On Saturday, 16 April 2022 18:03:47 EDT Torsten Curdt via Emc-developers wrote: > > > > > The splitting would not work for the servos that have the > > > > > driver > > > > > integrated though. > > > > > > > > Why not? > > > > > > There are no pins to connect to :) > > > > That I should point out, is generally NOT a problem for a CET. > > LOL ... I agree. > > > At least not until one would "fix" that inside the driver itself. And > > I> > > > am not so eager to do that. > > > > It might be difficult mechanically, but the points to grab ARE in the > > circuit. Generally useing a scope probe to help in identify them. > > I am pretty sure I *could* do it - but I am pretty sure I don't want to > make things more complicated than they already are :) > And you are right. There isn't much space mechanically. > > > > So that would NOT be a recommended setup? > > > > I think it would be good, given that todays hardware is considerably > > faster, Nyquist (time delay phase shifts) caused instability stuff > > s/b > > much less of a problem and I expect it would be quite easy to do > > today. > Except for the problems you are mentioning it would kind of make sense > - to me at least. At least for steppers. > (Not sure this would work for servos. I guess they usually always come > with their own PID loop?) > > > Particularly if you pay attention to the addf order in the hal file. > > > /me doesn't understand that yet, but makes a note for later :) > > > I am slowly running out of ideas what is :) > > > > Tell us what you want to do? Probably not me, but there are folks > > here > > with far more knowledge than I've experience with, that can give you > > an idea how to do it. > > Well, this is the dev list - so I rather wanted to focus on the > protocols and how things are supposed to work conceptually to > understand my options. But since you are asking that directly I am > happy to share... > > I've built a smallish CNC (1000x700mm) and I still have some JMC 180W > Servos (V5) that I wanted to use on the machine. > Now I am looking at my options for driving them. > > The options for the controller: > - old GRBL board (nah) > - RPi3 with a Protoneer GRBL hat (maybe until I find something better) > - Esp32 GRBL (didn't find good boards, price difference to a Mesa is > getting smaller) > - Teensy GRBL (sounds pretty good for a GRBL, maybe, price difference > to a Mesa is getting smaller) > - Some old PC with a Parallel Port (but it seems hard find and I am not > such a fan of the idea, I rather have the stepgen on a board) - Some > old PC with a Mesa 7i96e (would probably have been my choice but not > going to happen due to availability, at least in the EU) > - Some old PC with a Nvem and Remora (not so super eager as Remora > seems still to be a one man project and still quite beta) > > ...and I think I really want to go with LinuxCNC :) > > As for the motors. People are bitching how hard it is to parameterize > those servos. > I am told the two motors on the Y axis can become a real problem. > But I am still tempted to at least give that a try. > > It would be nice if I could write some LinuxCNC integration that talks > via modbus to help with the configuration. That will also need 4 > UARTS/RS232 on the PC though. > Icing on the cake would be if the LinuxCNC could monitor the modbus and > slow down the motion if the following error becomes too big. > > That said In retrospect I am also not such a fan of the integrated > servo drivers anymore - and with all the things still in limbo... > ...it also crossed my mind to just get some closed loop steppers and > probably be done with it.
As long as they are 3 phase, I think thats decent advice. Those I have used so far have had the fault outputs wired into the e-stop circuit. Works well when tested, but has never actually occured while running a program. So "nuisance" trips have not ever occurred. > BUT my ballscrews are 05mm and planned for servo speeds. > > I don't really want to go from the idea of the dynamic servo driven > machine to the stepper turtle :) All my stuff is steppers, but I wouldn't call a g0 move at 250 ipm a turtle. The whole steel framed table its on shakes. > Bottom line: If the Mesa wasn't out of stock for the unforeseen future > I would have probably just gotten one and tried. > Now I have to come up with a plan B and was wondering about the > alternatives. > So I find myself looking through mach3 boards and wondering about the > reasons they cannot be used with LinuxCNC. Mach3's bob's can be used but my being a "CET" means they're not OOTB when they go into service, the opto's are often bypassed in order to get the needed, repeatable speeds. That back of the spindle motor encoder on my GO704 comes in thru such a 5 axis board, but the noise filtration of that board has been removed. I bought that board specifically because it didn't claim slow opto's in its 5 inputs, turns out it had 470 ohm and .1 uf monolithic caps as input filters making it even slower than the opto's would have been. For folks who aren't comfy with a hot air rework soldering iron surgically implanted in a right hand, that need does remove those $20 boards from consideration. Mesa and cnc4pc both make better bobs, but bring more money. Needless to say those caps which look like grain of sand resistors, aren't there now. And an encoder with 50+ kilohertz output cuz its turning 7k+ revs at the rear of the spindle motor when that 90 volt motor is getting 125 volts wide open and nearly twice its nameplate amps. And in 7 years, it has not even needed fresh brushes. Its a well built motor. But I do have a 4 second, resistor limited soft start rigged in its power supply cuz turning it straight on trips a 30 amp breaker instantly. Now it runs the whole machine AND a shopvac on a 20 amp. And it does it so quietly that my only clue its overloaded is the iron in the motor chirping because Jon Elsons Pico brand pwm-servo has current limited it to 18 amps. Thats as close to a bulletproof driver as you can buy in these here parts. But,if you are going to use it to drive a spindle, which is "CCS" service. be sure and tell Jon when you order it. he'll change the toroid filters from ICAS to CCS, the ICAS version gets hot, the CCS versions doesn't. Ferrite is funny stuff, and has a "curie" temperature for some of it below the boiling point of water. So you don't want it running hot, ever, because the magnetic properties are changed forever if it hits the curie temp while magnetised. Something they don't teach EE's... Arnold and others of that ilk have whole web pages devoted to that if you want some bedtime reading. > Which made me curious and I started digging - down the rabbit hole ;) Locally, that hole is more likely a gopher or ground hog hole. ;) > Hope that explains the status quo. Somewhat, but the ball screws at 5mm pitch is pretty much stock in what's commonly available. If 5mm is too fast for a stepper, belt drive the screw at some convienient gear down, 2/1 is commonly done. Take care and stay well. Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
