Is Force Measurement Evolving into Materials Testing?
December 30, 2008
Remember when force measurement was force measurement and materials testing was materials testing? Each discipline enjoyed a unique place in the measurement world.
In the past, force measurement generally meant obtaining a peak load measurement on a product, part or material to verify or validate that the product or part could exceed or withstand a specified load. Force measurement was generally accepted as a fairly innocuous test performed in the lab or on the production floor.
Materials testing, however, is considered the science of determining a product’s physical characteristics carried out by highly skilled engineers and scientists using sophisticated software analysis. Materials testing involves a more comprehensive evaluation of a material, such as determining its break load, modulus of elasticity or yielding characteristic through exacting measurements to recognized industry standards.
Functionality, accuracy and precision formerly reserved for more expensive, more complex materials testing systems now are common attributes of many force measurement systems. Driving this evolution is the demand from manufacturers to employ more testing directly on the production floor and the need to validate incoming products from global sources. The functionality of materials testers, formerly reserved for research and development applications, is being applied on the production floor.
More testing means an immediate response to nonconforming products. More testing means nonconforming products and their related processes can be measured, analyzed and corrected faster. More testing means increased production efficiency, higher yields, improved on-time delivery performance, reduction in nonconforming product, lower manufacturing costs and a significant reduction in scrap.
Testing on the Shop FloorThe production environment now is an in situ testing lab, where the skilled personnel who assemble and work with the materials, parts or products on an everyday basis perform quality tests in real time. The production worker’s knowledge and experience is critical to the ultimate product’s quest for optimum quality. The force measurement systems used by today’s operators are more sophisticated, more capable, more efficient and more accurate than ever before.
Force testing has become an integral part of the manufacturing process. The forces required to insert or extract a component; make or break an electrical contact; and prove that a component can withstand an applied load after a number of cycles all are common measurement attributes that can be attained on the production floor. These measurements are used to validate a product’s ultimate performance, helping to determine its lifecycle, safety factor and warranty period. The measurements also are used to identify nonconforming products more immediately within the manufacturing process so that efficiencies in production and eliminations in waste and scrap can be achieved.
Today, a force measurement system can be used to measure peak loads, but can also be used to determine average loads, break loads based on varying sample break characteristics and statistical analysis such as mean, percent variation and standard deviation. Real-time pass/fail analysis based on tolerances is common. Measurement accuracy of better than 0.1% is the norm. A modern force gage can sample measurements at rates of up to 5,000 hertz and save results in its internal memory.
Results and data can be exported to central computers that use third-party quality control software packages to generate detailed product and process quality reports. These reports are used to improve the materials used in the production of the product or to improve the processes used to produce the product. Detailed production data from real-time measurements can be shared with research and development and quality functions, allowing correlations to be made between controlled laboratory results.
Of course, a key to making this integrated testing and measurement work well for the manufacturing environment is to keep performance and operation easy to use and easier to understand, while keeping the system’s lifecycle costs affordable and practical. Menus built into the force tester’s operation help the operator select the appropriate measurement and method of measurement for the application. And because of today’s global manufacturing environment, modern force systems can display setup menus, prompts and measured results in multiple languages.
Computer-Integrated TestingDigital computers found their way into the production environment in the late 1960s and early 1970s. Computer integrated manufacturing became increasingly popular in the 1980s as a means to automate industrial processes and to maintain a level of manufacturing consistency.
Programmable logic controllers (PLCs) were first adopted by the automotive industry and developed from digital computers. They were used as a way to improve the manufacturing process while reducing the costs associated with changing manufacturing methods and the hundreds of relays, cam timers and drum sequencers, and dedicated closed-loop controllers. These initial computers operated under rather sophisticated and arguably difficult-to-use application software.
Automated testing has evolved from programmable controllers in which a computer and software were used to perform a particular test on a component, material or product. These automated testing systems precisely controlled the speed to ensure repeatability, enabling results to be measured against one another. With the computer came sophisticated software packages that allowed the operator to test multiple points, collect large amounts of data at high sampling rates and produce detailed and sophisticated reports to improve the process and product quality.
Today's FunctionalityModern force testing systems incorporate the principles first developed for the programmable logic controller with many materials testing functions. This type of force testing system allows the operator to create multistage, albeit, logic-testing steps without the need for a separate computer or proprietary third-party software package. Test recipes can be created by the operator based on individual testing methods or industry testing standards and procedures. Test creation is intuitive and knowledge of computer programming is not required.
Very precise speed and motion control algorithms use sophisticated proportional integral derivative controls and combine with a high-resolution optical encoder enabling some systems to test at multiple speeds during a test, to very precise load or distance limits, while collecting data points at up to 1,000 samples per second. Today, systems can automatically correct for load cell and frame deflection. They can accurately measure sample heights and be used for complex spring testing, top load testing and texture analysis on food products.
Testing results can include tabular readouts that are color coded to distinguish various tolerance limits. Results may be displayed graphically for quick analysis or comparison. Data can be saved for later use, archived or exported using serial data communications or USB flash memory sticks to ancillary computer systems for data collection and analysis. Systems can be configured using flash memory so multiple, like-testing systems can be “cloned” in seconds by an authorized supervisor.
System configurations can be e-mailed to multiple manufacturing sites around the world and uploaded to other systems in seconds, ensuring consistency in testing and ultimately the measurements used to identify nonconforming product.
Certainly, there will always be a need for extensometers, thermal chambers, computers and sophisticated analysis software for materials testing applications. These testing systems are optimized for comprehensive material evaluation and analysis and play an important role in all research and development efforts. However, the emergence of advanced technologies, formerly reserved for materials testers, has greatly expanded the capabilities of traditional force testing instrumentation, particularly as they become integrated within the manufacturing process.
Force measurement has evolved and will continue to do so, driven ostensibly by the need for more sophisticated and more economically feasible testing solutions for the factory floor. The combined features, functionality and simplicity of today’s modern force measurement systems-as well as their comparatively low lifecycle costs-should be carefully and thoroughly considered when evaluating and qualifying a testing solution for manufacturing requirements. Q