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Laser seam tracking sensors from Meta Vision Systems are increasing the efficiency of automated welding cells producing exhaust treatment products for heavy vehicles at Swenox’s factory in Nykoping.

European legislation on exhaust emissions is becoming increasingly stringent, which has prompted advanced on-vehicle treatment solutions to be developed by companies such as Swenox to meet the requirements of lorry and bus manufacturers.

The products catalytically convert carbon monoxide, unburnt hydrocarbons and oxides of nitrogen to their harmless gaseous constituents and water vapour and include filters to trap particulates.

They are integrated into complete exhaust systems that Swenox also fabricates to customer requirements.

The design and manufacture of such systems are demanding, requiring gas-tight joints on convoluted shapes.

There are often conflicting criteria, such as a requirement to minimise weight while maintaining durability and operational reliability.

A considerable amount of arc welding is needed to join the individual components.

The nature of the constituent materials results in spring-back and heat distortion, making automatic welding difficult to achieve and so calling for the use of seam tracking.

However, owing to the large variation in reflectivity of the materials, most ordinary laser sensors struggle to detect the seams.

Meta Vision Systems’ new SLS sensor, which forms part of the Smartlaserpilot system, has overcome this problem thanks to its ability to remain unaffected by varying surface conditions and reflections from the metals being welded.

It does this using the real-time, automatic intensity control of the laser stripe, allowing the vision analysis software to deliver a high-quality image at all times.

The Meta sensors are used in two twin-robot welding cells at Swenox, a single robot controller driving both ABB robots in each cell.

The sensor head contains a megapixel camera and more computing power than a powerful laptop computer.

With its weaving, seam search and reframing functions, it collects information on the position of the joint being welded and communicates it to the robot controller via an Ethernet link and switches.

Based on this data, robot motions are continuously adjusted when effecting multi-layer lap joints with tacks as well as circumferential and other welds.

The welding equipment was supplied by Fronius CMT.

Meta Vision Systems

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