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FEATURE WIND TURBINE MANUFACTURE


WINDS


Rob Coppinger finds that wind power is being made possible with light


CHANGE OF


Whether they are out at sea or dotting the brows of hills, wind turbines have become a very visible part of national energy grids – despite the concerns about consistency of supply due to variable wind speeds. Those massive blades that rotate slowly, capturing the energy from the force of the atmosphere and feeding it to turbines, need to be as efficient as possible – and lasers have become a key part of the manufacturing process to ensure the composite blades are also geometrically accurate. Germany’s laser technology specialist Z-Laser has provided laser projectors to a turbine blade manufacturer so the company can produce the huge structures efficiently. ‘We are speaking about laser projectors, not line lasers or point lasers; it is a bigger device with a PC onboard that can project free contours,’ says Dr Roland Fritz, Z-Laser’s sales and key account manager.


Fritz explains that the first installation was in 2007 in Mexico, for the company TPI Composites, which has a manufacturing plant there. ‘The first line was installed with five projectors over a mould,’ says Fritz. ‘They have about 40 projectors that are still in use at TPI.’ Blades are made with large moulds, with the projectors giving key production information. The projector system works by pointing a laser at two galvanometer motors, which are orientated at 90 degrees to each other. With this mechanism, a user can derive any point on the contour and follow it. ‘That is the principle


16 PHOTONICS FOR RENEWABLE ENERGY 2013


of laser projectors; this way you can project CAD files or contours onto a 2D or 3D surface,’ says Fritz.


When Z-Laser started selling in the US


through its sales partner, Carter Products, it was not possible for the customer to provide the coordinates – so there had to be a manual digitising process, point by point, to collect the outline contour of fibre mat. Because this is a slow manual process that has to be done for every mould and for each complete blade, Fritz says it can ‘take up to a week to teach all the patterns’. However, now that the manufacturers have the 3D outline contour in a digital format, Z-Laser can import the files to the laser projector. ‘Normally we can project 3D files – which means that, if you have the outline contour with 3D coordinates, x y z, we can align our projector directly to the mould. We can exactly project the outline contour inside the mould, but we need 3D data from the outline contour.’


A question of precision


The lasers do not cut the composite materials. The turbines are made of pieces of glass or carbon fibre, generally called mats, which are laid down in a particular order to give the blade its strength. Fritz explains: ‘The projectors are meant to guide the workers through the lay-up process and sometimes these mats are pre-cut on a cutting table or by hand and then positioned inside the mould.’ The cutting is carried out by workers who


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