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Affordable Automatic Paint Spray Characterisation Systems from Oxford Lasers

Published on 2007-08-17. Author : SpecialChem

Oxford Lasers VisiSizer range of cost effective optical spray characterisation systems have the ability to measure down to 1 micron with high data rates, high resolution images and real time data analysis. Other characterisation systems may be able to provide some of these facilities but Oxford Lasers can provide sizing, velocity measurement and images all in the same system. These are the features that can improve efficiency and save costs for manufacturers large or small. VisiSizer provides unique insight into three key aspects of the paint spraying process - the break up of the spray into droplets, the size and velocity distribution of the droplets, and the adherence of the droplets to the component surface.

Visualization provides insight into how the nozzle parameters affect the drop sizes. Drop sizes can be measured at up to 7680 drops per second.

The cost and quality of paint spraying operations, especially in the automotive industry, are of vital importance to manufacturers. For small manufacturers using air guns to apply coating to components, large quantities of paint and adhesive are frequently wasted because spray guns are unable to target coating material with any accuracy. For large manufacturers using electrostatic spray coating systems (not suitable for small components) it is essential that accurate quality assessment can guarantee that paint and adhesive are being correctly deposited on to target surfaces. For manufacturers large and small, government guidelines continue to place ever more stringent requirements on all kinds of spray processes and any resulting emissions.

By using VisiSizer to obtain measurement data and images it is possible to see exactly where paint is being sprayed, if it is missing the target component, if the paint is being distributed evenly, if the paint is adhering to the surface, and if the paint spray nozzle requires adjustment or a different design. Significant cost savings can be made by more accurate paint spraying with consequent reductions in the amount of paint, adhesive or solvent used. More efficient use of coatings, either liquid or powder, also results in reduced emissions. Optical spray characterisation eliminates the time consuming and expensive traditional measurement techniques currently being used by many test engineers.

The impact of droplets onto a glass slide when viewed as a movie shows that most droplets do not stick to the slide until considerable numbers have merged together.

The VisiSizer sizing technique operates by using a very short flash of light from a laser to illuminate a diffusing screen in order to backlight the subject. A digital camera with a microscope lens captures images of the spray cloud which are processed to extract data regarding spray size, shape and velocity. Even non-spherical droplets can be accurately sized - a facility that is almost impossible by any other method.

By using dual laser flashes in short succession, image quality is greatly improved and a greater range of information is obtained. A paint spray plume contains particles often moving at such high speeds that conventional lighting would result in problems with motion blur. VisiSizer is able to completely eliminate motion blur and by using proprietary VisiSizer software it can measure the movement of paint particles and paint velocity, allowing velocity vs. size distribution analysis to be computed.

These automatic calculations can dramatically boost the efficiency of paint transfer allowing manufacturers to use less coating material more effectively. For electrostatic spray systems, VisiSizer can provide accurate, quality control information for the product coating process. Spray gun manufacturers can use VisiSizer to see for themselves how liquid or powder products are distributed after leaving the nozzle and giving them the opportunity to optimize nozzle design and provide their customers with the best possible coating results.

Oxford Lasers has had 30 years of experience in the manufacture and integration of lasers and laser systems worldwide. Their team of highly qualified and experienced engineers is available to advise on the best spray characterisation system for all coating purposes.

Source: Oxford Lasers

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