Prototype Mechanical Pencils

pinshape

These pencils aren't quite up to par for everyday use. They're more suited to share my prototyping thoughts instead. The pencil is printed in one solid piece without needing supports. Here's a link to the Google plus page: https://plus.google.com/u/0/community/collection/MR4s3kUWqQFZB6eE9 that shows how you load the spring and graphite. This was printed with PLA, 2 shells, 10% infill, no supports at all. You might need a screwdriver to pry the spring off of the base of the pencil. When I remixed one mechanical pencil https://pinshape.com/items/2821456-mechanical-pencil to work for 0.7mm lead, it had some issues. The moving carriage was too easily pushed back when writing, which could be fixed by making deeper gear teeth on the rack. The pencil is a bit awkward to hold, but that can be remedied without changing the mechanism itself. However, the graphite would break off in the carriage and get stuck; that's harder to fix. These pencils work with a mechanism more like existing mechanical pencils. Ordinary BIC mechanical pencils use a spring-loaded chuck. You push the eraser on the back, which opens the collet chuck, allowing the graphite to fall through. The spring then pushes the eraser back, closing the collet chuck and holding the graphite in place. This is essentially the same mechanism, but I replaced the circular collet chuck with a planar gripper and the helical spring with an embedded ribbon spring for easier printing. These pencils don't really work because the gripper doesn't hold the graphite tight enough for writing. The problem lies in the grooves not being deep or precise enough on the gripper to hold the lead in place, even with a stiffer spring and a mechanism that pulls tighter, the graphite can slip off of the line of action. The 3D printed gripper has much looser tolerances than the collet chuck, and the grip opens too widely without a collet. This comes back to the same problem I faced with the remix: how do I hold and release a thin, fragile piece of graphite consistently? I'm exploring other mechanisms that deal with this issue.