CNC Build Part 4: Motors and Ball Screws #3DThursday #CNC
Now that the rails and linear slides are in place, the next step is to install the motors and actuators to drive them. The Pilot Pro CNC rails are actuated via ball screws on all 3 axis – including dual synchronized ball screws on the Y axis to drive each side of the gantry without racking.
The ball nuts that ride on the screws have channels filled with recirculating ball-bearings that ride in the precision ground grooves of the ball screw. This results is very low friction and wear compared to an ACME profile lead screw.
The ball screws are fitted with axial bearings on each end resist the axial loads. This avoids stress on the motor bearings which are only designed for radial loads. The axial bearings are pre-loaded to eliminate any backlash. The ball-screw is held in tension between the bearings on each end. The pre-load washers are tightened down just enough to eliminate any backlash.
The high-torque NEMA-24 motors bolt to the ends of the rails and are joined to the ball screws with flex-couplers. Wires from the motors are routed via drag-chain cable carriers to the back corner of the cabinet where all the electronics will be installed.
Inductive proximity sensors are installed as limit switches on the X and Y axis rails. These determine both the home position and the limits of travel.
Polycarbonate shields on the Y-rails help protect the ball-screws from dust and debris during operation.
Next 3D Thursday: The Electronics
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