Hacking the HP45

Powder and inkjet printing
acastel
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Re: Hacking the HP45

Post by acastel »

The pulse duration of the primitive line is also much longer than that of the patent, which is 1.875us.
I guess the primitive can be between 1.9μs - 2.3μs, depending of the head temperature.

Dragonator, do you have a waveform on oscilloscope of the output primitive with the TLC59213 driving it?
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dragonator
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Re: Hacking the HP45

Post by dragonator »

I do think that the primitive time can be assumed to be constant. I have no reason to believe otherwise with the C8855 manual. Given the high power nature of the signals, giving us rise and fall times that are significant, and the measuring hardware, some variance is to be expected/. This seems to be confirmed by the fact that the warmup pulses are also varying by 1-2 dots or 200-400ns and the addresses overlap sometimes. The printhead varies the power of the head by varying the voltage, not the pulse time. This is at least the case according to the manual.

There are a few things that do stand out. The first is some chatter over the address lines before printing and in between the calm areas. I have absolutely no idea what this is. The addresses are high for around 14us when pulsing, but only 3.8us when there is warming pulses. There seems to be jetting, then warming, and then more jetting. I do not know the context of then this was taken to know if this is some sort of calibration (which I do know occurs).

What was it that you were printing here. Is is possible to get a waveform of the printhead when it is printing something like text. You mentioned the idea that the printhead might actually give warming pulses when it was not printing, and that is an idea that seems intriguing. The waveform here seems to suggest all black.

I can get a scope waveform of the TLC59213. However this is of my setup, and not something HP original. I do still have a C8855 laying around here, which I might actually try at some point, but I have never tried to control this. I am getting a bit curious what is going on here. I have one unresolved issue that is a major headache. I cannot pulse all 14 primitives at once. I need to pulse 5,5 and 4. Else I am getting misfires. HP seems to manage just fine, driving the head as fast as humanly possible, all primitives on one address all at once. I have no clue whatsoever why they manage this and I do not. The idea of warming pulses when not firing seems reasonable, but this will be a bit hard for me to implement right away. Fixing this issue will effectively triple my printing speed at once.

I cannot promise a waveform tomorrow, but I will try to get a scope to my controller in the next week.
math
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Re: Hacking the HP45

Post by math »

dragonator wrote: Mon Sep 14, 2020 6:32 pm I have one unresolved issue that is a major headache. I cannot pulse all 14 primitives at once. I need to pulse 5,5 and 4. Else I am getting misfires. HP seems to manage just fine, driving the head as fast as humanly possible, all primitives on one address all at once. I have no clue whatsoever why they manage this and I do not.
I think this problem is due to the simultaneous supply capacity of the tlc59213, which is a maximum of 200mA when all 8 outputs are activated at the same time. To generate enough energy for the ejection of the ink, you need 400mA for 1.875us, according to the patent and c8855m.
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