BN-20 printing dark colours on clear vinyl using a white ink base

I have a CMYK+Wh configuration for my BN-20 and I use a white ink base when I need to produce stickers printed on clear vinyl. I have been doing this for over 12 months with reasonably good results.

Recently, I have been experiencing some issues and I have been playing around with different techniques to rectify it but the results have not been consistent. I feel it could be a media or ink cartridge problem - see attached photo.

My machine was serviced 3 weeks ago by a Roland Tech and I shake the white ink everyday. This effect is only seen on dark colours or black.  The lighter colours print perfectly.

I also, for the first time, was forced to use a 440ml black ink cartridge (due to lack of stock locally) which seemed to work fine initially but most of the time I am having problems printing black on the white ink since buying this cartridge. When I print black on the clear without the white ink then it is perfect.

I do a 2 or 3 times overprint (white only) and allow a minimum dry time of 3 hours before printing CMYK over the top. I have also tried printing a Wh->CMYK over the top but still cannot get it to work as before.

Does anyone have any thoughts or suggestions? I really need some guidance. TIA

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i think its from over inking that particular  media.

if you think the white is not as opaque as earlier this may be due to lack of agitation presuming all nossels firing.

most printable media only likes around 300% ink max at a guess you are laying 400 to 500% in total as a guide

printing just wt is around 100% if you print cmyk+wt the rip reduces the white level to  to try and limit the total ink load to within limits set for that media in the profile.

presume the new black cart is the same type as before just a 440 instead of 220

Thank you for your reply. This makes sense but I hadn't had any issues until recently. The issues commenced a few weeks ago and I have since had the Roland Tech out for routine maintenance - all nozzles were firing upon testing.

I haven't had to adjust the ink limits before so I am not how all this works. I usually do a 3 times Overprint as part of my own created media profile. I need this to get the appropriate opacity. After a 3 hour drying time, I then print CMYK over the top. 

Can any adjustments to the ink limits help or am I just using too much ink? Is there a tutorial on this that explains things well? I am still confused why it has only just started to happen. It's the same media and the black ink cartridge is the same except for the size.

Any guidance would be helpful. I have wasted so much media and I am not even close to the deadline where my customer has just launched their new product. If I can no longer do this kind of work then I'd have to walk away from more than half of my business. I am totally lost. You are the only one that has provided some sort of explanation that makes sense so I really appreciate it.

You stated you had a tech come out, what service did he/she preform?

Was the top included?

What type of file is that - raster or vector?

Which palette are you using for your black?

Reviewing your posts, seems like it has been an ongoing problem. So do you have the Roland Manual for printing with white which gives you multiple options?

As far as wasting media - if you know you have an issue - I recommend, either printing a smaller version, or cropping just the problem area until you get the correct recipe for your desire results.

Thank you for your comments.

The Tech came out for routine maintenance and replaced the cap top as part of the service. 

The file is a vector file. 

I have tried a few palettes - Pantone, BK21A and someone suggested 30/30/30/100 which I have tried most recently.

I have been printing in this manner with white for some time. I had opacity issues with white which is why I have to do the Overprint. This problem with the black ink only started about 4 weeks ago. The Tech was out 3 weeks ago. It is only an issue with very dark colours. Yellow, orange, light green and light blue print perfectly. 

I agree that I should use smaller tests but I am starting to panic a bit....

from experience i have never got to empty a white cart and always seam to change them with probably 20% left because the ink has gone weak despite shaking and extra re circulations. when this happens the print does not seam to dry as quickly and looks weak

to me the crazing is due to shrinking   while drying out as its printing lighter colours well tends to prove the over inking point of view

I replaced the White Ink and everything is printing fine again. Thanks for the suggestion. People I had spoke to had never heard of such a thing but reckon it makes sense. So happy that it was an easy fix in the end. Thanks to you and Irving for your support.

More important, thanks for your follow up which will help others.


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