This thread seems to be bouncing around a bit, but I’d like to share my thoughts on the matter of shutting down the controller versus leaving it on.
When it comes to intricate carving work like inlays and 3D reliefs, I’ve experimented with shutting down or rebooting the controller and attempting to return to the EXACT same spot at a later time. I must admit, achieving accuracy within 0.5mm to 1mm (0.0197" - 0.0394") has proven to be a significant challenge. I believe one of the primary reasons for this difficulty is the process of homing the machine. Even when using limit switches, let alone stall homing, attaining sub-millimeter precision is a tall order.
The closest I’ve seen this level of precision is with one of my 3D printers, which employs an inductive probe for Z-axis bed leveling, achieving a 0.01mm (0.0004") precision and approximately 0.005mm (0.0002") accuracy. Nevertheless, I still find myself fine-tuning the Z offset by about 0.005mm back and forth every dozen or so prints. Even with such a high level of precision, it still remains a formidable challenge to power down the controller and expect the printer to home itself within 0.5mm accuracy and seamlessly pick up where it left off.
As a result, I’ve adopted the practice of leaving my CNC machine on when doing multi-step detail work. The primary concern with leaving the machine on is the constant energization of the stepper motors and their drivers, which may potentially reduce their lifespan. However, I believe this is only a genuine concern over a time frame of weeks or months of continuous power-on operation.