Chocolate Hydro 3D Printer

Students at Lund University have developed a number of chocolate 3D printers that print on water. An entire class of students, in a digital prototyping course, were given the challenge of developing proof-of-concept 3D printers that could print in chocolate fast.

One of the challenges of 3D printing with chocolate is getting the chocolate to solidify as quickly as possible so that the next layer can be printed on top of the first. And because we don't want to wait for our chocolate forever... :-)

In a different course, in the previous semester, a class of students were given the task of testing different methods for solidifying chocolate as quickly as possible.

?Most of the students used 'conventional' cooling methods involving Peltier devices to create cold air, or a cold print plate. But one of these teams figured out that printing chocolate on cold water almost instantly solidified the chocolate. It also has the great advantage of allowing overhangs to be printed without support material because the overhangs could float on the surface of the water.

So this was developed into the idea of first printing a layer of chocolate on the bottom of the print container, and then flooding that layer with a layer of water of the same thickness, which very quickly solidifies the chocolate. Water surface tension prevents the water from flowing onto the chocolate. Then the next layer is printed on top of the first layer of chocolate and, if necessary, can overlap/float on top of the previously added layer of water.

So the challenge for the next semesters students was to take this idea and develop it into a fully working proof-of-concept 3D printer. Five student teams were tasked with developing the best way for the system to work. This project was particularly tough as the students only had 6 weeks in which to create a working prototype of the chocolate printer. In order to be able to achieve this within such a tight time-frame, each team was given a low-cost 101Hero 3D printer to hack into their chocolate printers.

The students were incredibly creative in the number of solutions they tested, both for extruding the chocolate, and for gradually raising the water level after each layer was printed. For the chocolate extruder, one team used a screw-based extruder, 2 teams used peristaltic pumps, and 2 teams used syringe based extruders. For the water raising system some teams used ultrasonic sensors to detect the water level, while others used 2 wires protruding from the print head that, when they made contact with the water triggered the water pump to stop pumping. They also showed great ingenuity in how to melt the chocolate, with one team building a little bain-marie directly on top of their printer.

?As for all students, there was a steep learning curve in getting familiar with all the digital prototyping technologies they had at their disposal, ranging from CAD to 3D printing, laser and water jet cutting, CNC machining, Arduinos and Raspberry Pi's, etc. It was also interesting to watch their progression as they stated integrating their ideas into the printers and gradually get them to a level where they worked reliably.

As with most product development, the project was very iterative where multiple ideas were tested to figure out which one worked best. The picture below shows the gradual progression of testing new ideas and tweaking all the system components to be able to print a little chocolate cat. Remember! This project was just done as a proof-of-concept to show the idea of printing on water could work. The next versions will have thinner layers, smaller print nozzles, greater precision, etc.

The next stage for this project will now be for the next class of students to go from the printers being a proof-of-concept to a fully developed product that prints well and reliably the first time every time...

The project was supervised by Olaf Diegel, Giorgos Nikoleris and Johannes Ekdahl Du Rietz. Says Prof. Diegel: "Never have I seen students put so much enthusiasm and energy into solving real technical problems. Their ability to creatively apply and adapt the theoretical knowledge taught to them during their degree in a project is simply astounding!". And, of course, the idea of printing with chocolate is just plain fun, so who wouldn't be excited by working on that?

But, ultimately, the proof of the chocolate is in the eating!

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