Please, somebody, post a link someplace so that JD's explanation above can be easily referred to.
It is a clear concise and non-technobabble sumary that should be required reading for any budding DIY CNC retrofitter.
I admittedly have a preference for servos. Why??? They do have feedback already designed/built into the system. It seems to me that addition of encoders et al to steppers is a way to try to do a back door conversoin of a stepper into a servo. Besides, my neigbor's HAAS has them and if it cost that much, it has to be better. 8-)
Steppers are a bit more economical and, if driven properly by well developed code/drivers, you should not have step loss problems. The thing to remember is that TIME becomes the factor.
Ultimately, can the stepper respond as fast as you plan to send the code??? If not, lost steps and unsatisfactory results will occur.
Remember: It is easy to get the electronics to respond at some gigamegahexahertz rate. Electro mechanical stuff is plagued with inductance, capacitance, slop, backlash and friction and F=MA issues that the computer, sadly, easily ignores...
These ultimately cause more problems than a "you should'a used a servo" or "darn overpiced servo didn't work any better than the stepper I just sold" moment....
Even with servos (well tuned and maintained) we still slow things down when we're trying for optimum accuracy.  |