24V question (calling Virtual Colin)...

Heh..., I'd feel guilty for sending Colin yet another question. Don't know how he does it! So..., I thought I'd try calling on Virtual Colin from the forum.

I'm leaning towards the 12" i3v. If I were to go with the "stock" configuration, I would probably stick w/ the RAMPS board, but my sense is long heat times for the 12" bed might start to bug me. (If anyone cares to share their heat times w/ the stock 12" @ 12V, that would be great, I've seen mention of 20min at 12V)

So.

I'm considering building a 24V system from the start.

One of the nice features of the RUMBA is that it can be run off of 24V directly, all necessary regulation being done onboard, without modification (i.e., no removal of diodes, etc).

I THINK that would mean that the build of a 24V vs 12V system would be exactly the same with the following exceptions:

• 24V 400W supply.
• RUMBA
• MK2B heat bed
• Maybe need to upgrade heated bed SSR.

This leaves the following questions in my mind:

• Does the RUMBA do all necessary regulation for the hot-end, fans, and steppers. I.e., would some additional work be required to either add necessary regulation or replace components to deal with 24V?
  
  • The reprap wiki for RUMBA mentions regulation for 12V fans/lights. And I THINK it suggests voltage is selectable for the hot-end. I've read conflicting things about the steppers. It may be a matter of firmware config..., not sure.
  
  
• Will the stock SSR for the heated bed deal w/ 24V OK?

Sorry for the verbosity..., I'll stop here.

Thx!

I have a 12" with Rumba running the stock 12v PSU.

I have two layers of 1/16" cork under my heat bed and print with blue tape. Initially I was having problems with the heatbed not reaching temperature. I would set it at 60*c and found it to be around 45*c, then I tested it at 100*c and it would only reach 70*c.

I resolved it by adding the second layer of cork and leveling my bed closer to the insulation, before there was probably 1/2" of space but now there is about 1/4th of an inch and the bed heats up to the proper temperature.

Also, it only takes 3-5 minutes for my bed to heat to 60*c.

I too have the 12" with Rumba running from a 12v 45A power supply and 10 gauge wire. I have two layers of cork each 5mm thick between the bed and the heater. The heat up time is less than 3 minutes.

12" heated bed take me about 10-12 min to hit 120C with 12V

I have not timed mine but i usually just turn the heat on while i am slicing my model, i like the idea of heat soaking my bed before i start a print anyway to remove any chance that thermal expansion might mess up my prints

Good info everyone, thx!

I suppose one possibility is to go 12V w/ the RUMBA to start, and if I just end up dissatisfied with heat times, do the 24V upgrade as what likely will be a not too challenging project somewhere down the line. Heck, for that matter, folks are running RAMPS on 24V w/ what seem to be fairly minor modifications but I do like the idea of RUMBA being a little more friendly to it.

A little follow-up...

It is done: 12" i3v w/ RUMBA and standard display. 0.40mm hex for 3mm hot-end. 1 spool ABS and 2 spools PLA.

Now the waiting begins!

Interesting aside: I broke down and sent another question to Real Colin wrt 24V. They've experimented with it somewhat in-house, and have observed faster heating times with the 12V pads compared to the 24V. Not sure wuzzup w/ that, but I figure I'd get the RUMBA on the off chance it'll be more 24V friendly somewhere down the line, and stick w/ 12V for the time being since..., well..., most everyone else is.