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screen printing => General Screen Printing => Topic started by: Dottonedan on May 24, 2018, 11:15:37 AM
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Just curious what others are doing.
Do you all leave the pressure where you normally do on all colors...or, when printing. a base, and doing Print-print (two strokes), do you decrease the pressure? Lets say you normally like 50lbs on all heads, do you decrease pressure when doing two strokes...or leave it at 50 and do the two strokes?
Maybe different for different ink types.
Before I post more info, I'll hold off. I would not want my next post to unknowingly or potentially sway opinions or answers based on what is mentioned.
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If 2 stroking for added opacity - I will back off as much as I can. Plastisol ink here. Otherwise we will create a ton of dot gain.
Now that may only be 5 lbs of pressure - or it could be 20 lbs of pressure - its situational on garment/mesh/blade/ink/heat etc.
Example: 150s mesh base. Triple duro 60/90/60 blade we will run 30 lbs (or less) of pressure on our 14 color sportsman and closer to 20 lbs on our 12 color sportsman that has shorter arms.
We will go up as high as 50 for 225s mesh halftone base plates. As everything gets hot, we can back off to about 40. This is on the 14 color with longer arms (more platen deflection).
What have you got going Dan?
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Brand new to our auto (workhorse sabre 8/10), but been testing different stuff everyday. Using 135S for baseplates typically, 70 duro blade, 10 degree angle, blade speed and stroke speed maxed. Single stroke takes about 45ish psi to clear 100% cleanly, double stroke takes around 37 to 40 psi, and the finished print is significantly smoother and more opaque with very little gain. We aren't running a roller squeegee yet, so we are defaulting to the double stroke at the moment. Have tested everything from 20psi to 80 psi and angles of 5 up to 20. Going to test other squeegee blades soon as well.
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YMMV - all presses are different pressure-wise, duh, disclaimer.
print ub single stroke at 28-30 psi.
print ub double stroke at 26-28 psi BUT ONLY UNTIL it can clear with ONE at 28-30 psi.
top colors start at 30 psi. if a big run or heavy wow will walk down from there.
so basically - everything at 30 psi. with tiny variations. double stroke ONLY if ink has sat too long after being shaken.
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When printing two strokes of white I (depends on screen mesh) try and back off as much as possible to get the ink to just lay on top of the garment but yet have a good opacity and smooth print.
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Would you all consider a different approach based the garment loftiness? Lets say a Ring Spun 100% versus a Comfort color?
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Base line response:
I will always make adjustments - mesh selection/squeegee/eom/flood depth/flash strength/hot head/etc - based on how the garment behaves and accepts ink.
We just ran close to 10k pcs of next level black garments with different designs. The garment was fuzzy enough to SOAK up the base white - made it look like it had half the normal coverage. We put in a hot head before the base white - smoothed out the fibers - better print! Went to a lower mesh count for the next design and used the hot head- even better print!
We get to play both Sherlock Holmes and McGyver alllll the time.
This is all part and parcel of this being a craft industry... even though we try and make it into a manufacturing gig ;)
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Pretty much what Colin said, as usual.
If you aren't satisfied with a plasti UB in one stroke, move to 2 faster and lighter strokes.
Alternately, you could spend some time dialing in the single stroke but not really worth it for most print runs given how fast presses can double stroke these days. We'll maybe spend that time for a monster run where single stroking would make the difference.
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People still double stroke plastisol?.....LOL Thats only for the HSA stuff. Get some thin thread mesh and live the single stroke life. Its been a while and figured I would drop in and say hi!
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People still double stroke plastisol?.....LOL Thats only for the HSA stuff. Get some thin thread mesh and live the single stroke life. Its been a while and figured I would drop in and say hi!
We print mostly comfort colors. Loftier garments. A little harder to clear the screen on those in one stroke. We use hard 70/90/70 printing at near vertical angle. Off contact is at 1/32. I prefer 1/16th but again, these are comfort colors...
Typically, on the sim process, we are using other garments and we get one stroke out of it. We are already using thin thread, stretched on roller frames at a good tension. 230's relaxed and work harden at about 30 newtons. 305's at about 25N. The 180's and 156's are even higher.
When I talk to the ink Co's, they say drop the pressure down lower if you need to print two times, so it's not 50lb and 50lb. Makes sense. They do show me on press, that the one stroke of 50lb is not enough to clear the screen fully. The 2nd stroke does for sure. So there has to be a better missing ingredient.
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Dan a 230 is not a thin thread mesh. Did you mean a 225-S? Its a big difference in deposit.
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Dan a 230 is not a thin thread mesh. Did you mean a 225-S? Its a big difference in deposit.
No, There are thin thread 230's. I tried the S mesh and am not fond of it. More ink defeats my purpose.
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Dan a 230 is not a thin thread mesh. Did you mean a 225-S? Its a big difference in deposit.
No, There are thin thread 230's. I tried the S mesh and am not fond of it. More ink defeats my purpose.
You tried the thin thread 225-230 and didn't like it or you tried various thin thread mesh and didn't like it?
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I tried the Murakami 225S and a few other mesh counts. Didn't like the ink lay down and dot detail for what we intend to use it for.
People say, Oh, you can use higher LPI. Well, yea, I guess you can (if) you always know that your art does not have anything less than X %. I feel, why worry and have to try to remember where your percentages are...and jump up mesh level when you need to hold. What if, I want good coverage (and hold small dots). Maybe I'm a little different in how I approach the separations and much of our work takes advantage of those dots below 10%.
My original intent for getting Murakami S mesh was to test out if I can really get higher lPI like some of the people have said here. I guess I take the term (holding a 60lpi) on a 225S thread more literally than many do, I suppose. I didn't want to take a chance on the (previous screen room where I worked) using a 225S to get coverage (and then I lose my dots under 5%) at 55lpi. Sparse, or (spread out more across the board),but still losing them. When you use a darker colored ink on a lighter colored background (white base), these missed dots show up as a peppered mesh pattern. At the same time, when I want to blend for sim process, I get better blends from other mesh (for me). I truly understand that people do different things and get good results in their shop. I support ya. For us, we'd have to go up to that Murakami 310 super duper sensitive mesh as a standard and in our shop today, we don't want to go that way.
Nawh, Murakami has a strong place and apparently works best for many shops. Just not to my personal liking and from what I gather, Tony's not fond of it either.
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I've never personally tested whether or not you can "hold higher detail on thin thread versus standard mesh" although literally every expert in this field says it's true. I don't think Joe has ever told me that directly but I do believe he stated it in his M&R Textile Bible. What I've tried to go by instead of the 4.5 rule, is with thin thread using more like a 4.0 rule when it comes to lpi. I wouldn't expect to hold a 5% dot at 60 lpi on anything under a 270/34 and a 225S wouldn't hold the detail well enough for my tastes either using your standard. At the moment, 270/34 is the highest mesh count I'm using, and it's working very well. It's not considered a thin thread mesh, but it has a higher % mesh opening than a 225/40 and everything near it on the spec sheet, at 41%. To give you an idea of what that means, comparably, it's a higher open area than a 156/64. I can even print some of the nasty blue colors through it with one stroke and I've printed regular white without altering it through the 270. I don't ask my artist to use 60 as the standard lpi for our high end process work, and I think he stays in the 50's for the most part since I've not seen any type of moire pattern in quite some time.
Not to keep this argument going for any longer than it needs to, but I'll finish with this: Do you ever do any spot color, normal 3-4 color jobs on dark garments not requiring 55-60 lpi work? I can understand bypassing what thin thread has to offer in some aspects and using what's best for a specific application which is what it sounds like you're doing, but if you're doing any type of work that most shops are full of, like I asked about above, it would benefit you to at the very least use the best mesh count for those jobs as well. But if you don't do anything like that then I envy you. I'd love to do nothing but sim/spot process jobs every day. This year we've done more of those types than the last 10 years put together and they usually turn out great, without much effort as long as the screens were burned correctly. And the art has to be decent, which is usually the only thing I have to worry about. But we are strictly thin thread regardless of lpi and halftone needs. When people say they would quit the industry if they lost their CTS and had to go back to film (I could convince them otherwise in an hour or two in our shop but that's not the point here), if I had to use standard mesh counts I wouldn't just quit, I'd burn this sum bitch down to the ground and walk away happy. That might sound hyperbolic, and of course, it is, but seriously, and I don't want anyone to take this the wrong way, but if there is anyone out there that has printed a 150/48 beside a 156/64, or a 120/54 next to a 110/81 and didn't see the benefits of thin thread, then I would say that that person does not know what they're doing with a squeegee and plastisol ink. Now I'm not saying that if you don't use thin thread then you have no credibility with me, I can see the logic in many shops not using it for many other reasons, I'm just saying if you can't use it and get better results than standard mesh, pretty much across the board, then the problem isn't with the mesh. There are plenty of good reason TO NOT USE thin thread, for example If you're a WB or otherwise anti-plastisol shop. And if you can't trust your crew to handle thin thread then you also don't have much of a choice. And if you don't have a way to stretch it properly, again, you're kind of screwed with thin thread. And I would also say that with thin thread, it's not near as important to retention/maintain the tension on your screens as it is with standard mesh since, for example, a 150/48 might slip down to 20 newtons in tension yet still perform really well, especially compared to a 156/64 stretched to 40 newtons and maintained to a high standard.
And if anyone is offended, then read my post again, I'm not "implying" anything or trying to say something cryptically, read it as if you had written it yourself. And most of what I said is as true as saying the world is round, and of course there are plenty of exceptions to the rules but I have to speak in general/average terms as to not turn a few sentences into a 15,000 word post trying to cover all of the exceptions and what not. And ALL of what I said really only applies to exclusive plastisol shops.
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Quick reply.
No argument. :). Happy guy here. :D
Yes, it's true, you can hold more (when comparing similar mesh counts like a 230). But what drove me to testing it was the comments that were mad e of using 55-65lpi on a 225S. STILL, you cannot hold a full tonal range of 3-97% AND, more important to me, is to get optimum blending capability. It's similar to printing sim process or 4 clr process on a 156 mesh. You just wouldn't want to.
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Ell Dan your 3% dots are probably more like 10% in reality if your not linearized and those should hold fine at 50 LPI on a 225-S. Long swaths of low percentage areas may give you some issues depending on angle. Depending on the transitions we can get a lot of 55 lpi to work as well.
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The first time of testing these 225-S and other mesh sizes, I was at another shop, with a perfectly linearized Film output using a densitometor. Then, we measured and linearized their the I-Image STEll to match the FILM. I can't say really where that was, without permission.
I later went to work for a small screen print shop and used film there. I linerized the films there and used Accurip to adjust. I didn't really like that rip, or more so that film printer along with that rip, but it worked for what we did. I'm sure to, the 3's were not 10% there, nor were they at the first shop were we tested and I'm sure they are not 10% where I am at now. Positive. No pun intended.
If my 3's were rally 10% at any shop, then I'd be holding more of my gradation in the 225-S wouldn't I.
Still tho, 3's to 10 aside. Too much ink for my preference is all.
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Just some measurements and thoughts on all of this:
1. 225/S = 42% open area and 73 micron openings. Mesh thickness: 59 microns - Ink Volume: 25cm3/m2 - Tension Range: 18-29
270/34 = 41% open area and 60 micron openings. Mesh Thickness: 41 microns - Ink Volume: 21cm3/m2 - Tension: 17-29
For highly viscous inks like white base plate ink the mesh opening is also a part of the mix of things to look at. Less pressure needed with larger mesh openings, but as thread diameter and mesh thickness grow so does pressure. 135/S, 150/S, 160/S, 180/S, 225/S are all a family of base plate meshes, or high end water base/discharge meshes. I have just found more opacity with a bit more ink volume and a mesh thickness in the 225/40 range vs 270/34. But the 270/34 is an equally good choice just more modifications of ink may be needed. It does have more mesh openings and threads for halftones to form. Toss up in my mind, but opacity should be better on 225/40 with careful squeegee settings.
To answer the question on pressure here is my set up technique for 225/S/40.
Set air pressure to 40 lbs
Triple duro 65 or 75 (depends on design for me, every design requires different choices.)
Increase angle from: 0 degrees to 10-15 degrees. (Crucial to obtain bright opacity with sim process printing.)
Slow down squeegee stroke in the beginning to 1/3 of desired speed. (We are icing a cake with the base plate and not trying to drive the ink to the back of the shirt that typically occurs with a 0 degree setting and scraping the ink at too high a squeegee pressure.)
Back off mechanical pressure until the ink doesn't print.
Add mechanical pressure slowly until image starts to clear. (The squeegee should barely bend, keep squeegee sharp with a straight edge for absolute minimal pressure.)
Then as inks warm up on test shirts, speed up squeegee speed gradually. At 160-190 degree pallet temp you will achieve as fast a squeegee speed that is possible without changing the set up or ink adjustments. (A turnabout ink mixer with white base ink helps keep white ink sheared to keep ink soft when added to screen. Really helps in the winter time.)
Once mesh clears with the least mechanical pressure possible and the inks are warmed up and shearing well, back off air pressure slightly to reduce pressure as much as possible. This helps opacity as well as the negative dot between the printed halftones and is often the key element that makes the tonal values have as much tonal range as possible and smooth transitions.
All pallets need to be leveled to each other well to obtain absolute minimum pressure needed as described here.
Slight adjustments to ink viscosity help, but typically not needed for 225/40. Less adjustments to ink = best opacity it can yield.
If I am holding the space between the 70-85+% dots of well linearized film with a pre press curve to compensate for 10-15% ink dot gain, then all other percentages will print fine. It's these tiny negative dots that are the hardest to print well. Easy to hammer down squeegee pressure, but the balance point of opacity and great halftone reproduction requires modifications to angle, pressure, air pressure, and mesh choice.
2. Next is image setter: Ink jet is all over the map in terms of making good halftones. An older unit with a lot of mileage on it doesn't focus it's pico liter dots well. So at low dot% it varies tremendously from shop to shop. Some are scattered pico liter dots that never form a discrete dot. Even well focused pico liter dots are no where near what an image setter or true film can produce, nor as opaque as wax. So quality halftone reproduction on screen varies from shop to shop, even if linearized, depending on the quality of the dot. Even low % perfectly formed dots below 4-6% are tinier than the thread diameter, so the dot may image but be blocked by thread diameter.
3. Then what shirt brand/ Open end? Ring Spun? singles count? Fine weaves can handle far finer dots than a coarse open end 4.8oz fabric
Every job is different, what I would spec on one job with fine shirts with sim process would be far different than a job on an open end with solids and halftones within the same color. This is a subjective business where if you and your client like what you see and it sells, great, job accomplished. But for high end printing the small tweaks we give to mesh, squeegee and inks can make a difference with many different paths to get to the 'best' result. Once you dial in your #1 head for the baseplate leave the squeegee in, and on new jobs slow down the squeegee speed only and increase speed as the inks shear and warm up.
Al
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Quick question Al:
Do you see many shops running their presses and getting board temps in the 160-190 range?
Here, we put the breaks on board temp around 150 - we HATE 160 or higher - so many issues crop up....
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Hello Colin
All depends on ink type, ink print area, amount of ink to be flashed. Just numbers from my head long ago. Lots of low temp polyester inks out there that would favor much lower pallet temps. The number of flashes is another issue and it gets to the point that pallet temp and ink flashing needs may push pallet temps higher with 3 flashes and not enough cool down stations. Once we hit good prints and flash times it was a juggling act of temp, time, and whether we got enough of a gel. Add fans here, slow down a squeegee to cool down large plastisol base plates, and so on. It amazes me we aren't all crazy with the magic acts we perform on press by making slight adjustments to keep the job running and explains why repeating a difficult job is harder the second time around. Jobs we did in winter with excellent pallet temps and 3 flashes become a nightmare in 100 degree temps with no ability to keep them cool enough. This is one reason I like S meshes and even the 270/34 since you put down less ink, flash faster, and have that precious 1 second extra cool time when trying to run as fast as possible.
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Here's the thing about wet ink DTS printers that people always overlook. If the dot is linerized before screen, and total dot gain is controlled after, (on screen to on shirt), then there is no debate. In this case, a 5% is a 5% (there abouts). So the whole "Wet ink doesn't form a good dot statement (made by anyone), not just Al, doesn't hold up. Now, I will concede and agree, that everyone who has wax, getting great hassle free dots, is doing great. They love those machines...and why wouldn't they? They bought (invested in their decision). Same for the I-Image users. That wax is working for you. It's hassle free (so you think), as it looks great on the surface. Is it correct? Is it really great? I know it's not (from the standpoint of a dot snob). Now, neither is a wet ink device.
The wet ink DTS I am most familiar with is the I-Image. I started out at two different shops at the forefront of WAX dts in two different shops. I'm familiar with wax output, but in recent machines. I've studied wax dots/shapes density in today's machines but not in great detail about the guts of the wax machines so I am a novice in that area compared to WAX dts experts.
The standard print setup of an I-Image has been tested and proved to provide a Dmax 3.6-3.9 based off of multiple shop setups readings from a transmission densitemeter. Since Dmax represents the area of the darkest opacity, and should be as high as possible or, above 3.0 I can safely say, this ink in the I-Image, with the settings of a typical installed 12 passes at 900 x 1200 ink output resolution at 8 picoliter, using bi directional printing provides higher than the minimum. I have not read the Dmax of WAX but I'm sure it's solid. Both of these 3.8 and solid will provide enough density to reproduce a dot shape (whatever the shape) accurately with no visual difference.
The old idea of (must have a hard, clean, round, vector like circle or oval shaped dot) bares little to no fruit when you know and adjust for gain. That's the key tho isn't it? You need to know where you are. You can expose the right tone percentage using a crusty 24 day old dried booger. As long as that size represents yours targeted %, you can expose all of the boogers you want.
Wax is opaque, I give you that. No argument. Having said that, know this. The idea, that WET INK is not, is not and accurate statement.
This is why WAX dots (on the surface) or in general, look good. The wax forms non uniform blobs of wax drops. (It works for screen printing) and that's what matters. It's rounder...and easier to hold as a result of it's lacking the ability to reproduce exactly in a minute manor. A wet ink dts can form the 1% (pixel cross). That's how accurately it reproduced a bitmap image. How do I know? Been there, done it.
So I know, we cannot print a 1% dot in a 65lpi on a 300 mesh...or insert S mesh. Bare with me for a moment here, I'm not referring to holding. I'm referring to SHAPE. There is a common statement that WAX is better and I'm here to say, WAX is great...and so is WET. I am not a believer that WAX is "better". Just different.
I used to ONLY believe in high end film image-setters but I've been convinced that it's not the shape that counts, it's the tone that is represented. Think about it. Sim and 4 color process can be printed with pixel squares (stochastic dots), Not even perfect squares. Many are more like (individual pixels hanging out on the outskirts of a a fade to 0%. We can print with mezzo tints, line patterns, etc. You pic a shape and you can print with it. So the fact that WAX can only put down little blobs is of no concern. It works.
Some low end RIP devises and auto sep programs are using 300 ppi bitmap halftone dots every day and the customers love the prints (regardless of how much we feel they are inferior). Some people prefer not to buy a RIP at all and will do theirs manually in Photoshop. I recommend 600ppi myself.
So how do I know that the true shape of a WAX device is not reproducing the same cross as a 1% (in a very high lpi)? Because I have had a few files (The tif files) from ripped images. They are simply a 600dpi tif image. The Wax devise used this to image onto the screen...but it does not reproduce it idential (or close to) identical as what is in the tif image. It can't. The wax itself is too thick in consistency (for the lack of a better word). Here is a WAX devise tif filed used to image onto the screen.WAX_DTS_halftone dots_720dpi_rez output...600 dpi printer_BitmapTIF_55-60lpi_small
So the WAX .tif file used is the same quality as the WET INK PRT file. The lpi dots are made up of 600dpi pixel dots in both. Both look chunky. The WAX device puts that shape down (less chunky) since it's wax consistency can't duplicate the smaller shapes exactly as in the file. THIS, is the "visual benefit" to the screen printer, but that's all it really is. An optical lie. It's not "better" or more superior. It's actually the opposite that is making the WAX owner think it's better. Does this matter? No. It's working. Good is good. Easy is easy.
The WET INK is more of an accurate reproduction of the 600dpi printer. Therefore, "looks less clean or less rounded and more "600 dpi pixel like.
If I'm wrong, I don't mind someone clarifying. This is what I've found to be true, but I can be mistaken and I'd rather learn that I'm wrong and find new or more accurate answers. Lastly, All of this detail, (the explanation), doesn't really matter. Doesn't matter if it's WAX or INK. They can both do award winning prints in the right hands.
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Dan, here's a question to you........
Does emulsion surface tension and RZ value effect the way the wet ink lays on screen?
From my testing emulsion surface tension has more to do with quality dots on mesh then almost anything else....... And from what I have seen surface tension and rz have little to no effect on wax dts but I dont know how many shops I've been in that switch emulsion and all of a sudden their ink jet dts cannot print worth a damn.
lets hear your thoughts on that as in my shop huge difference between wet ink and wax specifically because emulsion surface tension
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Dan, here's a question to you........
Does emulsion surface tension and RZ value effect the way the wet ink lays on screen?
From my testing emulsion surface tension has more to do with quality dots on mesh then almost anything else....... And from what I have seen surface tension and rz have little to no effect on wax dts but I dont know how many shops I've been in that switch emulsion and all of a sudden their ink jet dts cannot print worth a damn.
lets hear your thoughts on that as in my shop huge difference between wet ink and wax specifically because emulsion surface tension
Danny
Is emulsion surface tension measured in newtons like mesh or duromatur like blades?
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What he is referencing - as I understand - is the receptive nature of all emulsions to being directly printed on.
Some emulsions the ink will wick like crazy going all over the place - others the ink will stay right where it dropped - think water proof Vs. non waterproof etc.. inkjet film.
Within the wet ink direct to screen machines/families - the different inks used all have different results when hitting the screen. I personally saw more "dot gain" when we switched to t6 then with D2a. I needed to recalibrate my machine. The actual difference was up to 4%.
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Good question from Danny and I would say that Colin is correct.
What Danny mentioned, (RZ value), Is about the only KEY question where WET INK loses in comparison.
WAX ink, is not as sensitive to extreme or poor environment differences and processes. In other words, With WAX, you can relax your grip on process control more and allow your shops environment to be less than adequate. THIS, is good news to some people and more appealing to go wax.
For example,
RZ VALUE
* Your coating technique can be (too thin) causing the screen "mesh" to be more obvious with a vacuum like form fitting skin after it dries. That's too thin for good stencils in most peoples book, yet it's very common. People want to get away with the least effort in their screens. This will interfere with your stencil durability and quality, but you coat faster, dry faster and expose faster, but people like it. To point out that a good emulsion surface (good RZ value), a smooth surface was still desired back when using FILM POSITIVES. This smooth surface helps forma good gasket between the stencil surface and the substrate (garment) during production. This forms good side wall and image detail. Lower RZ (rougher surface where you see mesh thread shapes) are prone to permit ink being pushed out for the sides leaving some smearing or bleeding from one color into another.
Heat as I understand it is not normally an issue with WAX nor WET INK. Not too many people hit a re-melt stage in their environment. That has always made me wonder about people who expose on a metal halide with long exposure times on really low mesh, but I've never heard of it re-melting.
Since WAX is not affected by RZ value (as much), it wins in that category. Your screens surface can be of a lesser quality and that does not have an negative impact on dot imaging. To elaborate further and provide an extreme scenario as an example, It would be affected by the hills and valley's of mesh thread if in this extreme example, you can visualize a really low mesh like an 80 mesh where the dots (if you were to use dots on an 80 mesh) are not able to lay flat ...since there is no real flat surface on an 80 mesh with a fast coating of a 1:1 coat. The WAX dots would lay more at an angle as they land on and are formed on the side of an emulsion thread. That's about the only way were RZ value has an impact with wax.In this same scenario, WET INK would also from on the side. In general or in 95% of all cases where I had done installs or had came to a shop to provide assistance and trouble shoot in over 300 shops, any issues with the imaging onto screen, exposure, or dots on the surface were due to poor processes. Rarely if ever (in my experiences) was there an actual issue with someones emulsion. If there were, we would look at changing other ares to accommodate that emulsion. Having said that much on emulsion, there (were) some or one that just didn't do as well with the LED exposures). ;) That's another story. In fact, I don't recall ever suggesting to a customer that they cannot use their current emulsion myself, but I know when we do trouble shoot on the phones, that's one of the questions we ask, (what emulsion are you using), but that's more to understand the characteristics of that emulsion.
HUMIDITY
Another extreme scenario would apply with low humidity...where the air is too dry. People can work in a very dry humidity and never notice any affect (on themselves) that it's too dry. They just work though it and use lotion. With some older I-Image inks (K ink), was very sensitive to low humidity. It would leave a dull surface in solid black areas of say "bold type" and would even crack like a dry desert. If not exposed right way, you would see this in your washout. Again tho, this is in extreme scenarios. K ink was used widely with no ill affects while in some environments, they would not use it. They may have tried other emulsions that might have helped them in those cases, but in general it's not your emulsion but your environment.
HIGH HUMIDITY can be a problem as well. Since the ink is WET, if your emulsion stencil is still damp, (not dried well),or your humidity is way up, you can have your wet ink sort of (soak into) your soft stencil and fatten/spread and worse, become less defined. Again, tho, this negative that is found when using wet ink...is due to an extreme scenario in your environment...and not the ink. If you have these problems, the WAX will not be a problem and the issue (while still an issue), would go unnoticed as it pertains to imaging the screen. you will just have other issues further down the road with soft stencils during washout.
EMULSION TYPE
Like mentioned, I'm not aware of any specific emulsion that I could not get good results from using a WET INK. emulsion TYPE is not typically an issue or "your" issue. I would lean in other directions for finding answers to any specific issue. Changing to get better results would not be my suggestion (as it pertains to imaging onto screen and wash out). Some have different characteristics but can be worked with. For example, While out in the field, there was one emulsion that had a certain feel to it. I can only describe it as a velvet rubber. It was very sooth and provides a great surface. I believe it is in the Chromaline family. I didn't like the feel of it...but it worked VERY well. In fact, we use it now in our shop and we get great results. We print as high as 85 lpi in actual production and typically at 65lpi and burn plastisol and discharge screens coated 2:1 with an auto coater.
The answer is CORRECT, WAX due to it being WAX, is not affected by environment in the way that WET INK is. Know this tho, None of that is a negative about the WET INK. It's a negative about your specific issue in your processes or your specific environment that is affecting other areas such as the wet ink. It's like not having a dehumidifier in your drying room and then complaining that your screens take a long time to dry so you blame the emulsion.
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Dan, this is really really really helpful information, and i'm really excited you posted about it.
I would love it, if there were more references, specifically videos on how to test and measure things like EOM and RZ. Especially for dummies like me, where I understand the concept, but never really know if i'm testing it correctly.
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RZ (smooth surface) is more important with film FOR EXPOSING PURPOSES
RZ (smooth surface) is less important with wax CTS FOR EXPOSING PURPOSES except in extreme scenarios
RZ (smooth surface) is of middling importance with wet ink CTS FOR EXPOSING PURPOSES
i can see that.
but in my shop, the PURPOSE of a decent RZ is how it PRINTS not how it plays nice or not with various art on screen methods. RZ helps with exposing film, less helpful to expose wax dot. OK. But 90% of the function of RZ is printing not exposing.
am i missing something there?
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I know I'll sound like an idiot but I must of missed it what is "RZ"?
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RZ (smooth surface) is more important with film FOR EXPOSING PURPOSES
RZ (smooth surface) is less important with wax CTS FOR EXPOSING PURPOSES except in extreme scenarios
RZ (smooth surface) is of middling importance with wet ink CTS FOR EXPOSING PURPOSES
i can see that.
but in my shop, the PURPOSE of a decent RZ is how it PRINTS not how it plays nice or not with various art on screen methods. RZ helps with exposing film, less helpful to expose wax dot. OK. But 90% of the function of RZ is printing not exposing.
am i missing something there?
YOU ARE CORRECT.
Years ago, before it was semi-common to have DTS, the only reason we desired a smooth surface was for two reasons that I am aware of. Yes, in film. Most had light sources with light scatter, so the better the stencil surface, the better the contact. Thats why vacuum is important as well. This results in less scatter affect. 2ndly, is in production for contact to garment or in production to improve imaging to substrate/garment via a better gasket/seal from stencil to garment surface.
Now that we have these discussions about WAX or INK for example, it's possible for these examples/comparisons to get pushed towards favor of one or the other. In many cases in my opinion, some facts only apply in exaggerated or worse case scenarios. Similar to how one might say (This emulsion is no good because you can't run 100,000 prints on it without it breaking down). Ok, in reality, the typical shop can stop and load in another set of screens if it only last for 50,000 prints. Sure, it's "better", more profitable if you don't stop production, but most shops don't get these orders every day and the common emulsion they normally use might be jsut as good but perhaps you may stop and load new screens. It's a give and take or a decision as you get into many of these examples. It's common and not too costly to burn two sets of screens (just in case) on a 100,0000 piece order. A manufacturers may give you a worse case scenario fact as an example for every day production. It's selling point.
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I know I'll sound like an idiot but I must of missed it what is "RZ"?
Copied from google.
Rz[/size] is the average maximum peak to valley of five consecutive sampling lengths within the measuring length.[/color]
[/size]Basically, a measurement or appearance of the surface of your stencil. Smooth or irregular. [/color]
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Gotcha, Thanks Dan.
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What he is referencing - as I understand - is the receptive nature of all emulsions to being directly printed on.
Some emulsions the ink will wick like crazy going all over the place - others the ink will stay right where it dropped - think water proof Vs. non waterproof etc.. inkjet film.
Within the wet ink direct to screen machines/families - the different inks used all have different results when hitting the screen. I personally saw more "dot gain" when we switched to t6 then with D2a. I needed to recalibrate my machine. The actual difference was up to 4%.
I initially said you were right, and you still are, but there is more to that. As described in that book I wrote about it, the RZ value or what Danny was referring to is not just the emulsion "type" and characteristics, but also the way it's coated and dried or not dried. Ideally, there should be at least enough emulsion on each mesh type to provide a smooth surface. Ideally, the costing technique for a high mesh should not be the same for the lower mesh. You are looking for minimum of 10% and a max of 25% EOM and also looking for consistency as well. With that, comes a good RZ value.
Not everyone does this and a roughness, doesn't make it less durable. It just helps in other areas like forming a good gasket between garment and stencil. A good smooth surface also makes for a more visually appealing imaging onto the stencil from a DTS. I say visually appealing since a lesser quality stencil does little actual affect to the image quality of dots. Your stencils smoothness does not cause satellite dots or "scatter dots".
The impact of any wet ink in DTS on a screen for sim process at a typical lpi (55-65) on a typical high mesh (305)...is of little concern. Does it have any slight impact. I'd say yes, a minuscule affect. The surface would have to be extreme (and there are some out there), maybe 10% of all shops I had visited I'd guess were extreme. The more common affects is so little it's negative affects to wet ink are not visible to the naked eye and certainly not visible in wash out or print.
Smoother is better but not a requirement to burn good screens. I'd say medium to good is desired. You can burn screens and print jobs with very rough thinly coated screens (know as poor screen quality) where the mesh threads show up like waffle patterns...and still run an order. (I would not), but many do and just not as good. Like running your DTS at it's fastest settings for production. For typical jobs, (bold lettering), run it at it's fasted speed. You can still do 55lpi at fastest settings, but it's not as good as running is a bit slower for your finer detailed jobs.
Changing a DTS ink type can affect the gain, thus needing to adjust your curves in your RIP. A mechanical Re-calibration of the device actually does nothing to improve gain on the stencil. The difference will be a result of the chemical makeup of the ink or, (the thickness) of said ink.
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So, back when ink DTS was first introduced - there were more than a handful of emulsions that did not work with the system.
The ink would not adhere/dry/stay properly and there was running/pooling/lack of proper adhesion of the ink to expose a screen.
As I remember - and I could easily be incorrect - The emulsion manufacturers needed to adjust their formulas to assist with the grip of wet ink DTS.
Yes, peaks and valleys in the emulsion will make for an uneven wet ink image, but the emulsion still needs to accept the ink. Not repel it like oil and water.
And like you said, the thicker the ink used - the sharper and more precise your printed image will be.
Just another point of view :)
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So, back when ink DTS was first introduced - there were more than a handful of emulsions that did not work with the system.
The ink would not adhere/dry/stay properly and there was running/pooling/lack of proper adhesion of the ink to expose a screen.
As I remember - and I could easily be incorrect - The emulsion manufacturers needed to adjust their formulas to assist with the grip of wet ink DTS.
Yes, peaks and valleys in the emulsion will make for an uneven wet ink image, but the emulsion still needs to accept the ink. Not repel it like oil and water.
And like you said, the thicker the ink used - the sharper and more precise your printed image will be.
Just another point of view :)
Not to my knowledge. Never experienced any brands other than one brand that the DTS wet ink didn't work well with. That emulsion Co did modify their emulsion but were reluctant until they saw enough evidence that the WET ink and DTS was not going away and would make an impact on their business. Again tho, "other factors" may have been in play and were never known about or addressed at the time any of those other brands (multiple ) you are suggesting were having difficulty. Pooling/running/lack of proper adhesion are all part of environmental issues.