2012/3/17 Roger Holmquist <ro...@abcnc.se>: > Thanks for your responses. > It seems I have to give LinuxCNC a closer look. > > There is a low cost commercial alternative in MACH 3. > I guess you have an opinions on that system too?
That is pretty much provocative question :)) Here is my thoughts, why Mach _is not_ an alternative to LinuxCNC (but that is just my personal opinion): http://www.cnczone.com/forums/1046479-post76.html I address some of Your points there, like being realtime and also the looks of the application. > It also seems to be mainly focused on stepper motor systems who I > believe is off topic in heavy duty systems. This will run in a little off-topic by me... You can run heavy duty machines with steppers, but then the performance will suffer - You will have to leave big safety margin in terms of load to motors (either move slower or use way much larger motors) as currently there is no safe and reliable way to recover "on the fly" from lost steps. Last year I had a discussion with Festo people in Hannouver Messe about this topic - they are offering pseido-servo control system, which consists of: 1) stepper motors 2) encoders on motors for feedback 3) controller, in which error in feedback loop is fixed in classical manner - add throttle, when motor is falling behind I managed to left their representative without any arguments as this approach totally sucks - if the load on motor is large enough for it to start losing steps, then there is no sense to increase the RPM - it will continue to lose steps. It has been proposed on this mailing list that completely new approach would required - all the remaining joints should slow down so that the one with lost steps remains in the correct place with respect to other. I guess some special drive, that could increase the current for a short time to increase motor torque, would allow to use the classical approach, but I will leave that for people, who actually do understand something about stepper drives and the principles, how they work. Kirk mentioned that he has a mill with steppers, there must be tons of other examples of serious stepper-equipped machines. I am now struggling with my first servo machine. The conclusion - steppers may not look attractive in terms of their performance, when compared to servos, but at least I am able to set them up and get running. For me servos is different story... On the other hand, Keling motors, USDigital encoders and Mesa drives are not that much more than cost of stepper system, which makes servos very attractive to use. Viesturs ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
