This is a servo driven pen tool head for XY Plotter. Along with standard Contraptor components, the head uses experimental "mini-Contraptor" angle. The mini angle has 1/2" pitch (compatible with Erector set), with 5/32" holes for standard 6-32 screws. It's 1/16" thick and relatively easy to fabricate. The head also uses a couple of custom components - servo bracket from the same 1/2" angle and 1" => 1/2" pitch adapter. Springs are Mcmaster#9654K947. Servo is Hitec HS-311. The pen would be attached with zip ties.