Yet another design of extruder for Prusa i3. X carriage is compatible with other style direct extruder with NEMA17 stepper.

Key Features:

• Compact and lightweight X carriage, no zip-tie LM8UU bearing mount.
• Quick filament change locking lever.
• Robust cooling with 40mm fan shroud and 52mm blower nozzle.

BOM:
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• MK7 extuder gear 10.5mm effective diameter
• Spring 5mm ID
• 624ZZ bearing
• E3D hotend V5, (the long one/clone)
• 40mm fan
• 52mm blower
• 3pcs LM8UU bearing

Hardware:

• 8pcs M3 x20mm socket head screw, 3 for NEMA17 stepper, 1 for locking lever, two for E3D clamping. 1 for blower top mount, 1 for extruder spring tensioner.
• 1pcs M3 X6mm flat head countersunk screw for top right NEMA17 mount.
• 1pcs M4 X16mm screw for 624zz bearing mount
• 6pcs m3X12mm, 5 pcs for 40mm fan/shroud, 1 pcs for blower nozzle support
• M3 nuts and washer as necessary, Fan mounting holes on printed parts are intentionally designed to be smaller, such that they can be mounted by M3 thread tapping in the hole without nuts.

Design considerations:

• X carriage is designed with thin wall structure for rigidity yet not over constraining LM8UU bearing. Two bottom LM8UUs are responsible for X-Z plane load, while top LM8UU holds up for Y.
• An eccentric locking lever is added to facilitate filament handling.
• Minimum fastener usage.
• No zip-tie.
• Robust cooling fan mount.
• No constrains for NEMA17 motor length so high torque stepper is highly recommended.
• Top LM8UU bearing holder have reduced stiffness to accommodate X carriage rod misalignment.