Thickness measurement of the insulation layer on magnet wire

Control of enameled wire 

Electrical insulation on magnet wire is often achieved by surface coating of enamels such as PI (polyimide) or PAI (polyamide-imide).
These materials are usually partially transparent to white light and their thickness can therefore be measured using confocal chromatic technology.
Marposs STIL offers a wide range of electronics and optical sensors based on confocal chromatic technology that can be used for this purpose.

Control of PEEK extruded flat wire

With the need to improve performance on components for the automotive sector, the use of extruded PEEK flat wire is increasingly widespread, a material capable of ensuring better thermal and electrical behaviour, and which can be produced with a lower environmental impact.
The PEEK coatings most frequently used for this purpose are normally opaque and cannot be controlled with confocal technologies. However, these materials are usually transparent in the Near-infrared (NIR) wavelength band (0.75 – 1.4 µm) and their thickness can be measured with interferometric sensors. The same type of sensors is then clearly also able to measure the thickness of enamels such as PI/PAI.
The Marposs Horizon interferometric product line is therefore the ideal solution for measuring thin thicknesses of this type of coatings.

Off-line thickness measurement

One single sensor (confocal or interferometric, depending on the specific needs) assembled into a dedicated gauging tool can be used for laboratory analysis, with off-line measurement of the enamel thickness on samples of the wire taken from production. The enamel coating or PEEK extrusion operations are usually slow trend processes and they can be controlled through a periodical off-line check of samples.

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In-line thickness control

In-line sensors can be integrated for continuous control during production. A "fork" configuration, with two facing sensors, allows continuous measurements of the thickness of the insulation layer on two opposite sides, together with the total thickness of the wire. Two forks positioned at 90° can be used to measure all 4 sides of the flat magnet wire.
The same technologies can also be used to check the quality of the wire in a subsequent operation in the production of hairpins, where the control of thickness and symmetry of the insulating layer is essential to guarantee the correct execution and stability of the bending process.