Changing colors during a 3D print is notoriously difficult. Either you need multiple heads ready to go during the print which increases operating and maintenance costs for your printer, or you need to stop the print to switch the filament and then hope that everything matches up when the print is resumed. There are some workarounds to this problem, but not many of them are as smooth an effortless as this one which uses erasable pen ink to add colors to the filament on the fly.
Erasable pen ink is a thermochromic material that doesn’t get removed from paper when erased like graphite from a pencil. Instead the heat from the friction of erasing causes it to become transparent. By using this property for a 3D print, the colors in the print can be manipulated simply by changing the temperature of the hot end. Of course the team at [Autodrop3d] had quite a learning curve when experimenting with this method, as they had to run the extruder at a much lower temperature than normal to have control over the ink’s color, had to run the print much slower than normal, and were using a very sticky low-temperature plastic for the print.
With all of these modifications to the print setup, there are bound to be some limitations in material and speed, but the results of the project speak for themselves. This allows for stock 3D printers to use this method with no hardware modifications, and the color changes can be done entirely in software. While everyone catches up with this new technology, there are some other benefits to a 3D printer with multiple print heads, though, and some clever ways of doing the switching without too much interruption.
Now that’s a hack!
Isn’t there a color additive that’s changes between 150-300 more drastically?
Not to distract from the awesomeness of this technique, but I didn’t know that’s how erasable ink worked.
Is there some way to make the transparent ink visible again? Like invisible ink with lemon juice?
Yes. You can freeze it to restore the marks on a piece of paper.
Yeah, heat to erase, put in freezer to restore. It’s pretty fun.
Pilot makes a line of pens called FriXion that use this ink. The pens have a rubber “eraser” to create heat from friction to hide the ink.
The ink is also water-soluable which Rocketbook takes advantage of to make reusable notebooks.
Their first generation of notebooks weren’t washable; you were actually supposed to microwave them erased.
(You’d put the notebook in the microwave, and set a glass of water on top, and run on high for 5 minutes or so. A design on the cover, in a different type of thermochromic ink, would disappear when the optimum temperature was reached, and then reappear when it cooled.)
I wonder if you could add a a UV activated colourant into the filament instead?
Eraseable ink pens of the 80’s used a thick ink that didn’t penetrate the paper. The eraser rubbed the ink off the paper in little blue or black balls and strings.
It’s interesting, but what use is filament that extrudes – i.e. melts- at 50C? You can’t make anything practical with it because it’s going to end up melted in a car or even a sunny window.
I guess that makes it perfect for printing tugboats!