Welcome to the forum

As max said, so long as you are planning to enter it into the featherweight competition, that acrylic wont cut it... sorry. If you like the clear look then go for Polycarbonate (Or lexan to some) otherwise you can use HDPE.

This is my first year in competition and my first machine was a mix of 10 and 20mm HDPE but it withstood, mostly, hits from possibly the most destructive spinner in the uk: NST.

Most of us get it from here... http://www.directplasticsonline.co.uk/

Note- Don't make your base out of Nylon 66 like I did, NST shattered it with a single hit so I spent the rest of the fight with the robot dragging on the ground... not so good!