Differentially Heated HBP

• What? A heated bed optimized for low energy consumption: Differential heating could allow localized heating of the heated bed for small prints.
• How? Through the use of small size heating elements distributed across the whole area of the heated bed and the use of materials with low heat conductivity.
• Why? While prototyping small parts or producing small quantities of small parts there are large areas of the heated bed that are not in use but which still get heated.

Is it possible? Likely.
Is it useful? Yes, as far as energy consumption is significantly reduced. Aim? 30% reduction.

General description of the concept

A main plate made of a material with low heat conductivity (ceramic, glass-ceramic [1] ) with a thickness of around about 3mm. The plate could be a standalone plate or could be fitted or manufactured with a lattice for rigidity if necessary. Small individually controlled heating elements are fitted (glued, painted) on the underside. The heated elements can be painted using conductive graphite ink directly on the bed material or on small mica squares or hexagons [2] that could later be attached to the bed.

Challenges

1. Low cost, locally sourced and produced bed material. (Can I bake my own ceramic bed and grind it flat?)
2. Ink adhesion and incorporation of terminals for soldering of wires.
3. Pattern and thickness of deposited ink to achieve optimal efficiency.

• Conductive carbon/graphite ink: graphite powder in a matrix of water glass (sodium silicate / Natriumsilikat) or ZnBr2 [3]

cayrex2 in YouTube commen: To simplify this is,.... you add 20,5 grams of NaBr2 into 100 ml of water and 28,7 grams of ZnSO24 (heptahydrate) in 100 ml of water. But if you use ZnSO4 anhydrous then you need 16.1 grams for 100 ml of water. Another way to get a ZnBr2 is if you make with copper (II)bromide solution and metalic zinc, but CuBr2 can be expensive, so stick to first method. When you make a solution of NaBr2 and ZnSO4 then you need to heat the solution so long that the Na2SO4 start form a cristals on the bottom (from 200ml to boild down to about 75 - 50 ml) and for the finish you put the hot solution in cold water and you wait that the solution will be cooled down. On the bottom you will see cristals of Na2SO4 and the solution will be ZnBr2 + H2O