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NEED HELP ...Coroplast Screening

Posted on Sat, 2 Apr 2005 at 17:58



I used to print shirts , and recently decided to screen coroplast signs ... WHAT A MESS !!

I am using 28"x36" screens ( maybe this is too small) ... and have tried 200, 255, 305 mesh. Tried Nazdar 59-000 ink & Cericol Ink.
So far I either get TOO MUCH ink and have to pry off the coroplast ( this does not give the ideal result ) ... or the ink SKIPS over the flukes ( I am printing ACROSS them, not with them).

I am helping the coroplast industry profits with my waste, but little else.

Would appreciate any advise on TWEEKING my operation. I am thinking my screens may not be large enough and since I am using a 1/8th inch ( or so ) OFF CONTACT, I may be expecting more elasticity from the screen than it is willing to give.

I doubt that I am going to be a real threat to the industry as a whole, so hopefully some of you KNOWLEDGABLE printers will pass along some knowledge and show me where I am going wrong.

Thanks ........... Richard

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Comments

Anonymous says: try different dur. squeegie that will probably help a lot. posted on: Sun, 04/03/2005 - 12:56pm
Anonymous says: Different How ?? Harder ... Softer... I think the one I am using is a 70. Thanks ... Richard posted on: Sun, 04/03/2005 - 1:30pm
Anonymous says: Richard, First use nazdar 79000 series corogloss ink. Use reducer or slow evaperating thinner 1/4 Off contact, Print quickly! this is not like t-shirts! you need to pull the squeegie at least 5 times ...

Richard,
First use nazdar 79000 series corogloss ink.
Use reducer or slow evaperating thinner
1/4 Off contact, Print quickly! this is not like t-shirts! you need to pull the squeegie at least 5 times a minute! Make sure you flood the screen with ink in between prints.
Do you have a vacume table? if not you may need more off contact to keep them from sticking to the back of the screen. I use 32 x 44 screens for 18 x 24 signs.
If any of this doesn't help send me the artwork and spend your time on t-shirt!
Bruce
State Line Graphics
877-506-7446

posted on: Mon, 04/04/2005 - 12:41pm
Anonymous says: Hi Richard, 1- what size is the image that you are trying to reproduce on your screens? If your image area is too large for your frame (e.g. full coverage reverse type, with only 2" of free ...

Hi Richard,

1- what size is the image that you are trying to reproduce on your screens?

If your image area is too large for your frame (e.g. full coverage reverse type, with only 2" of free mesh on each side) the screen will have too much surface area to snap out of the print correctly. The ink deposit will also be inconsistent across the print because when you push the image to the out sides of the screen the squeegee needs much more pressure to make good contact to the substrate .the screen tension increases as it gets closer to the frame. Causing the ink to flow faster through the screen and uneven print results.

I would not recommend putting any image bigger that 16 x 24 on a screen that size.

2- what type of frame are you using, Static or retensionable?

If you are using a static frame you need to be aware of the inside screen dimensions and the frame profile. If your screen out side dimension is 28x36 but your frame profile is 1 ½ x 2 ½ then you have to subtract the frame profile from your free mesh area. With a roller frame you measure from the centre of the roller to the next roller to get the inside dimensions and the free mesh area. The same applies with roller frames will a box beam.

3- what is the screen tension you are running on these screens?

If your screen tension is 20 Newton’s or higher you should have no problem with the screen snapping out of the print at an of contact of 1/8 to ¼ of an inch, depending on mesh count, and thread diameter. (If you are using 305, 34 micron mesh to print with, you will have a very easy time pushing the ink through the screen Vs a 305, 40 micron thread which will require much more pressure to get the ink through the mesh.) If your screen tension is below this, then you will have to raise the of contact to get proper snap off out of the print, but again at the risk of uneven ink deposit, image distortion, and possible mesh failure.

4- what is the size of the squeegee you are printing with?

Try to keep the squeegee around 1 inch past the image area on both sides as a rule of thumb. Anything more that this is just going to make life harder for you to make contact with the screen to the substrate, and will cause the same problems as low screen tension and not enough free mesh area. (Think of snowshoes or skis. The more surface area you have will require you to have more pressure to deflect the mesh into contact with the substrate.)

5- How much free mesh do you have from the edge of the squeegee to the frame?

I kind of went over this already. But I would say that a good rule of thumb again would be to have a minimum of 5 to 6 inches of free mesh on all four sides of the image to help with uniform ink deposit, snap off, and lower off contact distances that can be used.

I hope you do have some kind of vacuum table to print with. If not that might be the cause of most of your problems.
It sounds like a print problem more that ink issue, but trying to thin the ink might help with the release, like some one else had mentioned.

Just some more things for you to think about, I hope this helps.

Best Regards, Peter Duff.

posted on: Mon, 04/04/2005 - 10:58pm
Anonymous says: I thank all who have taken the time to respond. Many of your ideas have been VERY helpful, although I see that there are various ways to approach this artform. I actually ran 100 18x24 signs 2 days ago, ...

I thank all who have taken the time to respond. Many of your ideas have been VERY helpful, although I see that there are various ways to approach this artform.

I actually ran 100 18x24 signs 2 days ago, and MOST of them came out OK. What I learned was using DEAD-ON contact worked pretty well for me, this may be because of the size screen I was using ( 28x36 Outside ) since some of you say you use OFF CONTACT .
ALSO .. I thinned down my ink A LOT and found the release from the bottom of the screen improved. I used 260 mesh ( do not know the Micron rating ) and printed ACROSS the flukes with a 19 inch squeegee.
I cannot say that ANY of them came out PERFECT since there were very small flaws, like cobwebbing and such, but my customer was satisfied with them and wants more.
I am still confused if I should print ACROSS or WITH the flukes, or does it really matter?
One person mentioned using a 10 inch squeegee and making 2 passes ...does anyone else do this?

Richard

posted on: Tue, 04/05/2005 - 7:46am
Anonymous says: HMMMM - the small squeegee 2 pass thing is going to look like crap if the image is bigger than the squeegee. thin your ink some more if you are getting tendrils. Are you peeling the prints? the off contact ...

HMMMM - the small squeegee 2 pass thing is going to look like crap if the image is bigger than the squeegee.

thin your ink some more if you are getting tendrils.

Are you peeling the prints? the off contact will help you get a nicer print. Vacuum?

print with the squeegee parallel to the flues

next time use a bigger squeegee and a bigger screen - 19" is tight, how big was the image?

Hey if the guy wants a reorder, you must be doing somethings right, just keep at it.

posted on: Tue, 04/05/2005 - 9:14pm

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