Loosen and remove the bed leveling thumbwheels, then lift the heated bed and set it aside.

The heated bed will later be re-installed on the new carriage plate using the original mounting hardware.

Loosen the (6x) mounting screws that hold the Y axis extrusion in place. Take the complete Y axis extrusion off the S1 base.

Detach the GT2 belt from the Y Carriage by sliding it out of the notches on each side.

Loosen the (2x) M3 screws on each side of the belt tensioner, then remove the belt tensioner from the Y axis extrusion.

The GT2 belt is routed through the center channel of the aluminum extrusion. Carefully remove this and set it aside.

The belt will be re-used after installation of the MGN12 linear rails, adapter blocks and new carriage plate.

Detach the Y axis stepper motor assembly from the extrusion by loosening the (2x) M4 button head screws.

Remove the M4 screw and washer from the carriage plate and set these aside. They will be re-used at a later stage.

Place the Tensioner Bracket (A) on the front, and Motor Bracket (B) on the rear of the Y Beam (C), then secure in place with the included hardware.

Slide the stepper motor assembly on to the rear of the Y Beam, attaching it with the original M4 screws.

Insert the GT2 belt through the center of the Y Beam, then route it up and through the stepper motor assembly.

Route the GT2 belt through the belt tensioner, then slide it on the front of the Y Beam.

Use the original (2x) M3 screws to fasten it on each side.

Place the complete Y Beam assembly on to the S1 base, aligning it with the original holes.

Use the M5 mounting hardware included in the package (C) to secure it. (2x) M5x6mm screws in the front and (4x) M5x18mm screws in the rear.

Place the MGN12 linear rails (D) side by side on the Y axis beam. Use the (12x) M3x6mm screws included in the package to loosely secure them in place.

Insert the printable alignment guide between the (2x) MGN12 linear rails in the front, then tighten down the front of the left rail.

Move the alignment guide to the rear and repeat the process, then tighten all screws on the left rail starting from the back.

Note: The base of the Ender 3 S1 has been omitted for clarity.

Mount the new Modular 3-Point Y Carriage Plate using the (8x) M3x6mm screws included in the package (E).

Install the original M4 endstop screw and washer from Step 5.

Attach the GT2 belt to the front and back of the carriage plate, then tension the belt as needed.

Install the heated bed with the stock springs and bed leveling thumbwheels.