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Case Study -?Hypodermic Needle Flaw TestCustomer ProblemTo help ensure flaw free delivery of products, a leading manufacturer of hypodermic needles wanted to test 100% of their hypodermic needle tubing for flaws. The tubing is formed and welded stainless steel that is drawn through forming dies and annealed. The manufacturer wanted to detect through-wall cracks down to 0.100 inches (2.5 mm) long x 0.004 inches (0.1 mm) wide in needles down to 0.011 inches (0.28 mm) in diameter.? 100% visual inspection or leak testing is impractical for the volumes produced. The SolutionEddy current testing is very well suited to finding flaws and defects in metallic tubing.? For this application, the manufacturer installed the eddy testing solution just prior to the needle cutting process where defective materials could be easily cut out in-line, in real-time.?The needle manufacturer used a MIZ? 23 eddy current instrument and custom eddy coil for their solution. When a flaw is detected, the MIZ 23’s Industrial I/O sends a signal to an in-line cutter which removes the flawed section of material. The eddy current coil uses TTZ (Trans-Toughened Zirconia) ceramic coil inserts to protect the electrical coil windings from continuous wear and damage caused by burrs and snags in the tubing.? A single coil can accommodate a number of different tubing diameters.The manufacturer has recently upgraded their systems to use Criterion NDT’s CR-11 eddy current test instrument. Doctors, hospitals and individuals depend on the highest quality hypodermic needles to administer medicines and draw fluids.? Unfortunately, 100% visual and/or water leak test inspection of the needle tubing or finished product for microscopic cracks or defects is nearly impossible. ?A hypodermic needle manufacturer has integrated automated eddy current testing solutions from Criterion NDT in their production lines to test 100% of their material for cracks and defects.SituationMedical grade hypodermic needles are available in numerous diameters and wall thicknesses.? A hypodermic needle manufacturer The manufacturer’s process commences with the forming and welding of medical grade stainless steel.? The tubing is drawn through forming dies and annealed.? This process is repeated until the desired diameter is achieved.? The tubing is then straightened prior to cutting.? The manufacturer wanted to ensure the quality of the tubing just prior to the cutting process.SolutionEddy current testing is very well suited to finding defects in metallic tubing and components.? For the hypodermic needle application, the manufacturer installed the eddy testing solution just prior to the needle cutting process where defective materials could be easily cut out in-line, in real-time.? The test is designed to find defects in both the weld and raw material.? The testing solution consists of an eddy current encircling coil and eddy current test instrument interfaced to the production line cutting/sorting mechanism.The eddy current instrument induces an electromagnetic signal into the material under test via the encircling coil.? Eddy currents are generated within the tubing material and then sensed by the same encircling coil and fed back to the instrument.? The instrument compares the received signal with a “known good” signal and determines whether a defect is present.? If a defect is present, the instrument sends a control signal to a PLC in the cutting/sorting mechanism which automatically removes the defective material from the production line.? Criterion NDT’s eddy current instruments are capable of testing tubing at various rates depending on flaw size.A typical eddy current signal is shown on the left. The InSite eddy current instrument allows the operator to adjust the detection threshold to set the flaw detection criteria and eliminate false alarm readings.? Besides providing a good/bad sorting process, the data can be stored and used to identify process control issues and significantly reduce scrap rates.? By installing testing equipment at various stages in the manufacturing process, each process can be easily monitored.As the hypodermic needle manufacturing process runs continuously, the eddy current encircling coils are subject to extreme wear conditions.? To provide maximum durability and life, Criterion NDT uses TTZ (Trans-Toughened Zirconia) ceramic coil inserts.? The hardness of the TTZ protects the electrical coil windings from wear and damage caused by burrs and snags in the tubing.? A single coil can accommodate a number of different tubing diameters.The tubing manufacturing process can introduce both permeability variations, which influences thetest results by adding a significant amount of consistent electromagnetic noise, as well as local areas of residual magnetism, which can result in large, intermittent eddy current responses.? Small permanent magnets installed in the encircling coil will realign the magnetic domains within the material as it passes through the coil, therefore greatly attenuating the permeability variation and residual magnetism noise.? Once the tubing leaves the coil, the material returns to its’ original permeability properties while the residual magnetism is permanently removed.Benefits100% in-line, real-time eddy current inspection can help ensure the overall quality of the product without sacrificing production throughput.? It also helps manufacturers identify problems early on in the production process helping with continual process improvements while reducing scrap and saving money by not adding value to sub-standard materials.? Eddy current testing is a green technology and does not require the use of chemicals or dyes and allows the capturing of production line statistical data.? Eddy current testers can also be used to validate heat treat processes and condition.About Criterion NDTUSA based Criterion NDT specializes in providing engineered eddy current application solutions for the non-destructive testing of critical or essential components.? For more information please visit?. ................
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