Spindle Assembly
Final Design
The spindle assembly rigidly holds the spindle motor and bearing and allows for the bit to raise and lower to cut traces and drill through-holes. The motor, bearing, and collet chuck are from a cordless dremel.
Motor V-Blocks
The motor is held to the mounting plate by a pair of milled aluminum v-blocks. The lower block is designed to be tangent to the motor for maximum security and accurate location to ensure that the motor is held at the right height to keep the shaft straight. These blocks also serve as heat sinks for the motor to help prevent overheating on long cuts.
Bearing Block
The motor bearing is securely held by a two part bearing block tightened by screws into tapped holes in the mounting plate. This form of attachment has a lower profile than nuts which avoids interference with the frame. The blocks are machined from aluminum and are designed to fit 0.010” apart when contacting the bearing so the screws can be tightened to clamp the bearing firmly.
Iterations
Sprint 2
The whole assembly was originally designed as a laser-cut mortise and tenon part made from ¼” MDF. Because there were no through-holes in the motor or bearing blocks, there was a second mounting plate used to hold the whole assembly together. It was important to measure the motor and bearing when designing this part so that the motor and bearing blocks wouldn’t bend the motor shaft. The first and final versions both used the linear bearings and custom lead-nut holders.
Sprint 3
In sprint 3, we added lead-screw actuation to the z-axis with milled aluminum ways holders, the same lead-nut hardware as the other axes, and an MDF motor mounting plate.
Final Push
In the final version, the mounting plate was replaced with 0.190” waterjet aluminum and the motor/bearing blocks were made from 0.5” aluminum. The thicker stock in a stronger material allowed us to drill holes through the blocks to clamp them together with screws and eliminate the second plate.