Dumb question about inkjet printers - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 13, 2025, 03:56:47 pm
content: How exactly is the ink held in the container and dosed out to the nozzles? I always assumed the cartridge is filled with the same kind of felt stuff that's inside markers, a kind of sponge that can hold lots of ink but also can dole it out in tiny amounts through capillary action to the nozzles?And the refill kits just let you inject ink to the sponge?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 13, 2025, 04:14:11 pm
content: That's the way it works in all of them I have opened. Many also have serpentine vents and or ink paths to help meter flows. The former could be compromised by the hole you sometimes need to drill for the refills, but I have never seen a clear impact.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 13, 2025, 04:44:45 pm
content: Well ... I'm asking because the other day I cleverly decided to take apart a really old cartridge that I assumed was long dead and dry and 3mL of black ink came gushing out.I mean it got everywhere and boy is it hard to wash off your hands!It was a HP 51604A from a printer that's decades obsolete.

author: amyk
author_rank: Super Contributor
timestamp: September 14, 2025, 02:07:26 am
content: Sponges are common, but some older cartridges used a "bladder". Some of the newer Epson cartridges are actually rather complex.http://web.archive.org/web/20030801235732/http://www.anestoday.com/epson2200/anatomy.htm

author: jpanhalt
author_rank: Super Contributor
timestamp: September 14, 2025, 10:57:04 am
content: I don't know for sure, but based on taking some cartridges apart years ago, it looked like the head is effectively a piezo pump with tiny orifices. The ink is retained in the reservoir because the holes in the print head are smaller than the bubble point of the ink at atmospheric pressure. That explains why the reservoir still had plenty of ink. It had dried in the tiny holes and the pumping action was not sufficient to make it work.You could test that with a centrifuge, but not in my house.

author: Stray Electron
author_rank: Super Contributor
timestamp: September 14, 2025, 12:37:02 pm
content: AFIK HP and Canon developed the first ink jet printer jointly and HP had a good description of how it worked in one the HP Journals back in about 1985. You should probably go look that up and read it. It shouldn't be hard to find a copy online. HP sold their printers under the name ThinkJet (THermal INK Jet) and Canon sold their's as Diconix printers but they both used the same ink cartridge.The very short version is that each print head has nine tiny ink nozzles in a vertical row and each nozzle has a very tiny resister built in and they pulse each resister at the proper time with a very high current pulse and that vaporizes a tiny amount of ink and the resulting pressure pulse shoots a very small of ink onto the page. So every printable character is formed by matrix of very tiny ink drops. But as you've noted, if you don't use the printers very often the ink tends to dry up in the nozzle and plug it and you get malformed characters. Some brands of printers only replace the ink but the better ones replace the printhead as part of the ink cartridge in an effort to avoid the clogged nozzle problem.When I didn't use my inkjet very often I would take out the ink cartridge and store it nozzle upright in tightly capped pill bottle in order to try and prevent them from drying out and clogging the nozzles.

author: tooki
author_rank: Super Contributor
timestamp: September 14, 2025, 01:22:42 pm
content: Quote from: Alex Eisenhut on September 13, 2025, 03:56:47 pmIt varies wildly.1. Some, especially smaller cartridges, usejust a saturated spongewhich holds and doses the ink.Examples: Canon BC-01/-02/-03,Canon CL-52,HP 74,HP 99,HP 564, and many, many more. Most of those are the kind with the printhead built in, but a few (like the HP 564) are just ink tanks without heads.2. Many, mostly ink tanks without printheads, use ahollow chamber full of ink and a saturated sponge, where the sponge doses the ink, and the chamber essentially just refills the sponge.Examples: CanonBX-3, BCI-3, BCI-6,CLI-8, and many, many, many others. I suspect, but cannot verify, that the HP 564XLversions work this way, too. (That is, in the non-XL version they just block off ink chamber, in the XL they fill it with ink.)3. Many usejust a hollow chamber full of ink. They use various methods to dose the ink, from the complex channels in Epson cartridges to actual valves in some Brother ones, to theExamples: EpsonT060, BrotherLC3239XL, and many, many others.4. A few usejust a pouch of ink, either inside a cartridge or box, or just with some minimalist connector and handle. Presumably they use valves to prevent ink from pouring out, but I can’t say for certain. These were originally found only on very-large-format inkjet printers (like the kind that print onto poster-width roll paper), which is still their primary application, but have since moved into some higher-end desktop inkjets.Examples:Epson T11,HP 88One could argue that the great-granddaddy of all thermal inkjet cartridges, theHP 51604used in the HP Thinkjet, the very first desktop inkjet, falls into this category, but it’s unique among the pouch-type cartridges in that it also has the integrated thermal inkjet printhead.5.Bottled inkused by ink tank printers, which simply decant the ink into internal tanks built into the printer.Quote from: Alex Eisenhut on September 13, 2025, 03:56:47 pmIt depends. That is how it works on cartridges of type 1 above. I used to do that with the Canon BC-02 cartridges in our Apple StyleWriter (original version) printer. Those are robust as hell — I used “real” refill ink, dye-based fountain pen ink, etc. and it just worked. (I suppose pigment inks would likely have been problematic.)In the other types, you need to fill the hollow chamber or pouch instead. The process varies by cartridge type. In particular, some require special steps to prevent air from entering, or require the air to be sucked out.

author: tooki
author_rank: Super Contributor
timestamp: September 14, 2025, 02:15:00 pm
content: Quote from: Alex Eisenhut on September 13, 2025, 04:44:45 pmThe 51604A is, as I mention in my first reply, the very first desktop inkjet cartridge.Amazingly, HP still makes those, even after discontinuing many, many, later cartridge models. In fact, they market it, as well as the hardware needed to build printers around it, as their OEM “TIJ 1.0” platform. What sets it apart from basically every other inkjet currently in existence (as far as I know) is that the printhead does not need to be capped when not in use, meaning that it can be embedded as an extraordinarily basic print engine using no moving parts, as long as the paper can move beneath it. So it has found use for things like printing tracking numbers onto scanned papers, using nothing but the document scanner feeding the sheet. In the past, it was also used for some printing calculators, receipt printers, etc., which had just a super simple carriage to move the head back and forth a few inches.In googling to find the links on this topic, I came acrossthis fluff piecethat did contain an interesting tidbit: at some point, when HP moved production from USA to Malaysia, they changed the printhead material and cartridge construction of the 51604 cartridges. Originally* they used a glass printhead substrate and a rubber bladder to hold the ink; now it’s a silicon printhead (like all other thermal inkjet heads) with a sponge reservoir.*See theHP Journal, May 1985, pp.21-24 This issue covers the entire development of that printing platform, and is what Stray Electron was referring to.P.S. To anyone who is a printing technology nerd like me, theHP Journal archiveis a goldmine of information on the development of modern-ish printers. And of course on the development of test equipment. HP stopped publishing it in 1998, by which point they’d already become more secretive about their R&D. I could only hope for companies today to return to the kind of information openness that was practiced earlier.(The independent HP archive I linked to has higher-quality scans than HP’s own archive website (or worldradiohistory, which copied HP’s scans).)

author: tooki
author_rank: Super Contributor
timestamp: September 14, 2025, 03:24:38 pm
content: Quote from: jpanhalt on September 14, 2025, 10:57:04 amHP and Canon (and Lexmark) use thermal inkjet, where tiny resistors heat and cause the ink to boil, and the resultant bubble of vapor displaces ink and forces it from the nozzle.Animation and description:-https://youtu.be/IynAnyjhNQY?si=3exMTWYutJgDtK6Z(Canon)-https://youtu.be/waOyCB9xLq4?si=sbQDr_aG-JyMrAmG(HP, newer)Almost everyone else uses piezo, where each nozzle contains a piezo element that flexes, impinging on the volume of the nozzle and similarly forcing out a droplet.Animation and description:-https://youtu.be/TSGfitxlkzI?si=UFKeG_HRtSLk4GcG(Epson)Both of these are so-called “drop-on-demand” (DOD) inkjet, where drops are only generated when they are needed.The other branch of the inkjet family tree is “continuous inkjet” (CIJ), where a continuous stream of droplets are generated continuously, which are then selectively electrostatically charged. The charged droplets are deflected to guide them onto the item to be printed and “scan” across the print width, while unwanted droplets are not deflected and continue into a gutter for ink recirculation. Today, CIJ is used for industrial marking, like the expiration dates on packaging. It’s super robust because you just use a simple pump to create a stream of ink, and then electrostatic charging is used both to break the stream into droplets and then guide those droplets to where they’re needed, so the actual printhead has no moving parts, just an umbilical containing hoses and wires. CIJ was introduced in the 1960s, but the principles go back to the 1950s.History and diagrams:https://packagingnews.net/all-about-continuous-inkjet-cij-printers/Animations and descriptions:-https://youtu.be/99Jz2JFmp1c?si=xYKxXGtV4RI0e8xV-https://youtu.be/VtW0wkZ3chg?si=LTti7T7j_PitRAhKIn the past, CIJ technology was used in the Iris printers once used in the prepress and art print worlds. They did 1850dpi color printingin 1985!!!(Of course, they also cost $126,000, around $380,000 today.) Those worked slightly differently, in that each printhead used a piezo crystal at 1MHz to break the super-fine ink stream into droplets, and rather than diverting ink onto the paper, they diverted it into the gutter (and since all 4 ink colors got mixed in the gutter and thus could not be recycled, the amount of waste ink these things generated was enormous!). They used 4 heads, with the paper mounted on a drum, much like a drum scanner. The Iris printer line changed hands before ultimately ending up at Kodak, which finally killed them off in 2008, by which point DOD inkjet had completely caught up with — and in fact exceeded — their capabilities, at much lower cost.

author: tooki
author_rank: Super Contributor
timestamp: September 14, 2025, 04:20:34 pm
content: Quote from: Stray Electron on September 14, 2025, 12:37:02 pmEhhh… sorta.Canon and HP developed thermal inkjet technology independently at the same time, unbeknownst to each other. When HP discovered that Canon had actually invented it slightly earlier, HP reached out and made some kind of technology sharing agreement with them.* I have no idea whether this agreement still stands, and of course all the core patents expired ages ago.I cannot find anycrediblesources supporting Canon releasing a printer based on HP’s printhead. (They much later OEMed it for printing calculators.) Canon itself consistently states that their first bubble jet printer was the BJ-80 in 1985, which definitely did not use HP’s printhead cartridge, since the 51604A has 12 (not 9) nozzles and the BJ-80’s head had 24 nozzles and was permanently installed.** Canon always specifies it was their “first bubble jet” (and not their first inkjet) because they actually released a color piezo inkjet model (the PJ-1080) in 1984.Quote from: Stray Electron on September 14, 2025, 12:37:02 pmDiconix was an unrelated company that ultimately ended up at Kodak.Canon marketed their inkjets under the “bubble jet” brand (hence BJ- and BJC- model numbers on many of their printers, for B&W and color models, respectively, other than PJ — “piezo jet” — for the 1984 outlier) for many years before eventually changing to Pixma, imageProGraf, etc.Quote from: Stray Electron on September 14, 2025, 12:37:02 pmWell that could not be more incorrect, sorry. It’s thecheapermodels that get the integrated printheads. Better printheads are too expensive to throw out each time, so they’re permanent. This is nothing new; Canon has used permanent (or “semi-permanent” which nobody ever replaced) printheads for their better printers since 1993. Epson and Brother always used them. HP switched to them for better printers at some later point. Nowadays, only the very cheapest inkjets use cartridges with disposable printheads.It is true that such models let you easily replace the head if it clogs. But their outrageous page costs make such printers entirely pointless IMHO. Inkjets do best when they’re used with some regularity. Those cheap printers’ inks are too expensive to use frequently, yet like any inkjet, they should be. But since they’re expensive to run, people use them infrequently, then they dry up and clog, and the user throws out the printer and buys a new bottom-of-the-line printer rather than replacement cartridges, rather than buying a decent printer with moderately-priced ink, as they should have done all along.*HP Journal, March 1984, p.44 (rear cover)**https://www.druckerchannel.de/artikel.php?ID=4971&t=hp_thinkjet_modell_2225

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 14, 2025, 06:49:01 pm
content: But we can all agree that if you crack one open, wear gloves.

author: cunningfellow
author_rank: Regular Contributor
timestamp: September 14, 2025, 10:22:09 pm
content: Thank you Tooki for saving me having to write about DoD and CIJThe other player I would like to mention is Tektronix. Although their "solid ink" printers were just a DoD piezo system the fact that they used melted wax and had a page wide print head made the construction very interesting. The tech lived on for many years after being sold to fuji xerox, but they eventually retired the line five or ten years ago.

author: Analog Kid
author_rank: Super Contributor
timestamp: September 14, 2025, 10:40:52 pm
content: @Tooki, since you seem to know a lot about inkjet printing, I wonder if you know anything about using solvent-based inks instead of the usual water-based ones.I ask out of curiosity because I spent quite a bit of time investigating this for the company I worked for back in the late 1990s. We were trying to develop (or acquire) a printer that would print directly onto CDs (and not the coated ones that were receptive to water-based ink). Over the course of a year or so I did a lot of research into this; several companies were working on this, but nobody actually had a product available. The project was eventually abandoned. But it would have been a perfect fit for us, as we sold CD/DVD duplication systems, some with disc printers, and this would have allowed a very good quality integrated printing solution that didn't require specially-coated discs.Someone out there must have come up with a solvent-based inket printer ...

author: cunningfellow
author_rank: Regular Contributor
timestamp: September 14, 2025, 10:57:37 pm
content: Obviously the CIJ units that print "Best Before" dates are solvent, but that would not be useful for putting a label on a CDAll the Mamaki and Roland units that do stuff like print onto vinyl for making billboards are DoD solvent based.The difference between them and the consumer epson type piezo type ones is that there isn't any plastic and glues in the ink path. They possibly use sheets of etched stainless welded together with gold foil.It is not going to be the miniscule amount of gold or other exotic material that makes them expensive, just volume/supply/demand. They are more niche and lower volume.I imagine that recent kickstarter for the UV printer is in the same category of print head.

author: Stray Electron
author_rank: Super Contributor
timestamp: September 14, 2025, 11:57:11 pm
content: Quote from: cunningfellow on September 14, 2025, 10:22:09 pmA friend of mine had two of the Tektronix thermal wax printers and we just cleaned out his ham shack and pitched them out along with a small mountain of brand new supplies this past Friday. I took home his HP 54540C scope :-)

author: BradC
author_rank: Super Contributor
timestamp: September 15, 2025, 12:02:21 am
content: Quote from: Alex Eisenhut on September 13, 2025, 04:44:45 pmI have a mix of cloudy ammonia, a bit of dish washing detergent and some isopropyl alcohol as an "ink cleanup" fluid. Works a treat on hands. I have similar without the detergent as a head soak to unclog nozzles on my HP DesignJet.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: September 15, 2025, 01:20:56 pm
content: I wasted a lot of money and had lots of headaches with inkjet printers. Now that I've discovered laser printers, life is soooooo much simpler.

author: tooki
author_rank: Super Contributor
timestamp: September 15, 2025, 01:29:35 pm
content: Quote from: Analog Kid on September 14, 2025, 10:40:52 pmThey're common now in commercial/industrial settings.HP's TIJ 2.5 OEM platform has a bunch of different inks for different substrates. Most of these are solvent inks. The impression I get is that these aremostlyused in similar applications as CIJ printing, like expiration dates and lot codes. But HP does say that the TIJ 2.5 platform supports specialty applications like adhesives (!) and conductive coatings:https://www.hp.com/us-en/specialty-printing-solutions/specialty-applications.htmlSee also:HP Thermal Inkjet 2.5Technology (TIJ) Family(PDF)HP TIJ 2.5 Ink Guide(PDF)Large-format, full-color solvent inkjet is also really catching on in significant style for things like product packaging. For example, many Coca-Cola bottles and cans here in Switzerland are now inkjet-printed, allowing them do to promotions like bottles with first names on them. Coca-Cola has even done events where you could have them custom-made on-site:https://www.rolanddga.com/blog/adobe-max-and-custom-coke-bottle-printing(The embedded link to the printer used is now dead, so here's a link to a datasheet for it:https://www.rolanddg.com.cn/-/media/roland-apac/dgc/images/products/printers/truevis-series/overview/15_3_vg2640_dual_cmyk.pdf)Another type of widely used non-aqueous inkjet used, can print on all kinds of substrates, is the "UV inkjet", which is shorthand for inkjet used to deposit droplets of UV-cure lacquer. The printhead has a UV lamp on it and immediately cures the lacquer. Because it's not actually drying the ink, but just curing a resin, it doesn't matter whether the substrate is absorbent or not, etc. (I do believe these contain solvents, too, but the hardening isn't based on the solvent evaporating.) These are used to print onto all kinds of things, from phone cases to front panels to pens to signage. Because the lacquer does not seep into the surface of the material (even on porous ones, it's usually cured too fast to soak in much), it is possible to build up thick layers by printing over and over. This is now starting to be used to make things like business cards. Hollywood propmakers are now using that technique to print out things like leather patterns for prop books.This is a decent overview of the technology and applications:https://mimaki.com/application/solution/uv-printing.html

author: tooki
author_rank: Super Contributor
timestamp: September 15, 2025, 01:40:04 pm
content: Quote from: cunningfellow on September 14, 2025, 10:57:37 pmWho knows.Phoenix Contact's new BLUEMARK E.CARD UV printer (it's a black+clear printer for electrical marking, like terminal blocks, nameplates, etc) uses HP TIJ 2.5 cartridges, so it's a simple thermal inkjet with UV-cure ink. So an expensive piezo head is not strictly needed for UV.

author: tooki
author_rank: Super Contributor
timestamp: September 15, 2025, 01:52:04 pm
content: Quote from: BILLPOD on September 15, 2025, 01:20:56 pmEach techology has its advantages and disadvantages, as well as HUGE differences within each techonology, based on the concrete implementation. It does nobody any good to make sweeping generalizations.Most people's experience with inkjet printers is with garbage entry-level models. Or with early models that really did suck, after which they swore them off forever, unaware of just how much the midrange and high end improved over the years.I'm still using my 2008 Canon inkjet MFP. (It's so old that at this point, I can get ink for free on local classifieds, when people clear out their spare supplies after their printer died.)Meanwhile, modern entry-level lasers are... a weird mix of wonderful and awful. They print nicely, and are small and quiet, but the print costs, in particular for color models, areoutrageous, making even cartridge-based inkjet look cheap!!The only true advantage they have over inkjets is that they simply do not care how long you go between prints, so for people who print very sporadically, a laser is better. Even midrange color lasers have shocking print costs, with a full set of toner (good for just 1-2 thousand pages) often costing hundreds of dollars.Meanwhile, the lowest print costs (for desktop or office printers) on the market today, by a wide margin, are the bottled-ink, tank-based inkjets like Epson EcoTank. For context, a typical one of these prints 5000-10000 B&W pages on a single $20 bottle of ink. The flip side is that you actually have to pay for the printer for real, rather than the heavily-subsidized price of cartridge-based printers.

author: kite31
author_rank: Regular Contributor
timestamp: September 15, 2025, 11:20:03 pm
content: Quote from: cunningfellow on September 14, 2025, 10:22:09 pmI had one of those for personal use. The print quality was lovely though despite the solidity of the ink it did not seem well suited to occasional use -- the warm-up time was horrendous (said the man known to have told his toaster to get a move on).

author: tooki
author_rank: Super Contributor
timestamp: September 16, 2025, 07:08:11 am
content: Quote from: kite31 on September 15, 2025, 11:20:03 pmI set up a few of those for clients way back when I was computer consultant. The solid wax printers were very much intended for heavy office use. They had various standby modes with various warm-up times. But the very worst you could do is actually turn them fully off, because then on power up, they do a full head purge, which wastes a huge amount of ink. (Something like 1/8 of a stick per color!) The ink sticks weren’t super expensive, but they weren’t free, either. (Actually, for some models, Xerox actually did give you the black ink for free. You just paid for color ink.)

author: BILLPOD
author_rank: Frequent Contributor
timestamp: September 16, 2025, 02:02:49 pm
content: Printer ink can cost up to $12,000 per gallon, making it one of the most expensive liquids you can buy.

author: tooki
author_rank: Super Contributor
timestamp: September 16, 2025, 06:05:15 pm
content: Quote from: BILLPOD on September 16, 2025, 02:02:49 pmAnd? I gave you a detailed reply worthy of more than this lazy response.Again, it is afactthat the lowest-page-cost printers on the market today are inkjet. This doesn’t rule out the existence of inkjets with absurdly high ink costs. Both can be true at the same time.Just as it is simultaneously possible for there to exist laser printers with low page costs, and ones with absurdly high page costs.But just repeating “waaah, inkjet ‘spensive!” is lazy and dishonest.