Aram, measuring torque on an AC servos is definitely possible. It is not as simple as measuring current but this does give some feedback.
I don't think that the current used by the servo drivers is a measure but you try Stan's setup that way. There are servo drivers with force-feedback but I an not sure if you would be able to add force-feedback to an existing machine / servo system. Maybe the easiest way is to add strain gauges, these are cheap can easily be mounted on any existing machine and you can 'calibrate' the output using a weight (with a pulley for X-Y direction). Force applied on your cutter tool will travel through the whole machine, but the further away the strain gauges are placed from your milling spindle, the more acceleration will influence the measurements. The strain gauges are long strips of electrical risistive material that will change their resistance when being pulled (or pushed) on. Glued to a piece of metal (rod or plate) the resistance varies when the metal is bent. Two placed on facing sides and connected into a wheatstone bridge give a real good feedback. I have a pair bicycle cranks operating this way (made by http://www.srm.de) : The bottom bracket is connected to the outer ring holding the chainwheel using a 4-armed spider (I have to guess but the arms are about 10x8 mm or so) and 4 gauges are glued on two facing arms and the resulting signal is converted into a frequency that is linear with the force applied. The system is calibrated (in Hz/Nm) once every two years and the zero point is determined (frequency at 0 Nm force) before each trip. Use force feedback using strain gauges and cutting using a constant force always looked good to me but that may be because I never got any proper training in machining :-) Regards, Rob > Hi > Can you measure torque on AC servo motor? > Can I put that if torque exceed some certain level STOP machine or go to > feed hold mode. It is very important because torque can directly show > condition of cutter. If can stop machine when torque start increase I may > or better will prevent break of cutter. > I think in program need be include variable that limits maximum torque to > axis. > ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
