AUTOMATION
applied to applications where the product again remains in the same plane from pick to place. The design utilizes a parallelogram and produces three purely translational degrees of freedom driving the requirement to work within the same plane. Base mounted motors and low mass links allow for exceptionally fast accelerations and therefore greater throughput when compared to their peer groups. The robot is an overhead mounted solution which maximizes its access but also minimizes footprint. These units are designed for high speed handling of lightweight products and offer lower maintenance due to the elimination of cable harnesses and cyclical loading.
Parallel robots are deployed into many solar cell processing steps. They offer high speed transfer of solar cells through manufacturer lines and processes. Three examples are diffusion of process equipment, wet benches and PECVD anti- reflective coating machines. In these applications the tables and trays have large placement opportunities which could be equally serviced by a Cartesian however the parallel robot out performs the Cartesian from a throughput standpoint. The Quattro parallel linked product from Adept Technology, Inc recently achieved 300 cycles per minute illustrating the capabilities for this class of machine to handle products at high rates.
Robots within the Solar Process
The diagram below shows typical PV process steps. The steps are broken into four basic groups where high concentrations of robots are deployed. The ingot processing step predominantly uses Cartesian gantries and large articulated arms due to the requirement for heavier payloads and large workspace optimization. Wafer manufacturing uses a variety of arm types depending on volume and process requirements. Cell processing tends to use gantries, SCARAs and parallel linked robots and the decision usually lies with the reach and repeatability considerations. Module build uses a variety of arms with a high concentration of articulated and Cartesian arms for reach and flexibility, but some specific tasks utilize the services of SCARAs and parallel robots.
Robot Comparison Example: Anti- Reflective Coating Load/Unload Process.
Following is a comparisons of the four robot categories when considering their use in an anti- reflective coating load/unload process. If we look at a Cartesian robot it is optimized from a reach
standpoint. However, the majority of solutions here would prove too slow and would require in excess of a single head EOAT. This complication would drive the need for pre-alignment and further complications in pre-conditioning the product and therefore may drive prove a Cartesian solution to be considered less flexible.
Cartesian Robots
Too slow for loading/unloading using a single- head EOAT
Because multi head EOAT is often used, cells require pre-alignment
Less flexible when reconfiguring for different size wafers is required
SCARA robots would give us increased speeds and, prove more flexible than a Cartesi. However if we look at a traditional table top version it would limit the workspace and therefore may not be optimal in reaching all points on the load and unload areas of this machine.
SCARA Robots
Faster and more flexible than Cartesian robots when used with vision guidance
Table mounted versions could limit work space and multiple robots may required to cover pallet/matrix
Wafer manufacturing uses a variety of arm types depending on volume and process requirements. Cell processing tends to use gantries, SCARAs and parallel linked robots and the decision usually lies with the reach and repeatability considerations
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www.solar-pv-management.com Issue II 2010
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