On Saturday 26 December 2020 04:57:38 andrew beck wrote: > hey everyone > > just for your interest here is a cnc lathe I am retrofitting here in > NZ > > link to video on youtube <https://www.youtube.com/watch?v=TphcwK45zyc> > > still got a whole lot of work and need to sort out analog servo drive > stuff tomorrow but thought I would send a email anyway > > also what do people do for E stop circuits with analog systems? I have > only used a step direction system before this > > the servo drive has a "servo on input) that allows power to motor. I > think the enable input from 7i77 should trigger this on and off. I > want my big estop to also cut power too though so that I am not > relying on software as that is not safe. current plan is to just put > a relay in the servo enable circuit from 7i77 to servo drive. which > gets cut by the Estop switch circuit. seems simple enough > > would love any ideas though > > and any things to watch out for. > > I know about checking encoder direction first and leaving motors on > bench at first and all that sort of stuff. I will just take it easy > > regards
Wow, Andrew. That is a lot more machine than anything I've got. And separate e-stop circuits are something that I have been lacking in doing. I have tended to make all that stuff as slaves to the motion enable signal, controlled by the F2 key on the keyboard, which in turn controls all other machine power, and has worked flawlessly. But it is not a guard against a computer crash which really needs an independent way to shut down the power. I've considered a multipole relay which would be in series with the enable signal, which could shut off all power to the machine independent of the computer, and I bought several of the latching switches from the mini-lathe parts list, but haven't found that famous round tuit yet. But I think that idea has the best merit, bypassing, and over-riding anything the computer might decide to make the machine do. I did change the motors and drives on my Sheldon this fall, from normal steppers to the newer 3 phase stepper/servo's and I am very happy with the results of feeding the FAULT signals back into LinuxCNC, effectively toggling the F2 button there. I traded a 1600 oz/in nema 34 on the z screw for a 3NM nema-23, as much because the 1600 shook tools off the whole machine, doubling my Z speed rapids, and pulled a 270 oz/in nema-23 off the X in favor of a 2NM version of the 3 phase drive. The whole machine now can move 2-3x faster, and moves like casper the ghost. I haven't tested the X because the screw is so small and I might damage it with the 2NM motor geared 2/1, but I can now mount a carbide tool, position it to hit a chuck jaw, and drive it into the chuck jaw at 2 ipm, from the Z, it detects the contact and faults, with the Z bouncing back from jaw contact by about .010" as the power goes off, without damage to the chuck jaw or to the carbide chip in the tool. With a 25mm Z screw, that 1600 would have crushed the chip and bent the tool if it were pinned to the carriage, which it is not. That to me was worth the nominally $250 to swap the motors. And although I've been warned that some have noted the stepper servos can lose counts, the 3 phase drives I have used so far haven't lost a step. I'd submit that those reporting such as problem have noise in their systems or are pushing the step timing. Anyway, that's my take on it, but if anyone has a good pattern to make round tuits that isn't already copyrighted, I'll make some for my friends as several have lamented they haven't found one yet. That would be a piece of cake for my 6040 with its new 2.2kw spindle. Now, lets all hope that 2021 will be a better year, 2020 was/is the pits. > Andrew > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
