Mach&servos

[lgalla]

Just read Mach does not support servos,you need servo amps that accept step&direction.My silly question,does this mean you are running your servos as if they were steppers?Would DESK CNC work better with servos?
Thanks
Larry

[Halfnutz]

No, they are not being run like steppers. Mach works great with servos, as long as the drivers accept step & direction commands. Traditional servo systems use a central controller that does all the measurement, calculation and command in a dedicated computer and sends an analog signal to the servo drive that is bassically just a current amplifier. These are called analog drives sometimes.

Modern digital servo drives are capable of doing the position measurement and control calculations themselves and only need to know how much and in what direction to move the servo motor. They can monitor events like limits and shut down the motors in case of problems on their own. Some of the older digital drives and most of the new ones will accept pulse commands as well as traditional +/- analog command and even serial commands through a RS 485 or 422 network or ethernet, modbus, etc.

As long as the drive accepts step and direction comand inputs it should work great with MachX or DeskCNC or any step & direction CNC controller.

Here are pic's of my latest CNC project. These are the Y and Z axis slides of a gantry type router with Omron (made by Yaskawa) AC Servo drives and motors. I am getting 600IPM rapids and 300IPM feedrates with Mach3 easily. Gecko, Rutex and others have powerfull DC servo drives at very reasonable costs designed for step and direction systems.

[ger21]

Originally Posted by lgalla Just read Mach does not support servos,you need servo amps that accept step&direction.My silly question,does this mean you are running your servos as if they were steppers?Would DESK CNC work better with servos? Thanks Larry

DeskCNC won't work any different than Mach, with the exception of being able to possibly spin the motors faster due to the higher step rate (vs Mach using the parallel port)

[lgalla]

Halfnutz and Ger21 thanks for the excellent replys.It was very informative and easy to understand.Answered questions I had not asked yet.Everything I read on steppers vs servos say servos can self destruct if there is a problem and steppers will just stall.Good to know the servo drivers can sense fault or error.Again thanks.
Larry

[ger21]

If you have get a bad encoder or broken encoder wire with a servo, it can run away at full speed and crash the machine. That's what limit switches and E-Stops are for. A stepper may stall if you have a problem, but it may also have enough power to damage the machine. Again, limit switches are your friend when these problems arise.

[Al_The_Man]

Originally Posted by lgalla .Everything I read on steppers vs servos say servos can self destruct if there is a problem Larry

This can depend on the type of controller, in a true closed loop system, it is common to monitor the following error, if it is out of limits due to run-away etc, the controller can shut off the Drive enable or operate the E-stop, and also issue an alarm message pin-pointing the axis.
Al.