A driving force for quality control
17 April 2013
Force testing, where a known force is applied to a sample in a controlled manner, has become an integral part of the manufacturing process, as Carl Bramley, export sales manager, AMETEK Test & Calibration Instruments, explains
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 measurements that can be made on the production floor. These can validate a product's ultimate performance, helping to determine its lifecycle, safety factor and warranty period. The measurements also are used to identify non-conforming products more immediately within the manufacturing process, frequently with a real-time 'pass/fail' analysis based on tolerances, so that efficiencies in production and eliminations in waste and scrap can be achieved.
Modern force testing Force measurement systems can be used to measure peak loads, average loads, break loads based on varying sample break characteristics and statistical analysis such as mean, percent variation and standard deviation. Test data can be displayed graphically, or as an overview showing batch results or as statistical results. Use of the appropriate sample holder or test jig means that these forces can be applied in such a way to allow tensile testing, compression testing, sheer testing, flexural testing or advanced multi-stage testing to be carried out.
Tests can also be carried out to conform to ISO or ASTM testing procedures.
Touch screen menus help the operator quickly and easily select the appropriate method of measurement for the application. With USB and Ethernet connectivity, data can be saved to a flash drive or exported directly to Excel or OLE2 formats.
Testing examples Force testers can be used to test raw materials, finished product and packaging materials as part of a factory floor quality control process. The rich array of sample holders and test jigs available include bending and flexural jigs; compression plates; peel and friction grips and wire, yarn, thread and cable grips. There are chuck fixtures for holding small cylindrical samples during tension or compression testing and self-tightening eccentric roller grips for all types of flat samples such as rubber, plastic film, plastic dumbbells, paper and cardboard, sheet metal and foils. There is also a specialised range of fixtures for food testing.
Testing of raw material before the manufacturing process even begins helps minimise waste by ensuring defective material does not enter the process. Force testing of raw materials such as metals, plastic, wood, wire, fibres etc, provides a good measure of their mechanical properties.
Once manufacture begins, force testing could be used at a variety of stages of the manufacturing process right up to testing of the final product. By testing during the manufacturing process, early identification of problems can reduce the amount of waste and rework that may be required. With literally thousands of different tests possible, I shall just highlight a few from different industries: Automotive and aerospace: quality testing of gaskets through a pull to break test; force required for push button activation; spring clip insertion and extraction Electronic components: solder strength on components; insulation crush strength on cables/looms; keypad actuation strength Plastics: compression strength of plastic containers; peel strength; snap on/snap off Cosmetics: lipstick break strength; liquid soap dispenser action; soap/wax hardness Medical devices: in-line testing of catheter and cannula components to test the bonding strength of the parts; metered dose inhaler actuation strength.
Finally force testing also has a key role to play in packaging testing for the finished product, from testing bottle tops and enclosures to inline compression testing of 'egg tray' packaging used to protect mobile phones in their boxes.
Latest generation The latest generation of digital force testers brings some of the functionality, accuracy and precision previously reserved for more complex, dedicated materials testing machines to the factory floor. For example, the new Chatillon CS Series of single column force testers from AMETEK Test & Calibration Instruments (Figure 1) feature the latest linear guide technology, pre-loaded ball screws and advanced software compensation systems, ensuring a high level of precision displacement measurement.
Control is provided via an industrial-grade touch screen (IP65), with no external PC.
Key to the versatility of these systems is the availability of an extensive range of grips (Figure 2), fixtures, extensometers and software options and a wide range of work tables which means that they can readily be adapted to applications in plastics, packaging, medical devices, automotive, electronics, textiles, rubber and pharmaceuticals.