Changing from 12v to 24v - have I forgotten anything?

I'm currently building a Core-XY printer, and now is a good time to change my plans from 12v to 24v working. I already have some parts from a previous printer project, so I need to make sure that I have a good grasp of what's required!

Control board - I have a Duet 0.6, which I believe is capable of working at 24v unmodified.
IR Z-probe - powered by the Duet.
NEMA17 motors - I don't need to change these, do I?
Heatbed - mine is dual-voltage, so not a problem.
Print cooling fan - I'll need to replace the current 12v fan, as the Duet will be feeding it 24v.
Hot-end cooling fan, Duet cooling fan, LEDs, etc. - all 12v, but I can power these with a simple 12v regulator like a 7812 as the total power required is quite low.

Finally, applying 'P=IV', I presume that I can buy a PSU with a lower amperage output? At 24v, the heatbed will need about 5A, the hotend about 1.7A, so anything with a comfortable margin above that should cover all the rest of the system's needs, shouldn't it? I was thinking of a 24v PSU of about 15A.

So - have I missed anything?

Edited 1 time(s). Last edit at 10/22/2015 11:16AM by David J.

You have missed out the hot end heater. You need a 24V one. If it is a standard size cartridge heater, measure it and look for a 24V version with a similar power on eBay. Typical power is 25W for E3Dv6 hot ends (I bought a 24V 30W one when I converted mine to 24V), and 40W for most other sorts of hot end.

Yes you can use a lower current rating PSU with 24V. With a 120W bed heater and single extrusion, 10A would be just about enough, but I suggest at least 12A. 15A would give you more margin for turning up the power supply voltage if the bed heater is a little slow.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The hotend heater was the first thing I thought of - then forgot to write it down in my original post!

My hotend is an E3Dv6, so I'll probably get one of theirs (unless it's stupidly expensive).

Thanks.

I had a look at the E3D website - they offer 25W and 40W in 24v. Is there any advantage to using a 40W? Any disadvantages?

My current 12v 25W heater comes up to temp fast enough.

40W is usually just not needed, but it's easier to tune things down if needed than the other way around. I would go for the 40W and maybe even restrict maximum PWM for the heater in the firmware to make it more controllable.
The more powerfull the heater is the more care you have to take with PID adjustement to prevent serious overheating and damage t the hotend.

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[www.bonkers.de]
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I think you're telling me what I'd already guessed - 40W is a bit harder to control, and isn't usually required.

As 25W has worked acceptably on my existing 12v printer I can't see much reason to go to the higher power. It takes about 20 seconds to get up to ABS temperatures, and I'm patient enough to wait that long. If I was running a high throughput hot end like the E3D Volcano then maybe it would be more useful.

Thanks for the input.

As it is an E3Dv6, the standard heater for that is 25W, so that is what I suggest you use. I used a 30W heater sourced from ebay uk when I switched to 24V.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The advice E3D gave me was that the 40W could cause the heater block to melt if you get thermal runaway while the 25W can't. This factored heavily into my decision to stay with 25W on my E3DV6 and my Chimera.

Hope this helps.

Richard

OK everyone - I'm convinced!