Quality issues - Can't print black correctly on yellow substrate

Hello everyone!

I have a recurring print quality problem

I use an HP Latex 315, for most of my production I use as a substrate Metamark MDP-H (White substrate with excellent adhesion), the printing quality is okay, but that's fine because I only print adhesives for industrial use. MDP-H never gave me any problems at all

Sometimes I also use Oracal 641 Yellow for certain types of adhesives, I print black at 10 p, 110%, d 95 ° and I have never changed these parameters 90% of the times the print quality is excellent (black is applied evenly) and I am very happy about these results, but 10% of the times the print quality sucks, Black has holes in the color application (see attachment) and I can't figure out why

• I used a substrate 641 which until late December 2019 did not give problems. Yesterday I used the remaining half and I can't print correctly
• I also used a new 641 Oracal Yellow substrate but the problem persists
• The print on the MDP-H doesn't give me any problems, tested it five minutes ago
• The problem occurs even before the material enters the curing area, print quality problems can be noticed immediately after printing
• I'd rather not change the density and optimizer levels because 90% of the time they are perfect
• I have already done the "Optimize print quality" on a white substrate just before printing
• I have already printed all the test files (on white substrate) and I have not encountered any problems

How usually I resolve this problem? I just don't, I put back on the MDP-H and when I finish the white substrate I try again with the Oracal 641 until the problem resolves itself

In the attached image the triangles have a base of 54mm

Thank you very much for you time

Davide

Sidenote: sometimes this problem appears mid-production: I start the production on a new roll, everything is good. After maybe 20-25 meters using the same work file from the rip the problem appears. I put on the MDP-H, I wait a few days and (most of the time) the printing is fine with the yellow substrate

#2 hi, try to print composite black (40% max from cmy 100% k) not only black... Oracal 641 isn't the best performer not only with white but the colored vinyls mostly... Much problems when humidity is high..the surface itself is problematic

#3 hi! thank you for your reply, already tried in the past with reinforced black, but didn't get me any result. Tried it again one more time but no results.

Yeah... The surface can be very problematic, we're considering another substrate. For sure humidity may be a problem, but in my office it's very dry (and I have a costant 20° Celsius)

This morning I tried again to print on 641 Oracal, and I noticed that the first row from the bottom (circled in image 1) is perfect, then the black is not solid anymore.

Every file printed after this has the black with the dots, but after waiting for 30 minutes I tried again and same thing, first row perfect, second row half good half bad, following rows and files all bad.

Maybe the plotter became too hot? Or is it a problem with aspiration of the substrate? Again, the problem is not in the curing area, I can see from the glass that the black is not solid before entering the curing area.

Thanks in advance for any suggestions

In order to solve this type of issue : • Rise optimizer level • Warm media before loading inside the printer

in my observations - when this vinyl (641) is placed on the path of blowers like conditioners or ventilation ducts the silicone paper is making condense or silicone residue is copied over printing surface (even sometimes in you can read "orafol" inscriptions). Our room is 24° Celsius, but the substrate is still giving this effect and it happens only when winter comes the floor temp (where vinyl is stored) is still under these 24degrees - so better switch to another makers if possible And Sonia is right substrate must be heated or stored in heated dehumidified room

Warming the media did help but didn't solve the problem, thanks Sonia and ivoslbg5445 for your advices!

#7 Hi, you can try to use a lint free cloth to wipe and clean the substrate surface. then do a test print. this may help.