Building the frame
The first assembly step is mounting the two vertical side rails onto the printer base. These form the gantry that will carry your print head up and down. Getting the correct rail on the correct side now is critical for everything that follows.For this step you need the two M5x45 screws (the long ones) and the number 5 Allen wrench (the largest).
Step 1: mounting the side rails to the base
Unwrap and identify the rails
1
Remove the plastic wrap
Carefully slit the cellophane along each rail with scissors, cutting away from your body. A small loose screw may fall out of one rail - set it aside (it is only there for shipping). Watch the sharp edges.
2
Identify the two different rails
The rails are not identical. One has two screw holes on the same track, about eight inches apart - this is the right rail. The other has two holes near the bottom in separate tracks - this is the left rail.
Mount the right rail
1
Position the base
Move the printer base to the center of your workspace. Face the dragon/Ender logo toward you - that is the front. The LCD will go on the right.
2
Line up the right rail
Take the rail with two holes on the same track and set it on the right side, holes closest to the inside (toward the bed) and near the bottom.
3
Screw it in from underneath
Tilt the printer to access the bottom. Push an M5x45 up through the base hole and into the bottom of the rail. Hand-thread it, add the second screw, then tighten both fully with the number 5 Allen wrench until the heads sit flush and the rail does not wiggle.
Mount the left rail
1
Position the left rail
Take the remaining rail (two holes near the bottom, about one inch up) and set it on the left side, holes toward the inside.
2
Screw it in the same way
Tilt the printer, push M5x45 screws up through the base into the rail, hand-thread both, then tighten fully. The screw heads should disappear flush into the track.
Both rails are bolted on with no wiggle, the screw heads sit flush with the bottom of the base, the two-holes-same-track rail is on the right, and the two-holes-near-bottom rail is on the left. Give each a firm wiggle to confirm.