On the right lines

A portable laser-projection system that can be used to help in the accurate alignment and assembly of products has been developed by Canadian engineers.

The new system, introduced by laser specialist Virtek, incorporates indoor GPS technology, which enables it to be far more flexible than existing laser projection systems.

Laser projection, a technology more readily associated with the cinema experience, is increasingly being employed in manufacturing environments to give engineers precise instructions on how to assemble systems.

Such systems use CAD data to project design or build instructions on to an assembly showing workers how to perform a task.

The projected image could also be a map of where to install parts, complete with instructions on how to carry out an assembly or an outline of plant locations.

One of the drawbacks of laser projection has been that to project an image on to a 3D object the projector must know its location and the location of the target to a high degree of accuracy. However, without a global, factory-wide positioning system, the projector cannot be easily relocated or moved around the plant. This limitation has slowed the adoption of such devices.

The work carried out by Virtek represents the first time that laser projection technology and indoor GPS have been used together, said the firm.

Indoor GPS doesn’t actually use satellites. Instead, small infrared laser transmitters dotted about a factory emit laser pulses that are picked up by a network of sensors. The information gathered by the sensors can be used to calculate a ‘measurement universe’ which, when hooked up with the laser projector, enable it to be moved anywhere within a factory.

This eliminates the need to place and survey reflected targets within the field of view of the laser projector and allows operators to move the projector or part around freely at any time.

Bob Sandness, president and chief executive of Virtek, explained the difference between conventional laser-projection technology and the new system: ‘Traditional laser projectors have to use targets to figure out where they are projecting,’ said Sandness. ‘And that means you have to drill holes or mount something specifically on a fixture to do the work with the laser projector. With the GPS you eliminate the need for that.'

We have broken new ground in combining laser projectors and indoor GPS, said Sandness. ‘Basically the key thing is using the laser without the targets. To our knowledge no one else has done that.’

This technology has a number of applications, but most recently the company began working with Lockheed Martin on the F-35 Joint Strike Fighter. Here the system is being used to apply appliqué gores on to the aircraft’s exterior.

This material, used instead of paint, is pre-cut from a large sheet or roll of paint replacement film in a manner that enables it to adhere to the contours of the F-35. The system aids this by accurately projecting the correct sequence of optical positioning templates on to the outside surfaces of each fully assembled F-35.

‘Where we are installing appliqué on the surface of the plane it would be impossible to drill holes for targets. So indoor GPS allows us to do that,’ said Sandness.

He said that the accuracy obtained by the system was comparable to a conventional targets-based approach. ‘The accuracy is still quite good. With targets you can get accuracy to around 10,000th of an inch, whereas with indoor GPS you are looking at more like 20–30,000th of an inch. For most applications, though, the difference is negligible.’

A further aerospace application identified by Sandness is using laser projectors to enable engineers to line up and then accurately hook aircraft wings on to a fuselage.