Here at oomlout we’re massive fans of building, rather than buying, tools and equipment. A lot of the devices we use on a daily basis we’ve designed ourselves and shared on Thingiverse, and we keep an eye out for others who have done the same - like Botmaster, who has shared a handy-dandy razor guillotine which is designed for safely cutting heat-shrink and similar tubing to a user-defined length. While our weapon of choice is a laser cutter, Botmaster uses a 3D printer - and if you don’t have one lying around your work area, get in touch with your local hackspace to see if they can get you started on theirs.
I needed a way of cutting heat shrink tube into repeatable short lengths. It also needed to be safe and not have any exposed blades. It is all 3D printable, the only extras are the guide rods - these are K&S stock #508 5/32 music wire that can be purchased at any model shop - a single-edge razor blade and two lightweight springs.