The 3D printing market continues to grow at an astounding pace and new products keep appearing that increase the range and value of what can be produced. I just discovered a company that makes 3D printers that are, as far as I can determine, unique in that they build 3D models using standard office paper in full color.
A 3D model produced by an Mcor Iris printer
The 3D printers made by Mcor Technologies use stand A4 or US Letter sized paper, have a maximum build size of 9.39 inches by 6.89 inches by 5.9 inches, and a resolution of 0.0004 inches on all three axes.
The way the color printer, the Iris, produces a model is very clever: All of the layers of a model are printed with bar codes to identify each page using a proprietary water-based ink (it soaks into the paper to prevent white edges) with a customized inkjet printer. The printed pages are then placed in the 3D printer. Mcor's other 3D printer, the Matrix 300+, prints only monochrome models so the printing step I've just described isn't used.
The 3D printer applies glue selectively to the previous layer so that the glue is thicker in the model areas and minimal elsewhere which makes "weeding" (removal the material that isn't part of the model) easier. The printer then loads the next sheet and using heat and pressure bonds the new sheet to the previous sheet. Finally, using a fine computer controlled blade, the model's parts on the new layer are cut from the new sheet.
This sequence repeats until the model is complete. Finally the model is "weeded" and voila! You have a high-resolution, full color 3D object and because the ink soaks into the paper full color is visible under overhangs.
Another attribute of these paper model is they are tough; being made of thousands of layers of carefully bonded paper the end product is more like wood than paper (which also means it's more environmentally friendly than plastic models). If you need a tougher model you can apply resin to produce an object that can be drilled and cut.
As for cost, building models from paper is cheaper than many other 3D printing technologies. While regular 3D printing materials cost more than $10 per cubic inch the models below build by Mcor printers cost between $0.07 per cubic inch (the monchrome architecture model) to $0.92 per cubic inch (the full color GIS map).
The potential for this technology is enormous and, while priced at $47,600 for the Iris color 3D printer and $36,400 for the Matrix 300+ monochrome printer, they are out of reach for home users they are a very affordable technology for small manufacturers and shared "maker" operations.