Recent Updates:

Here is the progress since the last build log:

- I figured out a way of designing and manufacturing PCBs that works well for me so that it will be possible to build the needed circuits for the project as proper PCBs.

- I built a TL072-based amplifier by myself to replace the AD620 amplifier that I used so far, which never worked reliably. The new amplifier seems to work much better, while the amplification is currently very low.

- I built a test stand for the printhead, similar to the drop breakup test stand, but out of 2020 profiles and only 500mm high.

- I tried out many different resins for replacing the PVB and ended up using gum sandarac, which is plant-based and has better solubility, finish, and adhesion than the PVB.

- I added filters to the printer to keep the ink clean and prevent the lines and nozzle from clogging.

- I got a new oscilloscope that has 4 channels so that a trigger signal + the signals of the 2 new amplifiers can be displayed in the same timescale to verify that both work correctly.

Will try to write more buildlogs with text and footage of the work I did over the last months when I can find the time for it.

Future Plans:

I'm currently working on a time-of-flight counter for measuring the ink stream's velocity. This will ultimately be used for manual and later automatic pressure adjustments to compensate for changes in viscosity which appear when the machine is used after being off for some time.

Currently, the printer can measure a relative viscosity reading while heating/cooling the ink inside the printer to 25⁰C since the viscosity changes with temperature.

Hardware-wise, there is also a peristaltic pump installed for adding ethanol to the tank to compensate for evaporated ethanol and keep the viscosity steady.

While the feature is currently not activated, it would already be possible to use the viscosimeter reading for automatically adding ethanol.

The stream velocity reading + (auto) pressure adjustment will be used for a finer adjustment in addition to the viscosimeter which can bring the ink stream velocity to the right level immediately.

This, in combination with the viscosity regulation, the right piezo frequency, and the nozzle drive, will ensure that the stream breakup will always occur at the same position (inside the charge electrode). 

Once a favorable piezo frequency, nozzle drive setting, and stream velocity are found, these settings can stay as they are since the TOF-based pressure compensation will keep the stream velocity constant at all times during operation and also when the machine is started again after being off for some time.

Even the older CIJ printer models use a TOF counter, so I think this will be a very important step in getting the machine running.

Once this is working, the next thing will be trying to get the phase test working again.

When I tried that last time, I had no way of knowing the ink stream velocity, so I worked with random conditions and only got random results.