No, the piezo heads do in fact open up - it just take lots of use to see this happen. I've seen this again and again over the years. For many high volume shops it requires re-profiling all their papers more than once per year, if there isn't a linearization option.
No, they really don't. The Thin Film and the crystals do not physically become larger or more open as a result of wear and tear. Each head is characterised at the factory and a specific data set is input to the printer that associates with that head to ensure that the electrical interaction with the crystals provides the correct amount of ink fire (with genuine inks). If the head is changed, the data set is changed. Over time, wear and tear will impact this, but linearisation or driver or firmware (or both) level calibration has been possible since the K3 models.
This is very definitely not the heads "opening up".
As to lots of use - I have clients who end of life machines in 6-12 months. They can't be used any more than that.
Exactly. Linearization is a form of calibration, so: Profile once, calibrate (linearize) often. It's *really* nice when the printer can perform the re-linearization itself using on board sensors. I'm just trying to give credit to HP and Canon for doing that first. It really makes a difference.
Yes, Linearisation is a form of calibration, but it is not reprofiling. HP and Canon did do it first, because they had to (and kudos to them for doing it, no doubt). It's a pity that HP doesn't use an ISO standard in the backing colour but I expect that may change. I haven't heard any first hand reports on how well they cope varying between media with OB and those without, but I presume it's quite functional.
While I don't know what their volume is like, I suspect they are more towards quality then quantity. And they probably switch to the lastest generation printer every time they come out. I have clients with 10 44" printers that are kept running all day long - sometimes during multiple 8 hours shifts for 4-5 years on end. That's high volume!
None of the printers (from any manufacturer) can run 16 hours a day, 5 days a week, for 4-5 years without massively exceeding their expected end-of-life levels. Anyone who is doing that much work, should easily be factoring in replacement units (possibly for free, based on an ink burn contract) into the cost of business - with so much volume, it's tiny.
That said, all of the big three make printers that will work beyond their rated life and mostly just need counters reset and some decent maintenance to keep them clean and functioning. But I really just want to clarify that it's not a case of "opening up" as you describe it in the heads. That's just not what happens.
which, when coupled with regular linearization can actually lead to greater consistency over their lifespan in comparison to piezo heads that go unchecked without re-linearization.
No one who needs colour accuracy fails to linearise their machines on a regular basis. Most proofers are doing daily checks at a minimum, some each print run and some every job, to validate the colour accuracy of the proofs being created. Photographers are fast learning to check regularly. There's no one with any real experience who lets their printers go unchecked and anyone using a RIP and a spectro already has all the equipment needed to do this and frankly, better than the onboard solution for HP or Canon and in many cases than the built in Epson. Sure, it's manual, not automated, and that's clearly the reason Epson added their spectro option for those proof makers who want to automate it or get print by print validation for things like FOGRA.
For proofers, consistency has to be perfect, every time. If it's not, it can cost them a fortune. Epson owns the proofing market, and there's a reason for it.
So they both have advantages and thus appeal to different market segments. It's just not fair to say that one is better than another - we have to look at the whole printing system.
I totally agree with this. This is a photography site, but photo is smaller than the other market segments when it comes to print volumes and printers in use and so forth, so sometimes we don't see the big picture (no pun intended). I think your last sentence about the whole printing system is the key summary.
I really only joined into this thread to comment on your description of peizo heads opening up. They just don't do that, it's not an accurate description and if someone has told you that they've explained it to you poorly. You're right, of course, that over time they wear but the degree and rate are both very small within the expected life of the printer and both are easily compensated during normal linearisation (which for those who care about colour accuracy is as common place as calibrating monitors).