Busting Screens On Press

[alan802]

stupid questions... (sorry if you answered them before/already)

1. when was the last time you retensioned the screens?

2. how much tension are you running.

3. when was the last time your tension meter was calibrated?

I've only had them pop in the middle of the screen like that when we were running too much tension.

The one in the pic is either the first time it's been through a production run or at the very most, the second.  So I can't say that it's been retensioned yet but my answer to number 2 should tell us whether or not it's the issue.  I tend to think it's not but  maybe I'd have better luck running them in the mid 20's which is not a problem.

I'm running the 180's at about 28 newtons and the max recommended is 35.  I've gotten bolt 180/48 up to almost 40 newtons before but only briefly to see if I could do it.  I used to run the 180's at 33-34 but have cut down on that.

Tension meter is going on about a year without calibration, but it's been babied to the point of ridiculousness and it's never even been dropped a millimeter and I'm the only person in the entire shop that has ever touched the thing so I'm fairly certain it's good.  The last time I tested it against another meter was about 6 months ago and they were within a newton of each other.

I'm leaning towards mishandling at some point and then the damage happens completely on press OR something getting in the ink.  I've been watching my guys and I'm going to have to correct some things and it's not that they don't care, they just don't realize how delicate the mesh is.  I can handle a screen in a way that might seem rough to some but I can pick it up and spin it around, twirl it, grab 3 in each hand and walk across the floor without doing any damage.  But someone that doesn't grasp just how you have to handle them can damage one without ever knowing.  My new guys think they are handling them very carefully but they're really not.  I just have to catch them doing it then show them exactly what they did wrong.  I've already corrected one issue that they (2 new guys and press op) have been doing recently, I'll take a pic of that for yalls amusement, it's amazing that anyone would think that it's a good thing to do that to a screen on press.  I'll get that pic up asap.

[Colin]

2 cents....

It looks like you guys ran the left chest first.  Is there any chance someone hit/nicked it while cleaning out the ink before resetting the screen up?

I have received panels of the 180/48 mesh that developed holes fairly quickly while others lasted a long Long time before getting a nick on an edge.... delicate mesh.....

[alan802]

2 cents....

It looks like you guys ran the left chest first.  Is there any chance someone hit/nicked it while cleaning out the ink before resetting the screen up?

I have received panels of the 180/48 mesh that developed holes fairly quickly while others lasted a long Long time before getting a nick on an edge.... delicate mesh.....

The highest likely scenario going through my head is this ^.  My "skillet handed" new guy is awkward when slinging ink and he looks like a dear on ice skates when trying to get the screens out and ink back in the bucket.  My screen guy with the most experience has told me to watch him because he sees him doing things when I'm not back there that have raised his suspicions as to where the new screens busting is coming from. 

I should have mentioned on this thread but have in other posts about an increase in screen failure since the new guys started but that's pretty much a given at any shop.  I lose some confidence in my opinions about where the problems are from outside influences like my printer and one of the new guys who has handled much higher and more delicate screens when he worked at another shop (decal printer).  They both think it's the press or sq/fb and not due to mishandling.  It's a self-fulfilling prophecy to some extent with them (especially my printer) because he'll now go out of his way to prove himself right that it's the print head since that was his conclusion after yesterday's bust.  He's done it over the years pretty much any time there is a problem that pops up and we disagree with the cause.  For example, since the purchase of the Vastex LED we've had emulsion failure at the edges of the squeegee blade. He would tell everyone that would listen (and me) that it was the flood bars wearing the emulsion down and that we were also using crappy emulsion so I finally got tired of hearing other employees telling me his opinion on the matter and on the next big run I offset the sq and fb about half an inch and 200 impressions later we got our answer and although I could have really rubbed his nose in it I only did it a little bit.  I know, I know, that's not the proper way to handle it but when someone goes out of their way to undermine their boss and try to prove them wrong any chance they get I got a little bit vindictive and used that to show everyone that I really do know a few things about this thing we do every day.

I think we have the age old problem of everyone wanting to be right (I'm guilty as well), it's human nature.  Some are more willing to admit defeat or that they were wrong, and others couldn't admit it even if there was 100% certainty that they were wrong and everyone could see it.  So with that said, I'm trying to reach out to you guys and approach this without bias, and it certainly might read that I'm also trying really hard to be right, but you'll just have to trust me that I'm answering all of the questions truthfully without skewing them in my favor.  If I am wrong on this I'm a big boy and I can take it.  A little humility goes a long way.

[ABuffington]

One other trick is you can drop tension in the narrow direction of the screen 1-2 newtons.  Most of the print force of the squeegee is in the long direction of the screen.  Dropping the narrow width of the screen 1-2 newtons won't affect registration or square openings.  It will however absorb the tension from the squeegee corner to the capture point which can be high if off contact is excessive.  I have lowered tensions to 20n on test prints here and have seen no loss of print quality.  20-22n seems to be a sweet spot for these screens.  Higher tension 24-28n will help peel off when printing over a plastisol base, especially with large spot color areas.  You could try a retension of 24 in long direction, 22 in short direction.

Al

[alan802]

I guess I'm not living right.  3 in 3 days.  This one was on head 8 instead of 6, so at least that eliminates one theory.  This is a 300/34 stretched in July, and I've been keeping decent records of the screens I've stretched since April.  This screen has been used between 8 and 10 times and retensioned 2 times and stabilized at 22 newtons.  Last retension was 1st week in August and has been used at least 6 times since the last retension.

 

Could it possibly be something that I've been doing the same way for 5 years now?  I have dynamically tensioned about 10 screens since learning how to do it but this isn't one of them so aside from the few that have been stretched differently (which will substantially decrease mesh failure by the way) I've stretched the vast majority of our screens the exact same way.  I've become better at it and can consistently get them above the recommended tension levels although I don't do it other than to make sure I'm doing things right, meaning I don't put a screen into production that is close to being at the highest possible level.  I just find it hard to believe that we're seeing all these mesh failures due to my stretching technique.  I'm not trying to be boastful but I think I'm rather good at stretching screens and over the years we have never had mesh bust like this unless we had new employees or the year that we had the worst employee we've ever had.  I've had screens bust recently that were 4 years old, some were brand new, and everything in between.  I'm going to try like hell to figure out if I'm doing something wrong, I don't believe that's the issue but I can't leave a stone un-turned here. 

[ebscreen]

Checked your pallets? We've had high tension mesh bust due to a lint/glue booger of just the right shape
and size in just the right place. When it happens twice in a row you're super stoked.

[ABuffington]

Stretching above recommended tension recommendations is asking for trouble.  I only recommend stretching to the mid point.  150/S:  Recommended tensions: 18-28
28 is the tension at which the threads and mesh reach the 'staging' point.  This is the point at which the threads and knuckles have a hard time getting any more tension and also it is our labs determination of the breaking point of the mesh.  They are ticking time bombs at this point.  We stretch our statics at 25n on our stretcher and after cut out we are reading 20-22 newtons on average.  S Mesh doesn't need that high a tension to print well in register.  Our show shirts are printed at these tensions and I would doubt a higher tension could make them any better.  Dot on Dot reg, easy smooth release of inks and good surface quality.  The one area where you may want to consider a 160/T over the 150/S is on large spot color prints.  Like a red 8" circle or similar type solid print.  Then going to a 35 newton 160T would peel a little better if there were any hot tack issues from the base plate.  I could print the same with the 150/S at 20-22n by modifying ink flow slightly, adjusting squeegee speed/angle.   High tension is usually reserved for the graphic and electronic industries who have far better presses with less of the textile issues.  As mentioned, bumps on pallet, handling, and abuse are common in textile shops.  High end graphic shops routinely use 380/S for UV, electronics even higher mesh counts with no issues due to better handling practices.  Textile uses many more screens and we tend to put them  as you show in your photo and handling is far rougher.  In my seminars I always ask if their mother allows them to throw dishes in the sink to wash.  It amazes me how rough textile reclaiming is in most shops I visit.  Try a lower tension, if the results aren't what you are looking for move to T mesh for the higher tensions.  160T is a good sub for 150S, However the 150S will print with less squeegee pressure and obtain a better base plate.

Al

[starchild]

Has offcontact distance changed on press? Have you checked?

Screens busting on press is due to force.. If it occur near the edges then it's due to too wide an image area and squeegees .. If it's happening in the center it's due to excessive offcontact.. If it's happening in both palaces then the press needs to be calibrated or improper mesh stretching with isolated tension areas

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[DannyGruninger]

Same thing was happening here for a while....... It was my guy scraping ink using the edge of the spatula digging into the mesh. Showed him how to scrape the screens and problem went away 

[jsheridan]

I maybe reaching here put to me that screen looks like to gave way in the middle from maybe a very small hole and high tension and not really over tension just high...look right at the left of the I on Kids about a 1/2 inch down that's where the rip looks like it started to me.

Yep, looking at the exact same spot. You can see some threads on the left side that show exactly where it broke.

small hole or nick with the high tension.. pow!

Looking at the 2nd screen above, same thing. Both screens popped below the image being printed, the same area ink is left after a print stroke before a flood.. I'd place my bets on whoever is removing the ink, is using to much pressure or digging the corners. Listen for a zipper sound.. that's bad when removing ink.

[Screen Dan]

I'm leaning towards mishandling at some point and then the damage happens completely on press OR something getting in the ink.  I've been watching my guys and I'm going to have to correct some things and it's not that they don't care, they just don't realize how delicate the mesh is.  I can handle a screen in a way that might seem rough to some but I can pick it up and spin it around, twirl it, grab 3 in each hand and walk across the floor without doing any damage.  But someone that doesn't grasp just how you have to handle them can damage one without ever knowing.

I'm leaning towards this.  Especially if you are using rollers with covers on the bars.  I've seen people (and myself) pick them up in the middle...especially if grabbing more than one frame at a time...and the their thumb (or mine) goes over the cover, the cover slips a little and now your thumb is on the mesh right past the insert...a little bit of over exertion right there and it develops a microscopic (or bigger) tear under the split tape that develops into a full blown problem on press.  I know the sound of it, I know the feel of it.

Might not be, but given where the tear is and seems to originate from I'm inclined to think it may be this.

[JBLUE]

New guy + screens failing out of nowhere= new guy f'n up the screens. Been there done that about a month ago.

My guy is only allowed to touch the mesh with the cheap Bondo spreaders from Harbor Freight. Once I took the metal knives from him all the issues went away. Even with no nicks on the blade he was able to score the mesh. Well except for yesterday when the dumbass put his foot through one. Just happened to be a really nice 150-S roller too. Had less than 6 jobs on it. Those cheap spreaders are soft enough that even if they get nicked they wont tear the S mesh.

I no longer change the material I use in the shop to try and fix the stupid stuff people do. I get rid of the stupid people.

[jsheridan]

I'm leaning towards this.  Especially if you are using rollers with covers on the bars.  I've seen people (and myself) pick them up in the middle...especially if grabbing more than one frame at a time...

Grab and carry the frames by the corners, and you won't pinch any rails. I've put a thumb through a top rail a time or two myself.

[kingscreen]

The couple of occasions this has happened to us, they were both at the hands of new(ish) employees and ink spatula corners; even with the corners rounded off on a belt sander.

[alan802]

Update:  I've spent a lot of time watching the new guys handle the screens, mostly during teardown and I made some changes to their technique.  The guy with prior experience is used to using UV inks and high mesh screens and is better at handling versus my other new guy.  The one that I think is doing the damage is even clumsier than I had thought previously.  When cleaning squeegees and floodbars in the parts washer he literally drops a floodbar at least once every few minutes.  I've gone through all of the FB's and polished them up, they were fairly rough by my standards but I didn't find anything that I think was causing any damage, but we're going to cover everything here.  The pressure being used when scooping ink from the screens was excessive in my opinion but it's kind of hard to really get an accurate account of how hard someone is digging from 3 feet away but I got him to back off with his pressure. 

They all know I'm looking at them really hard and I'm getting lot's of pushback with my opinion of the problems stemming from human error.  I'm trying to tread lightly here so we don't get self-fulfilling prophesies or better yet a blatant attempt at proving me wrong by purposefully damaging screens in another way (I hope this wouldn't happen but I don't rule it out).