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News Release from: Mitutoyo (UK) | Subject: LSM-500H laser scan micrometer
Edited by the Engineeringtalk Editorial Team on 02 December 2004

Laser scan micrometer aids fibre testing

Dia-Stron uses a Mitutoyo laser scan micrometer to help evaluate the tensile properties of cotton, hair, carbon fibre, Kevlar and other fibres as thin as 5um in its automated testing machines.

Dia-Stron, the market leader in miniature, automated fibre-strength testing machines uses a Mitutoyo laser scan micrometer system to help rapid evaluation of the tensile properties of cotton, hair, carbon fibre, Kevlar and other fibres as thin as 5um This performance is unmatched by any other product on the market today

Testing the mechanical properties of various types of fibre is very important nowadays in the medical, electronics and textiles industries, amongst others.

This is particularly true in the personal care and cosmetic sectors where regulations require consistent, reliable data in support of product claims.

Performance testing in this area involves large-scale measurements of human hair strength and elasticity properties, both of which affect ease of combing.

Previously, an important problem was the wide variation in breaking force seen within a batch of hair samples.

This was a serious drawback as researchers frequently look for small differences in hair strength produced by different treatment formulations.

The effect was identified as due to variation in sample cross sectional area (CSA) within a batch, indicating that breaking stress was a better measure to use than pure breaking force and raising the requirement for accurate measurement of very small diameters.

This requirement added to the already considerable time needed to process a typical hair-sample batch, which could take anywhere between two days and a week due to the amount of handling and preparation time necessary.

Dia-Stron's FDAS fibre dimensional analysis system was designed to meet this need by providing a fully automated fibre-diameter measuring capability to submicron resolution and so allow an accurate CSA to be calculated.

Accurate tensile strength properties could now be derived using the company's well-known MTT175/675 Series miniature tensile testers.

The FDAS system uses the same method of premounting fibre samples in PVC-lined brass ferrules as is used with the tensile testers.

This allows fibres to be directly transferred between the FDAS and the MTT675 tensile tester, resulting in reduced batch processing time, down from days to just a few hours.

The huge increase in efficiency associated with automated sample handling and state of the art measurement systems is driving expansion into applications in the textile, polymer, renewable fibre and carbon fibre industries.

Key parts of the FDAS are a Mitutoyo LSM-500H laser scan micrometer measuring unit and associated LSM-6100 multifunction display unit.

This is an automated, noncontact measuring system for measuring thin fibres and coatings.

The principle of operation is that a laser beam, rapidly swept through a 2mm-wide band, detects the size of any object obstructing the beam in the direction of sweep.

This system can be configured to measure outside diameters, or gaps, to a resolution of 0.01um at an accuracy of 0.4um and transfer data to a PC via an RS-232C port.

A fibre sample can be measured at just one point along its length, or divided up and scanned in 24 x 1mm slices.

An optional version of the FDAS has the sample suspended within a chemically inert tank so that it can be measured while immersed in various solutions to investigate changes in CSA over time due to chemical treatment.

A crucial ability of the FDAS is the sample rotation feature, which allows a more accurate measurement of CSA by rotating a sample in the laser beam while taking multiple measurements at predetermined angles.

"The individual human hair varies in diameter along its full length", says Dr Nigel Winsey, Dia-Stron Director.

"Also, the cross section is more or less elliptical depending on the ethnic origin of the fibre, resulting in a single reading not giving a true measurement of the cross sectional area".

"This measurement is only possible with a laser instrument, as a hair tends to rotate to the position of least diameter between the anvils of a conventional micrometer".

Once scanned in the FDAS, the sample is automatically transferred to an MTT175/675 machine for tensile testing.

Dia-Stron's UvWin PC software processes the FDAS data to determine the actual CSA of each sample and, combining this with the tensile breaking force-strain data, produces a complete stress-strain analysis report for the whole batch. Request a free brochure from Mitutoyo (UK) ...

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