Heated bed issue

Has anyone encountered this problem? I can get my PCB round 300mm heated bed to 110+ degrees no problem by itself. I have a mdf board covered in foil just underneath it. the screws aren't flush with the pcb so in order to put a glass plate on it I have to space it up some, I use 2mm thick silicone CPU heatsink material to do so. The problem is that with the silicone rubber and glass plate, the bed will reach the temperature, but the glass plate never really makes it to 100C it stays around 80. Am I using the wrong material to space the glass plate up? I thought that heatsink material would transfer the heat from the heated bed dramatically to the glass plate.

Well, I scrapped the foil covered mdf board idea, and instead added another 2-3mm mdf board underneath. Both boards are pinched together and then the heated bed is pinched to the boards. Then I place the glass plate with build tak on it on top of a silicone rubber thermal cpu heatsink material I got off of amazon, and place that on top of the heated bed. The extra insulation from the boards now leaves the glass plate at 96 or so C, when I set the repetier host bed temperature at 125. As it prints the plate raises temperature to around 105. So it is workable, but I still wish I could get a solid 110-120 degrees C on this glass plate.

Glass is an thermal isolator so the heater needs to do more to get the top at the correct temperature, I put my heater on a 1.5 mm aluminum plate and then I used double sided tap ( carpet tape ) to directly mount the aluminum to my borosilicate glass plate that is sprayed black. I reach 100 degrees when I set the temperature to 110. When moving the Y carrier the temperature goes down again. I am now putting a IR temperature sensor on my x carrier, so that I can measure the glass plate temperature instate of the temperature on the heater. This I will use at the beginning of the print to check if the glass plate is reached the correct temperature. Now I have a 5min delay in there. I still have to put an isolator below the heater.

---

P3steel DXL, with Due/RADDS/Raps128 dual Wade's extruder

You'd never buy a car that had windshield wipers that only cleared rain off of half of the glass, and required you to buy longer wiper blades and install them. But a 3D printer that doesn't have a bed that's flat enough to print on? That's OK! So now you add a piece of glass to try to provide a flat enough surface to print on and discover that the heater is underpowered. So now you try adding stuff to the underside of the bed to insulate it and hopefully raise the temperature. When that fails you finally open your wallet and buy a higher powered heater. Then you discover that the power supply can't handle an adequately powered heater, so you buy a bigger power supply. Then you discover that the controller board can't handle the current for an adequately powered heater so you buy a replacement with properly heatsinked MOSFETS and PCB traces that don't catch fire when the heater turns on. So much for cheap kits!

You can simplify things dramatically by buying an adequately powered heater and power supply from the start. 0.4-0.5 W/cm^2 of bed surface area will deliver adequate heat to print any material and won't have you waiting for hours for it to heat up. Stick that heater to a piece of cast aluminum tooling plate which comes milled flat and is rigid enough to stay that way and you won't need to put glass on top of it. You won't need insulation on the bottom side, either. Put Kapton or PET tape on the aluminum to get ABS and TPU to stick, and blue painter's tape for PLA and you're good to go. I've been using that setup in my printer for about 3 years. It works:



That's a 250 mm diameter ABS print on clean Kapton tape on a 1/4" cast tooling plate bed supported by a 3 point leveling system. There's no insulation under the bed plate. The heater is rated for 450 watts and gets the bed plate up to 105C in about 5 minutes.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Very interesting, thanks for the input guys.

My power supply is a 240W power supply, so that's obliviously a power issue. If I were to get another powersupply can I use that to power the printer and heated bed using a relay through the Ramps 1.4 board I use or two seperate power supplies?? Or do I have to modify the board to handle the wattage, because I really hate modding the board if I don't have too.

EDIT: This is the power supply I have [www.reprap.cn]

Edited 2 time(s). Last edit at 04/20/2016 05:14PM by Nate523.