Testing without destruction at Nordic Lights

Manufacturer of industrial lighting benefits from the use of computed tomography

Posted on 30 Oct 2018 and read 1047 times
Testing without destruction at Nordic LightsFounded in 1992 and based in Pietarsaari, the Finnish company Nordic Lights manufactures premium lights for the workplace and for heavy-duty vehicles deployed in extreme conditions.

Its products are used throughout the mining, construction, forestry, material-handling and agricultural industries, and its customers include industry leaders such as Caterpillar, Liebherr, Sandvik, Komatsu and Volvo.

Lighting assemblies are typically made from aluminium, steel, plastic and glass, and their components are manufactured by a range of processes, including die-casting, injection moulding and machining.

Products are subject to rigorous testing and rely on industry-leading inspection methods for quality assurance.

Tests include: lumen output and light distribution; resistance to chemicals, vibration, shock, dust, humidity, heat and cold; electromagnetic compatibility; and performance under abnormal conditions.

Many components incorporate ribs, pins and cylindrical holes that historically were inspected by Nordic Lights using a ‘white-light’ system.

However, scanning components with narrow or tight features is difficult when the details are too deep for the light to detect; another problem with this inspection method is that, to avoid unwanted reflections, smooth surfaces have to be painted or powder sprayed; this can introduce measurement errors on critical surfaces where precise tolerances are required, slowing the whole inspection process.

Furthermore, as the white-light system was only capable of line-of-sight external surface inspection, internal defects were neglected.

To gain a comprehensive picture of the inside, samples and products were subject to costly and time-consuming destructive testing.

New solution

The white-light system needed to be replaced by a new measurement solution that was capable of dealing efficiently with a variety of materials and offered both internal and external feature inspection.

The Nordic Lights team consulted various suppliers to determine the best solution, finally selecting an XT H 225 ST computed tomography (CT) machine from Nikon Metrology (www.nikonmetrology.com).

The primary purpose of the CT system is to validate samples from suppliers, new parts and modified parts from new moulds. A secondary purpose is troubleshooting.

If there are any failures during the test phase, complete assemblies can be scanned to identify the cause without having to open or destroy the product.

For example, the system has been used to search for air pockets or voids in the silicone glue between the aluminium housing and the lens of a light that has suffered water leakage.

This would not have been possible with the white light system.

Test engineer Carl-Anton Manns said: “The instrument needed to be able to analyse smooth reflective surfaces with high precision, which the XT H 225 ST does with repeatable accuracy. Being a non-destructive process was also a big plus point.

“Furthermore, verifying the tool that makes the prototype part at the beginning of a project avoids a lot of trouble later on.

“With Nikon CT, we can easily verify all dimensions and check for defects without having to destroy samples, which is important so they can be preserved for other inspection tests.

“There are also important savings in time and money by avoiding sample preparation tasks such as painting or cutting.”

A major factor in the decision-making process was the open-tube source of the Nikon machine, which allows straightforward maintenance and results in lower costs and down-time.

The availability of rapid and comprehensive service from Nikon support engineers was also a key factor.

A further advantage of the CT system is that it can provide the precise results for dimensions and tolerances that Nordic Lights’ customers demand for optical parts, lenses, light guides and reflectors.

Defects can be identified, traced and eliminated during the development phase, before the parts pass to production.

Likewise, samples from suppliers, new parts and new moulds can be compared to their CAD models before assembly.

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