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.
And that is especially true in 3D printing. I’ve used filament based printers long enough to know that no matter how fast the print head can move there will always be a limitation on how fast the filament is extruded through the hot end. Warping, accuracy and calibration can all be solved with relative ease but speed is bound to remain the same because – whether it’s ABS or PLA – plastic can only melt that fast without burning. On the other hand, SLA and SLS run significantly faster and give more “polished” results on the final print but in exchange you are limited at one material and post processing (washing off residuals) is a pain to handle and can involve substantial waste not to mention the encumbrance of owning such a machine. Therefore SLA and SLS seems more suitable for big factories and industrial workshops rather than on your desk. The only technology that shares the best of both worlds is Polymer jetting, it’s considerably faster than FDM without the downside of SLA and SLS. Moreover, Polymer jetting is built on the foundation of Inkjet, a technology that has become mature and can now perform with amazing speed and accuracy.
I guess everyone is now familiar with 3D printing given the media hype that’s been building up during the last few years. After digging around the Internet for a while, I was surprised how people get so easily excited for the FDM technology that’s been around for over 2 decades. Additive manufacturing is nothing new, it’s an old and very established industry based on technologies that have now become mature. Which means the technology you are buying now already existed in the 90’s but big corporations were too dumb to realize they could have made it affordable for the masses before their IP expires. That led us to the current era where countless startups are trying their best to market their own repackage of the same obsolete technology while adding few to none innovation to it. Therefore, I believe the industry is currently taking the wrong direction and most 3D printing startups will be wiped out once the technology has lost its factor of novelty.