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Polymer Jetting 101

January 13, 2014

After much digging, here is what I found.

There are two ways to selectively jet liquid through a print head.
Thermal printers make use of heat to cause a small portion of the ink inside the jetting chamber to instantly evaporate thus creating a bubble capable of pushing the ink out through the nozzles. This method only works for low viscosity ink or fluids that have a chemical composition close to water and therefore cannot be used to jet photocurable resin because it would harden instead of evaporate under high temperature.
Piezoelectric printers use the vibration generated by a piezoelectric crystal – a material that can shrink or expand when submitted to electric pulse – to push the liquid out of the chamber. Since this method is less dependent on the nature of the fluid jetted, it’s the way to go if you want to jet high viscosity resin.

With that idea in mind I took my old Epson printer out of the closet, drained out the ink and started to feed SLA resin into the cartridges. Somehow I managed to trick the software into thinking the cartridges were full of ink but in the end I couldn’t even get a single drop out of the nozzles. Worst, my printer couldn’t even revert back to jetting ink. It turned out the nozzles were so tiny that they got clogged by the resin before they even start jetting.
Way to be crippled by advanced technology.

Later on, I realized that the fluid was too viscous even for a piezo head. Most photocure polymers stay at around 100cp at room temperature while they need to be at 15cp to be jetted properly. Therefore, a head with wider nozzle would not suffice, it must also be capable of heating the material before jetting it. And such a head can be found in industrial 2D printers that jets high viscosity ink.