Digital BW, The Print

"Bob Frost" <bob@...> wrote:

> I thought some of you might be interested in this 
> post by Elena on the EpsonWideFormat list ...

Yes, thanks for the information -- to both Bob and Elena.

Elena wrote: 

> >  It definitely looks like compatible inks really can cause 
> > some level of degradation to the printer head precision.

No doubt some inks are better matched to the printer than others.  I expect the OEM to do a good job.

> > Only a special, straight nozzle test ... can
> > show how effectly good and straight the nozzles are firing.

I examine real prints at 1600 dpi.  One example is at  
http://www.paulroark.com/BW-Info/Eboni-6.pdf at page 10.
 
> > ... installed my CIS, which I filled with InkSupply's MIS K4 inks.
> > ... Once the printer was properly purged and primed ...
> > the first nozzle check started showing an high percentage 
> > of deflected nozzles! ...
> > after some cleaning cycles I noticed absolutely no changes to
> >  the results. 

So, it sounds like with a normal nozzle check there was some 
evidence of the problem.

> > Again, remember that a normal nozzle test would never show 
> > the problem so well as a "straight" nozzle test does:
> 
> > http://www.elenadomain.it/pub/NozzleCheckBad.png

A subsequent Wide Format post noted the posted images were a 
1" swath the size of the 4800 head.

When I take these images into PS and look at "Image Size," if 1 inch is set as the Height it appears the Resolution is 637.

So, I re-sampled my 1600 dpi scans to 637.  I've poseted a screen grab of a scan of test of Carbon-6 in a 2200.  See 
http://www.paulroark.com/BW-Info/NozzleCheck-comparison.jpg 

The scan is gray scale; the ink shown from Elena's scans was that on the right -- I suppose the LK position.

Of course in my test print there are multiple channels firing, but the scans of the ends of my test strip where only the light and dark inks are firing look about the same.  Nonetheless, I often do see occassional microbanded patches, particularly where one one reasonable dense ink is printing.  If this artifact can be reduced, it might well improve the final image.

(I'm suspicious I'm not making a good comparison here.  If someone sees an error in my math or approach, let me/us know.  I'd like to be able to compare the significance of the scans to the inks and workflows I actually use.) 

> >  I, as a ... programmer, planned and found a solution
> > to fix the problem!

Excellent, I hope this is going to be posted somewhere.  If there is public information that individuals can use to improve their workflows, I don't see that it's a problem pointing us in that direction.

In a subsequent post, US patent 6,984,010 Jan 10,2006 was noted.  I'll take a look at that later.

> > ... Epson heads are calibrated at factory level against
> > the little and unavoidable manufacturing defects. 
> > Calibration is obviously made using the Epson inks ...
> > it comes out in the form of a so called Head Rank ID - 
> > ... codes you have to enter when you replace a printer head...

Yes, I've heard an Epson service person say about the same thing.

> >  but the concepts behind the code at least are documented 
> > in some patents assigned to Epson.

An explanation of the content of patents would seem to be innocuous and part of what is expected from publishing them.  That's part of the deal -- the quid quo pro of a legally granted and temporary monopoly.
 
> > Compatible ink manufacturers try to make their liquids 
> > as compatible as they can to the originals as for rheology ...
> > but they will never be AS the originals. 

The OEM inks also vary from one to the other in terms of  
compositions and rheologies.  One nice thing about Epson 
piezo heads is that they are relatively tolerant of minor differences.

It's not easy to measure, but one difference I see that produces 
results similar to these is the mix of surfactants.  This affects not 
only apparent deflection by the head but also how the ink penetrates 
the paper.  I think the OEMs probably are a bit ahead in these parts of the formulas.  Whether a third party ink is still OK may depend on the printer and other variables.  Speed of printing and droplet size seem to affect the smoothness issue.

> > So, it's unavoidable that a head calibrated with a particular 
> > ink won't perform as good with a liquid having different 
> > characteristics. 

I don't think it is "unavoidable" that one ink will not perform as well as another.  If the ink is within the parameters of the head, as calibrated, then that ink should be able to perform as well.  Unless Epson is having the ink cartridge chip-related software intentionally sabotage third party inks (and I'd like to see the new administration handle that case) I see no reason a third party ink could not match all the relevant parameters and work as well or better than OEM inks, which themselves vary.

> >  the solution was obvious: tweaking the head rank id to match 
> > the caractheristics of the new inks. 

That's one solution.  

Another approach is to make inks that work well in the first place.

> > How to do that is perhaps over the scope of this posting, ...

Again, I do hope this calibration procedure is posted and explained by Elena.  I think it could be a significant contribution.

> > ... it's unfortunately not a job for any people, it's
> > strong, heavy technical stuff.

No doubt.

> > After some attempts and trials and errors I could identify 
> > what seems to be the parameter for the correction strenght.
> >  I brought it to an higher value and here's the result:
> 
> > http://www.elenadomain.it/pub/NozzleCheckGood.png
> 
> > nozzles fire perfectly straight again, now!
> 
> > I hope my story have been of some interest.

Definitely.

Thanks.

Paul
www.PaulRoark.com