UP Plus2 compared to some other pp3dp printers out there has a proper temp sensor and can be set to a specific temp, the problem with UP Plus2 bed is that it takes an age to get to the print temperature... normal petg print temp I use is 85C and if I leave the bed as is it takes approx 20min to get there, I use a piece of cork to insulate bed on the top and I glued a lot of 3mm cork on the bottom of the bed to trap heat so this way I can get to 85C in ~10min... to 100C to print ABS it takes without cork insulation almost 45min sometimes, and getting over 100C is not possible .. if my room is extremly hot (like 30C+) it will go up to 104-105C but that's the max and it takes age to get there ... with cork insulation we get to 100C inside 20min, it's terribly slow but works (before I start designing part I let the bed start heating and when I'm done I can print usually)... anyhow it really gets on my nerves so I decided to check the heater element and replace it .. well, to my surprise heater element in standard 6mm diameter but much longer then anything I seen so far, 30mm length. The whole is 6.00mm so if you have heater that's slightly oval it will not fit .. I measured the heater and, just like the one in extruder it's 18W .. no wonder it takes an age to heat the bed :(
now, since the wires bringing current for the heater look puny (it's a plastic flat cable) I just used the heater output as a trigger for mosfet driver, external mosfet and external 12V to drive heater, I used two PRC made 6mm heaters in parallel that I pushed into the bed heating block from both sides, they protrude few mm on each side but work like a charm, they combine 70-75W and bed finally works as expected :D ... wiring is bit ugly but not a big deal..
attached is the first test (bed is controlled attm with on/off as there was no need for any PID control with that puny 18W heater so there's some overshoots, I'll see if I want to switch control to pid but it works acceptable as is) ... I really wonder why would anyone put such a puny heater for bed :( on machine that's supposed to be printing ABS
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