| Spindle Bearings |  |
| Tapered roller bearings constrain the spindle shaft both radially and axially. The back-to-back layout allows for thermal expansion of the shaft. A spring (Belleville) washer is used to preload the bearings to the appropriate ammount. This preload level is determined experimentally through the tradeoff between shaft stiffness, which improves machining accuracy, and the torque required to rotate the shaft, which can potentially overload the motor. Shaft runout of less than 0.001" was achieved. | |
Spindle Bearing Layout |
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| Drive Mechanism |  |
| A V-belt drive system is used to transmit power from the motor to the spindle. A V-belt is used to allow for slippage (as opposed to gears and timing belts) and for its desirable alignment and power transmission capabilities. The drive ratio is determined from the expected torque during machining and the desired speed, in conjunction with the torque-speed curve of the motor. The belt is tensioned by adjusting the bolts on the motor mount. | |
Spindle Drive Mechanism |
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