The cartridge heads have a super curious digital protocol - the cartridge electronics have no power supply. There is no power rail internally either.

Instead they use the fact mosfet gates have capacitance, and can therefore store 1 'bit' of information. Through a network of hundreds of MOSFETs, the right bits can be put on all the nozzle gates as needed, and then a 'fire' pulse is sent which for around a microsecond turns on a tiny heater (or not, depending on mosfet gate state). The heater boils some ink, making a pressure wave which travels down a pipe and makes a drop of ink fly out towards the paper. That heating and cooling again can happen around 10,000 times per second per nozzle (and there are ~300 nozzles).

I suspect this decision is because the custom silicon process needed to manufacture these nozzles is cheaper if they only have n type MOSFETs - and without p type MOSFETs you can't make a typical push pull logic gate.

The nozzles themselves are quite a lot of silicon - perhaps 100mm^2, with deep etched holes, and are effectively disposable, so I assume huge efforts have been taken to reduce costs - including this curious electrical design.

The protocol also is hugely irregular, which I suspect might be to avoid any wires on the chip needing to cross eachother.

This sounds fascinating. Do you have a reference?

Impression v. Lexmark is directly relevant to the patent situation here; in a case involving reprogrammed ink cartridges, the Supreme Court held that patent rights are exhausted by first sale doctrine; that is, if you sell me something patented, you can't sue me for patent infringement for using the thing you sold me, even if I do something later that makes you upset.

It's also been widely held that ink cartridge compatibility tools/hacks are allowed under DMCA.

However, it does seem likely that there's probably some shenanigan involved in the area - one example I could think of would be if HP have patented the way the ink cartridges are retained in the printer, for example, that would have to be carefully audited. And there will be license and trade secrets issues with the use of the cartridges, although if they were reverse engineered cleanly and the printer doesn't come with cartridges, those are probably pretty easily side-stepped.

These cartridges were first released in 2004, and there don't seem to have been any major design changes since then. The electrical and digital interface for printing has remained the same, as well as the mechanics. There is a new DRM system using another chip, but that is one-way - ie. It prevents an original printer from using the cartridge, but doesn't prevent use of an original cartridge by a third party printer.

Any patents are probably expired or very close to it.

A sea of patents designed to inhibit competition & promote rent extraction, and we are running around in circles chasing our tails wondering how we can compete with China.

China is changing stance on patents... Thier companies are now filing for patents at great speed, and I wouldn't be surprised if they start mass suing American companies for violations.

I could totally imagine a rapid upheaval of the patent system as soon as we see it being used against us.

> I agree that the bigger challenge is going to be patents.

Surely most/all of the patents around the actual inkjet printing function have expired though, right? I had inkjet printers in the mid 00s and if anything I feel like your average inkjet is worse these days.

In medicine, it's a regular trick to find some new patentable formulation or tweak to switch to manufacturing shortly before the original patents expire, so that you continue to have a patent-protected product.

It would not surprise me if something similar was happening here: HP's current cartridges have at least one piece that is under active patent protection and they don't manufacture any designs that have no patent protection. I don't know enough to state that's the case, but it wouldn't surprise me.

Mentioned elsewhere in this thread, but the print heads are a very specialized silicon chip with internal microfluidic passages, microscopic heaters, etc. Who else would even make them? The kind of thing you would need millions of dollars to reverse engineer and replicate just to enter the lucrative market of... making inkjet cartridges.

I would be shocked to discover that there are counterfeit print heads out there the same way there are counterfeit STM32 microcontrollers.

Unless the patents have something to do with the shape of the cartridge or they somehow have a patent on "technique to fill printer cartridge with ink" which would not be so surprising.

Maybe they should have purchased a design from Canon or someone that isn't really in this market anymore. It seems like not only are they locked into a specific older technology generation (which could be ok idk) but they also risk HP just discontinuing that cartridge. It seems like the printers for this cartridge were released around late 2017 so they could deprecate earlier than they normally do. Seems like they provide 10-20 years typically. At the same time , maybe this is just meant for a small user base of nerds and maybe HP wont care.

I did some research on weird inkjet printers a few years ago. We wanted to do stuff like print white[1] graphics continuously onto rolls of black heat shrink tubing.

One thing I discovered was that there's whole Chinese industries supplying this stuff in the forms of industrial printers and the application-specific cartridges they consume. And they all had one thing in common: They were based around the functionality of an HP printer cartridge. That was the universal interface.

This leads me to believe that a print cartridge format can be supported by the marketplace for a very long time whether HP likes it or not.

[1]: Printing with white is neat. It sounds impossible and there are those who say it can't happen, but it exists. It's just problematic. The head gets perma-clogged with solids within minutes of disuse in open air. So starting a print job is a race: Get everything set up, uncap the cartridge at the last moment, and then put that cap back on ASAP when the job is over.

Are you referring to the numerous Chinese UV printers?

>The head gets perma-clogged with solids within minutes of disuse in open air. So starting a print job is a race: Get everything set up, uncap the cartridge at the last moment, and then put that cap back on ASAP when the job is over

Decades ago I helped manage a local's school IT systems and we had these Epson C84 printers that used a very photo grade ink. The printheads would clog after a year of teachers printing like 1 document in that year. During that time it seemed like regular purging of ink regardless of print or not was what kept the printheads going. Strategies used by third party repair firms included submerging the head in a cleaner to dissolve the ink on the outside, connecting pipes with the same fluid to the inputs of the top to the printhead and then finally pulling pressure to try and dislodge the material through the head. Due to the non removable design of the Epson print heads, my attempts at trying this would destroy many printheads. I'd like to think this would be a solved problem in 2026. In your case why not run a purge liquid the printhead after each print? The printhead could then be primed with fresh ink each time.

I don't know what a UV printer is. :)

We were using fixed-head printers that we found at the bottom of a deep rabbit hole. The work moved through the machine while the printy-bits remained stationary. We were doing this with HP-style monochromatic carts that came loaded with high-solids "ink" (closer to paint, really) that used opaque white pigment.

Unlike Epson's ecosystem, HP carts most-commonly come as assemblies, with a new print head included in the same disposable cartridge as the ink is. The only connection between the carts and the rest of the printer is electrical; there's no plumbing or functional fluids that are external to the carts.

This self-contained nature means that when ink runs out or heads gets clogged, replacement of everything involved with fluids is fast and easy. Production can continue immediately.

It's not problematic at all...other than being expensive. :)

Canon is still in the market, they just supply parts and license IP to the printer manufacturers like HP. They make some high value stuff to sell to the OEMs but I don’t think they can make a whole print head anymore.

Why would they bother? They make all their money on the ink cartridges. If this drives more cartridge sales it’s a win/win for them. They generally don’t make much, if anything, on consumer ink jet printers themselves

> Why would they bother?

Many corporate and government types, especially lawyers, want control. They will go broke trying to control everyone and everything.

This printer will use refilled cartridges. It could even use cartridges that have been sent out under the 'instant ink' subscription scheme. People in that scheme usually end up with a drawer full of spare cartridges, as they send them to you like they are worth the pennies that they actually cost.

People willing to use refilled cartridges will use them regardless of the printer they’re going in, so again it’s no lost sale for HP.

Heck, it may actually save them money. At one point they were losing money on every printer sale and making it back in ink No idea if that’s still the case.

big companies seek control, not money, because money alone is a weak shield against disruptions

It’s negligible revenue and carries some risk. Say the printer works well, and these enthusiasts drive a couple of thousand more cartridge sales. And that encourages someone to develop an alternative cartridge, which is mechanically and electrically compatible with HP’s.

It just seems easier to fire off a cease and desist than to take a risk of other people messing around with your ecosystem.

> And that encourages someone to develop an alternative cartridge, which is mechanically and electrically compatible with HP

This already happens for basically every commercially-available ink cartridge.

No, those are just repackaged OEM cartridges. And usually they've already been used, which is why they're cheaper.

I don’t see why HP would want to do that. They have huge margins on ink, right? I’m sure the increase in cartridge sales would offset lost subscription revenue from useless cloud services, if only because the people who are gonna use an open source printer would never pay for that anyway.

Looks like the intended use case here is you buy the cartridge once, and refill it, and OpenPrinter won't lock you out after doing so like HP does.

Yea, but then the print head clogs up after the second time you refill it and you buy another expensive print head + ink from HP.

Frankly, I think 99% of the reason they started integrating the print head with the cartridge was to avoid all the problems you so frequently see on printers that don’t use disposable heads.

Yeah, if you’re buying the ink they would be happy, I’d think. The ideal razor-and-blades business model!

The crowdsource page says it has refillable ink tanks rather than cartridges. Unless they are modifying HP cartridges, which is probably not smart from a legal standpoint.

The tech specs say it uses HP 63 cartridges (or HP 302/803 outside the US), and that the cartridges can be refilled using a refill kit.

The photos clearly show HP cartridges installed.

Well, they can just make the printer support multiple cartridges - problem solved.

In the case of DRM it might be easier to use third party cartridges.