Pumpkin Keychain - Print-in-Place Chain and Clip

A Halloween pumpkin keychain that prints in one piece. The pumpkin, the chain and the clip come off the build plate already linked together, so there is nothing to assemble and no glue. The jack-o'-lantern face is cut through, and the edges of the pumpkin are rounded.

PRINT IN PLACE Everything is printed flat in a single job. Every moving part is separated from its neighbors by at least 0.5 mm, so the links break free after printing instead of fusing.

THE CHAIN The chain is made of round-wire oval links, like a real chain. Neighboring links are tilted 45 degrees in opposite directions, so each link sits at a right angle to the next one, just as it does in a metal chain. Because every surface rises at 45 degrees or less, the links print without supports. The pumpkin's stem and the bottom of the clip each have the same tilted link built in, so the chain is joined at both ends with no separate parts.

THE CLIP The clip has a flexible gate on one side. Push it inward to open it and hook the keychain onto a bag, a zipper pull or a key ring. Pushing the gate from the inside does not open it, because the tip rests behind a small hook. The gate is designed to flex about 4 mm, which keeps PLA well within its limits for normal use. It is meant for clipping on and off now and then, not for hundreds of openings a day or for carrying heavy loads.

WHY A BRIM IS NEEDED The links touch the build plate only along a thin strip, so a brim is needed to hold them in place while the rest of the model prints. The bottom of each link is cut flat to give it about 1.6 mm of contact.

AFTER PRINTING 1. Remove the brim. It joins the links together on the first layer, so cut it with a hobby knife or bend the links until it snaps. 2. Wiggle each link until it moves freely. 3. Press the gate inward a few times to free its tip from the hook.

PLEASE DO NOT ROTATE OR SCALE The gaps between the links and the angle of the links are set for the model exactly as it is. Rotating it breaks the 45 degree tilt, and scaling it changes the gaps, so the links may fuse or need supports.

SIZE About 40 x 87 x 6 mm. The pumpkin is 40 mm wide and each link is 10.2 x 7.2 mm.

FILES pumpkin_keychain.stl contains the whole keychain as one file.

THE STORY BEHIND IT I wrote about why I made this for my kids and how it took five versions to get a real chain into a single print (in Japanese): https://note.com/camp_agni2018/n/n289345749898