Four-Colour Retractable Pen Mechanism with Latch Ring, Enlarged for 3D Printing

Enlarged four-colour retractable pen mechanism, designed for 3D printing. 32 mm barrel, 228 mm long, carrying four 6 mm refill tubes on a 12 mm circle Four identical sliders, each with a thumb button, a pin for the refill tube and a latch tooth with a 45 degree cam One turning latch ring in a groove at the barrel joint, with four lugs and a small return spring Push a button: its tooth cams the ring aside, passes the lug and is held under it after a 16 mm stroke, so that tip is out Push any other button: the ring turns again, the first slider is freed and its spring returns it. A half press retracts the pen without choosing a new colour Return springs sit around the tubes on a printed plate, 28 mm released and 12 mm at full stroke End cap with four keys that close the slots and set the upper stop, plus a pocket clip Latch overlap is 1.5 mm along the ring and 1.2 mm radially. Sliding clearances are 0.2 to 0.4 mm Every part checked against every other in 3D for zero overlap, with one slider latched and three up. About 93 g printed in PETG Files: STEP of the tip, lower barrel, upper barrel, cap, latch ring, sliders and the full assembly (opens in SolidWorks, Fusion 360, Inventor, Creo and Onshape), STL of the printed parts, a drawing with sections and mechanism data (PDF and DXF) and presentation renders. This is a design model. It has not been printed or cycle tested yet, so the cam angle, latch overlap and spring rates still need tuning on a first prototype. Refills and springs are shown as placeholders and should be replaced with the real purchased parts. The model is parametric, so tube size, stroke and barrel length are quick to change. Message me if you have a push-button or spring mechanism that needs working out in CAD.