DIY printhead
Posted by johnrpm
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Re: DIY printhead August 29, 2012 02:43AM |
Finally I got it to work 
I am using micro dispensing heads (luer lok) with 50 um or 100 um holes. Dispensing needles will not work but these "Micron-S Precision Nozzles" works just great. Much better flow rate than in needles and no air bubbles back when properly tuned.
I am using 30 mm od piezo (with 20 mm diam. piezo layer). It is connected with o-ring seal into chamber (chamber has 20 mm diameter and approx 0,2 mm depth). It works even without constant pressure. Fluid level can be as low as the upper part of the chamber. Piezo is vertically mounted.
Driving electronics is pretty simple. 555 timer with pulse width and frequency tuning. Output is done by h-bridge mosfet driver and voltage can be tuned with step-up/down converter.
I did also add a led in parallel with piezo. The drops are lighted in air,
Now I want to do the piezo and led driver with arduino. I would add two different leds, for example red and blue. Even and odd pulses would be with different colours. This would help to tune the piezo driver so that it is easy to see if the drops collisions in air. Led pulses should be with constant pulse length and with ~ 1 Hz below piezo firing frequency. This will give a vision of slowly moving drops where even and odd drops are with different colours.
Could somebody help me with arduino code? I am not sure how to implement such kind of timers.
So how to do this kind of pulse generator, where the frequency (200-4000 Hz) and pulse duration (0,5-5 us) are controlled and another frequency (depended on the first freq) with fixed pulse duration (several us) is generated? Is it even possible with arduino?
If odd and even led pulses can not be done by arduino, it is easy to do it with discrete logic. So that two channel led driver is optional.
I am using micro dispensing heads (luer lok) with 50 um or 100 um holes. Dispensing needles will not work but these "Micron-S Precision Nozzles" works just great. Much better flow rate than in needles and no air bubbles back when properly tuned.
I am using 30 mm od piezo (with 20 mm diam. piezo layer). It is connected with o-ring seal into chamber (chamber has 20 mm diameter and approx 0,2 mm depth). It works even without constant pressure. Fluid level can be as low as the upper part of the chamber. Piezo is vertically mounted.
Driving electronics is pretty simple. 555 timer with pulse width and frequency tuning. Output is done by h-bridge mosfet driver and voltage can be tuned with step-up/down converter.
I did also add a led in parallel with piezo. The drops are lighted in air,
Now I want to do the piezo and led driver with arduino. I would add two different leds, for example red and blue. Even and odd pulses would be with different colours. This would help to tune the piezo driver so that it is easy to see if the drops collisions in air. Led pulses should be with constant pulse length and with ~ 1 Hz below piezo firing frequency. This will give a vision of slowly moving drops where even and odd drops are with different colours.
Could somebody help me with arduino code? I am not sure how to implement such kind of timers.
So how to do this kind of pulse generator, where the frequency (200-4000 Hz) and pulse duration (0,5-5 us) are controlled and another frequency (depended on the first freq) with fixed pulse duration (several us) is generated? Is it even possible with arduino?
If odd and even led pulses can not be done by arduino, it is easy to do it with discrete logic. So that two channel led driver is optional.
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Re: DIY printhead August 29, 2012 02:50AM |
^ For next setup I will maybe add a flow through channel for liquid. I have seen that kind of solution in some industrial print heads (Xaar maybe?). So there is liquid in and also out. Liquid flows constantly through the chamber so the bubbles will flow back into tank. I will use a peristaltic pump or a small printer pump.
In my case the liquids are pretty expensive (starting from several thousand euros per ml).. So the liquid volume must be kept as small as possible. This is why I did not do that flow-through channel in that first prototype.
In my case the liquids are pretty expensive (starting from several thousand euros per ml).. So the liquid volume must be kept as small as possible. This is why I did not do that flow-through channel in that first prototype.
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Re: DIY printhead September 28, 2012 02:27AM |
laser = many times faster than resistor!
A small resistor has first to heat his body with the driving current to something to above 200°C and below 400°C (so he won't wreck itself and the surrounding parts) to start a small steam-bubble, popping up fast enough, to drive a sufficient pressure-front. This will take some ms to create a droplet and is limited to the max energy you can transform by the resistor-volume (where only a fraction will be 'productive').
With a laser you can heat a specific volume of the fluid (essentially the laser focus) instantly to some thousand centigrades, so you'll get a sort of micro-explosion with starting times and durations of nanoseconds, so the resulting pressure-front can travel with hyper-sonic speeds, if wished!
I've tested a similar application twenty years ago with a 5Watt-CO2-RF-Laser and pure water ... but you can use dark ink, which will absorb the N-IR-wavelengths of common high-power-IR-diodelasers or the cheap blue 445nm@1W-diodes. I have small 975nm-IR-types with 5 to 25Watts optical power, focussable to a spot of smaller than 0.1mm, so more than enough 'brute force'
Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]
Call for the project "garbage-free seas" - [reprap.org]
A small resistor has first to heat his body with the driving current to something to above 200°C and below 400°C (so he won't wreck itself and the surrounding parts) to start a small steam-bubble, popping up fast enough, to drive a sufficient pressure-front. This will take some ms to create a droplet and is limited to the max energy you can transform by the resistor-volume (where only a fraction will be 'productive').
With a laser you can heat a specific volume of the fluid (essentially the laser focus) instantly to some thousand centigrades, so you'll get a sort of micro-explosion with starting times and durations of nanoseconds, so the resulting pressure-front can travel with hyper-sonic speeds, if wished!
I've tested a similar application twenty years ago with a 5Watt-CO2-RF-Laser and pure water ... but you can use dark ink, which will absorb the N-IR-wavelengths of common high-power-IR-diodelasers or the cheap blue 445nm@1W-diodes. I have small 975nm-IR-types with 5 to 25Watts optical power, focussable to a spot of smaller than 0.1mm, so more than enough 'brute force'
Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]
Call for the project "garbage-free seas" - [reprap.org]
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Re: In need for a working piezo inkjet nozzle November 05, 2013 05:10PM |
I'm a bit late arriving, although I thought I would put forward a possible idea to make piezo inkjets a bit easier to make. I haven't got a clue if this would work or not. Let me know if you think it has potential. The following design shows how the print head is constructed:
The basic idea is to make almost the entire thing 3D printable. After 3D printing you would give the plastic some sort of treatment to make it watertight and ink resistant. Varnish may work for this. Once you have the printed part you can then make the small nozzle by using the epoxy/hot glue and a needle method. The piezo then sits on an O-ring to create a cavity for the ink. Next to that cavity is a reservoir to hold the rest of the ink. The main reason for this is to remove the need for the tubing and other equipment. To prime the nozzle you would fill the cavity with ink up to the top of the O-ring. A 3D printed clamp could then be used to secure the piezo on top.
Edited 1 time(s). Last edit at 11/05/2013 05:12PM by samp20.
The basic idea is to make almost the entire thing 3D printable. After 3D printing you would give the plastic some sort of treatment to make it watertight and ink resistant. Varnish may work for this. Once you have the printed part you can then make the small nozzle by using the epoxy/hot glue and a needle method. The piezo then sits on an O-ring to create a cavity for the ink. Next to that cavity is a reservoir to hold the rest of the ink. The main reason for this is to remove the need for the tubing and other equipment. To prime the nozzle you would fill the cavity with ink up to the top of the O-ring. A 3D printed clamp could then be used to secure the piezo on top.
Edited 1 time(s). Last edit at 11/05/2013 05:12PM by samp20.
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