Looking for some basic information for Orac electrics rebuild
Posted: Tue 05 Sep , 2023 22:28 pm
I have just acquired an Orac which seems in reasonable condition mechanically, but I'm less sure about the electrics!
I understand that it came from a school originally; the next owner stripped out the original electrics and replaced it, and the last owner (now deceased), I was told, had it running and then decided to once again renew the electrics. So, apart from the steppers and spindle motor, there is nothing left of the original setup to give me a guide. It is working, after a fashion.
The spindle drive looks OK - new VFD driving the original motor and the spindle turns at varying speeds. The original spindle encoder(?) has disappeared and there is a single hall effect sensor which is not currently wired to anything. The plan is to put in an encoder to do "proper" threading. I can get speed and so on sorted once I have an encoder in there.
Motion control is currently via some almost-undocumented Chinese USB board driven from Mach3. By trial and error, I have both axes moving. The stepper drivers are on a 3-axis TBA6560 board driven from 24V. Even at the maximum current setting, the slides move somewhat jerkily and lose steps except at very slow speed and there's no way they would achieve the brochure's claim of 1200mm/min. I suspect that the combination of those drivers and too low a voltage means that the steppers just don't develop enough torque. The PSU in there is 24V/20A so I doubt that there is any current limiting there. The steppers also seem to buzz rather a lot - is this normal? Would anyone like to suggest suitable voltage and current settings for the original steppers to get the machine moving properly - I don't mind sourcing appropriate drivers and PSU to suit. I have built a couple of CNC routers and rebuilt the electronics in my CNC mill so this kind of thing is straightforward for me - if I know what I'm aiming at! Do the original steppers cope with microstepping or is it full steps or nothing?
Is it worth upgrading the steppers as well? What should I be aiming at in terms of NEMA23/34 and torque ratings if so? The original motors seem a bit on the low power side, but maybe they are OK?
Motion control. I gave up on Mach3 on my router and mill in favour of UCCNC and UC300ETH cards, but it seems that they still don't have the lathe side of that sorted and there is no predicted date for it. At the moment I'm thinking of PlanetCNC which does seem to support lathe mode, proper synchronised threading, and so on. Is this a reasonable choice? I have seriously looked at LinuxCNC (I have used this in the past, but on a CNC router) together with Mesa cards, but from what I have read LinuxCNC can be a challenge to set up for lathe use, and the Mesa cards seem to be unavailable anyway. My machine does not have an ATC and I doubt that I would ever find one, so that's not really a deciding factor.
A lot of questions at once, I know, but it would be great to get a steer on what direction to take without any clue as to what was in there to start with!
Thanks,
I understand that it came from a school originally; the next owner stripped out the original electrics and replaced it, and the last owner (now deceased), I was told, had it running and then decided to once again renew the electrics. So, apart from the steppers and spindle motor, there is nothing left of the original setup to give me a guide. It is working, after a fashion.
The spindle drive looks OK - new VFD driving the original motor and the spindle turns at varying speeds. The original spindle encoder(?) has disappeared and there is a single hall effect sensor which is not currently wired to anything. The plan is to put in an encoder to do "proper" threading. I can get speed and so on sorted once I have an encoder in there.
Motion control is currently via some almost-undocumented Chinese USB board driven from Mach3. By trial and error, I have both axes moving. The stepper drivers are on a 3-axis TBA6560 board driven from 24V. Even at the maximum current setting, the slides move somewhat jerkily and lose steps except at very slow speed and there's no way they would achieve the brochure's claim of 1200mm/min. I suspect that the combination of those drivers and too low a voltage means that the steppers just don't develop enough torque. The PSU in there is 24V/20A so I doubt that there is any current limiting there. The steppers also seem to buzz rather a lot - is this normal? Would anyone like to suggest suitable voltage and current settings for the original steppers to get the machine moving properly - I don't mind sourcing appropriate drivers and PSU to suit. I have built a couple of CNC routers and rebuilt the electronics in my CNC mill so this kind of thing is straightforward for me - if I know what I'm aiming at! Do the original steppers cope with microstepping or is it full steps or nothing?
Is it worth upgrading the steppers as well? What should I be aiming at in terms of NEMA23/34 and torque ratings if so? The original motors seem a bit on the low power side, but maybe they are OK?
Motion control. I gave up on Mach3 on my router and mill in favour of UCCNC and UC300ETH cards, but it seems that they still don't have the lathe side of that sorted and there is no predicted date for it. At the moment I'm thinking of PlanetCNC which does seem to support lathe mode, proper synchronised threading, and so on. Is this a reasonable choice? I have seriously looked at LinuxCNC (I have used this in the past, but on a CNC router) together with Mesa cards, but from what I have read LinuxCNC can be a challenge to set up for lathe use, and the Mesa cards seem to be unavailable anyway. My machine does not have an ATC and I doubt that I would ever find one, so that's not really a deciding factor.
A lot of questions at once, I know, but it would be great to get a steer on what direction to take without any clue as to what was in there to start with!
Thanks,