Assemble the Y-Motor and Y-Idler
Slide a drive timing-pulley onto one of the stepper motors. The distance from the mounting surface of the motor to the pulley should be about 8.5mm, or enough so that the bottom flange of the pulley just clears the y-motor-bracket when mounted. Tighten the set screws before attaching motor.
Attach the motor to the y-motor-bracket as shown using M3x20 and washers if using MakerBot steppers. If not using MakerBot compatible steppers then use bolts of equivalent length that will match the threading of your motors.
Assemble the belt routing pulleys as shown. Note that there are 3 M4 washers sandwiched between the fender-washers, if you accidentally leave one of them out the belt will rub.
Step 4 - Optional
Run the bolt and washer through the front and attach the two spacer nuts then tighten. Then mount the opto limit switch and snug down with washer and remaining nut.
Attach the belt routing pulleys to the y-idler-bracket as shown. The pulleys are identical to those for the y-motor-bracket above.
On to Phase 2