Dave, Thanks for the clarification, and the education.
I'm strictly a hobbyist, with a box full of NEMA 34 stepper motors. Anytime steppers are mentioned, I pay attention. Obviously, the size of the motors limits my design options, hence my interest in using 2 together. I saw you were using stepper motor signals and incorrectly assumed you were using stepper motors. Thanks again for the informative reply. Raymond Julian Kettle River, MN The things we admire in men, kindness and generosity, openness, honesty, understanding and feeling are the concomitants of failure in our system. And those traits we detest, sharpness, greed, acquisitiveness, meanness, egotism and self-interest are the traits of success. And while men admire the quality of the first they love the produce of the second. -John Steinbeck, novelist, Nobel laureate (1902-1968) On 01/10/2015 10:49 AM, Dave Cole wrote: > No.. the Automation Direct servo drives are full blown digital servo > drives. > > They can operate in at least three different modes. Position mode (the > drive accepts step and direction signals from the CNC controller), > Velocity mode (the CNC controller outputs a +/-10 volt signal that is a > velocity command signal - ie how fast do you want the motor to rotate in > forward or reverse direction), and torque mode (the CNC controller > outputs a +/- 10 volt signal that is a torque command - how much torque > should the motor output to the system.). > > LinuxCNC can output a step and direction signal which is oftentimes used > to control stepper motors, but can also be used to control smart servo > drives that can accept a step and direction signal (like a stepper > drive). In the case of a smart servo drive, the drive itself closes > the position loop itself by receiving the encoder signal from the motors. > LinuxCNC is also frequently used with servo drives in velocity mode. In > that case LinuxCNC outputs a +/-10 volt signal which indicates a > velocity command to the drive (how fast and in a positive or negative > direction). I believe that LinuxCNC can also drive servos in Torque > mode but torque mode is trickier to tune, and I have never used that > with LinuxCNC. (I don't see any advantage of using torque mode with > LinuxCNC for most applications.) > > So in the situation we are discussing, the smart servo drives are doing > their own closed loop position control and the CNC controller just sends > a step and direction pulse to them to rotate in the positive and > negative direction and at a speed dictated by the the pulse stream > rate. The drives themselves receive the encoder feedback pulses and > also the step and direction pulses from the CNC controller so the drives > themselves knows where they are suppose to be (via the position command > from the LinuxCNC controller) and where they actually are (from the > motor encoder). The difference is the following error. If the > following error becomes excessive the drives themselves are intelligent > enough to shut themselves down. When they do that they usually output > a fault signal. That fault signal can be wired to the opposite servo > drive as a shutdown signal. So if either drive has excessive following > error (like something has jammed up) then both gantry drives will > shutdown preventing the gantry from becoming racked out of shape. > > In the particular case of the gantry machine I did a few years ago, I > also had a PLC in the system. So I wired the servo drives into the > PLC. If either servo drive output a fault signal, I shutdown the > opposite servo drive. But I only did that because I had a PLC in the > system. I could have cross wired the servo drives directly (it might > have required a relay) to make the logical connection. > > This is the servo drive and motor I used for that machine. > http://www.automationdirect.com/adc/Shopping/Catalog/Motion_Control/Servo_Systems/Medium_Inertia_%281KW_-_3KW%29_Servo_Systems/1KW_Servo_System_%28Med_Inertia%29 > > > Machmotion.com sells Teco servo drives (as do a few other distributors > in the USA) and they work almost identically to the Automation Direct > drives but cost about 30% less. > > Dave > > > On 1/9/2015 5:08 PM, rayj wrote: >> Dave, >> >> Thanks for the reply. >> >> So you have position feedback from the motor shafts, essentially a servo >> system with stepper motors, kinda? And if the detected position differs >> from commanded position by a specified amount, it stops? >> >> Did the motors come with the feedback hardware or did you add it? If >> you added it, what hardware did you use? >> >> >> Raymond Julian >> Kettle River, MN >> >> The things we admire in men, kindness and generosity, openness, honesty, >> understanding and feeling are the concomitants of failure in our system. >> And those traits we detest, sharpness, greed, acquisitiveness, meanness, >> egotism and self-interest are the traits of success. And while men >> admire the quality of the first they love the produce of the second. >> -John Steinbeck, novelist, Nobel laureate (1902-1968) >> >> On 01/09/2015 03:40 PM, Dave Cole wrote: >>> Hi Raymond, >>> >>> I used Automation Direct servo drives on that job and they can be setup >>> to shutdown on excessive following error. (Deviation from the step and >>> direction commanded position). They can also be shutdown by an >>> external input. So if you cross wire the drives so if one shuts down >>> on following error, it shuts down the other drive and visa versa, it >>> becomes a self protecting system. If either drive has excessive >>> following error it kills itself and also the other drive. That >>> prevents the gantry from being racked out of position if something goes >>> wrong. >>> >>> A common reset wired to both drives can also bring them back to life >>> after a shutdown. >>> >>> It works well and is quite simple once it is implemented. >>> >>> Dave >>> >>> On 1/9/2015 4:03 PM, rayj wrote: >>>> Greetings Dave, >>>> >>>> I have some long term plans to build a gantry similar to the one you >>>> describe. >>>> >>>> When you say it kicks out the controls, I'm not sure what you mean. Is >>>> there some physical safeguard, like a detent or or clutch, or is it >>>> something in the software you're talking about. >>>> >>>> TIA >>>> >>>> Raymond Julian >>>> Kettle River, MN >>>> >>>> The things we admire in men, kindness and generosity, openness, honesty, >>>> understanding and feeling are the concomitants of failure in our system. >>>> And those traits we detest, sharpness, greed, acquisitiveness, meanness, >>>> egotism and self-interest are the traits of success. And while men >>>> admire the quality of the first they love the produce of the second. >>>> -John Steinbeck, novelist, Nobel laureate (1902-1968) >>>> >>>> On 01/09/2015 10:47 AM, Dave Cole wrote: >>>>> I did one of these several years ago. The machine has 1 KW servos on >>>>> each end of the gantry driving ball screws. The gantry was quite >>>>> rigid so when the power was removed it self squared. There was one one >>>>> home switch. I ended up using servo drives in step and direction >>>>> mode and fed them with a pulse train from LinuxCNC. That worked out >>>>> fine. I fed the same step and direction signal to each gantry drive. >>>>> If there is any significant following error on either drive, it kicks >>>>> out the controls so the gantry cannot become racked out of shape. >>>>> It has been running like that now for over 3 years with no issues and >>>>> the machine runs up to about 700 ipm. The machine runs every day, >>>>> sometimes two shifts per day. >>>>> I considered doing two separate closed loop axes back to the PC, but I >>>>> thought it would be easier to try the step and direction approach >>>>> first. That worked, so I stuck with it. >>>>> No regrets on that decision. >>>>> >>>>> Dave >>>>> >>>>> On 1/9/2015 10:57 AM, Eric H. Johnson wrote: >>>>>> Hi all, >>>>>> >>>>>> >>>>>> >>>>>> I am looking to do an upgrade on a large XY table where the gantry is >>>>>> driven >>>>>> by to oppositely mounted servo motors. Both sets of encoders run back to >>>>>> the >>>>>> existing controller. Can I just give a generous deadband to the slave >>>>>> axis, >>>>>> or is there a better way to address this configuration so the motors >>>>>> don't >>>>>> fight each other. I believe it uses a single home switch which can then >>>>>> be >>>>>> fed to both axes for purposes of homing. Anyone done this? Anything else >>>>>> to >>>>>> look out for? >>>>>> >>>>>> >>>>>> >>>>>> Thanks, >>>>>> >>>>>> Eric >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> <http://t.senaltres.com/e1t/o/5/f18dQhb0S7ks8dDMPbW2n0x6l2B9gXrN7sKj6v4LCQRN >>>>>> 7fcnk8RJ6s6N8rBF7Rd3_yKW18Chwm1k1H6H0?si=6453247850577920&pi=8828d77849c9460 >>>>>> b95fcaf96870fbe9d> >>>>>> ------------------------------------------------------------------------------ >>>>>> Dive into the World of Parallel Programming! The Go Parallel Website, >>>>>> sponsored by Intel and developed in partnership with Slashdot Media, is >>>>>> your >>>>>> hub for all things parallel software development, from weekly thought >>>>>> leadership blogs to news, videos, case studies, tutorials and more. Take >>>>>> a >>>>>> look and join the conversation now. http://goparallel.sourceforge.net >>>>>> _______________________________________________ >>>>>> Emc-users mailing list >>>>>> [email protected] >>>>>> https://lists.sourceforge.net/lists/listinfo/emc-users >>>>> --- >>>>> This email has been checked for viruses by Avast antivirus software. >>>>> http://www.avast.com >>>>> >>>>> >>>>> ------------------------------------------------------------------------------ >>>>> Dive into the World of Parallel Programming! The Go Parallel Website, >>>>> sponsored by Intel and developed in partnership with Slashdot Media, is >>>>> your >>>>> hub for all things parallel software development, from weekly thought >>>>> leadership blogs to news, videos, case studies, tutorials and more. Take a >>>>> look and join the conversation now. http://goparallel.sourceforge.net >>>>> _______________________________________________ >>>>> Emc-users mailing list >>>>> [email protected] >>>>> https://lists.sourceforge.net/lists/listinfo/emc-users >>>>> >>>> ------------------------------------------------------------------------------ >>>> Dive into the World of Parallel Programming! The Go Parallel Website, >>>> sponsored by Intel and developed in partnership with Slashdot Media, is >>>> your >>>> hub for all things parallel software development, from weekly thought >>>> leadership blogs to news, videos, case studies, tutorials and more. Take a >>>> look and join the conversation now. http://goparallel.sourceforge.net >>>> _______________________________________________ >>>> Emc-users mailing list >>>> [email protected] >>>> https://lists.sourceforge.net/lists/listinfo/emc-users >>> --- >>> This email has been checked for viruses by Avast antivirus software. >>> http://www.avast.com >>> >>> >>> ------------------------------------------------------------------------------ >>> Dive into the World of Parallel Programming! The Go Parallel Website, >>> sponsored by Intel and developed in partnership with Slashdot Media, is your >>> hub for all things parallel software development, from weekly thought >>> leadership blogs to news, videos, case studies, tutorials and more. Take a >>> look and join the conversation now. http://goparallel.sourceforge.net >>> _______________________________________________ >>> Emc-users mailing list >>> [email protected] >>> https://lists.sourceforge.net/lists/listinfo/emc-users >>> >> ------------------------------------------------------------------------------ >> Dive into the World of Parallel Programming! The Go Parallel Website, >> sponsored by Intel and developed in partnership with Slashdot Media, is your >> hub for all things parallel software development, from weekly thought >> leadership blogs to news, videos, case studies, tutorials and more. Take a >> look and join the conversation now. http://goparallel.sourceforge.net >> _______________________________________________ >> Emc-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users > > --- > This email has been checked for viruses by Avast antivirus software. > http://www.avast.com > > > ------------------------------------------------------------------------------ > Dive into the World of Parallel Programming! The Go Parallel Website, > sponsored by Intel and developed in partnership with Slashdot Media, is your > hub for all things parallel software development, from weekly thought > leadership blogs to news, videos, case studies, tutorials and more. Take a > look and join the conversation now. http://goparallel.sourceforge.net > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Dive into the World of Parallel Programming! The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
