Stepper driver voltages - using different levels

I'm upgrading my old machine in nearly every area (not yet complete but getting close to operational) and this includes twin X axis steppers rather than one central one.

To do this I bought an M542 type driver to hook up as a slave for the second X axis. The main board is a system3 all-in-one so everything needs to be run at 26v, otherwise I start to get lost steps.

I think initially this will all be fine and I intend to run it like this for a while, but on the odd occasion on the old machine I was limited by the speed and torque of the system. I've also developed an interest for machining more aluminium so am sure I will upgrade the electrics later this year by keeping the new M542 and selling the system3 all-in-one board. So my questions are for that upgrade:

1. The new M542 is rated at 48v which will be a big increase in torque over 26v - however, the manual suggests 36v is typical which seems like only a small improvement for the investment. What are people's experience of running at close to 48v on these drivers? For about £90 I can get a 5 axis breakout board, 48v power supply, and another 3 M542 drivers to create a 48v complete 4-axis system. But I only want to do this if I can get a reasonable performance gain (more like 48v than 36v).

2. If the real peformance of the M542 is 36v than I'd be tempted to buy 3off ~60v drivers (M752 etc.), and a 60v power supply, leaving the Z axis on the existing M542 at 26v (or I could turn this up to about 32v). In principle is it OK to run X1,X2, and Y on 60v and run the Z driver on 26v? Are they independant electrically?

Thank you

Which motors are you using?

You should be fine running the M542 drivers at 48V with a linear PSU, but I'd be inclined to get higher voltage drivers (e.g. DQ860MA) and run them at about 70V as the difference in price shouldn't be that great. The current ratings of the higher voltage drivers will be greater, so they should last a long time as they wont heat up much.

From an electrical point of view there's nothing wrong with mixing drivers of different voltages, so long as they are each supplied with the correct voltage which you plan to do, so nothing to worry about.

Hi Jonathan

Thanks for that. I have a big spreadsheet of my configuration - here is a cut and paste of the motor data:

Axis Model Configuration V A Nm mH
X1 M60STH88-3008DF Bipolar Series 5.46 2.1 3 12.8
X2 M60STH88-3008DF Bipolar Series 5.46 2.1 3 12.8
Y* SY60STH86-3008BF Bipolar Series 5.46 2.1 3 12.8
Z** ? Bipolar parallel 1.8

* this is the new motor but to keep the X axis motors the same the old Y motor will go on the X2 axis.
** can't remember why I bought the Z axis motor at 1.8Nm but it's been working fine for years.

I'll look into the higher voltage drivers and weigh it all up . . . .

Don't think about it just do it.!! . . . . .Buy 80Vdc drives and Run the motors Bi-polar parallel with 65-70Vdc and the differance will be night and day.!!

Just having proper drives running decent volts instead of the tin pot System4 setup will make a big enough differance. The above will transform into a real machine.!

Thanks Jonathan and Jazz,

I've been pretty happy in general with my 'tin-pot' system3 but it is now time for an upgrade so when the mechanics of the machine are complete (about 90% now, but garage time is very limited) I'll look into the driver options, especially the higher voltage ones.

Yep .. with those 3Nm motors the ideal voltage is 70V. Buy the 80V rated drivers and you certainly wont regret it. However, do check that the inductance of the Z-axis motor isn't significantly lower than the other motors as if that's the case it may overheat on 70V, in which case you would have to run it wired in bipolar series, but it'll still be far better than the current system.

Edit: Forgot to mention in the first post - cutting aluminium is no reason to upgrade the motor drivers. If you use single flute tools you'll be cutting at 600mm/min, so no doubt well within what the machine can currently manage. Clearly higher feedrates are required with more flutes, but still much less than that of cutting wood.

Hi Jonathan,

Thanks for the Z axis motor info. It has been many years since I looked at the data for the Z axis motor so I will check it when the time comes and follow your advice accordingly.

I hear what you are saying about cutting aluminium and the feedrates / driver requirements, and that in itself it does not justify an upgrade. My experience has been that cutting aluminium on the MK2 machine (which is about to be replaced with my MK3 machine, details to follow) was a bit hit and miss with aluminium sticking to the tool and lots of vibration etc due to the wooden gantry sides (!) and unsupported wooden bed (!). The new machine should be so much better structurally that I felt that to make best use of it overall I wanted to match it with better drivers and that was really driving my questions.

There seem to be alot of sellers listing the MA860H drivers such as below:

CNC Kit CNC Breakout Board +Cables+ 3 Axis MA860H Stepper Driver Controller 7.2A | eBay

How would you rate these compared to the DQ860MA mentioned in post #2?

I know you like to make you own linear supplies, but I would prefer to go for another ready made switched mode such as:
CNC Power Supply 350W 60V 6A For CNC Stepper Motor Driver MA860H M542H NEMA34 | eBay
Any views on that one?

Thanks for your help.

The MA860H looks to be the same as the DQ860MA, except rated for 80VAC instead of 80VDC ... which is quite a big difference. It implies you could just get a toroidal transformer with a 50VAC (or 2*25V etc) secondary winding and connect it to the drivers, which is quite convenient.

However they are quite a lot more expensive than the DQ860MA - have you checked on AliExpress.com - Online Shopping for Electronics, Fashion, Home & Garden, Toys & Sports, Automobiles from China. You can also e-mail wantai-motor directly and they'll probably give you a good price. They did for me at least.

Why do you prefer to go for the SMPS? It's a much more expensive option.

The specs say that the MA860H will take both 80VAC and 110V DC, which is probably why it is more expensive.

I'll check out AliExpress and add DQ860MA to my list of possibles.

I don't touch mains projects and am quite happy to pay extra for a ready made SMPS.

Thanks

Quote:

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Originally Posted by routercnc

The specs say that the MA860H will take both 80VAC and 110V DC, which is probably why it is more expensive.

I'll check out AliExpress and add DQ860MA to my list of possibles.

I don't touch mains projects and am quite happy to pay extra for a ready made SMPS.

Thanks

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Here PS806-5 Linear power supply. If you don't want to build one. ..Clive

Thanks Clive that's good to know. Hadn't consider the ready made linear route. I see it also gives 5v which would power the types of BoB which use terminals rather than USB power. All good info . . .

Quote:

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Originally Posted by Clive S

Here PS806-5 Linear power supply. If you don't want to build one. ..Clive

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£114 including VAT and shipping ... wow.

So long as you don't need it within the next 2 weeks, I'll make you one for £65, but using a 600VA transformer not 500VA as 500VA is a bit on the small side for 4 motors. It wont look as pretty but it'll work.

I'm not going to try and encourage you to start touching mains projects, as I don't know your reasons for not doing so. However, should you decide to then there's a good thread detailing what to do and if you want any advice it wont cost a penny....

I don't need the electrics yet - not for a month or so. Need to finish the machine first.

That's a kind offer thankyou - but am I missing something then with this sort of thing?:

600W 60V 10A Switching Power Supply With Current Control Charger LED CCTV UKD | eBay

I've read that the back EMF of the steppers means you need to overspec the current of the SMPS - is that where the above would limit the performance of the 80V driver setup over the linear 600VA type?

As for mains there are just too many risks for me. Not only the first switch on, but later on with perhaps a poor earth or even a fire. I need something which has been built, tested and warranted so that I can get on with the bit I enjoy which is the Engineering and machining.

Thanks

This is what Leadshine say

"Regulated or Unregulated Power Supply
Both regulated and unregulated power supplies can be used to supply the drive. However,
unregulated power supplies are preferred due to their ability to withstand current surge. If regulated
power supplies (such as most switching supplies.) are indeed used, it is important to have large
current output rating to avoid problems like current clamp, for example using 4A supply for 3A
motor-drive operation. On the other hand, if unregulated supply is used, one may use a power supply
of lower current rating than that of motor (typically 50%～70% of motor current). The reason is that
the drive draws current from the power supply capacitor of the unregulated supply only during the
ON duration of the PWM cycle, but not during the OFF duration. Therefore, the average current
withdrawn from power supply is considerably less than motor current. For example, two 3A motors
can be well supplied by one power supply of 4A rating. "

Quote:

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As for mains there are just too many risks for me. Not only the first switch on, but later on with perhaps a poor earth or even a fire. I need something which has been built, tested and warranted so that I can get on with the bit I enjoy which is the Engineering and machining.

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I think this is a very sensible approach , in my opinion the unregulated power supply is best as it does not generate any noise type interference etc. ..Clive