What if an operator knew when a production process was unstable and fixed it immediately, Paul Hogendoorn wonders. What if a machine automatically shut off or alerted someone when there was a setup error? What if an error could be predicted before it even happened?
“Every so often a technological breakthrough reinvents the way manufacturing is done,” said Hogendoorn, President and Co-founder of OES Inc. “The assembly line was invented in the early 1900s, which permitted mass production of products at a fraction of the cost. We had the invention of robotics in the mid-20th century, which assured accurate and reliable performance levels at increased speeds. And now we have process monitoring systems, an advanced technology which will again reinvent this age-old industry.”
Process monitoring systems, technically referred to as process variation monitoring (PVM), is a true paradigm shift in technology for the manufacturing industry, according to Hogendoorn. PVM devices are putting the emphasis on refining and improving the manufacturing process itself and away from inspecting the finished part as with traditional methods. This proactive methodology focuses on preventing errors, rather than detecting them after they occur.
With today’s zero-defect tolerance, “manufacturers have to pay close attention to quality and have to be sure that they do not ship even one bad product to their customer,” Hogendoorn said. “Doing the latter can result in expensive consequences such as being put on containment by the customer, a complete product recall, or worst of all, lost future contracts. At the very least, it results in increased costs and a diminished reputation.”
Until recently, companies had learned to rely solely on postproduction inspection methods and devices to detect any bad products before they might be shipped. This practice followed the underlying assumption that a bad part can be produced at anytime and that catching these parts before they went out to customers was a priority. Little emphasis, if any, was put on the actual manufacturing process.
“Progressive companies are shifting their focus by putting less emphasis on the inspection stages and more emphasis on refining and improving the manufacturing process itself. Their conviction is that it is impossible for a good process to produce a bad part, unless something in the process changes. This revolutionary attitude towards quality assurance is simple: monitor the process. This paradigm shift derives from a basic scientific principle: If all variables in a process are stable and constant, the outcome of the process will remain stable and constant as well,” Hogendoorn said.
In many force-form manufacturing processes (including end-forming, tube bending, and wire crimping), it is known that anytime a constant or predicted force is used to modify a part, the strain that the machine experiences during that process is directly related to the resistance to that force. The resistance to that force is then any variable in the process and the strain is a measurable outcome of the process.
“When the strain is no longer stable and constant, we know that a variable has changed and that the process is now capable of producing a faulty product,” said Kiet Ngo, Director of Research and Development for OES Technologies, an OES Inc. subsidiary, and the inventor behind U.S. patent #7,216,519 B1, one of seven patents held by OES. The patent proves that a sensitive and stable strain sensor, coupled to an intelligent analysis device, can provide an accurate and reliable indication of process quality.
The variables in a process that might affect part quality include the raw material, broken or worn tooling, machine deterioration, equipment failure, lack of lubrication, or improper presentation of the raw material. If the outcome is altered, then a variable in the process has to have changed. The task then becomes effectively monitoring the process in order to detect the critical changes (or variations) in that process.
Consider the example of mandrel bending. Most bends are designed to be performed with a lubricated mandrel. If the lubrication is not present (automatic lubrication system failure or omission by the operator), it is possible that the product produced by the faulty process will continue to meet the acceptable dimensional and visual criteria—at least for a while, according to OES. At some point, the mandrel is likely to break, resulting in downtime for service. At that time, it is likely that the lubrication failure is discovered and only then rectified. The pipe in which the mandrel broke likely would be identified and isolated.
Regarding the pipes that were processed prior to the breakage, the material in each of those bends was exposed to a far greater amount of strain than the process was designed to exert. Even if they looked good and passed dimensional and visual inspections, they were not necessarily good parts.
PVM products allow the operator to set parameters (or tolerance levels) for deviation from the learned signature. This works to catch bad processes but also gives manufacturers control over their own quality standards. When a part has been made outside the tolerances of a known good process, the operator is alerted to make adjustments, and the situation is rectified before a real problem occurs.
OES’s ForceWorx products “check the pulse of the process” by measuring the strain experienced by a piece of equipment. The company’s products are suitable for all mobility industries using equipment in which force is used to form, shape, or fasten a part.