Hotbed, it’s necessary for 3D printer? what purpose actually.
thank you
Heat allows the plastic to stick to the bed, while allowing it to release properly once cooled back down. Not all filaments require it, but it can be handy in practically all cases. If you don’t have a heated bed, you’re likely only going to be printing PLA
It also keeps the filament above the glass transition temp, when it cools below tg it shrinks and warps… At least that is my understanding.
Sometimes, it seems like you even need a heated enclosure for ABS.
@Camerin_hahn Absolutely orrect about cooling below Tg causing warping. But to be clear, the print shouldn’t actually be ABOVE the glass point, just close to it. Plastic is rubbery and/or flows above the glass point, so you will tend to have print quality issues if the heatbed surface is actually over Tg.
The optimal heatbed temp is in the “creep” range for the plastic, below the glass point. That way it’s solid but residual contraction stresses can slowly relax a bit as the print builds up. That’s typically about 5-10C below Tg for the material… which is why you see people using 50C for PLA, 95C for ABS, 70C for PETG, etc.
Note this is referring to actual plate surface temp, NOT necessarily what the thermistor reports. Most bed thermistors aren’t calibrated very well for the true top surface temp. Even if the thermistor table is good, the amount of temp drop across the print surface will depend on the target temp, so you get more error at higher temps. This is a big reason why people often say to print ABS at 110-115C… they’re usually unwittingly compensating for measurement error in their specific printer.
@ThantiK is also 100% correct about improved adhesion and cooling-release effects.