Project Logs

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• Reducing Complexity

  Dominik Meffert • 5 days ago • 0 comments

  While there is still much work to do on the charging electronics, the current fluid system design can be considered complete. It's been working reliably for about a year now, with only minor changes from time to time to make it even more reliable.

  So, I thought now would be a good time to remove parts that are not essential to reduce cost and complexity. Currently, the frame has a large size of about 100*50cm, which I plan to reduce to at least half its size over time.

  Falling Ball Viscosimeter
  

  One thing that sometimes caused problems was the falling ball viscosimeter. When not used for a while, it happened that the steel ball got stuck at the bottom of it, and it was needed to disassemble it, clean all parts with ethanol, and assemble it again. Since the falling ball viscosimeter became redundant by using a ratio of pressure divided by jet velocity for the viscosity reading, I thought it would be better to remove it to have one less point of failure on the machine. So, I removed all parts of the viscosimeter, including the 2 inductive sensors, the polycarbonate tube with steel ball, and the fittings. 

  Peltier Heater / Cooler

  With these parts removed, there was still the brushless pump for circulation and the Peltier cooler/heater left. The circulation line is used for mixing the ink with solvent when the jet isn't active. It also has a higher flow rate than the inkjet and is used for pushing the ink through the main filter to keep it clean. So, the circulation line had to stay.

  The heater/cooler was used for keeping the ink at a reference temperature of 25⁰C when using the viscosimeter because viscosity changes with temperature. With the viscosimeter removed, there is no need to keep it.

  To still be able to take temperature changes into account, I finally added a temperature sensor to the nozzle assembly which reads the temperature as close as possible to the ink jet before it performs the TOF reading.

  Maybe this can later be used for temperature compensation of the viscosity reading.

  Brushless Pump

  Now the big question was what to do with the brushless circulation pump.

  At the time, I decided to remove it and replace it with another peristaltic pump to only have two different sorts of pumps on the printer instead of three. Later I found another solution to it.

  External Pressure Pumps

  Another problem that I wanted to solve for a long time was that the pressure pumps were located outside the printer frame. I used four small pumps instead of one large pump because when used as intended, they are only allowed to run for two minutes until they need a one-minute break to prevent overheating.

  To solve this, I decided to use one large 24V vibratory pump and run it on a lower-duty cycle while cooling it with a small fan.

  The pump I used for that is the ULKA EX5 24V, which is normally powered by AC. However, since these pumps already come with an integrated diode, they use only one half-wave of the AC cycle and can, therefore, be driven by pulsed DC without any problem. For driving it, I used the same BTS7960 H-Bridge that was used for driving the Peltier module before, because it was suitable for driving the pump, and I already had it wired to the printer controller and power.

  I used a signal with 50Hz and a 30% duty cycle to drive the pump. To keep it cool, I used a 40*40*10mm 24V fan, and to not transfer the vibration to the printer frame, I used two short pieces of gt2 belt and some zip ties to let the pump hang from an angle bracket. In addition to that, I used a silicone tube for the inlet and an NBR tube for the outlet because the vibration of the pump was transferred through the PE tube I used before, which caused a lot of noise.

  To protect the pump from overheating in case the pulse signal would freeze and expose the pump to DC for some time, I installed a bimetal switch that would...

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• Jet Velocity - Time of Flight Reading

  Dominik Meffert • 03/22/2025 at 12:40 • 0 comments

  Relation between Jet Velocity and Pressure, Viscosity

  In CIJ printing, there are two important key values that can change during operation, so it's important to track and control them.

  These are viscosity and pressure which both affect the jet velocity:

  - An increase in viscosity leads to a decrease in jet velocity while a decrease in viscosity leads to an increase in jet velocity when the pressure stays constant.

  - An increase in pressure leads to an increase in jet velocity while a decrease in pressure leads to a decrease in jet velocity when the viscosity stays constant.

  Viscosity is affected by temperature changes and solvent evaporation. A higher temperature leads to a lower viscosity and a lower temperature leads to a higher viscosity. A higher solvent content leads to a lower viscosity and a lower solvent content leads to a higher viscosity.

  Relative Viscosity is measured by a falling ball viscosimeter and the ink temperature can be controlled by a Peltier module. The solvent content can be controlled by adding solvent via a peristaltic pump or by adding pre-mixed ink to the ink tank. Adjusting the temperature and solvent content usually takes some time until the solvent has mixed with the ink and the set temperature is reached.

  In contrast to that, pressure is not affected by external factors and can be measured with a pressure sensor and controlled with a pressure regulator or a PWM-controlled pump, which makes fast and precise pressure adjustments possible.

  Since a constant jet velocity is important for reliable operation and good print quality I added a way for measuring the jet velocity to the printer.

  Great thanks to Robert H. and @Paulo Campos for helping me with that.

  The jet velocity is measured by counting the Time of Flight (TOF) that an ink droplet needs to travel between two sensors that have a fixed distance between each other. The distance is then divided by the TOF to get a reading in distance per time.

  This new TOF sensor should make it easy to keep the jet velocity constant by looking at the reading while adjusting the pressure. Currently, I'm using a bar with a "proven to be good" value in the middle and a small good range around it while adjusting the pressure regulator by hand. In the future, this could be automated if needed.

  S0 and S1 are timeout indicators that can help with troubleshooting by indicating which sensor has a problem.

  I also added another reading which shows the ratio between pressure and jet velocity to get information about how much changes in viscosity affect the jet viscosity.
  

  Recent tests have shown that with the viscosity of the currently used resin ethanol mix, small changes in viscosity caused by temperature variation have very little effect on the jet velocity. Since the printer is used inside the house the ink temperature should also not drop much below 20⁰C and rise not much above 30⁰C.

  Based on this, I think changes in room temperature across different seasons will have less effect on the viscosity and jet velocity than solvent evaporation over time.

  In contrast to that, each psi difference has a noticeable effect on the jet velocity, so that a more precise pressure control would have a positive effect on reliability and print quality.
  

  TOF Sensor as Functionality Test

  In addition to measuring the jet velocity, the TOF sensor can also verify the function of breakup and charging. It relies on charged groups of ink droplets for time measurement, which is only possible if both processes are working correctly.

  When no signal is detected on the TOF sensor this can indicate the following problems:

  - A clogged nozzle

  - A misaligned jet

  - Problems with the piezo

  - Problems with the charge electrode

  - Problems with the TOF sensor

  This can help with troubleshooting and could be used for pausing the print in the future if a problem is detected.

  Building the TOF Sensor...

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• New Ink for the Printer

  Dominik Meffert • 02/25/2025 at 06:17 • 0 comments

  Until now, I used a mix of polyvinyl butyral and ethanol as ink for the printer, and even though PVB worked well for regulating the viscosity of the mix, the dried-up ink layer had bad adhesion properties so that it was constantly peeling off into flakes which gave it a very dirty look. 

  Because of that, I started searching for other ethanol-based inks.

  Shellac
  

  The first thing I found was shellac, which was often used as an alcohol-based furniture varnish in the past. 

  So, I went to the hardware store to get a small bottle of it for testing out the surface finish.

  To test for the surface quality, I poured a small amount of it into the drip tray and let it dry.

  After waiting some time, I checked the surface quality, and it looked very promising.

  The shellac made a smooth, clear, shiny, and nonsticky surface with good adhesion to the stainless steel of the drip tray.

  Since the varnish is alcohol-based, it was also possible to fill up the bottom of the tray with ethanol and let it dissolve the shellac, which makes cleaning it up very easy.

  So, I ordered a bag of shellac for loading it into the printer.

  It turned out that the shellac flakes were easy to mix with ethanol, and depending on the concentration, the color reached from orange to dark brown. It also worked well to change the viscosity based on the concentration.

  When testing the charge + feedback signal it also worked as well as before.

  All in all, it can be said that shellac-based ink is superior to PVB ink with a nice surface finish and an easy preparation process.

  The only drawback of it could be the brown color and the fact that shellac is made by shellac lice, which could maybe raise ethical concerns.

  For this reason, I continued testing out other inks.

  Plant-based Varnish

  The next thing I tried was colophony/pine rosin.

  The good thing with colophony was that it dissolved very well when mixed with ethanol and the color was much more clear compared to the shellac.

  But when I then tested out the surface finish in the drip tray as with the shellac before, I quickly realized that this mixture would not be suitable for using it in the printer.

  While the surface finish looked ok at first glance, it turned out that it was rather glue than a varnish since it remained very sticky even when fully dried.

  For fast printing of text or binder jetting and also to prevent a sticky mess when working with it, it would be better to select an ink that fully dries as fast as possible while forming a smooth nonsticky surface. So, the search continued...

  Just to mention it, I also tried out gum dammar, which turned out not to dissolve in ethanol, and elemi, which dissolved, but the surface was more like wax than varnish or ink.

  Trying out solvent-based Varnish
  

  To leave nothing untested, I also tried out solvent-based varnish from the hardware store, which I think was important for gaining the experience, but I wouldn't recommend it or try it again, especially not in winter when opening a window brings the temperature down to frosty levels.

  I started with mixing 1l nitrocellulose-based varnish and checking how the mixture ratio influenced its viscosity.

  It turned out as expected - the varnish-to-solvent ratio influenced its viscosity.

  After working for some time with it, the smell got so horrible that I decided not to continue testing with it, since I'm planning to use the printer inside the same space where I live, like any other 3D or desktop printer.

  The next thing I tried was using alkyd resin-based varnish, which I mixed with white spirit "Reinigungsbenzin".

  It turned out that the...

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• Test Stand and DIY Amplifier

  Dominik Meffert • 01/31/2025 at 04:32 • 0 comments

  My next goal is to measure the speed of the ink stream by using two sensors and counting the time the droplets need to travel from sensor to sensor.

  To make work on the electronics easier, I built a new printhead test stand with a drip tray for catching ink drops that miss the gutter.

  After everything was in place, I tried building an amplifier for measuring the small charge that would be applied to the droplets by a Time-of-flight test signal.

  To verify that the amplifier works, I did a quick test of the new amplifier by applying a 0.1V 20kHz signal and looking at the amplifier's output.

  The test showed that the amplifier is turning the sent 0.1V square wave signal into a 0.25V triangle wave.

  While I didn't expect the output signal to be a triangle wave and I also thought that the amplification would be a bit higher, the test showed that the built circuit was working.

  So, I built a sensor out of a UHF connector that I connected to the amplifier for detecting the charge on the droplets and applied a test signal to the charge electrode.

  Conclusion after the first Test:
  

  For now, it looks like it's possible to send a test signal to the charge electrode and receive a feedback signal through the amplifier.

  This is an improvement compared to the AD620 amplifier that I have used so far since the old amplifier only worked randomly, and most of the time, it didn't work at all. 

  The new amplifier, however, is working pretty reliably so far.

  Here is a short video of the test:
  

  At the moment of writing this, I already built another one and added a TDA2030 amplifier and a high-pass filter to each one of the two to further amplify the signal and filter out the 50Hz mains frequency.

  I also built a new sensor assembly made out of a PCB. The new one provides two sensors with a fixed distance between them so that the jet velocity can be calculated by using the known distance and the measured time delay between the signal appearing on the first sensor and the signal appearing on the second sensor.

  The next step would be building a peak detector to get the signals ready for feeding them into a microcontroller to measure the time delay.
  

  When that's done, it should be possible to get a stream velocity reading, which would be the first real progress on the printhead driver electronics.

  After that, the same circuit could be used to test for the phase shift that works best for charging, but the current amplifier design is too slow to detect groups of charged droplets at the needed frequency. 

  So, a redesign of the amplifier circuit would be needed before it's ready for this test.

• Making PCBs

  Dominik Meffert • 01/31/2025 at 01:39 • 0 comments

  Some time ago, I bought a pulsed 1064nm IR laser (Sculpfun IR2) for metal engraving and I recently figured out that this laser is the perfect tool for removing spray paint from copper PCBs without any residue.

  A year ago I tried the same with a common 450nm laser, but this laser rather burned the paint off while leaving a lot of residue on the PCB. 

  My guess would be that the pulsed operation mode of the new laser is the decisive factor here, which causes the paint to chip off or evaporate when hit with the laser instead of just getting burned away.

  PCB Manufacturing Footage:

  I think having figured out a way of PCB manufacturing that works well for me will help move the project forward and will also be very useful for future projects.

  Until now, I always had to build circuits on perfboards and connect the components with solder wire. This was a lot of work and also looked ugly compared to the new design.

  It's also an advantage that the circuit and PCB layout can be designed on PC for lasering it 1:1 onto the copper PCB. 

  This makes the process similar to 3D printing, which will make it easy to share the design with others and will ensure that each copy of it will be identical. 

• Quick Update

  Dominik Meffert • 01/17/2025 at 09:11 • 0 comments

  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.

• CK Fittings, PE Tube, new Printhead and other Improvements

  Dominik Meffert • 10/08/2024 at 04:54 • 0 comments

  Latest Video of the Printer:

  New Tubes and Fittings
  

  For the past months while working on the test stand and code for the ESP32, I did not use the printer prototype, and while it was standing there, some of the fittings got leaky.

  Until now, it wasn't that big of a deal that the fitting's NBR seals got dissolved by the ethanol over time, because I changed the prototype's design over and over again, and with it the fittings, but after a lot of testing I thought that most parts of the current design were working reliable enough to keep them this way so that it was finally worth it to replace the push-in fittings with a more suitable type of fitting.

  A better option than the pneumatic push-in fittings are CK fittings (sometimes also called rapid screw fittings), which don't have a seal that can get leaky but instead use the tube itself as the seal by clamping it between the two halves of the fitting.

  Since I had to replace every fitting connection on the printer, I also wanted to replace the currently used PU tubes with PE tubes, which in contrast to the PU tubes, are suitable for long-time exposure to ethanol because of their better chemical resistance.

  No more Watercooling
  

  While I was replacing the fittings and tubes, I also thought about replacing the water cooler with an air cooler, so I could get rid of the water cooling pump, radiator, reservoir bottle, and tubes to end up with more space for other parts and less cost and complexity.

  Until now, the water cooler was used to get rid of the heat of the Peltier module when it's used for cooling the ink. 

  The Peltier module can be used for heating or cooling the ink depending on the room temperature to always keep the ink on a reference temperature of around 25⁰C for viscosity measurement.

  The ink's viscosity changes with temperature even if the ink mixture stays the same, so it's necessary to always measure the viscosity at the same temperature to be certain that changes in the viscosity reading also represent changes in the ink mixture.

  To keep the viscosity constant during printing, the printer can add more ethanol to the mix to compensate for the evaporation of ethanol, which would otherwise lead to an increase in the ink's viscosity.

  As long as the room temperature doesn't exceed 25⁰C by a lot there wouldn't be much heat to dissipate, so I think the cooling can be handled by an air cooler as well for the most time of the year.

  So, I replaced the water cooler with an air cooler.

  New Flushing Concept

  A while ago I added a flush valve and flush line to the printhead that could be used for flushing the nozzle and gutter line with ink for cleaning.

  It turned out that this wasn't the best idea because the ink would harden inside the tubes when the printer is not used for some time and when I recently ended up with clogged lines that I had to replace, I decided to change the printer design in a way that makes it possible to draw all ink from the nozzle and gutter line via vacuum and then flush these lines with ethanol without adding unwanted ethanol to the ink tank.

  To do so, I added two valves to the output of the return pump, which are both switched with the same relay. The valve that leads to the ink tank is connected to the normally closed pin and the valve that leads to the flush bottle is connected to the normally open pin so that the ink flows into the ink tank until the flush line function is activated which switches the relay so that the ink tank valve closes and the flush bottle valve opens.

  With this change, it's possible to flush the gutter and nozzle line into the flush bottle to prevent clogged lines and too diluted ink in the future.
  

  Some Footage

  Here are some photos I took while replacing...

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• Visualizing Drop Breakup

  Dominik Meffert • 09/11/2024 at 00:49 • 0 comments

  After taking a look at the charging and charge sensing, I also wanted to take a look at the drop formation. Both processes are crucial for building a working CIJ printer.

  On many CIJ printers, a stack of 2 piezo rings is mounted on the nozzle to let it vibrate at a fixed frequency. Normally all parts are designed to work together within certain constraints:

  The piezo frequency, stream/nozzle diameter, pressure, and viscosity need to fit well enough together to make a controlled breakup of the stream into equal-sized drops possible.

  So much for the theory...

  In reality, this seems to be a big challenge, and I'm constantly working to get it right at some point.

  To learn more about the drop breakup, I was looking for a way to record it on camera.

  Changes to the previous Test Stand
  

  For recording the stream on camera, I replaced the 1 1/4 pipe tank with a pump to be able to record a continuous stream breaking into drops instead of drops dripping from a nozzle.

  The next step was to let the stream vibrate at a certain frequency to get an even, non-random breakup. To make recording easier, I wanted to use a larger stream so that no magnifying glass or microscope would be needed. Because of that, breaking the stream into droplets now requires a more powerful source of vibration.

  For this, I replaced the piezo with a vibration speaker, like the type of speaker that can play music via vibration when attached to the surface of a desk or wall.

  I got an 8R 20W vibration speaker and used a TDA2030 amplifier for driving it which I powered by 12V DC.

  After verifying that the speaker could be used well for playing music through my desk, I attached it, together with the amplifier, to the test stand on which I also attached a 9mm hose fitting for using it as a nozzle, a silicone hose that was connected to the pump and some more fittings to hold everything in place.

  Now, I had two options for recording a slow-motion effect of the drop breakup:

  - Using a strobe light matched with the speaker frequency.

  - Matching the speaker frequency with the camera's shutter setting.

  At first, I tried using the strobe light, so I got a 50W LED mounted on a heat sink and did a quick test run. 

  Then later, while waiting on the parts for building a strobe circuit, I also tested out using the other method and it worked well enough that I actually never tried using the strobe for recording.

  Maybe later, when a higher frequency is used again, the "camera shutter effect" will likely no longer work that well, and so a strobe light will be needed to make the breakup visible.

  When I tested it at 50khz last year, I placed the stream in front of a 5mm LED which was also driven at 50khz. 

  So, it also was a strobe light - but just a small one.

  Testing with Water

  First, I did a quick test where I set the speaker frequency just below 60Hz and the camera to 60fps, which made it look like the water would flow in reverse. The pipe with the cap in which the stream flows is used to reduce splatter.

  Link to the video:

  While there clearly was some effect visible it was not close to what I wanted.

  So, I tried using a container with an overflow hole to reduce possible vibration that the pump could transfer to the stream.

  This is how the test stand looked after the change:

  In addition to that, I also tried using a smaller nozzle (4mm OD / 2mm ID tube)

  With these changes, it started looking more like individual drops, but there was also a lot of splatter, and it seemed like there was a lot of water breaking out of the stream and falling not straight down.

  Link to the video:

  Testing with Glycerin

  To get rid of the splattering, I wanted to try using a fluid with a higher...

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• Test Stand and Charge Testing

  Dominik Meffert • 09/08/2024 at 20:10 • 0 comments

  Proof of Concept:
  

  Over the past months, I worked on a few things, and I just found the time to write about them.
  

  The first thing I worked on was a stand for charging drops and testing if I could sense the charge somehow to start the work on the charging system from scratch.

  I started by building a pipe with a valve and a 1mm nozzle that I could fill with water, which I could let drop out slowly by slightly opening the valve. 

  Then I built a test stand out of two 1m 3030 profiles and a few shorter pieces for attaching the pipe on it with 3D printed mounting brackets.

  For charging the drops I soldered a 1.5mm² wire onto a 1/4 inch brass fitting and mounted the fitting on another 3D printed bracket.

  I used 56V DC for charging the drop while it passed through the fitting without touching it.

  The drops get charged at the moment they break loose from the stream, so I placed the brass fitting closer to the nozzle.
  

  At first, I tried to sense the charge on the drop with a piece of copper mesh in a funnel connected to an oscilloscope probe which was connected to an amplifier, but because I could sense nothing but the 50Hz mains frequency with it, I tried using just the tip of the oscilloscope probe for sensing the drop.

  I guess the mesh acted as an antenna and picked up noise from the environment.

  With the probe connected to the amplifier and oscilloscope, it was possible to sense the charged drops when they hit the probe's tip.

  It was also possible to sense the frequency at which the drops hit the probe.

  Here is a picture of the setup.

  I used the AD620 instrumental amplifier module for testing. It was needed to connect the S- input to GND to get a reading out of it.
  

  The power supply's ground was connected to the ground clip of the oscilloscope probe, the 1 1/4 pipe, the drip tray, and the frame of the stand.

  Based on the test result, it seemed like it would work to sense charged water drops with it, and to prove that it wasn't just luck, I tested 5 of the same amplifiers in the same configuration.
  

  I also tried turning the power supply off and reducing the charging voltage, which was visible on the oscilloscope. Without a voltage, there was nothing sensed when the drop hit the probe, and a lower charging voltage resulted in a lower amplitude of the sensed signal.

  When the tip of the probe was connected to the ground of the probe by water, there was also no reading visible on the oscilloscope.

  The result was the same on all 5 AD620 amplifiers I tested.

  A picture of the whole setup

  After finding out that it was possible to sense charged water drops, I wanted to try building a proper sense electrode to replace the oscilloscope probe.

  Building a Sense Electrode:

  What I want to build here is the gutter sensor of a CIJ Printer.

  Many CIJ Printers have such a sensor, and while some models also have a senseless phase detection sensor (sometimes in addition to the gutter sensor), I want to focus on the type of sensor that is located in the gutter for now.

  On the printhead of an older CIJ printer model, the gutter sensor looks like this from the top:

  The metal on the upper part is connected to the printhead ground and covers the plastic block from the top and sides.

  From the bottom, it looks like this:

  A small metal pipe with a wire connected is attached to the plastic block.

  Further down the tube, there is a small metal pipe which also has...

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• Monitoring Sensor Data with MYSQL and Grafana on a Raspberry Pi

  Dominik Meffert • 07/01/2024 at 22:00 • 0 comments

  For the last month, I tried out different ways to log and monitor the data that the sensors on the machine collect to get a graphical way to watch the operation of the machine over time.

  This way it is possible to verify that everything is working as expected and to find problems that would be otherwise hard to detect.

  It's also just nice to see your machine's sensor readings on a dashboard :)

  I tried out:

  - saving the data on my router's FTP server

  - saving the data on Google Sheets

  - saving the data on InfluxDB

  Finally, I ended up saving the data on a MYSQL database that I set up on a Raspberry Pi, which appeared to me as the most independent/universal solution.

  In addition to that I installed Grafana on the Raspberry Pi to get a nice way to display the sensor data.

  In the current picture, all values besides the pressure are as expected, so I still have to find a way to get a stable pressure.

  The readings I currently get from the machine are:

  - The room temperature

  - The nozzle temperature

  - The viscosimeter temperature

  - The conductivity

  - The fall time (the time an 8mm steel ball needs to drop around 100mm in a 10mm PC tube at 25⁰C - equal to the current dynamic viscosity)

  - The pressure

  Update:

  Today, I installed a new pressure regulator which finally outputs a stable pressure.

  It's also visible in the readings:

  Now, that all sensor readings are stable the work on the fluid management system is finished until new problems appear and I can finally continue working on the printhead design.

  Update:

  I just found out what caused the pressure regulator to fail:

  The pin inside the pressure regulator got stuck, because the used PVB/Ethanol mix is quite sticky. Maybe in the future I can find a pressure regulator with a different design that also works for adhesives or sticky fluids. At least it's no general problem of the system. Until then it's needed to clean and "unstick" the pin of the pressure regulator before running the system.

  Another Update:

  I switched to using another type of pressure regulator which also has a spring at the bottom for closing the seal so that doesn't get stuck open that easily.

  The next thing I want to do is learn more about things like electrostatic induction and conduction and how to measure the charge on droplets.

  For this, I'm planning to build a test stand for charging single water drops with variable voltage, detecting when the drops hit a copper mesh, and measuring their charge to learn how to do these things and which factors are important for a successful charge induction and measurement.

  Thank you for your interest in my project :)

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