep-seated work/life aggravations as well as issues that get in the way of doing the job humanely, safely and right ( “Frustration-Driven Process Improvement,” Schonberger, Business Horizons, 2018).

In a high state of maturity, cell members come to know each other’s likes and dislikes, stronger and weaker capabilities and career aspirations. The members act together to distribute tasks, jobs, responsibilities and job rotation accordingly. For example, one member with lofty career ambitions might pursue mastery of enough of the cells’ skills and responsibilities to be designated as cell leader or lead-person and be so recognized on the versatility matrix. The same or a different member may be designated on the matrix as qualified trainer of other members in certain jobs or tasks.

Cells, plural. In general practice, the term is not cell, singular, but cells, plural. A single cell is beneficial, but the preferred cellular configuration is that of a building or floor organized into two or more cells, each with its own equipment and dedicated to its own product or customer family, as if each were a company unto itself. With two or more cells in a facility, cell teammates become cross-trained within their cells and before long with associates in other nearby cells.

In advanced cases, cell teams may include certain of their own support staff, such as a process engineer, a buyer-planner, an accountant, and/or a customer service rep. Each support person may be shared with two or more nearby cells. For ex-ample an engineer, a buyer-planner or other professional may have a desk located astride two cells and could even fill in occasionally as a production operative. In such cases, every member, operative or professional acquires whole-process knowledge and competitive awareness, a high form of cognitive ergonomic benefits.

Simplicity and control. The cellular mode simplifies systems of planning, scheduling and control. Planning and scheduling are straightforward, involving use of equipment and materials within the cell, plus externally supplied materials (perhaps by kanban). Simple flows from station to station minimize or obviate needs for a planner or scheduler and related transactions, a system of high visuality easily managed by the cell team.

As for control, cells have little use for conventional “aggregated and monetized (accounting system) indicators,” calling instead for measuring performance in “natural units,” such as throughput time, setup and changeover time, various quality/rework indicators and stoppages and their causes. These indicators may be on display, visually and graphically within the cell, and updated by cell members and/or the professionals (engineers, accountants) assigned to the cell. All of this adds to feelings by cell members of having control of key elements of their work lives.

The disuse of a monetized control system is accompanied by reduced and simplified activities for determining costs of produced items and costs of the many flows within, to and from the cells. That is because a cell acts as a cost-containment center: The cell “owns” the floor space upon which it rests, the equipment and tools within, the cell’s direct labor and direct supervision (if any) and staffers assigned to the cell. The costs of all those resources are contained within the cell and rather easily totaled up as needs for costs arise.

However, by advanced thinking in management accounting, those costs no longer need be determined on a regular and frequent basis. Cost accounting activities may instead be re-served for special, infrequent decision-making purposes such as when the cell team needs to consider costly new equipment or equipment overhaul, costly expansion or re-layout of the area and the like. These days, an accountant (maybe located with the cell) may make use of the activity-based costing (ABC) methodology, which greatly improves the validity of costing. Thus, the primary indicators visually posted within the cell are readily understood and related to by cell members, further improving cognitive ergonomics.

Use in the field

These points about the connectivity between cellular management and ergonomics offer two concluding comments in regard to field implementations. First, designers of cells should be fully aware of the multiple, closely related ergonomic benefits of the cellular form. That includes weighing the merits of the various aspects of cells to include their ergonomic benefits, as well as giving weight to the ergonomic penalties of omitting certain features of good cell design.

Second, those in the practice of ergonomic engineering should treat the subject expansively, to include fostering the cellular form as another approach to gaining ergonomic benefits. For researchers in industrial and systems engineering, this article suggests building linkages between cells and ergonomics into their theoretical works and pursuing cellular-ergo re-search in special contexts such as health care, and in special conditions such as virtual cells.

References: IISE Magazine July 2020 (https://www.iise.org/iemagazine/2020-07/html/schonberger/schonberger.html)