Switching to 24v power supply
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@ InSanity - I didn't mention a power rating (for which you suggest against).
@dc42. 300W would be fine - I've not been able to find a fan less version of that wattage - do you have a link? (Meanwell's UK site has so many and searching for "fan less" doesn't yield any results). The bed is AC mains so it's only the hot end, X,Y Z steppers and fans. Even running 3 or more extruders I'm not likely to get close to 300W (but I do like to have plenty in reserve for who knows what the future holds).
If the bed heater is mains powered, you don't need anything like 300W. I use a 120W PSU in my delta, and it's only that high because I wanted the possibility of supporting dual nozzle extrusion.
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Mains powered bed heater really would change the game, with that I don't see why fanless would be an issue. For most using 300+ watts I'm not sure I would want a fanless power supply. The meanwell I'm using is just temp controlled, but still loud when the fan is on. Fannless would be fine if the caps and such are of good quality and temp rating. If anything I think a good temp controlled power supply would be best with slow ramp and only turning on when really needed i.e. max load.
Really it all boils down to the load on the supply and the efficiency. Find a 90% plus efficient supply and heats less of an issue.
Jeff
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Looks like TDK, Sampu, and some others have 300w fanless supplies. I'm still not crazy about the idea but sure would be nice to have less noise.
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David,
I'm working on a design for a 6 colour active mixing hot end. It may not come to anything but who knows….......
So my calcs go like this:
X and Y motors 2 amp each but being driven at 40% (CoreXY - build area 400mm x 400mm, big, heavy XY axes 600mm long, 400mm travel) =1.6 amp @ 24V = 38.4W. (Z is intermittent and won't run concurrently with XY so has been ignored)6 off extruders 1 amp rating but driven at 40% =2.4 Amps = 57.6 W
Hot end 2 x 40 W heater cartridges (it'll be big with 6 inputs and a big melt chamber is anticipated) = 80W
Mixing motor, fans, lights,electronics etc = 30W (guestimate)
Total = 206 Watt. Use 80% capacity so spec at 257 Watt. Hence me thinking that 300W (or 250 if I could find one) would be a good choice. The motor currents are actually set at 80% of their rating but I'm guessing that they actually draw about half this, hence me using 40%. Am I way off ?
Cheers
Ian
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The motors won't take that much power, especially with a 24V supply. See https://duet3d.com/wiki/Choosing_the_power_supply#Total_power_needed.
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I'm using a Mean Well HLG-600H-24B, which supplies 25A @ 24V (600 W). It's somewhat expensive, heavy, and quite overkill for my current printer, but it's fanless, elegant and works great. There are less expensive ones with lower output power, of course.
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Ahhh. Using rated voltage instead of supplied voltage brings it down a LOT - of course it does now that I thing about it. Sorry for being thick. 2 amps at 2.8V =5.6W and 50% x 2 steppers =16.8W instead of 38.4. Doing the same calcs for the 6 extruders brings the total down from 206 to 155W so 200W should be fine for all likely future requirements. Thanks
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Don't forget you always have to factor in the quality factor, 300w no name supply vs 300w top quality brand name supply. The cheaper no name or off brand supplies will almost always overrate their specs where as often the top brand name supplies might underrate a bit. In the end you get what you pay for.
I'm posting this more for others that might read this post then those who have already posted.
Jeff
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I'm happy to say that I received a reply from Sinton today saying 'if you use 24v , the resistance should be around 2.8~3 ohm.' So, using
Current = Voltage / Resistance
Power = Voltage * CurrentGives me between 192v and 206v which was a bit more than I was expecting. Coupled with my previous workings out that means I'm going to need 136.5w + 206v = 342.5v with a bit of wiggle room so lets say 350v. Shame really as I had just about settled in my mind on a MeanWell 300w PSU.
Steve
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I'm wondering if buying a different heated bed with a higher resistance would be the better way to go:
With 4 ohm of resistance that equates to 144w and so a total of around 280w with a happy amount of wiggle room lending itself nicely to a MeanWell 300w PSU. Possibly I have just answered my own question….......
