The most common type of home or hobbyist 3D printer is the Fused Deposition Modeler, or FDM type of printer, which works by melting a plastic filament with a heater element (the "hot end") and extruding the melted plastic out of a small nozzle, much like icing a cake.
Current hot ends can only handle one filament at a time, so the types of 3D printers that can handle multiple colors require a different hot end for each one. This causes a number of problems: the nozzles must be exactly the same height from the work surface, or they will damage each other’s work; the distance between the nozzles must be carefully calibrated and the printer’s software must make corrections to keep the output in the same place.
The Diamond Hotend developed by 3D printing specialist RepRap.me addresses many of these problems by combining three heating chambers with a single nozzle to create a new sort of 3D hot end that can extrude different colors.
The concept is deceptively simple. The heating element has three chambers that all meet at a central nozzle. The actual mixing area where all three meet is actually quite small. The resulting nozzle is shaped like a diamond, which explains the name.
The resulting extruder has several advantages over multiple-extruder systems. The single nozzle eliminates the calibration problems associated with having separate nozzles for each color, and the single output orifice alleviates the problem of out-of-level nozzles hitting the working surface being created. The Diamond also has the ability to mix colors or materials together to create new combinations, allowing more than three colors to be printed.
Peter Bøgely started RepRap.me back in 2012 as a hobby, and it quickly evolved into a business selling 3D printer parts and supporting 3D printer enthusiasts over the internet. After quitting his job and become full time in the summer of 2013, Bøgely was soon overcome with the volume of orders. He brought in Kenneth Weiss, who came from a leading medical company and has expertise in manufacturing and electronics, to cope with the demand.
"There are many ways of color printing with the Diamond Hotend and we are still finding new ways of making different color effects," Weiss told Gizmag.
The physics of how the extruder works create different side effects that can be exploited or compensated for, depending on the desired result.
Let’s say that the printer has been extruding blue plastic, and the user wants to switch to red plastic loaded in one of the other of the three chambers of the hot end. First of all, the printer can be programmed to create a "waste tower" or to deposit mixed color to a place outside of the working model. It makes a little square tower of the mixed color (red + blue) large enough to expel all of the blue plastic remaining in the chamber, then once pure red is being produced, go back to the model. The user can chose to just allow the 3D modeling to continue without waste, in which case the color will gradually change from blue to red. You can also create dramatic color shifting by changing colors from one side of your model to the other.
Mr. Weiss says that the main problem now is making the different software packages that drive the 3D printers (called Slicer programs, since they slice the model into layers for the printer) accept these types of color mixing in the print head.
"There is probably many more cool printing techniques that we just haven’t thought of yet, so I am really excited to see what our users will come up with," he says.
The Diamond Hotend is designed as a modification kit for existing 3D printers. It consists of the hotend itself, a single heating element, three chambers for filament, and three extruder stepper motors to drive the filaments into the heating chamber. The printer’s driver board must be able to send commands to three extruders, or it must be upgraded.
RepRap.me has developed interfaces for the bq Witbox and Prusa i3. The company is in discussion with other 3D printer manufacturers, and has interest from several in producing interface kits. There are plans for making conversion kits for popular 3D printers like Makerbot, Duplicator, and Ultimaker.
The Hotend is currently the subject of a Kickstarter campaign, and has doubled its goal of raising 150,000 Danish Krone (US$21,200). Production is expected to start in June of this year.
Future versions of the Diamond Hotend may accept up to five colors, which would allow full color printing and gray scales with red, green, blue, white and black filaments.