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.