Prusa i3 X assembly

thingiverse

The original i3 frame kit provided unusable plastic parts, and Prusa's SCAD files from GitHub were difficult to print well on another printer. To overcome these issues, the user redesigned certain parts to minimize long bridges, and utilized zip-ties for holding X rods and LM8UU bearings. The extruder was only slightly modified, with mounting holes repositioned to fit the X carriage properly. However, an asymmetrical bolt hole placement resulted from this adjustment. Laser-cut Z rod holes were found to be oversized, leading the user to create supports and increase the length of Z rods from 12" to 12.5" for proper fitment. The top left X rod support required significant carving for full Z axis volume clearance. The extruder motor might hit the X rod when at zero position in the X axis, possibly prompting consideration of a smaller extruder. The endstop components were detailed: a bigger one for the Z stop, secured with 2x12mm bolts and nuts, and a smaller one used for the Y endstop, attached with zip-ties. The standard Wade's extruder couldn't mount due to motor-X rod interference; the elevated design from Prusa's GitHub repository was utilized instead. Additional support material was added in the bearing pocket, with 3x50mm bolts used for carriage attachment. Extruder gears, sourced from a biohazard gear model (thing:53103), featured a proper hex depth and conical spacer between the spur gear and bearing. A washer/shim printed to the appropriate thickness ensured proper hobbed bolt alignment. The gear ratio was higher than standard Wade's at 43/13, but didn't stress the stepper motor. A hotend fan mount, secured with 3mm nuts and bolts, held a 40mm fan and J-head extruder via three 15mm bolts. The X carriage had an endstop adjustment screw provision, threaded using a 3mm tap, and a spring from a retractable pen half was used for tension. Z axis components employed zip-ties to secure X rods in U-grooves, with appropriate tightness. LM8UU bearings were attached with zip-ties to the front pieces, and 5mm nuts had float in the wells for Z axis threaded rod wobble reduction. The cavity was cleared using a needle file if necessary. On the motor mount side, an endstop switch for X axis limit was secured with 2mm nuts and bolts, while slot holes allowed belt tension adjustment. A spring applied tension to the Z stop bolt via a 3mm tap hole. The idler end required support material removal or drilling in the idler bolt hole, using two 5x10x4mm bearings, a 5x18mm bolt and nut for the idler, and optional .5mm spacers sourced from RC cars. Lastly, 3mm nuts and bolts clamped the z-support components, with 2.5x12mm screws attaching them to the frame.