Bicycle Chain Guard

thingiverse

Replacement chain guard for a Tern folding bicycle, or any with a hole pattern of 5 M6 holes at 180mm diameter. The bicycle shop quoted $20 and a week for this part, but this one comes to $2 or less in filament. Print in two colors or more and it will pop. Puzzle-fits with 5 identical pieces, so it can be printed on pretty much any printer that can do a 5" part, like a 4x4" Printrbot simple or my Kossel Air with a 6" diameter bed. Includes printed M6 threads. If you want a single piece, it's an easy change to the Inventor source. Instructions Prints without supports. I used 0.2mm layers with 3 bottom / 5 top solid layers, 4 perimeters, and 30% infill. Probably could have gone thinner. Printed in PLA @ 200ish, mostly 50mm/s speeds. Make sure your extruder is calibrated; over-extruding will yield threads that won't fit nuts at first, but you can correct this by using a socket with a nut to form the threads with pressure. Also make sure to have a really high minimum layer time, like 12 seconds, to have a chance of a single layer cooling on the threads. Unless your min area setting in the slicer setting is super-small, the thread will be a solid area; without sufficient cooling or waiting (such as printing all 5 at one), the threads become a big glob.