608 Ball Chain Idler with matching Pulley Hack

thingiverse

This project uses a ball chain pulley system as an alternative to timing belts for Prusa Mendel 3D printers. The nylon string ball chain, purchased from a craft store, costs $2.50 for 30 yards and is less expensive than the cheapest timing belts available online. The actual ball size is 4mm with a center-to-center length of 5.3mm. The user shares their experience in designing this product, highlighting key steps in the process. They advise measuring the ball chain size and link length to establish a baseline (e.g., 4mm ball with 5.3mm links). Adjustments should then be made to the code parameters, particularly increasing the ball size for better depth, grip, and no slippage. The user stresses the importance of getting the size and depth correct before moving on to other steps, as changing these later can affect the fit of the chain around the pulley or idler. They also provide instructions on printing a pulley or idler, checking its fit with the chain, adjusting link length in the code, and finally printing the missing piece once the first one is correctly fitted. They also mention additional considerations like determining extension lengths for Y-axis alignment, drilling out the pulley to match stepper shaft size, and modifying the code for grub screw placement. The OpenScad file contains comments and modifications made during the design process, which can be helpful for others looking to replicate this project. Overall, the user emphasizes thorough measurement and adjustment to ensure a proper fit and functioning pulley system.