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coro signs

Posted on Sat, 21 Jan 2006 at 5:17



have just started to screen print again after not doing it for 10 years and it's a slow progress. the ink keeps running and smugging the letters between the screen and board. I then have to clean everything and start again...???

what is wrong...?

give me a tip guys...?

is my ink to thin>>>???

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Anonymous says: shaun, how are you printing? manual or machine. If you are hand printing maybe the flood stroke is too thick, this together with too thin ink can result in what you described. if you wait too long between ...

shaun,
how are you printing? manual or machine.

If you are hand printing maybe the flood stroke is too thick, this together with too thin ink can result in what you described.
if you wait too long between flooding and printing.

also increase the off contact so the screen is snapping off better.

Pretty much the same advice for machines
try speeding up the print stroke so the ink isn't sitting in the screen too long. make sure the flooder isn't pushing the screen
down on to the stock when flooding.

are you using a vaccuum table, if not the stock can stick to the screen as it snaps off.

Just a few ideas
hope it helps.

posted on: Mon, 01/23/2006 - 6:43pm
Anonymous says: Maybe your screen mesh is not high enuff. I use 280 for corobut you probably can get by with 230 minimum posted on: Sat, 01/28/2006 - 11:28am
Anonymous says: Shaun: there are a couple possibilities. The ideal situation during the print stroke is to have zero pressure on the stock--all the pressure should be between blade and mesh. If you send basic dimensions; ...

Shaun: there are a couple possibilities. The ideal situation during the print stroke is to have zero pressure on the stock--all the pressure should be between blade and mesh. If you send basic dimensions; initial screen tension, mesh count and thread diameter, frame size, image size, detail or linecount, I will model proper off-contact distance, peel ETC and reply to you. I suspect this is the underlying problem.

The stencil guys will tell you to build a better "gasket" between the mesh and the stock. The mesh guys will tell you run a higher mesh count and a thinner thread. The ink guys will tell you to use an ink which recovers its initial viscosity faster--more like halftone inks. And they would all be correct.

If you are using a UV ink it is likely not too thin, if the ink is solvent based and you have been thinning it, try running it with half the thinner, if that works cut the thinner in half again. If you are using a "retarder" try substituting a faster evaporating thinner.

If you are not reading the Dyne level of the corougated stock you might call Diversified Enterprises (800 833 4644) and ask for a set of Dyne pens with instructions. These stocks are treated to make them more ink receptive--if they are under treated it doesn't help much, if they are over treated it doesn't last verey long--you need to measure.

Plastic corougate is (figratively) "teflon-like" and is not very receptive to ink due to its low surface energy. If the surface tension of your ink is too high (as in the case of many UV inks) the only way to get it to wet the stock is very high pressure and very slow speed--change inks or you'll go broke.

Good luck,

Joe

posted on: Wed, 03/08/2006 - 3:33pm
Anonymous says: Dyne testing to determine suface tension / treatments for substrates such as polyethylene and coroplast, as mentioned, should be a standard procedure when attempting the printing, especially using UV ...

Dyne testing to determine suface tension / treatments for substrates such as polyethylene and coroplast, as mentioned, should be a standard procedure when attempting the printing, especially using UV inks, of these products.

Manufacturers and distributers of these substrates are very good at trying to rotate their stock so as to eliminate supplying materials that have been sitting long enough to reduce the surface tension. That having been said, there are instances where the dyne reading of materials that may have been sitting around your shop and even that have been recieved in a timely fasion could be beyond that which would be optimal for screen printing.

There needs to be a distinction made between the use of the dyne "pens" and the dyne fluid itself. The dyne fluid's effectivness and reliablility is affected by contamination from contact with the ambient air and the surface of the material that is being tested. For this reason I would recomend buying the dyne fluid itself (supplied in bottles) and using a cotton swab to apply the fluid to the material being tested, then throwing away the swab and using a fresh one for subsequent applications. This reduces the chances of contaminating the fluid.

Also I've mentioned before that certain ink manufactures' inks work at a certain minimum dyne level (usually below what the ink manufacturer recomends) and rather than a range of dyne pen's/fluids a fluid rated at the bare minimum number that works for the UV ink utilized in your shop is all that's really needed. Unless you need to know the exact level of the material you have, a simple pass/fail dyne level tells you if the material is safe to print or not.

I feel a need to mention that I am by no means a chemist and all of my experience is merely anecdotal and comes from many years working with polyethylene and polypropylene container decorating and years of printing large format graphics on polyethylene banners and coroplast signs.

Good Luck
Rocky

posted on: Sat, 04/15/2006 - 3:01pm
balloonmatrix says: REMEMBER TO KEEP SCREEN OFF THE SUBSTRATE ABOUT 1/8 INCH! YOU KNOW, "OFF CONTACT"...LET THE SQUEEQUE MAKE THE SCREEN TOUCH THE SUBSTRATE, DON'T LET THE SQUEEGIE JUST LAY THERE CLOSE ENOUGH TO SUBSTRATE, ...

REMEMBER TO KEEP SCREEN OFF THE SUBSTRATE ABOUT 1/8 INCH!

YOU KNOW, "OFF CONTACT"...LET THE SQUEEQUE MAKE THE SCREEN TOUCH THE SUBSTRATE, DON'T LET THE SQUEEGIE JUST LAY THERE CLOSE ENOUGH TO SUBSTRATE, JUST TOUCHING IT.

posted on: Thu, 05/25/2006 - 6:00pm

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