Manufacturing automation can be designed to prevent, detect, and mitigate errors before they reach consumers.
Errors can enter the manufacturing stream from numerous sources. From flaws in the base material, to equipment that malfunctions, to problems with the design itself. But many of the most common—and preventable—errors can come from human origins.
Operators are necessary for many aspects of factory production, including changing out production tooling, handling assemblies that only happen in small batches, and performing tasks that are too complex and delicate to be easily handled by robotics. In accomplishing these tasks, operators are prone to become tired and distracted. When their attention shifts, mistakes are bound to happen.
Fortunately, there are steps manufacturers can take to prevent these errors from occurring. While manufacturing fail-safes have been around for a long time, the practice of intentionally examining each aspect of the workflow became formalized with the concept of poka-yoke.
We encounter many types of error-proofing in our day-to-day lives, as designers have built fail-safe features into consumer products. Error-proofing is what prevents washing machines from starting if the door hasn’t closed properly, it turns off irons that have been left unattended for too long, and it shuts the gas off at the pump when the tank is full.
Applying similar fail-safes to manufacturing operations prevents similar mishaps from occurring. Here are steps manufacturers can design into their automation systems to reduce avoidable errors.
1. Eliminate design elements that are prone to error.
In many cases, the way a part or assembly is designed can make errors more likely to occur. For instance, a design that requires two components to be glued together introduces the likelihood that the components will be misaligned, or that the glue will form a poor seal and break under certain conditions. Or it could be that a delicate component made of plastic is more prone to break during assembly.
These flaws can be eliminated by fabricating a part as a whole piece, so that it does not require gluing, or by using aluminum instead of plastic, to avoid breakage.
2. Create parts and assembly stages that make assembly error impossible.
An assembly process that requires two similar components to be fitted onto a product—something with a left side and a right side, for instance—is more liable to mistakes if the design elements are nearly interchangeable. This error could result in, for instance, one piece being inadvertently fitted upside down to the finished product.
This can be avoided if the components are subtly altered so that only a left-hand component can fit into the left-hand slot, and vice versa. Similarly, if a component has a front-facing and back-facing element, the assembly can be adjusted so that the parts won’t fit together unless the piece is facing the correct direction.
“Design for manufacturability opportunities are in almost every product we design solutions for. When these are identified a thorough vetting of benefits and challenges is conducted with all stake holders. Regardless of the outcome of this vetting a more robust process is the outcome.”
Keith Sawyer, Eagle Mechanical engineering manager
3. Design assembly instructions that reduce the likelihood of error.
Poorly written instructions can lead to frustration for many operators, as can parts that are hard to differentiate and easy to misplace. Clear instructions with technical illustrations can help avoid these errors, as can color-coded pieces, or other visual indicators.
Technology has played a significant role in this sector by providing operators with visual screens to guide them through different production stages. Augmented Reality (AR) is now taking this a step further, by overlaying operational instructions over an operator’s field of view. As one of the new Industry 4.0 technologies, AR shows great promise in aiding error-proof manufacturing.
4. Automation of tasks that would otherwise require operator assembly.
The best way to avoid human error and fatigue is to remove people from the production process. If an error-prone task can be automated, or if a machine can be used to expedite the task, then it will result in fewer errors.
A well-known example of this is bar code scanners on products that spare operators from having to manually enter product information. Data entry errors are easy to make, especially when typing in long strings of numbers, but scanners and other digital tags spare operators from significant amounts of busywork.
5. Detect errors at the source, rather than downstream.
When an operator does make an error, the sooner it is identified the better. The further a part makes it down the assembly stream, the more value is lost when it has to be removed due to a defect. The same holds true for machinery. After all, while equipment can be more reliable, its efficiency also means that an error can be rapidly reproduced hundreds or thousands of times if not identified and addressed quickly.
Using error detection systems at the source can prevent this. If an operator is using a technical interface, one way to eliminate error is to prevent the user from entering data or moving to the next screen if the data isn’t in the correct format, or if a required field is missing.
In other areas, mechanical and sensor technology means can be used to prevent a part from progressing forward—such as an integrated vision system that detects build processes or sensor array that detects build quality checks that prevent the assembly from advancing forward. Advanced testing technology can also be used to detect anomalies and alert operators to a problem.
You should expect a thorough understanding of error-proofing techniques from your automation partner.
Production errors are costly, damaging a manufacturer’s reputation, causing consumer distrust, and in some cases, contributing to serious accidents and recalls. While some error-proof practices are simple and easy to implement, others take time. Almost all require careful thought and consideration to prevent these problems from reaching consumers.
Yet manufacturers who make the effort are rewarded in the long-run by reduced recall rates and a reputation for high-quality products. Making production fool-proof has never been more of a no-brainer.
“Detecting process errors is central to every custom machine we build. Critical Process Characteristics identification early in the design cycle insures that the proper method of error detection is utilized. With these identified our engineers use their extensive design experience to select the best method to detect errors and insure they don’t exit the process.”
Keith Sawyer, Eagle Mechanical engineering manager
Brandon Fuller, Eagle Technologies
Eagle Technologies, headquarters in Bridgman, MI