Printing Woes - Aluminum

[gerg]

I'm a noob .
Screen printing aluminum signs with nazdar 9700 inks and catalyst and I'm having a terrible time.   Lots of globbing and I'm really not sure what I'm doing wrong.   
I've done a couple of jobs where everything turns out great and the next job , ink has spread under the screen.   
I made a vacuum table and my off contact is somewhere around 1/8".   

As far as my print stroke, I'm pulling printing and push flooding.   I suspect that I may be pushing down too hard but sometimes when I try and do a lighter pull, I don't have enough ink coverage.

[Itsa Little CrOoked]

Welcome! We were all noob's at one time!

I believe your ink is "running through" the mesh between the flood and the print stroke. It could be too low a mesh count, and it could be that you are over-reducing your ink. In a perfect balance, each mesh cavity just "fills" with ink during the flood, awaiting your print stroke to transfer each droplet to the substrate. If your mesh is too open, or your ink is too thin...its going to "weep" through the open areas and you'll see what you are seeing.

You might be able to "cheat" and not do an actual flood stroke, at least not with every sign to get by with your current screen.

If I recall correctly I used 280 mesh for 9700 and it would have been a standard thread, but that has been a LOOOONG time ago.

Viscosity changes during a long run of 9700 as I recall, since it is an air dry product. Think "honey" when you are reducing. You can always add a little more ink to thicken it up.

I no longer print signs, so maybe someone who is a little fresher than I am can chime in here with a quick fix.

Good luck!

[Ross_S]

Try using a 230 plus mesh screen and get some retarder for the ink. 

Are you using a clam shell, one arm bandit or manually by hand?

[gerg]

I'm just using speedball-type clamps attached to the vacuum table. 

I'm using a 230 mesh.   The ink is nazdar 9700 with nb80 catalyst and no reducer or any other additives. 

Another thing, don't know if it would matter that much is there were a few pinholes and a slight scratch that I taped with scotch tape.   Its pretty thin tape, so I didn't think that it would have much of a bearing on the flushness of the screen to the aluminum. 

Also, whats the proper way to clean up a glob on the bottom of the screen?  I"ve tried wiping with a paper towel and also with a bit of screen opener , but it just seems like I'm smearing the ink around.   Almost seems like the best way is just to clean the entire screen and start over. 

[Sbrem]

If the 9700 is their multi-purpose, you may not really need a catalyst, I used to print a fair amount of signage. And I'll agree, I think you're pushing your flood stroke too hard...

Steve

[pwalsh]

I'm a noob .
Screen printing aluminum signs with nazdar 9700 inks and catalyst and I'm having a terrible time.   Lots of globbing and I'm really not sure what I'm doing wrong.   
I've done a couple of jobs where everything turns out great and the next job , ink has spread under the screen.   
I made a vacuum table and my off contact is somewhere around 1/8".   

As far as my print stroke, I'm pulling printing and push flooding.   I suspect that I may be pushing down too hard but sometimes when I try and do a lighter pull, I don't have enough ink coverage.

Sorry to hear that you're having some struggles with printing Nazdar 9700 Series Multi-Purpose Screen Inks onto aluminum sign blanks.  Your post didnt mention if you were printing onto raw aluminum or polyester coated material.  In any case help is not far away!  Email InkAnswers@nazdar.com to tap into the Nazdar team of technical application specialists.
 

[gerg]

I checked with my local nazdar reps today and they also thought I may be pushing a bit hard, flooding too hard and might not be too bad to thin it out a bit.

Im printing on white painted aluminum.  Isnt that baked enamel ? 

[Doug B]

  I printed a ton of these way, way back. You are most likely printing on an enamel coating and so
you really will get the best adhesion by printing with the same kind of ink. I will agree with the
flood being too heavy but you might think about using NazDar's 49000 or 59000 enamel inks.
IMO they are a little easier than the all purpose you are using and do not need a catalyst. Another
ink would be NazDar's industrial lacquer. The odor is not nearly as bad as the enamel and they
dry faster than the 9700 or the enamel.

[UnderPressureSP]

Try S-mesh it will make a big difference when print by hand.  Also make sure your doing a hard flood.  You could raise your offcontact where the blurred print is happening in the front.   

[Itsa Little CrOoked]

Try S-mesh it will make a big difference when print by hand.  Also make sure your doing a hard flood.  You could raise your offcontact where the blurred print is happening in the front.

Did I read that right?!

How would that work printing aluminum? Enlighten me, please. If it works, the OP ought to know.

@ Doug, I agree the 59000 series might be a better choice than 9700. But I knew a guy that printed EVERYTHING with 9700 and their catalyst for decades.  (His shop always smelled like 9700, even in the office.) (He has now gone all UV and is quite happy.) 

Do you think the 9700 would actually "creep" more than 59000? Also 59000 offers easier clean up, or at least I always liked it better. We only used 9700 for printing on PVC sheet goods, like Sintra. 59000 on all aluminum signage.

[Sbrem]

Try S-mesh it will make a big difference when print by hand.  Also make sure your doing a hard flood.  You could raise your offcontact where the blurred print is happening in the front.

Did I read that right?!

How would that work printing aluminum? Enlighten me, please. If it works, the OP ought to know.

@ Doug, I agree the 59000 series might be a better choice than 9700. But I knew a guy that printed EVERYTHING with 9700 and their catalyst for decades.  (His shop always smelled like 9700, even in the office.) (He has now gone all UV and is quite happy.) 

Do you think the 9700 would actually "creep" more than 59000? Also 59000 offers easier clean up, or at least I always liked it better. We only used 9700 for printing on PVC sheet goods, like Sintra. 59000 on all aluminum signage.

Yeah, that make my antenna perk up too; what am I missing? I ran a Filbar flat bed a lot, and the only pressure on the folder was it's weight; the idea being that while flooding fills the cavity with ink so it shears nicely, a hard flood will push ink through the mesh, giving him those round corners he's gettng. He really just needs more practice I think...

Steve

[UnderPressureSP]

That is how is run the flood on our press but I do have a semi-auto flatbed...    We found that leaving to much of a ink coat on the surface flood was causing bleed through when printing really thin inks with lower mesh counts.   And Smesh does help a lot when printing by hand its night and day...

[mimosatexas]

i can see the logic in using a very high angled hard flood working for really runny inks if the time between print strokes is long enough for gravity to cause the weight of soft flooded ink to push excess ink through the mesh, BUT it would also make the ink more prone to dry-in on longer runs, and it could definitely cause blurring and gain if the flood isnt super dialed in. 

[gerg]

Another thing that I'm wondering might be an issue....  My imprint area is 10x14.   My frame ouside is 20x24, ID 17x21. 

With larger screens, I don't have to push as hard to get the screen to touch the substrate, but with the smaller screens, because the span isnt as great, it seems like i need to push twice as hard to get the screen to touch the substrate.   Would I be better off going with a larger screen?

[Inkworks]

Random thoughts:

We usually flood right before the print, not right after for solvent based stuff, if you clear the screen and keep moving at a steady pace it's usually fine, unless it's really fine text on a 330 or the like then you may need to flood right away. Make sure you have everything ready to go...everything...! make sure the parts are not sticking to the screen (a vacuum table can help) and that you're getting good rolling snap off on the print, with a decently tight screen ~.100" off contact and make sure you have room to finish the print 2" or so past the image. 230 mesh should be fine, but don't be afraid to go higher mesh counts.

that screen size should be okay for that size of print if it's not too loose of screen. but screens have a sweetspot just like a tennis racket, if you are doing super high tolerance work like +/- .005" over 12", you'd want to go bigger but for signage and the like you should be fine.

Throw some packing tape or plastic pre-mask on a part and practise on that so you can wipe it off until you get it right