[lesthegringo]

Hi all, I have just completed the physoical part of a DIY X2 mill conversion to CNC, using the Heavy Metal kit. It was not as straightforward as I had hoped and certainly shows that it is built down to a price, but after a bit of faffing around it is all working nicely.

Now I am building a new controller box based on the Planet CNC Mk3 board, which calls for 8 to 24v power to the board itself, and I have a 24V 25amp power supply for it. However the stepper motors are NEMA23 2.8NM units, and I am driving them using DM542 driver boards, and I am wondering whether the 24v supply I have is going to be good enough. Should I get a separate 36v power supply to power the steppers? For info the mill will be used for mainly aluminium and other soft parts in the main, with some mild steel work now and then

Cheers

Les

[JohnZ]

Are you using the DM542T drivers from stepperonline or similar from another seller? If so, that controller supports up to 50vdc, so I would use a 48vdc power supply. You will have significantly better performance with your stepper motors at higher speeds than you will with at 24vdc supplying the controllers.

I hope that this helps.

John Z

Sent from my SM-G991U using Tapatalk

[dazp1976]

Are you using the DM542T drivers from stepperonline or similar from another seller? If so, that controller supports up to 50vdc, so I would use a 48vdc power supply. You will have significantly better performance with your stepper motors at higher speeds than you will with at 24vdc supplying the controllers.

I hope that this helps.

John Z

Sent from my SM-G991U using Tapatalk

Same here.

[joeavaerage]

Hi,

and I am wondering whether the 24v supply I have is going to be good enough. Should I get a separate 36v power supply to power the steppers?

No way. With a 24V power supply your steppers would likely start missing steps or stalling at 100 rpm, 36V would be better but still under-done and maybe start missing steps at 250rpm.
The rule with stepper is to use the highest voltage you can, in your case 50V is the limit of the driver....so use it.

Craig

[dazp1976]

Hi,
No way. With a 24V power supply your steppers would likely start missing steps or stalling at 100 rpm, 36V would be better but still under-done and maybe start missing steps at 250rpm.
The rule with stepper is to use the highest voltage you can, in your case 50V is the limit of the driver....so use it.

Craig

250rpm would give you 1250mm/min on a 5mm pitch screw.
Exactly where mine stalled on 36v. Pretty poor tbf and 24v will be even worse
You want to use the max you can that the drivers support.

I never use DM542 drivers with nema23/24 any longer.
DM860T and 60v or more all the way.

To be brutally honest, I wish I'd never wasted my money on my X2 and bought the PM25 clone to convert in the beginning.

[lesthegringo]

Thanks all - I will take the advice and go for a 48V unit.

Les

[lesthegringo]

Any suggestions on current rating for the 48V power supply?

Cheers

Les

[dazp1976]

Any suggestions on current rating for the 48V power supply?
Cheers
Les

Minimum of 10A should do the job for 3 motors. I'd go with a 12.5A to give a good safety buffer.

[lesthegringo]

All, I have now made the controller box, using a 24v PSU for the PlanetCNC board and ancilliaries, plus a 48V PSU for the stepper drivers as suggested. For the most part it is working well, and I have dialled in the steps per mm to the point where I am getting about 0.1mm accuracy over the 200mm or so X axis travel. For my purposes that's just fine, the backlash is about that.

However I am getting some odd behaviour in the movement of the 3 axes of the mill. I tested it out physically with a CNC controller used on my Router, which while it's low power allowed me to see that the movement of the axes was smooth in all directions. However with the new PlanetCNC controller connected, the movement is jerky, with it stopping during travel momentarily in any direction, despite the job being constant and there being no load. The connection cables are twisted pairs for the stepper motors, and the connections are made with Cannon 'aircraft' type G16 connectors, so are secure.

If anyone has any guidance on where to troubleshoot this I would be very grateful

Cheers

Les

[JohnZ]

As a quick first step to troubleshooting, if all you swapped out was the controller, would be to duplicate the acceleration and speed settings on the new controller to match the controller from your router. Then gradually increase them until the problem resurfaces. Back off that setting, and increase the other until you know the limits of the new setup. Also, only change one setting at a time while troubleshooting.

Hope that this helps.

John Z

Sent from my SM-G991U using Tapatalk

[lesthegringo]

Thanks, I will do so and report back here - wish me luck!

Les

[lesthegringo]

Well, I can't get rid of the jerky movement, but here's a curiosity - if you run a Gcode program, the mill works smooth as you please, no stuttering, but every time you use the JOG function it comes back. Any ideas?

Cheers

Les

[JohnZ]

What changes did you make in the controller config?

What were the speeds in the Goode vs manual jog?

There must be a difference between the two… or you may have a wiring issue with your pendant or similar, or are you using a wireless keyboard?


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[lesthegringo]

I worked out what it was - essentially the speeds were mismatched, so it was trying to move faster than the allowable maximum, so it would stop when it reached the limit. Simple but had me wondering!

Les

[dazp1976]

I worked out what it was - essentially the speeds were mismatched, so it was trying to move faster than the allowable maximum, so it would stop when it reached the limit. Simple but had me wondering!

Les

Not very clever software program by the sounds of it if it let's you manage to do that.
Things like Mach will show you your velocity limit on axis pages based on your microstepping, steps per and kHz settings.
You can't exceed it.