Hood, thanks for the reply. If I just replaced the servo's with steppers, where would I be?
That to me is a backward step. Steppers have their place but I am presuming your machine is a medium sized mill and for that servos are superior. I have had a Bridgeport CNC with steppers but also have a Beaver NC5 with servos. The rapids are 4 times greater and could be more and the acceleration (most important in my opinion) is 8 times more with servos.
Would I still need an encoder to guarantee proper position?
Mach is open loop and to guarantee your axis is in the position Mach tells it to be is to have servos with encoder feedback and the motors/drives need to be tuned well to allow a small following error to be set. If you had steppers then as long as they are properly sized they are accurate but there is no real guarantee that they will be where Mach thinks they are. But as said if they are properly sized then the likelyhood of them not being where Mach thinks is very minimal, the only time that has happened on my Bridgeport was when I tried to rapid through the vide
There is a board sold by Ron Rogers which allows you to hook up encoders to monitor the commanded position and the actual position and fault Mach if it is outwith a user set following error but to me it is not really a great idea. Sure it will stop if you are out of position but if that is the case then your steppers are not up to the job so thats all that it is really telling you. Of course others may have different opinions on that
Would I still need motion controllers or does Mach3 do that?
If using steppers then the parallel port could be used, this could also be used if using servo drives that can accept step/dir input but if your encoders are high count then rapids could be limited. I get over this issue by using the SmoothStepper, it pulses externally to Mach and is a very smooth pulse of up to 4MHz per axis.
Do I understand correctly that a breakout board is optional but offers protection to your pc.
Thanks.
Depends on the way yougo, if using one of the cotrollers mentioned in the first post they will likely need some form of making easy connections. If using the parallel port or the SmoothStepper then again a BOB makes connections easy. Most BOBs can also buffer the parallel ports voltage which means you can use the modern computers 3.3v ports and the BOB will buffer it to 5v.
So to answer your question, a BOB is probably best but not always needed but is a big convenience.
Hood