The two dominant plastics in 3D printing are ABS and PLA, both of which are known as thermoplastics; this means they become soft and moldable when heated and return to a solid state when cooled.
Heated beds are used for improving the print quality by keeping the extruded plastic warm and preventing it from warping. Warping is caused when layers of printed plastic on the edges of the part begin cooling down at an uneven rate and shrink slightly. When this shrinking process does not occur throughout an entire printed part evenly, the result will be a warped part.
Printing on a heated bed allows the printed part to stay warm during the printing process and allow more even shrinking of the plastic as it cools below melting point. Heated beds usually yield higher quality finished builds with materials such as ABS and PLA. A heated bed can also allow users to print without rafts.
A phenolic board works well with a 3D printer. When attached to a heat bed, it disperses the heat evenly across its entire surface (unlike the metal plates underneath which have hot spots). When printing with a cold board a phenolic board helps the extruded plastic stick to the surface better than kapton tape, masking tape or glass.
The single greatest hurdle for accurate parts in ABS will be a curling upwards of the surface in direct contact with the 3D Printer’s print bed. A combination of heating the print surface and ensuring it is smooth, flat and clean goes a long way in eliminating this issue.