I’ve been working with Johnrpm on the Reprap forum on a DIY, single nozzle, drop on demand, inkjet print head. The print head itself was designed and built by Johnrpm, whereas I’ve been testing it with different nozzles and approaches to making it work reliably as a drop-on-demand device. It is constructed using a piezo disk designed to be used as an inexpensive (around $1 in single units) audio buzzer, and the entire device including driver electronics (but not including a microcontroller to control it) can be built for around $20, maybe less.
At this point the device works, as evidenced by the following images, but the drop size is currently rather too large so the next step is to experiment with smaller nozzles.
One of the potential uses for the print head is for powder printing (where the print head drops a solvent and/or binder on a bed of powder in order to bind the powder together in the appropriate places) of smaller objects. As such, I’ve been experimenting with a tiny manual powder printing bed using the sugar-sugar powder recipe on Open3DP as a base and I have successfully created several small, and very rough, 3D prints.
This diversion explains why I’ve not made any progress of late towards printing the final parts needed for constructing a Reprap Mendel. Well, that and the fact that I need to construct a larger heated bed for my Repstrap before I can print any of the remaining parts.
For more details follow the link above (or here) and read on. There is a lot of detail buried in the forum posts.