|
|
| Y-Y-Z axis positioning for high-end solar panels | |||||||||
The Energy Research Centre of the Netherlands (ECN) is a large organisation responsible for developing high level knowledge & technologies for sustainable energy systems and coordinating their transfer to profitable production. | |||||||||
|
ECN have developed a new solar cell design which is essentially made up of several thin layers of positive and negatively charged silicon arranged in 5 to 10mm diameter star shapes to create a larger effective surface area and higher efficiency. Laser machining is used to provide interconnection and insulation between the layers by tracing these circular and star shaped patterns with contoured interpolation of the X and Y axes whilst controlling the Z axis depth - all within accuracies a just a few microns over a typical travel range of 200x200 mm. Maximum contouring speeds to 250mm/sec and up to 0.1g acceleration/deceleration performance were also critical to the application.
Accuracy therefore starts with the mechanical structure. Initially, the decision had to be made as to whether the product or the laser was to move. Since the latter has a relatively large mass and high throughput speed was of prime importance, it was decided to mount the solar cell work-piece on the X-Y table which in turn was mounted on a steel and granite machine base. This enabled the system to achieve a high stiffness with Aerotech ALS5000 series direct-drive linear tables chosen for their high dynamic and zero backlash performance. The lower axis used the ALS5000WB wide base version to increase the support area for the upper stage and prevent any deflection when the moving carriage is at either end of travel. The wide base stage was also equipped with dual linear motor drives to ensure the demanding acceleration performance required for the application. The laser was mounted on a separate ATS165 Z axis positioning stage fixed to a vertical mounting bracket on the granite base. Rather than use linear motor driven stages with counterbalances for vertical high precision axes, Aerotech are often able to specify conventional servomotor driven ball screw stages where gravity simply counteracts any backlash or lost motion. To ensure the optimum protection from laser processing debris, all axes used hard cover designs with side sealing strips and pressurised clean air forced into the inside of the stage to form a complete barrier. Working surfaces were also treated with a Rockwell 62 Teflon impregnated coating for added durability. For such micron level applications, optimum system mechanics alone will not provide the required accuracy and precision. Aerotech’s engineered system approach includes motion and machine control, features such as axis calibration, tuning and harmonic filtering, and laser firing control to ensure that the complete system will perform. | |||||||||
|
| |||||||||
| |||||||||
|
| |||||||||
Copyright © 2008 Thomas Publishing Company