Do I require a new K head?

[Colin]

Does anyone know what sort of warranty one has with a recently installed Roland head?

 

[Gino]

Not really sure, but if the whole machine is warranted for 2 years, I highly doubt you have anything close to the 9 months on that one.

 

[MikePro]

If your nozzle test print is 100%, then you may simply need some better alignment.
there's multiple procedures of alignment for the different print modes and your tech may have cut a corner OR you simply knocked it out of place along the way.

doubtful you can fall back on a printhead warranty, at least after this amount of time. ...if there was any available to you at all in the first-place.
Printers come with warranties, but printhead replacement is up to the service tech to honor the quality of their work.
a lot of factors that could cause a head to fail, aside from years of use, but it's typically user-error. Or at least they'll find a way to blame you.

service tech headaches is what lead me to learn to replace my own printheads. That $1800 service call became a $600 part and an afternoon of my time, after my first printhead replacement took weeks of printer downtime to finally get fixed.

 

[Colin]

If your nozzle test print is 100%, then you may simply need some better alignment.

Thanks for the reply. As I mentioned, the alignment test print is all bang-on, thus my confusion.

there's multiple procedures of alignment for the different print modes

OK, but if I've gone through the ones shown in the manual, what am I missing?

...and your tech may have cut a corner OR you simply knocked it out of place along the way.

It did print the RVW-BK grays properly after the recent head change, but now it's not. Nothing has been bumped; no strikes etc.

Doubtful you can fall back on a printhead warranty, at least after this amount of time. ...if there was any available to you at all in the first-place.

OK, I guess that was the main thing I was wondering about. It would still be nice to figure out this RVW-BK issue though, as I like to use those for grays, as they are more neutral, and predictable.

 

[P Wagner]

I should add, it prints a CMYK and RGB gray perfectly (although we all know that these are not neutral grays, and have green or pink casts to them). it's only on the more-neutral RVW-BK blacks/grays that the "banding" (for lack of a better term) occurs.

I would agree that the issue that you are experiencing is directly related to the nozzle performance of your K (black) printhead. Black does tend to cause nozzle deflections before other colors. Avoiding head strikes and regular and meticulous cleaning of the head (using swabs to physically clean around the nozzle plate, as well as very regular replacement of wipers 2-3x/yr) is all that can be done to forestall this, but issues such as deflections and obstructed nozzles will still eventually occur with use, or based on the passage of time.

The basic issue is the number of nozzles that are dedicated to delivering each color of ink. With DX4 and DX5 heads, there are two channels per ink color when you are running in a CMYK ink configuration. There are a total of 180 nozzles per channel in these heads. Therefore, a total of 360 nozzles are delivering each color of ink. If a handful of nozzles (say fewer than 10) are moderately deflecting, it will probably not be noticeable when the inks are being mixed.

However, when printing using the Roland Color System (RCS), specific colors such as gray are being produced with K ink exclusively, and that is why the deflections are so noticeable as a banding artifact when printing those colors. When printing other colors, all four colors of ink are being mixed to produce process grays and the deflections in the K head are not nearly as visible. Using all four inks to make grays also tends to place a premium on your color management configuration, and any imbalances in it will be manifest as gray tones outputting as non-neutral grays (pinkish or greenish grays), and lighting conditions can make this effect (called Metamerism) even more noticeable.

By way of comparison, the thermal printheads in use with HP Latex machines use many more nozzles to deliver ink. Each printhead in those machines have a total of 2,112 nozzles (1056 per channel, with 6 heads resulting in 12,674 nozzles), and in addition, there is a 'fault tolerance' built into the printheads. This means that the printer will automatically reassess current nozzle performance, and use 'reserve' nozzles to mask any missing primary nozzles, in order to preserve image quality.

My experience across three generations of Latex printers has been that these systems result in significant improvements in the uniformity and consistency of solid colors (less banding), compared with many piezo-based solvent printers. The bonus is that the amount of user-involved maintenance time and effort is also dramatically reduced with HP Latex.

 

[Colin]

I would agree that the issue that you are experiencing is directly related to the nozzle performance of your K (black) printhead. Black does tend to cause nozzle deflections before other colors.

Thanks. Yes, given the higher carbon content of the black ink, that would be the likely issue, but it's odd that all the test prints are good & clean. One would think that if the culprit was indeed the nozzle performance, then one would see some deflections in the test print.

I’ve just now tried various profiles, including the one for the Orajet 3651-M I'm using, MCVP, Generic 1, Generic 2. Also tried “Use Default Media Settings” for Feed Calibration Control in VW, and also tried Nearest Neighbor, Bi-Cubic, Bi-Linear settings, all with the same results. Even printing in Hi-Quality it did the same thing. So given this, and the fact that it printed the RVW-BK grays properly after the head installation, it's a head-scratcher.

Also just now, I did find one minute piece of lint on the K head, and hoped that this would be the culprit, but removing it and cleaning the heads & wipers made no difference. Dang.

Given the inherent higher carbon content of the black ink, is there some sort of cleaning/purging that might help? *Although, part of me thinks that that might not be required or helpful given the clean test-prints. Shrug.

Thanks for the input.

 

[MikePro]

i think the tech has you derailed, with the "carbon content" line. Even if this is the reason that black printheads may fail quicker than the others, its still no reason your printhead should be dead within a year of replacement. My black printhead lasted 4 years before needing its first replacement.

 

[MikePro]

if your alignment is 100% & nozzles firing at 100%, then it could just require a media feed calibration.

 

[Colin]

i think the tech has you derailed, with the "carbon content" line. Even if this is the reason that black printheads may fail quicker than the others, its still no reason your printhead should be dead within a year of replacement. My black printhead lasted 4 years before needing its first replacement.

Yes, but I wouldn't say that it's "dead", just not quite 100%.

 

[Colin]

if your alignment is 100% & nozzles firing at 100%, then it could just require a media feed calibration.

The feed calibration is bang-on, so would you suggest that noodling with it until it solves the problem be a good idea?

 

[Colin]

Just for interests sake:

 

[P Wagner]

That nozzle test looks close to perfect for the K channel.

How does the Media Feed Calibration test print look (T-test) for the media that you are using? Note that the media feed calibration needs to be individually dialed-in for each media that you print on.

 

[Colin]

That nozzle test looks close to perfect for the K channel.

How does the Media Feed Calibration test print look (T-test) for the media that you are using? Note that the media feed calibration needs to be individually dialed-in for each media that you print on.

Yup, bang-on.

 

[Colin]

I’ve double-checked the Feed Correction and Bidirection test prints, and they’re all perfect.

I thought that the head might like to have some ink pushed through it, so I printed a 14” x 16” rectangle of just RVW-BK21A (which is K only), and that didn’t help.

I wonder if I should gently place a new, cleaner-soaked cleaning swab against the head. But again, there’s no deflection showing on the test print – gah!

 

[MikePro]

not 100% familiar with your machine but:
how does the printer clean the heads during its normal cycles? is it a wiper?
on my jv3, it would wipe with a rubber wiper during ink cycles. So when I wanted to "scrub" the printhead, I knew I could saturate a foam swab with cleaning solution and give it a single-wipe across the printhead in the direction the wiper normally operates. Repeat with new clean swabs, until desired, as to not scrub old bits of ink into the nozzles.

a good head-soak is always good too. part of maintenance routine on the Jv3 was to fill the capping station (plastic caps the heads parked-on, machine pulled ink through to flush heads with fresh ink) with cleaning solution and park the heads for up to 90min. I, however, would run this cycle and unplug the machine overnight... allowing the cleaning solution to sit on the heads for 8+hours before I would then wipe heads with clean swabs. This always recovered major deflections.


still. your nozzle test looks like it should be firing on all nozzles. the banding has to be result of some other issue.
does the banding occur during single-direction printing? leading me back to you potentially missing one of the steps in the alignment process, which (for me) required running for single/bi/hi-pass/low-pass/etc. print modes & adjusting feed calibration for every different material run through the machine when noticeable banding occurred.

 

[Colin]

How does the printer clean the heads during its normal cycles? is it a wiper?

Yes, one wiper for each head. The machine actually turns on all by itself every ~8 hours and does a little clean. I never let the machine sit for more than 3 days without doing an actual print of C, M, Y, and K blocks to keep the heads happy.

.....I knew I could saturate a foam swab with cleaning solution and give it a single-wipe across the printhead in the direction the wiper normally operates. Repeat with new clean swabs, until desired, as to not scrub old bits of ink into the nozzles.

With my particular Roland (SP-540i) it's been recommended to hold a soaked swab against the head for a short while, but not to drag it in any way. *shrug*

Still, your nozzle test looks like it should be firing on all nozzles. The banding has to be result of some other issue.

Ya, that's what I'm thinking too.

Does the banding occur during single-direction printing?

I just tried that now, and no change. I also just tried some banner material, same problem.

Leading me back to you potentially missing one of the steps in the alignment process, which (for me) required running for single/bi/hi-pass/low-pass/etc. print modes & adjusting feed calibration for every different material run through the machine when noticeable banding occurred.

Yes, but the fact that it prints flawlessly with RGB or CMYK grays, makes me think that it can't be an alignment issue. It's got to be something with the K head, or the ink, or something like that.

 

[P Wagner]

Can the OP post a high resolution image of the current Media Feed Calibration chart (not the entire thing, just the current selection and maybe one or two adjacent)? The chart looks like a series of capital T letters...It needs to be high res to be able to see the diamond pattern inside of the T.

Also, unless the newer SPi models have changed from the old SP, that is a two-head printer, with one channel dedicated to each color (180 nozzles). The implication of this would be that nozzle issues will be more noticeable as banding artifacts in the output, particularly when only one ink is going down, as is the case with the RVW grays.

 

[Colin]

Can the OP post a high resolution image of the current Media Feed Calibration chart (not the entire thing, just the current selection and maybe one or two adjacent)? The chart looks like a series of capital T letters...It needs to be high res to be able to see the diamond pattern inside of the T.

As you wish (although we're limited to 800 px wide here).

I also just daubed the K head with a wet sponge cleaning tool; no change.

 

[player]

I still think you have a clogged damper. It lets some ink pass, so your test prints are fine, but it is restricting ink causing issues when in full use.

 

[Colin]

I still think you have a clogged damper. It lets some ink pass, so your test prints are fine, but it is restricting ink causing issues when in full use.

Interesting hypothesis. How would one test for that? If I apply, say, RVW-BK20A (95% black), it will pump out a bunch of black to achieve that, but still with the fine lines.