Extruding batter at a constant, desired rate that could be stopped and started immediately on command was one of the largest challenges in this project. While the design we settled on could definitely be improved to be more professional, we feel that we have created a reliable system that fulfills the constraints of our system.
The Extrusion Method
When first developing the extrusion mechanism, we tested several options and ultimately decided on the forced-air method. In this method, we utilize a 6V air pump, which is designed for use in aquariums, to essentially push batter out of the bottle. This manner of extrusion has several benefits. Firstly, as opposed to other pumps, there is no contact between the batter and the air pump, which means it remains contained within the bottle. This makes cleanup significantly easier. In addition, by simply adjusting the voltage that the Arduino is supplying the air pump, it is possible to tune how much batter is extruded.
While researching pancake art, we noticed that many artists use a bottle that looks similar to a condiment bottle to hold and extrude their batter. Following this, we purchased several condiment bottles and found that they did indeed work quite well for extruding clean lines of batter. As we iterated through bottle design, we found that one of the pain points was the need to flip the bottle over in order to fill it. While this wasn’t too much of a problem for earlier testing, at later stages, it was a major inconvenience. For this reason and others, we combined two bottles, which enabled us to have a cap at each end of the bottle.
Pictured above: One of the final iterations of the full extrusion mechanism. The air pump (to the right of the coil of tube), two bottle design, and solenoid are pictured.
During early testing, we found that batter would slowly drip out of the bottle when held upside down, even when the air pump was not on. To prevent this, we added a solenoid valve to the end of the bottle. A solenoid valve is a one-way valve actuated by an electromagnet. This allows us to electronically control when batter should flow out of the bottle.