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screen printing => Screen Making => Topic started by: alan802 on October 20, 2015, 05:15:06 PM
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We made it the 1st 8+ years without ever busting a screen on press during a run, and now we've had 3 bust in the last 6 weeks, 2 in the last 2 days. I'm fairly certain they've all been on the same print head, number 6, right next to the 2nd flash unit. They've all 3 busted at different locations, one on the left side, one right down the middle and the other on the right side closest to the flash. Also, 2 have been bolt mesh and the one today was a brand new, never before used S Mesh Shurloc panel stretched to 28 newtons, max tension for that mesh is 35 so I feel good about it not being because I'm tensioning them too high. We've had one 225/40 and two 180/48's. We've been using thin thread mesh for going on 4 years now so it's nothing new to us. One thing I find interesting is it's started around the time I got the latest crop (a whopping 2) of new employees. My printer is dead set on it being something wrong with the print head and I've watched it off and on for 3-4 hours today and have used it on every job and I have not seen anything that would cause a busted screen. Flood bars are polished well, most mesh is below max tension and corners are good and softened. We print next to the 1st flash all the time, but it's usually a lower mesh, but a more delicate mesh than a 180 or 225.
Does anyone have an idea where all I need to be looking? I've covered a lot but want to make sure I don't overlook something. I noticed my screen guy has started using the sharp edge of the scoop coater and he started using it on Wednesday of last week. And I specifically told him to not use the sharp edge because it was scuffed up but he said he polished it really good before he used it. I'm thinking that maybe the one 6 weeks ago was an anomaly and the last 2 were related but I'm all ears/eyes on this one. I have my suspicions, and I also am very good at finding issues like this but I'd like some help from the gallery here because I think I'm too biased in what I think is causing it and want to get some outside perspectives.
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it's like chasing a pig.. when you finally catch it, was it worth the chase.
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Look at all the other places screens rest. It could be coincidence they are breaking on that head.
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I think we're still within the tolerance of it being coincidence given a lot of the other factors that exist that are hazardous to mesh, 2 new guys being the biggest concern of mine. And one of the new guys has skillets for hands, a bit on the clumsy side.
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Same print head? What is your ceiling made of? I'm serious
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Also:
Where within the mesh area, did the tears start?
That will give us a good starting place :)
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I never busted one in 3 years, but since we got the auto we have busted at least 15 in the last 8 months. Different printheads. Pressure is not too high. It busts right at the edge where the flood bar wing is. Thought we figured it out that it was a bent flood bar, but still does it now and then. Haven't quite figured it out yet though.
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I've only had it happen a couple of times but it's always the worst time. My culprit was very dry days with the back door open and vehicles traveling back and forth across the dusty alley in back. Needless to say a little dirt managed to get in the ink. At first I noticed a little unusual single streak in the ink during the flood and then next was contastrophy.
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Some things to watch out for.
Avoid laying any tools on the mesh during set up. This can be a hard habit to break for workers used to laying the flood bar, squeegee and clips on the mesh.
Avoid very aggressive wash pads. If they are soft, no problem, if they can scrape the back of your hand they are too harsh and could nick the threads that may not pop until frames are degreased and put in sun, or as a print run starts.
Avoid dry wall spatulas with sharp edges to remove ink.
Round off the corners of your squeegees and polish them smooth.
Check all flood bars for nicks. Place tape on the inside of the screen where they and the squeegee land to absorb the impact. Check flood bar and squeegee pressure. With S mesh less is better.
If screen is next to the flash aim an infrared thermometer gun at the frame after the flash has turned off. If the frame heats up a lot it can expand and increase tension. Try protecting the frame with a heat barrier so frame doesn't heat up.
Check off contact and pallet level. overtime pallets can go out of level on some machines. balance off contact front to back and side to side.
As mentioned watch other areas of the shop. Are frame corners resting on mesh? Are frame corners dragging across mesh when pulled out of a dip tank. Try putting only one at a time in a dip tank when reclaiming. The time to blast out a screen allows enough time for one in the dip tank to be soft enough to reclaim.
Have you switched tape recently? Sometimes tape becomes so bonded to the emulsion it can rip mesh on removal.
Check squeegee pressure and durometer. Avoid high durometer squeegees set vertically. 70 duro at 5 degress more angle than 'normal' angle of 10 degrees helps. Think about the squeegee action and pinch the ink rather than attacking it with a high vertical angle, especially at high squeegee speeds.
Quite often the reason for the popping of mesh isn't present when it does. You can nick mesh, abrade mesh with long runs, scrape with tools or scrub pads and not notice a popping of the mesh until later downline, usually after reclaiming when it is drying. Your tension seems correct, but I have found that with most of the S meshes a mid point tension works better in harsh handling that is typical in textile shops.
If you stretch on your own avoid super glue type glues. They create knives out of the mesh. Any flexing over the glue can cause it to cut the mesh. We use a 2 part Poly glue that is softer for this reason. If you must use super glue, (cyanolates) keep glue within frame width. Avoid glue on the mesh to the inside of the frame. Again this will be a knife that will cut the mesh.
For plastisol, especially white, it can help to wipe down the inside of the stencil area with some curable reducer so that the squeegee has a lubricated surface to begin printing on. White can be very viscous and need some working to soften up. Fresh white can cause a lot of friction until it is softened in the screen. Use a turn about to keep white bases soft. In the morning the ink in the screen can really get stiff. Remove most and add some that has been worked with a spatula or in a turn about. Especially on long runs since the printing process will pick up a lot of fibers that accelerate thickening of the ink.
Send some photos so I can check out location, this helps.
Alan
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I've had issues with the sharp side of the squeegee not being 'dressed' properly by the supply house.
Funny edit: I don't know why I said squeegee, I hope you figured I meant scoop coater. ;)
If it's one of those types, you may want to check that the edge is flush with the end caps.
Does sound weird to me though, screens here pop after reclaim or after retension, *almost without fail.
*What, like I never mishandle one? ;)
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I would make sure that print head is level. We had one that was so far out the flood bar was not touching in the back of the screen and pushing .125" in to the screen at the other end.
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Here's the one from yesterday. The one that busted the day before was about 6" to the right, and the one from 6 weeks ago was about 2-3" to the left of the pictured rupture. We've had a floodbar wear a hole in a screen on a few occasions by coming down at an angle when using a hard fill, but having a huge failure like the ones we've seen is new on press. Over the years I've found many in the dark room that have busted after a retension or after a coating but having it happen on press concerns me even more.
(http://i485.photobucket.com/albums/rr211/alan802/SRI%20Pics/IMG_20151021_081220_zpsc9r31ffi.jpg) (http://s485.photobucket.com/user/alan802/media/SRI%20Pics/IMG_20151021_081220_zpsc9r31ffi.jpg.html)
If the rupture wasn't so far to the middle I could see it being something within the print head, a bad floodbar or way out of calibration. It's been about 4 weeks since I checked calibration of the press and it wasn't far out at all. It's actually in tighter tolerance than some of my first attempts at press calibration so I think we're good there. I checked the floodbars for imperfections and didn't find anything. I double check Alan's list and make sure we're good on all of those but first read through looks like all the precautions we do but it's easy to get complacent with some of those.
I don't have a pic of the other 2, we've already stripped them and the frame are waiting in line for stretching. They are identical in length and direction to the one pictured, but just more to the side closer to the edges of sq and fb, but they DID NOT bust right in line with edge/end the sq and fb and were about 1/2"-1" towards the inside of the edges.
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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.
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^^If it's random like that I'd tend to agree--it would point to excessive tension, or the 'crap in the ink' theory.
Had one of the part timers shatter a glass mug and got glass in the white. That was a fun month.
In retrospect, I would have saved money just tossing the whole gallon.
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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.
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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.
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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.....
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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.
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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
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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.
(http://i485.photobucket.com/albums/rr211/alan802/SRI%20Pics/IMG_20151021_134529_zpsxkwfj6ey.jpg) (http://s485.photobucket.com/user/alan802/media/SRI%20Pics/IMG_20151021_134529_zpsxkwfj6ey.jpg.html)
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.
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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.
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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
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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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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 ;)
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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.
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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.
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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.
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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.
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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.
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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).
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The key is to be gentle with everything once you go to s-mesh I learned. Every time i hear a screen hit the floor I run and tell the offender no. When we 1st went over to s-mesh we would bust screens a lot and usually it was always do to ruff handling. Also have every thing smooth on all the flood bars and squeegees helps. I had to retrain people how to handle screen when we went to s-mesh. Literally I had to go over the whole process start to finish and why we do it this way and only this way. Than everything was gravy. They need to be treated as a baby...
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The key is to be gentle with everything once you go to s-mesh I learned. Every time i hear a screen hit the floor I run and tell the offender no. When we 1st went over to s-mesh we would bust screens a lot and usually it was always do to ruff handling. Also have every thing smooth on all the flood bars and squeegees helps. I had to retrain people how to handle screen when we went to s-mesh. Literally I had to go over the whole process start to finish and why we do it this way and only this way. Than everything was gravy. They need to be treated as a baby...
Jacko would have had problems with S-mesh
(https://kaitlynfaebarrett.files.wordpress.com/2015/04/mjchild.jpg)
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But what about tis couple?
http://eng.inyarwanda.com/articles/show/OtherNews/66200/White+woman+gives+birth+to+black+baby+claims+the+g (http://eng.inyarwanda.com/articles/show/OtherNews/66200/White+woman+gives+birth+to+black+baby+claims+the+g)