Spool Holder for the Printrbot Simple Metal

This is a remix of emmett's Printrbot Spool Holder.

Main changes include:
• A more acute guide arm angle
• Threaded spool rod with an adjustable collar for securing different spool sizes
• A more refined aesthetic and form language

This part was an opportunity for me to practice some applied structural design and solid modeling so it might be a bit over-engineered for its purpose. Feedback is welcome and encouraged.