I didn’t like the look of the heated bed , so I added a 2D printed paper grid between the glass and the heated bed. That got me wondering if the insulative property of paper would effect the time to heat the glass.
With the bed temp set at 120c, it took about 7 minutes for the bed to reach temperature, slightly faster with the paper insulator. The glass surface was only 96c at the instant the bed reached 120c. However it took 11 minutes for the glass surface to reach 105c without the paper, and 13 minutes with the paper. Interestingly, the glass peaked at only 107c in both cases.
Note that I’ve checked the calibration on the thermocouple, and that it was insulated after being taped to the glass. The 200mm x 200mm heated bed is a fiberglass Printed Circuit type heater as supplied with the Mendel90 kit.
Is it worth the extra two minutes waiting for the glass to heat up?
Does anyone know the maximum temperature one can operate a PC type heater bed ?
Do you have anything under the heater? I haven’t ever checked the glass temp, but I know it takes a while for the top of the glass to get warm. But for a protection against shorting if the circuit ever pops off the board, I placed a no stick silicon mat under the heater and above the aluminum base. I’m wondering if a section of insulation under the heated bed would force all heat up through the glass and help.
Just one piece of cardboard with aluminum tape. I noticed that nophead added more cardboard on the latest kit instructions… Maybe I can get my two minutes back by insulating more under the bed. BTW, If anyone does this, note that the aluminum tape will short the heater
I also have the glass on top of the aluminium bed, that is on top of the hot plate printed circuit board. So when the board become hot, it transmits the hot to the aluminium very quickly, but then the glass takes minutes to reach the temperature, since glass is a heat insulator. This means that the temperature detected by the Reprap is in reality the hot circuit inner layer, and not the external glass surface, and this may cause to have the bed relatively cold at external side, while in the inside layer all seems ok at 60C…
I recently replaced my thick special tempered glass with a normal glass that is thinner hoping it become hot quicker.
