Test & measurement
COLOUR SENSORS AND MEASUREMENT SYSTEMS FOR SURFACE FINISHING APPLICATIONS
Significant improvements in measurement speed and accuracy of non-contact colour measurement sensors have led to their increased use in many different production processes, including surface finishing applications, says Glenn Wedgbrow, business development manager at Micro-Epsilon UK.
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urface finishing encompasses a wide variety of processes such as deburring, coating, polishing and texturing. The purpose is to modify a surface to improve specific properties such as corrosion resistance, durability, adhesion or appearance. To ensure high quality standards, measurement of colour is an invaluable technique in surface finishing. Micro-Epsilon offers a range of colour sensors and measurement systems for use in surface finishing applications – from sensors that recognise and distinguish colours, to systems that measure the colour of metallic components and coated flat glass, helping to ensure the quality and consistency of the final product. Here are some application examples:
COLOUR MEASUREMENT OF ZINC- COATED STRIP
Steel or aluminium strip material is used to produce punched, bent and deep-drawn components. The steel or aluminium is coated with zinc for refinement purposes, to enhance the appearance and to provide resistance. The zinc is deposited onto the cleaned strip from an electrolyte solution by applying a high electrical current. As well as receiving corrosion- and wear-resistant protection, the strip material also has a defined colour. Reliable testing of this colouring is necessary in order to ensure consistent product quality. In order to fulfill the high requirements for precision and speed, the colorCONTROL ACS7000 colour measuring system from Micro- Epsilon is used, which recognises colour shades to an accuracy of ΔE < 0.08. Manual, visual inspection is not possible in this area, as a trained human eye can only recognise colour distances up to a maximum of ΔE 0.5. In addition, the colour measuring system must keep pace with production and is able to provide high
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speed inline measurements. Influences induced by fluctuating temperatures are minimised by continuous referencing. Via an Ethernet interface, these high precision measurement values are directly transmitted and evaluated by a connected production monitoring PC. Should any deviations occur, the plant operator can rapidly intervene, which means waste is reduced.
DISTINCTION OF SHINY SCREW NUTS In fully automatic machining centres, the reliable distinction of supplied parts is critical. In particular, measurement objects with shiny surfaces place high demands on sensors. Here, colorSENSOR CFO100 sensors from Micro-Epsilon are used to reliably differentiate between glossy nuts made from aluminium and tin. An optical fibre is guided to the measuring point. The high accuracy of the CFO100 sensor then enables the reliable detection of the respective metal and transfers the measured value to the processing machine.
INSPECTING THE INTERIOR COATING IN ALUMINIUM CANS
During production of aluminium cans, the inside and outside surfaces are painted with transparent varnish that protects the can from corrosion and prevents any reactions with the filling media. For presence monitoring of the interior varnish, colorSENSOR CFO200 colour sensors from Micro-Epsilon are used which check the presence of the interior varnish using fibre optic sensors.
COLOUR DISTINCTION OF ALUMINIUM RIMS
In the automatic inspection of incoming goods, identical colour shades must be assigned reliably in order to be able to match identical colour pairs. For fully automatic recognition of colours,
the colorCONTROL ACS7000 colour measuring system is used. It recognises bright and dark colour shades in order to ensure the reliable assignment of relevant colour shades.
RECOGNITION OF ANTI-REFLECTION COATING ON LENSES
Optical surfaces of many lenses have an anti- reflection coating which should reduce surface reflections. These anti-reflective layers must be applied evenly; otherwise undesired colour gradients may occur which might impair the function of the lens. In order to inspect the visual colour impression (green-blue for highly sophisticated coatings) and the coating quality, colorSENSOR CFO200 color sensors are used. Equipped with the A1.1 sensor head (total reflection/angle of incidence=angle of reflection). Due to the high resolution, they detect even the slightest of colour variations reliably.
COLOUR SHADE INSPECTION OF FLAT GLASS
The colour of glass is the crucial and visually distinctive feature of many different glass products. This is particularly true with raw materials based on varying compositions, where continuous and
October 2025 Instrumentation Monthly
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