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Eddy Current testing is generally the best choice to inspect wire in line with cold heading operations such as spring making and other parts forming, and for checking continuity, alloy and other conditions. Eddy current tests are also frequently used to locate welds and splices in insulated cable.
The choice of equipment depends on the nonconforming conditions you wish to detect and the size and characteristics of the material. MAC instruments can handle a range of metal wire including cut lengths, continuous production, stranded, multi conductor and insulated cable. Carbon steels, stainless alloys, copper, aluminum, titanium and other non ferrous metals can be inspected. Additional items such as markers, controls, demagnetizers and components for mounting the encircling or segment test coils and saturation coils, and positioning and driving the material through the test, are combined with the instrumentation to make up a complete test system. |
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| Typical flaws and conditions that can be detected include: |
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- Chevron cracks
- Laps
- Seams
- Slivers
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- Weld line faults
- Welds
- Butt welds
- Breaks
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- Continuity checking
- Variations in heat treat, grade or alloy
- Other flaws & conditions
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| Testing Wire |
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Inspecting Cold Drawn Wire on a Header |
Cold Drawn
MAC eddy current systems are available to test cold drawn wire, on a processing machine such as a bull block or cold header. Two methods are available, depending on the types of surface defects likely to occur. Encircling coils, including DC saturation on magnetic steel wire, are used to detect short defects, and rotating probes are used for longitudinal defects.
Fine Diameter Wire
MAC has eddy current systems with specially designed small test coils that operate at very high frequencies for inspecting ultra small diameter, super conductor wire; tungsten filament wire, and other exotic alloy wire sometimes used in critical medical applications.
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Insulated multi conductor copper wire |
Insulated Wire & Cable
MAC eddy current systems for insulated wire and cable, such as multi conductor automotive and building wire, detect splices, welds and breaks at very high throughput speeds. Split coils are available to accommodate oversize splices.
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| Detecting Flaws and Conditions |
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Detecting Defects in Small Diameter Wire
MAC's Hi Frequency eddy current instruments are well suited for detecting small defects in wire, including nickel-titanium and tungsten-rhenium alloys frequently used in critical medical and other high performance applications such as guide wires. Test frequencies range up to 5 MHz and diameters as small as .0035" (.089 mm) can be tested with special test coils at test speeds up to several thousand fpm.
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Surface Cracks in Roller Bearings During Heading Operations
An eddy current tester, such as the MultiMac® , used with rotary test probes, can detect surface cracks in the wire as it is fed into the header for forming into a roller bearing or other part. The test output can be configured to activate rejection of the slug or finished part.
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Seam Type Defects in Wire for Cold Forming Applications
An eddy current tester such as the new MultiMac® test equipment used with rotating probe type sensors, is the method of choice to detect seam type defects in cold drawn wire in conjunction with wire drawing, spring makers and other parts forming applications. By rotating multiple test probes at speeds up to 6000 RPM around the wire, even relatively short, longitudinal surface flaws can be reliably detected in many applications, without sacrificing throughput speed. A range of output options allow rejecting or accepting formed parts further down line.
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Short Surface & Subsurface Cracks
For detecting typical defects such as cracks, butt welds, inclusions, and other defects in steel, stainless alloy or non ferrous wire, an eddy current instrument such as the MultiMac®, with encircling test coils is often selected. The MultiMac, with a high test frequency range, can also be used on small diameter material such as tungsten filament wire.
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Both Short and Long Continuous Surface and Subsurface Defects
For those applications that require the detection of both short and long continuous surface or subsurface defects, the new MultiMac; multi mode eddy current tester would be the right choice. The MultiMac with up to 8 test channels, allows simultaneous detection of both types of defects in magnetic or nonmagnetic material.
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Detecting Breaks in Wire Rope
To detect broken wires in magnetic grades of wire rope, a flux leakage instrument similar to the Wirerope Tester is the appropriate choice. A split test coil can be used to eliminate the need to rethread the wire through the test coil.
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Continuity Checking in Wire
To check for continuity in single or multi-conductor insulated wire and cable, the economic Minimac MAC 40 requires minimal operator time and can be installed directly on the production line. Split or segment coils can be used to allow clearance for intermittent dimensional changes in the outside diameter of the insulation.
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Alloy and Hardness Detection
Variations in alloy, heat treatment, case depth and hardness can be successfully detected by MAC's comparators. The Varimac® eddy current comparator can be used on a range of product shapes and materials including non magnetic stainless steels. Variations in carbon steel wire can also be detected with the Production Comparator low frequency electromagnetic comparator.
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Combined Systems
For applications where more than one of the conditions described above must be met, Multiple Test Systems using several testers can be assembled. In these cases, each tester is used to find the types of defects or conditions that it is best suited to detect. The result is often a more accurate test and fewer rejects to allow more of your product to be shipped to your customer.
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