I was changing my filament from black to white a while back and somehow the nice smooth change from black to white caught my eye. Since then I have been wondering if one could use this method to print with unlimited shades of gray or even unlimited colours to create a full color 3d printer.
Full color 3D printer
The main idea is to feed filaments of different colors to one print head. The filaments are melted together inside the print head and extruded from one nozzle. By varying the feed rates one can change the color of the 3d print.
Some problems are obvious - the volume of the printhead heating chamber will hold some molten plastic and the color changes are not instant. The gcodes need to be changed to be able to run multiple extruders and also the electronics need to be updated since this setup would need at least seven stepper drivers.
The same basic technology has been used for many years in normal 2D printers (ie. laser and wax printers) where varying amounts of color pigments are added and fused together to create a full color print. Since we are using solid materials, a substractive color model is used. The color model is called CMYK because of the colors used
When these are combined we can create a mix of almost any color.
Grayscale is somewhat easier to accomplish, black and white filaments are widely available and mixing them together will yield grayscale prints. The color (or shade) can be changed by varying the extrude rates of black and white filaments.
The same idea goes with full color prints.
This is something I will look into when I have some time. Most probably someone has already had the same idea and we'll just have to wait until new generation of full color 3D printers emerge =)