Originally Posted by Chris64  OK, so explain please. I've been meaning to ask how CNC lathes work for threading. For threading, do they engage the feed so that the sync is perfect? Or do they have an encoder on the spindle and somehow keep track of where to be?
I could easily see me converting this to CNC just because I'm a computer geek and I love automation. And I could build cooler stuff! |
Yes that is it in a nutshell with the added thing that the encoder also includes a single pulse per revolution so the controller knows the spindles angular position. The encoder is several thousand pulse per revolution.
The Z axis is positioned at the starting point and then a threading cycle is started. The controller starts the synchronization with the single pulse and electronically locks the feed motion on the Z axis to the spindle rotation. A little time and distance is often needed for acceleration before the Z is in synchrony.
When a machine has what is called Rigid Tapping the synchronization is so good that the machine can hold a tap in a rigid holder and the feed remains in synchrony throughout the decceleration and acceleration at the bottom of the tapped hole.