Losing steps/position, again

[ngwagwa]

whoops post twice

[dazp1976]

That's WRONG information your giving out, the drives don't regulate the voltage they regulate the current. 70Vac which is 98Vdc would destroy those little motors in no time at all. It would also make them run like a bag of shite.

You cannot stick any voltage you like into a stepper, there is a limit where it starts to have very negative affects. Namely iron losses and motor heating which kills them.

Those Large voltage Ac drives are only really any good for larger steppers Like Nema 34 or very high inductance NEMA 23's. Your typical 3-4Nm 4.2a Nema 23 with 3-4mh inductance doesn't like to be run much more than 80vdc and at that, you are pushing them past there design threshold so are shortening there life.

For the NEMA 23 motors, which this machine will have fitted he'll only need drives with a max rating of 70Vdc and would run them around 55-60Vdc. Or 50Vac drives running at 40-45Vac.

Steppers are generally all rated 2-3Vdc yes?. So if said nema 17 / 23 or 34 (2-3Vdc) were put on the same driver why would I only blow the 17? (unless I didn't change the current output).

Also inductance. There are Nema 34's out there that are abysmal running on 60V supplies and ideally need at least 120Vdc to work reliably.

Also there are now drivers on the market with direct 240Vac input connections so no need for psu's anyway. These are aimed at nema17-23 size. Why would these not burn them up either?

I and many others use 60Vdc at least using larger 34 size drivers to run nema17 & 23 size motors. Even that goes against the grain and it's worked for years.

[AndyUK]

Steppers are generally all rated 2-3Vdc yes?.

My understanding is that if you give a coil on the stepper the rated voltage (2-3V) it will draw the rated current.

If you give a stepper a higher voltage, the current will also increase and the thing will burn up.

But we're not doing that - we're using stepper drivers. These give the motor the full voltage in "punches" to limit the average current to a set value. Therefore its entirely reasonable that the voltage supplied to the driver is important for the reasons Jazz sets out.

Blanket recommendations are dangerous either way - you need to consider all the factors like the steppers inductance and current limits to determine what will blow and what won't. NEMA 17 or 23 is just a mounting size, and has no real effect on this.

[JAZZCNC]

Steppers are generally all rated 2-3Vdc yes?. So if said nema 17 / 23 or 34 (2-3Vdc) were put on the same driver why would I only blow the 17? (unless I didn't change the current output).

I didn't say it would blow it up, I said it would destroy them and this is true. They couldn't handle the heat and that would kill them eventually depending on voltage.

Also inductance. There are Nema 34's out there that are abysmal running on 60V supplies and ideally need at least 120Vdc to work reliably.

Also there are now drivers on the market with direct 240Vac input connections so no need for psu's anyway. These are aimed at nema17-23 size. Why would these not burn them up either?

You'll find that many of the drives that use 240Vac won't run small motors for the same reason I mentioned before, most don't even limit current below 5a. The drives you speak of which use AC voltage and can run Nema 17/23 use Low AC voltage which you transform down from 230Vac and that gets rectified to DC in the drive.

I fit 230 Vac drives all the time and I can tell you that if I fitted those little motors or nema 17 motors to the drives they would be fried within hours. Even with small (4nm) Nema 34 motors you have to be very careful and make sure you limit current correctly because current it proportional to Voltage and you cannot limit the voltage so they get hot.
This is physics it's not me making shit up and just because you haven't experienced it doesn't mean your correct it what your saying. Unless you know it to be true then I suggest you STFU because it's hazardous to components life and even dangerous in some circumstances.

I and many others use 60Vdc at least using larger 34 size drivers to run nema17 & 23 size motors. Even that goes against the grain and it's worked for years.

No it's doesn't go against the grain and it's perfectly acceptable because the voltage is much lower and the motors can handle it. Again physics comes into play and there is an ideal voltage where motors run with-in safe tolerances, most people running more than 60vdc with NEMA 17/23 motors are running past the motor's ideal voltage but only just so it's not a problem. Think of it like overclocking a PC, it works but will shorten the PC's life unless it's cooled better, same shit here.! . . . Running higher than ideal voltages your actually shortening the motors life but who cares because it's going to take years if only 10-20v over but double the rated voltage or more and it won't take long. (unless cooled massively)

[ngwagwa]

Would this be suitable for the transformer? https://cpc.farnell.com/multicomp/mc...%20transformer
Is that all I would need?

You will have to forgive my ignorance as I have an nane fear of magic blue smoke.

Can you suggest any suitable drivers preferably available in the UK? I did find these https://www.cnc4you.co.uk/Microstepp...tepping-CW8060

I will be using the existing 5 and 24V transformers.to power the bb-e

[JAZZCNC]

Would this be suitable for the transformer? https://cpc.farnell.com/multicomp/mc...%20transformer
Is that all I would need?

You will have to forgive my ignorance as I have an nane fear of magic blue smoke.

Can you suggest any suitable drivers preferably available in the UK? I did find these https://www.cnc4you.co.uk/Microstepp...tepping-CW8060

I will be using the existing 5 and 24V transformers.to power the bb-e

My advise is STOP don't buy a single thing until you have settled on exactly what your fitting or need. Also what you have in the machine already that you can re-use.

Those drives are a little over kill but that won't hurt, however, the advice you have been given regards the drives controlling Voltage is Wrong so ignore it.
Those little motors won't like being run much above 60Vdc so the extra capacity the drives allow you cannot really use, but it's always better to have drives that are under performing than being pushed to there limits.

Regards the transformer then the voltage is about right at 35V giving approx 50Vdc when rectified but the Va rating is a little on the low side, 500Va would be better. 300Va would work for those motors but doesn't leave any room for expansion or larger motors in the future 500Va would.

When you say you have 5 and 24v in the machine are you sure it's DC because if it's the original PSU then they tend to be AC transformer and it gets rectified on the boards for the drives to around 32V.

[ngwagwa]

Hi,

There is a 5v and a 24v transformer which I think are DC (I did take pictures but have left my phone in the workshop), I assume they were fitted when the machine was converted to Mach3 they are certainly not part of the original controller.

My spindle is controlled by a plugin and serial port which I am happy to leave as is.

I would prefer to purchase a PSU as opposed to building one unless there is an advantage going the toroidal route. Regarding your comment on the 300Va being sufficient but no room for expansion could I fit bigger motors if I needed to or would I need to if the new set up get the most out f the current ones?

As to using what I can I was assuming that with a new motion controller, PSU and drives apart from the 5 & 24V transformers everything else would be redundant bar the mains on/off switch.

[JAZZCNC]

There is a 5v and a 24v transformer which I think are DC (I did take pictures but have left my phone in the workshop), I assume they were fitted when the machine was converted to Mach3 they are certainly not part of the original controller..

Ok if that is the case then your sorted. It would be a good idea to post picturs of inside the control box.

My spindle is controlled by a plugin and serial port which I am happy to leave as is.

If you go with the AXBB and UcCNC software then you won't be able to use it and I would use the UcCNC software over Mach3 as it's getting long in the tooth.

I would prefer to purchase a PSU as opposed to building one unless there is an advantage going the toroidal route.

Ok well in that case look for a Unregulated Linear Supply. Gary at Zapp automation used to sell 48Vdc Leadshine Unreg PSU's give him a lookup.

Regarding your comment on the 300Va being sufficient but no room for expansion could I fit bigger motors if I needed to or would I need to if the new set up get the most out f the current ones?

With 300Va then no you would need more current and 300Va limits you to about 8.5A total which could be borderline with some motors, with the current ones you probably won't have any trouble. But if one dies on you then you'll struggle to get the same size and it would be the ideal time to upgrade and 300Va would limit this.

As to using what I can I was assuming that with a new motion controller, PSU and drives apart from the 5 & 24V transformers everything else would be redundant bar the mains on/off switch.

Ermm not really you will still want some safety involved so a few relays will be needed for a hardwired latching E-stop system that safely Kills drives etc and lets the controller know there's been an emergency Stop.

[ngwagwa]

I will getthe photos tomorrow.

And never thought about the E-stop either but there is at least one relay in there :)

[ngwagwa]

Doddy, that sounds like a decent plan and I will take you up on it. I already have a DIV268 doing nothing so I won't be needing that thanks. It may take e a little longer than an hour as I have no idea where the current X axis is fed from, maybe it will be apparent when I get behind the bits added for the conversion. When would it be convenient to pick up the PSU?
Thanks
Carl