Newbie looking at 6040 (China CNC) for polypropylene 15mm sheet

[njhussey]

The switch mode ones don't take back EMF from the drivers when the machine is decelerating. If you make a linear PSU with some nice big caps then this is best, and you can make it to the ideal voltage. You really want some nice 80V drivers and a 72V PSU...then it'll fly which is what you need to cut plastic. I cut UHMWPE at 8000mm/min, your matched set wont get near that.

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[JOGARA]

The switch mode ones don't take back EMF from the drivers when the machine is decelerating. If you make a linear PSU with some nice big caps then this is best, and you can make it to the ideal voltage. You really want some nice 80V drivers and a 72V PSU...then it'll fly which is what you need to cut plastic. I cut UHMWPE at 8000mm/min, your matched set wont get near that.

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Hmm good point.
I am not too good with power supplies. As in making them. I typically just get off the shelf.

Have you made your own?

[Clive S]

Hmm good point.
I am not too good with power supplies. As in making them. I typically just get off the shelf.

Have you made your own?

There are only 3 main components (toroidal transformer, rectifier & a couple of caps) or you could buy one from Zapp

[JOGARA]

Isn't there a way to dump excess power coming back from steppers?

Like resistors or something.

[Neale]

Isn't there a way to dump excess power coming back from steppers?

Like resistors or something.

Unfortunately not. There are two main problems with the switch-mode PSUs in this application, although they are great and very cost-effective elsewhere. One is the back emf issue as mentioned, while linear power supplies dump excess power into the smoothing caps (one way to look at it, anyway). The other is that linear supplies are much more tolerant of peak overload. A switch-mode supply tends to hard-limit, maybe even shut down temporarily, if you try to draw more than rated current where a linear supply output will tend to just sag a bit which is not usually a problem. If you are now looking at Mach3, you might also consider something like a UC100 or UC300 with UCCNC which is looking like an attractive option these days. Still need a break-out board but it's a better option than using Mach3 and parallel port.

[JOGARA]

Okay, so I looked into toroidal based supplies and they are easy to make. So should be no time to spin a board for one of those.
Do cost a bit to get them off the self, though I know of a place that do them for like 50 euros each at any spec you want.
So might be able to get a decent high amp one for not that much more.


The problem is, the high voltage stepper controllers are not Chinese cheap :p
Looking at £110 per axis :/

I have only looked on Zapp though so far.

Steppers themselves are around £30 each. Makes it around double the cost.
But I guess it is worth it because of needing that extra speed and power?



Regarding the steppers, they state a "Rated Voltage" of around 2-4v.
Do the drivers lower to voltage or because they pulse the stepper they are able to use upwards of 80v?

[Neale]

Ignore stepper voltage ratings. As you say, the stepper driver effectively pulses the drive voltage; the driver manages the current rather than voltage but the higher voltage allows higher current pulses which helps develop torque. Confused me at first but the stepper driver will have an adjustable current setting which is more useful. That's also why you use a linear power supply - better current pulse capability.