Lean and Safe Manufacturing

-- Control Engineering, 8/22/2007

Mike Taubitz, global regulatory liaison at General Motors Corp., says companies no longer have a choice when it comes to lean manufacturing. Eliminating waste in terms of motion, idleness, materials and other aspects of production has become a necessity and leaning out a process a matter of business survival.

“Companies that aren’t lean aren’t going to make it,” says Taubitz. “That’s reality.”

As the same time, he notes, safety cannot be ignored. A single accident can result in enormous waste beyond the loss of the injured worker. Production, for instance, can grind to a halt for cleanup, machine restart and operator retraining. But Taubitz knows that the two concepts—lean and safe—aren’t contradictory and together can be profitable. “You can't be lean without being safe and so the marriage of the two really offers, I think, some tremendous opportunity.”

He’s seen implementations with his own eyes that prove this to be true, but in the past those cases involved proprietary solutions and procedures not available to the industrial community at large. Now with the release of ANSI B11.TR7 report, “Designing for Safety and Lean Manufacturing”, automation and process engineers have a guide on how safety and lean manufacturing principles can be integrated into a sum that’s greater than the individual parts and that can be tailored for a given situation.

Leaning Out Safety Adds Waste
Bruce Main, president of the risk assessment firm Design Safety Engineering Inc., has witnessed several times what happens when lean manufacturing is considered without regard to safety and vice versa. The result is an operation that’s neither lean nor safe, if the total picture is considered.

He cites, for example the case of a lean team re-engineering a packaging line work cell that included a pneumatic press in it. In looking at the process with an eye toward making it lean, the team considered each of the seven forms of waste: correction or rework, over-production, motion of people and machines, material movement, waiting, inventory, and process. This examination was holistic, looking at the total cell and not individual units.

After examining the press in particular and watching its operation, the team came to an understandable but mistaken conclusion. They looked at the adjustable guards that ensured safe operation and concluded that the guards were slowing down operations, introducing waste. So they adjusted them out of the way, effectively taking them, their safety impact, and perceived waste off the machine and out of the picture.

Main, though, notes that the group only came to this conclusion because they weren’t considering everything and its effect on waste. “If you look at risk and the waste on an overall view, you've really increased the potential for injury, which leads to waste of another kind.”

When—not if—an injury occurs in the case of the press, waste will appear in multiple ways. For one thing, the machine will be down while being retrofitted with alternate safeguarding systems. Other waiting will arise while employees are involved in discussions about what happened and investigations take place. The injured individual will be harmed and potentially the equipment be damaged, both forms of waste. Finally, material may be reworked.

Beyond these waste adders lie others, driven by the increased risk. They range from citations during governmental safety inspections to lawsuits, the latter arising because the injury was due to willful actions that defeated safety features. In certain regulatory regimes, there’s even the chance for criminal penalties.

Viewed in this context, defeating the safeguards and leaning out safety only appears to lessen waste in the operation. In actually, though, the change adds waste and increases safety, compliance and tort risks.

Acceptable Risk, Lean Manufacturing
Main, however, notes other cases where considering safety alone adds waste. One such is a CNC, a computer numerical control, setup. Such machines might require adjustment by operators inside a work cell. In that case, shutting the machine down, allowing an operator inside the work cell, and then having him come out to make a change is safe but it introduces significant waste. In one situation, Main recalls a 25 to 50 percent increase in setup time, a substantial waste in idle time for both machine and man.

The solution in this case was to borrow techniques from the robot industry, which has certain techniques that are known to reduce risk to an acceptable level for those times when an operator has to be inside a work cell. “The machine is moving very slowly. It is under the complete control of the operator,” says Main in listing just two of the guiding principles.

Applying this to the CNC setup problem eliminated waste without increasing risk unduly. That type of approach is what is embodied in B11.TR7, which has a process model and a risk assessment framework. The key to achieving acceptable risk with lean manufacturing is to consider both early in the design process. Doing so allows both to be addressed, with neither suffering as a result of the other.

An example of the technique in the report involves the use of a custom designed power press brake mounted on wheels. This approach ensured that the press brake could not tip over while still allowing the work cell to be quickly reconfigured.

Another example found in the report concerns a manufacturing cell containing a deburring machine used to finish parts after they were stamped from a hydraulic press. Before going through a lean and safe optimization, the process took as long as 80 minutes, involved travel distances of 71 meters and 13 steps, generated noise and air borne contaminants, and was prone to injuring operators in various ways. After a redesign with lean and safe principles, the processing time was cut to 90 seconds with six steps and two meters of travel. Injuries, particularly the carpal tunnel variety, were virtually eliminated.

GM’s Taubitz notes that the guidelines in B11.TR7 were derived from the experience of the companies involved in its creation, and thus the report represents a sharing of best practice concepts and approaches. However, he’s well that what works in one situation may not be suitable for another. That’s one reason why the report has guidelines and case histories that make it possible to implement lean and safe design in a way that can be tailored for a given set of circumstances.

He explains this methodology by way of analogy, likening lean and safe practices at a large manufacturer to a big and complex house. Such an edifice may not be suitable for a smaller concern. “You want to start with a foundation and build your own house. It may be a lot smaller and less complex,” says Taubitz.