This is the most difficult part of the build. The X-axis is moved up and down by the Z-axis and the stepper moves the extruder over the X-axis.
The original Prusa X axis consists of a separate left and right side connected by two rods. I’ve made one large X-axis, using long technic bricks, for stability. The second image shows the compete X-axis with motor, extruder-carriage and belt. Start with building the right side, then build the left side with the stepper motor. Connect both sides without blocking the extruder-carriage bearings.
The LM8UU bearings are 24 mm long, exactly 3 studs. The bearings are placed between 2 new type technical connectors (gives 8mm distance, 3th image). Use loom bands or tie wraps to keep them in place.
Image 4 (frameside) and 5 show the right side of the X-axis. The 8 mm smooth rods (50 cm each) for the X-axis adapt between the two blue bricks and between the blue and white bricks (5th image). The 2 long red technical bricks are connected to the left side of the X-axis.
The stepper motor for the X-axis is placed at the left side. This is almost a copy of the right side. The difference is the 2 long technical bricks for attaching the motor (8th image).
The 5 mm Z-axis threaded rods are attached to the gray and black 1 x 8 technical brick (8th image). I’ve used 5 mm “metal hollow wall anchors “. These are placed between 4 long technical pins. The outer diameter of the anchors is 8mm. Use additional loom bands or tire wraps for the connection.