Our team for the past three years have used IPS extruded aluminum (similar to the Bosch stuff) - they are one of our sponsors! It's like an industrial Lego or Erector set - I highly reccomend it! Not everyone has the equipment or the skills to weld aluminum. It is very easy to build frames and structures with it and most importantly you can easily try things and make prototypes of an idea - and then make changes later! Our teams robot is about 98% built by students and a big part of this is because of the extruded aluminum that we use. I will agree with an earlier post about the weight of fasteners being a disadvantage, but you learn how to substitue lighter configurations once you finalize a layout. If you have any questions about using extruded aluminum feel free to send me an email or send a message to our team
roboclub@yahoogroups.com and many of the students would be happy to help.
Scott