Tank3d printer build

[Boyan Silyavski]

Now some electricity quiz. I need some advice from sb not electrically challenged like me. As you know I am wondering how to make the printer bed plate as simplest as possible, rigid and cheap.

After examining many options i came to the conclusion that could be achieved using 6-8mm aluminum plate, routed from bottom with cable channels and insulated heating cable inserted.

230V, plate connected to Earth, thermal fuse for overheating, current fuse for over current, thermistor integrated, that for safety. Plus SSr and probably Pid controller or just using the boards PID and separate board for the thermocouple signal if i go this way.



So according to my research ~500W will be right for the power. I used this simple Ohm’s Law calculator

I looked around and found the so called Minco Heat 12K Carbon Fiber Heating Cable 33 Ohm/m DIY Underfloor Heating Wires at ebay and ali express.
It sells around 15euro per 20 meters incl shipping which translates into less than 1 euro per meter

http://www.ebay.es/itm/10m-Infrared-...qQq-NrOxSvmuIw

here is the description:

Product Name: Carbon fiber heating wire
Insulating materials: Silicone rubber
Temperature: 200 degrees celsius limit
Heating conductor: 12K
High voltage test: 3000V
Leakage current: 0.05mA/m
The product can withstand the power of power: 25W/M
Diameter: 3±0.2 MM
Optional colors: Red
Infrared wavelength: 8UM-18UM
Conductor resistance: 33 Ω / M
Length: (custom, not less than 10 meters)

PS: Rated voltage is ~300V


Now from the calculator it seems at 230Vac to achieve ~500w i need a wire with resistance around 100 Ohms more or less :




Please correct me bellow if i am wrong before i burn sth:

1.Now as i understand it the wire resists temperature 200C. Obviously if use 3 meters of wire at 33 ohm per meter i will achieve the desired result.

2.They say :"The product can withstand the power of power: 25W/M" but thats for floor heating, so i assume if wire is connected to a temperature regulating device which does not permit it to go above 130C /+ the thermal and current fuses/ there will be no any problem????

3. I understand that also i have to push fit the wire in the channel/ 3mm/ so there is not any air gap between plate and wire which could cause overheating due to incorrect temp measurement.

I plan of: 6/8/mm plate=+ channel+tight fit wire+thermo conductive silicone flush with bottom surface. So no air there art all

Apart from that i will use some insulator sheet from bellow, still not clear but most possibly Teflon, Silicone, Mica ???



What do you think?

I know i can buy 40 euro 500 W ready heater from China for 40-50 euro, stick it to the aluminum bed from below and thats it. But that is expensive compared to what i propose, Chinese will not care to make trace separation properly and so on. I mean its expensive and i dont find it more reliable than sth i could make. Plus machining all will cost only around 10 euros with the plate, which is 1.3 kg

Calculation shows that 3000mm cable/400mm bed =7.5 which is roughly 7 channels on the long side. So ~200mm/7=~28mm separation between channels which seems quite right to me.