The major impact of minor stoppages in the metal manufacturing process

Minor stops on the shop floor go beyond overall equipment effectiveness (OEE) and total productive maintenance (TPM). They tend to compound and get in the way of the lean manufacturing journey. Getty Images

Total productive maintenance (TPM) and overall equipment effectiveness (OEE) programs aim to reduce or eliminate what’s known as the six big losses. One of these losses focuses on minor stops.

Individually, minor stops seem insignificant. Collectively, however, they can have significant negative impacts, and reducing or eliminating them can lead to tremendous improvement.

Putting Minor Stops in Context

You calculate OEE by multiplying availability by performance and quality. Availability incorporates (1) unplanned and (2) planned stops; performance considers (3) minor stops and (4) slow cycles; and quality comprises (5) production rejects and (6) startup rejects. Together, these components make up the six big losses.

When you blow the motor on a capacity-constrained machine and you find it will take three days to get a replacement, who knows about this? Everybody, from senior management on down. When an assembly is welded with incorrect components and a shift’s worth of production is scrapped, who is in the know? Probably the plant manager, department managers, supervisors, and maybe HR. The point is that these big events are rare, but when they happen, they get lots of attention.

What about the minor stops? They happen all day, every day, and in all areas of the business, not just production. Minor stops might happen five minutes here, nine minutes there, and six minutes somewhere else. Who knows about them? Not many—the person doing the work, maybe the person’s supervisor, but that’s about it.

If minor stops happen multiple times during someone’s workday, how much time might be lost—45 minutes, an hour, two hours? The person’s value-adding opportunity erodes throughout the day, but because it’s rarely measured, you just don’t see it. Unlike the blown motor or the shift’s worth of production lost to a quality problem, minor stops simply do not get attention.

Examples of Minor Stops

Seeing lean manufacturing’s eight wastes is a learned skill that requires focus, and the same goes for minor stops. Identifying them can be difficult simply because they tend to blend into the real work.

Consider a situation with a production welder we’ll call John. His job is to fixture components and create quality welds. That’s the value-adding work, but that’s not all John does throughout his eight-hour shift. He also:

• Walks to the tool crib to replace his weld nozzle tip—12 minutes lost.
• Rearranges incoming components because they are placed in the wrong location in the workcell–7 minutes lost.
• Waits for his supervisor to approve his setup before proceeding—9 minutes lost.
• Makes process adjustments—3 minutes lost.
• Tweaks the components in the fixture because of a loose locator pin—1.5 minutes 20 different times during the shift, adding up to a 30-minute loss.
• Looks for a misplaced clamp–4 minutes lost.
• Resets a limit switch—5 minutes lost.

John has lost approximately 70 minutes of what could have been value-adding production capacity. How many Johns are there in your shop?

Enter Mary, the material handler. Although she doesn’t operate production equipment, her minor stops still have an effect. Mary must deliver the correct material to the right location at the right time to enable the value-adding contributors (welders, machinists, assemblers, etc.) to keep doing what they should be doing. She needs to get the right material into or out of the workcell at the right time. Minor stops might prevent this from happening, which in turn can spur a cascading series of performance disruptions.

She might have no visual cue that helps her identify which material should be used first in a sequence. So she hunts down a supervisor to ask. This takes 6 minutes, and it occurs three times per shift. That’s 18 minutes lost.

Seeing the battery on her transport device is running low in the middle of her shift, she changes it. That’s 15 minutes lost.

An empty container she needs isn’t available in her area of the shop, so she walks to another department to find a replacement. That’s 12 minutes lost.

While delivering material, she waits for an aisle to be cleared of excess inventory before she can proceed. That’s 7 minutes lost.

Having no visual cues telling her where material should go (visual controls like kanban squares, for example), she asks an operator where he wants material placed. That’s 3 minutes lost.

She tracks down a missing shop traveler. That’s 9 minutes lost.

For Mary, minor stops caused 64 minutes of unplanned disruption during her shift, and the cascading impacts ensue as welders, machinists, and assemblers wait for parts to be moved.

Now consider Hank, the plant manager. He develops plans, assesses situations, makes decisions, and provides overall guidance, but he doesn’t run a machine or move parts. How could minor stops possibly affect him?

They do, and to see them, try taking a more liberal view of the minor stop idea. What about that meeting that was supposed to start at 9:00 but started at 9:07 because someone was late? That’s 7 minutes lost.

Someone stopped Hank to talk about the Friday night football game. That’s 9 minutes lost. He then attended the morning status meeting, only to wait for someone (who happened to be on his morning break) to deliver data. That’s 15 minutes lost. Hank returned to his office and looked for a report that was somewhere on a messy desk. That’s 3 minutes lost.

Throughout his day, various people interrupted Hank to ask for his input on issues that should have just been handled by others. That’s 30 minutes lost.

In total, Hank lost 64 minutes from minor stops that, unlike John and Mary, don’t have anything to do with equipment or material. They instead stem from processes that fail to manage the flow of information.

Of course, Hank probably wouldn’t want to eliminate every minor loss entirely. Neither he nor anyone else would want a workplace without any casual conversation, like the few minutes spent talking about Friday night’s game. Still, Hank probably wouldn’t mind a workday with fewer meetings and interruptions.

How to Reduce Minor Stops

What to do about the minor stops lies in the lean body of knowledge. In John’s weld cell, effective 5S might help—no more looking for tools, no unneeded fixtures in the area, and having a right-sized supply of items for John to do his job (remember the weld nozzle tips?).

For Mary the material handler, the clearer you can make what to process, the more effective she can be in keeping her value-adding customers (such as welders and machine operators) adding value. Visual controls might help clearly define material placement; standard work instructions could outline how and when to change the battery for her equipment; and containers sized to the right pitch (the amount of time needed to create one container of work), stored somewhere close to the point of use, could eliminate the time spent hunting for the next empty container.

Then there is Hank. How could he use lean concepts to help reduce or eliminate his minor stops? At the heart of lean is discipline and clarity of process. Take away the sources of ambiguity. Make the work easier. Have a clear expectation and purpose for the daily meetings. Everyone knows what information is needed, when they need to provide it, and what decisions or actions should result. Just like 5S can be applied in John’s production area, it can also be effectively applied in Hank’s office. And with clarity around expectations and authority, decision-making can be pushed down to those at the point of action.

Minor Stops Aren’t Minor

Minor stops might seem, well, minor, but nothing is further from the truth. Collectively, minor stops represent a large, untapped opportunity for improvements, many of which cost little to nothing to implement.

How many Johns, Marys, and Hanks are in your organization? The minutes they save could yield real operational benefits and increased profits. All those minor stops, it turns out, have seriously major impacts.