Annoying heated beds. Input on ideas

i am Really annoyed with how long it takes to heat the bed. And sometimes it doesnt stay hot.. in addition for some reason sometimes the bed just starts dropping heat and i pretty much have to reset everythign to get it heating again. I have a 12v power supply .. also a spare 24v but it's only 5 amps so that's not helpful and im not spending the $ for a 15 amp(ish) 24v so i had some thoughts.

Has anyone done a peltier unit well? i see they have big problems with pid (bangbang is just slower pid) and they degrade if you dont draw off the heat from the cold side so that's sortof out.

So i'm thinking.. has anyone tried dual heated beds mounted on top of each other with the thermistor between? Or a peltier mounted on bottom of a heated bed or something (this one isnt well thought out) to assist the bed? I guess i could keep a couple extra sheets of glass laying around but honestly i have enough "stuff" laying around related to my i3. Any ideas? it's ridiculous you have to wait 10-15 minutes for the bed to heat up and that then it BARELY makes it. And of course that last 10 degrees takes 800 years.

If you put more watts in, or keep the watts from leaking away, it will heat faster and be able to maintain a higher temperature.

If you aren't going to spend the $ to put more watts in, dual heated beds, or anything with more mass and surface area is just going to take longer to heat.

$-wise, you could work on reducing the watts out and insulate the bottom (I think Nophead had good results filling the space below with RSC cardboard) or a temporary insulator on the top. Neither of these will solve the intermittent dropping heat problem.

I have cork sheeting insulating the bottom and i usually use a cork sheet on top when it is heating. If i cant figure out an upgrade i guess i'll enclose the printer.. though i plan on avoiding enclosure of the steppers and cooling them. It's a shame you'd think this would be the easest problem to solve with repraps but it seems to be the hardest.

The enclosure will definitely help with keeping the heat stable, it is possible to keep the steppers and electronics isolated to cool them with fans/peltier elements/heatsinks.

Thanks i planned(plan) on it.
I cheated and turned it up to 17v when i remembered my voltage regulator was blown and thus unlikely to hurt anything. Works fantastic.. bed heats up fast now and holds temp with no problem. Bonus of course are that the fans turn faster and the steppers should in theory be capable of 25% more speed. Now that that's sorted time to work on extrusion rate, clogging and maybe upgrade to nema23 steppers

I also think my bed heat up is really slow Mine is 22 min for going 20 -> 100 deg C
What time do you get now with your improvement ?
Ha det gött
Bosse

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Prusa i3 Reworked, Delivered March 28 2014, RAMPS 1.4
Göteborg, Sweden

i'm not certain on time but it gets to the 90's within a minute or two it seems like.. and i had it at 95 or so flipped over to check fb and .. couldnt have been more than a minute i flipped back and it was at 110-113 and climbing. It's astonishingly fast now (note i have a piece of roll cardboard for shelving under it that helps some). The voltage upgrade is a huge plus. I'd watch my stepper temp and DEFINITELY have a fan on your ramps board if you do it though .And make sure you dont have the "wrong" board theres one that uses a cheap diode that will blow on it if you go above 12