HP Latex 315 Keeps Printing Gray as Blue/Purple After Replacing LC/LM and M/Y Printheads

[hhg98]

Hi guys,
I'm really hoping I can get some help here before I have to call HP or explain to my boss what's going on. I'm honestly at a loss and feeling really frustrated by my lack of knowledge about these large format printers.

I replaced a C/K and both M/Y printheads yesterday after noticing a print job had an off-color. However, the print still came out sort of purplish compared to the original (see photos). From my past experience, this was fixed after I replaced the LM/LC printhead so I went ahead and replaced that one as well. Almost all of the printheads have been replaced as of today except for one of the C/K printheads. I ran another sample and it still came out too purple.

I've cleaned the printheads several times and have run several printhead status plots. They're all working correctly. The inks in the printer have only been in there for a few months at the most. I haven't changed any of the substrate/color settings since the time of printing the original, so I don't know what the problem is.

 

[BigNate]

... just working from really simple color theory: if you are trying for a black (shade of grey) and you are using CMYK subtracting light to produce color - if your print is purple, it is not removing enough C and M from the light. (C and M inks do not add C and M light, they only remove Y and intensity - leaving the purple hue you see) As such, try replacing the yellow and black print heads - the yellow will allow for some removing of C and M light from the transmission of light (perceived color)... remember, an even amount of all CMY will give a "black" print when properly balanced. If you are seeing purple it can mean either too much magenta and cyan OR too little yellow.

These greys can be tough - I often change all the printheads and do a calibration before printing critical greys.

 

[hhg98]

... just working from really simple color theory: if you are trying for a black (shade of grey) and you are using CMYK subtracting light to produce color - if your print is purple, it is not removing enough C and M from the light. (C and M inks do not add C and M light, they only remove Y and intensity - leaving the purple hue you see) As such, try replacing the yellow and black print heads - the yellow will allow for some removing of C and M light from the transmission of light (perceived color)... remember, an even amount of all CMY will give a "black" print when properly balanced. If you are seeing purple it can mean either too much magenta and cyan OR too little yellow.

These greys can be tough - I often change all the printheads and do a calibration before printing critical greys.

I will replace the C/K that I didn't replace yesterday when the new one comes in tomorrow. All of the other printheads that are in now were put in today or yesterday. It seems really costly to have to change out the printheads every time we want to print a grey like this.

 

[BigNate]

I will replace the C/K that I didn't replace yesterday when the new one comes in tomorrow. All of the other printheads that are in now were put in today or yesterday. It seems really costly to have to change out the printheads every time we want to print a grey like this.

I agree it can be costly with printheads - though less than other printers I have used. you can keep the older printheads and swap them in for lesser jobs - we print a lot of posters that are not critical and just spot black - usually a scanned letter size sheet printed as 24"x31" - I can get 3-4 times the life expectancy of printheads printing these posters. save the new ones for the critical jobs.... just make sure to cap the heads correctly (I have not yet, but I think you can put the plug on backward and cross-contaminate the ink a little on the stored head... though maybe this is so little it will never be noticed.)

 

[Ronny Axelsson]

You should perform head alignment and color calibration after replacing the printheads.
Not sure how to do it on a 315 but my 365 has a built in spectrophotometer that makes calibration very easy.
Apparently, the 315 uses the on-board line sensor to calibrate colors but I have no idea how it works or how good the result will be.

HP Latex Printers - Performing Color Calibrations

 

[netsol]

You should perform head alignment and color calibration after replacing the printheads.
Not sure how to do it on a 315 but my 365 has a built in spectrophotometer that makes calibration very easy.
Apparently, the 315 uses the on-board line sensor to calibrate colors but I have no idea how it works or how good the result will be.

HP Latex Printers - Performing Color Calibrations

Yes!
I was reading and wondering why someone would “change all the print heads” rather than performing a color calibration.

and then swap the bad ones back in? i don’t get it.

 

[hhg98]

Yes!
I was reading and wondering why someone would “change all the print heads” rather than performing a color calibration.

and then swap the bad ones back in? i don’t get it.

I didn't swap the bad ones back in. I removed the old ones and replaced them. I had to replace more than I thought initially because the print was still not coming out correctly. I will try the color calibration Ronny Axelsson suggested. The 315 has the ability to do it itself, but I haven't had any luck with that so far.

 

[TopFliteGraphics]

Does it print the same on different media? I found that the colors shift depending on the media's base color - some whites are more yellow whereas some whites are more blue. The media can greatly affect grays in my experience. Another factor if using it can be the lamination shifting the colors. Some laminates are more blue which changes the print color as well.

 

[hhg98]

Does it print the same on different media? I found that the colors shift depending on the media's base color - some whites are more yellow whereas some whites are more blue. The media can greatly affect grays in my experience. Another factor if using it can be the lamination shifting the colors. Some laminates are more blue which changes the print color as well.

I've noticed that as well, but its definitely a much larger difference than what the material or laminate could account for. I found another old graphic from a different customer that had gray in it. It came out purple too and it was much more obvious.

 

[BigNate]

Yes!
I was reading and wondering why someone would “change all the print heads” rather than performing a color calibration.

and then swap the bad ones back in? i don’t get it.

if you run a lot of low-quality images that do not require all the nozzles to fire, older printheads can save a lot of money - the extreme of this is another poster here prints onto textured media. He even requests people to send him their old printheads so he can use those rather than purchase all new ones to be immediately destroyed by headstrikes on the texture of the media.

Maybe once a month I need to print high quality gradients. How many nozzles and colors do you really need to print a scanned 2nd grade worksheet and print at 36"x48"? if I have to swap out a printhead or 2 for a higher-quality print, I can easily swap in the older printheads for a month... keeps from buying new all the time when the old are good enough for most jobs. (yes, the computers in these printers are pretty amazing on being able to compensate for missing nozzles and get a pretty good calibration - ask a vendor if they just calibrate and print a 'money sample' on old printheads, or if the print quality really counts do they just put in all fresh printheads and know it will be good??)

 

[BigNate]

and then swap the bad [still good/not new] ones back in? i don’t get it.

Actually - isn't this EXACTLY what HP has us do with the white printheads? they just put a rotating chamber to store them in so the white ink hopefully doesn't clump too much.

 

[netsol]

i bought my first "large format" hp in 1993(?) the tabloid size inkjet (printing color 11x17 was a big deal then)
they do some odd things, however

 

[hhg98]

i bought my first "large format" hp in 1993(?) the tabloid size inkjet (printing color 11x17 was a big deal then)
they do some odd things, however

Our printer has been the least problematic of all of our equipment. I guess it's taking it's turn to become a thorn in my side, though I definitely think its not helped by my lack of experience. I've only been in this industry for 2 years and this is the only printer I've ever worked with. And I'm the only one at our company who knows how to at least use the damn thing.

 

[mattc5900]

If you are only printing 1 color grey you might try and try color correction off.. This is the only way i can get grey out of my HP360 otherwise i get like you shades of purplish colors. I can get really decent shades of grey with color correction turned off. But the real problem is when you have multiple colors then is a give a take on which are better to hit color wise.

 

[hhg98]

If you are only printing 1 color grey you might try and try color correction off.. This is the only way i can get grey out of my HP360 otherwise i get like you shades of purplish colors. I can get really decent shades of grey with color correction turned off. But the real problem is when you have multiple colors then is a give a take on which are better to hit color wise.

How do you turn color correction off?