Before You Went LED, What Were You Using?

[GraphicDisorder]

Has someone actually said they could for certain print a 2% dot on a shirt?  I missed that if so.

Yes the other Blue puppet was threatening to post pics of 2% on a Gildan or something... I hear there is a screen with 2% dots headed to Northern California for testing... stand by.. you might learn something

Which post? Quote it, I seriously missed it. 

[LoneWolf2]

I'm still trying to figure out how this became such a big pissing match   

[Screen Dan]

I'm still trying to figure out how this became such a big pissing match   

I'm not certain and I watched it happen apparently.  I've been a hawk on this thread.  Tons of great info...and at this point I'd love to see a proper 2% dot on your average 18 singles tee.  I'm not taking sides.  I'm here in the name of science.

[alan802]

When I speak of a 2% dot I'm talking about what's on our exposure calculator because I know our film is no longer calibrated properly.  I've got a lot of old imagesetter film and a few pieces of film from Exile (OYO) that are of much higher quality and calibration than what we're outputting on our old Epson.  I did some quick testing on Thursday on a few mesh counts and on the LED unit I couldn't get anything under a 10%, 65lpi on a 280.  I should have some time to play with it today and fine tune the burn time and I'm hoping to be able to get at least a 5% in the 65lpi column but with the test I did Thursday I'm not going to hold my breath. 

[blue moon]

We've successfully held the calibrated 4-5% dot at 55lpi on 330S mesh on the Vastex unit. Same thing with 3140 was holding 3%. BUT . . . . the exposure system was dialed in for the 3140 so changes in the RIP can be made to compensate for it. I am certain that with proper tools LED unit will expose 3%.

For anybody trying to see the calibrated 2% dot on a 305, it is not going to happen with ANY unit!!! As I understand, the physical limitation of the mesh is 3%. At that point the dots become too small to hold on. It would be possible to calculate the dot size and compare it to the opening size, but I'll take the expert's word on it. Anybody printing a 2% at 55lpi on a 305 and holding it is either not calibrated, on the wrong mesh or wrong lpi.

pierre

[ABuffington]

2% dots are smaller than the thread diameter in most halftone line counts, so the thread will block any dot even though my emulsion can image it.  Imagesetters have the best chance of capturing 2% dots, while most other methods except wax are too transparent a dot to image easily with ink jet methods where the 2% dot is formed by only a few small transparent pico liter dots.  The emulsion is capable, but vignette moire along the edge of a halftone fading into shirt will have moire stripes as it approaches these lower percentages.  At the other end (98%) like Pierre mentions, the dots fall off, or in some cases are imaged in the open area of the mesh and fall off immediately with nothing to adhere to.  You could try our 420 or 460 mesh if you really want to image every dot possible with image setter film.  Or if you have to image a 133 LPI 2% we do have Stainless 840 TPI at 16,700.00/yard!  We make incredibly high resolution screens for electronics, but hey these are t shirts we are printing!

Wasatch has a cool feature I haven't played with much, but would like to is you can tell the RIP to change to random stochaistic dots below a certain percentage. This can image a bit better due to random distribution of the dots.  This is common in UV printing where the entire yellow plate in CYMK can be entirely stochaistic while CMK are halftones. (Prevents dot stacking moire)  However I haven't heard of anyone trying this feature in Wasatch SP RIP for t-shirt printing.  I will test some positives today to see how that goes.  IMO a curved linearization of 5-95% dots is a lot easier to image in a t-shirt shop with common mesh counts.

Al 

[alan802]

I just shot 3 305's at various times with my least desirable emulsion (I'll reclaim and coat these same screens with my other 2, better emulsions) and wasn't able to get a 10% out with the 65lpi column.  I'll break down my results in a very simple way without going into a ton of boring detail, these are the basic, bare bones results in terms of halftones replicated on 305/34 roller frames stretched to 22 newtons.  I have a sample film from our Epson with 65 & 85lpi halftones from 0-100% and the Imagesetter film in 65, 85 and 100lpi, 0-100%, burned on the same screens and I'll give the results for both.  And I'm trying to keep it objective and only count the boxes that I got the VAST majority of the halftones out and in good shape.  I know there is some subjectivity involved in what one would consider a good box and a bad box but I'm doing my best to make it as fair and balanced as I can so we can deduct better info from the tests. 

65lpi, Imagesetter quality film, I'll give the range of halftones I was able to replicate.  Keep in mind this is my worst emulsion but we have to start somewhere and these are the screens I have so it's where we're starting.

45 SECONDS:
Imagesetter-65lpi=40-97%
                  85lpi=53-96%
                100lpi=75-94%
Epson-65lpi=23-90%
          85lpi=36-85%

20 SECONDS:
Imagesetter-65lpi=23-93%
                  85lpi=35-90%
                100lpi=57-87%
Epson-65lpi=10-90%
          85lpi=28-81%

12 SECONDS:
Imagesetter-65lpi=19-97%
                  85lpi=30-90%
                100lpi=49-87%
Epson-65lpi=15-90%
          85lpi=28-81%

I know this looks like a bunch of junk numbers and when I look at them it doesn't do much for me other than tell me that I need to try a new emulsion because this one isn't good enough.  And I might entertain a dual cure emulsion but PP emulsions are here to stay in our shop.  Only recently have I put even a second of thought in a dual cure due to the results we've always been able to achieve with our expo unit and PP emulsions.  But with our recent problems I am now thinking about things that weren't in my wheelhouse this time last year. 

I should have the HVP or Chromablue Test emulsion ready to test this afternoon.  I need to do a coat job today anyway.

[ABuffington]

In my tests here in the lab it is crucial that the D-max and EOM be as good as they can be.
When looking at halftones and EOM, an EOM of 6-7% is typical for graphics printing on 300+ mesh counts.
Textile companies tend to coat more EOM than this, often in the 15-30% range.  So if the emulsion thickness is far greater than the width of the dot
undercutting will probably occur.  If this was an ink jet halftone the D-max in lower halftone percentages is nowhere near as good as imagesetter film,
so less time is used and underexposure can result causing halftones to fill in with unexposed emulsion during development.

All exposures are a balance of film/image D-max, emulsion thickness and type, light source, distance to light, and mesh color.  You can only expose as long as the film's d-max will allow before burn through occurs, you can only image fine resolution dots if the emulsion thickness is geometrically capable of imagery without halation.  The light source plays a crucial part in how well halftones can be imaged, how strong the vacuum draw down is (DTS has a significant advantage here), age of the lamp, with time of exposure the area we use most.  Controlling the first ones as well as you can, followed by a time study helps in the quality of image on the stencil and prevents emulsion from breaking down before it should while holding "printable" halftones.  The reality is most dots below 5% can land in the wales of the t-shirt weave and never print due to nothing but air in the open part of the knit.

Al

[tonypep]

Don't forget the D-Min in your equation which the transparency of the fiml

[inkbrigade]

Man am I late to this party. We had (have) a 6K Trilight. I love the Tri-Light. It was one of the best purchases we ever made.

We bought a STE a few months ago that has LEDs for exposure. I don't feel like we have the LEDs dialed in with the Aquasol HV we use. For whatever reason we have to expose on almost the slowest setting to get the LEDs to expose the Aquasol HV.

Granted, no one has to tape up films anymore (except this week we're back to films again) we were burning more screens per hour with the tri-light.

We could have gotten the STEII (we just couldn't afford it) but since we're doing a pure photopolymer I didn't think we'd need it. I guess I was wrong. 

[Dottonedan]

We've successfully held the calibrated 4-5% dot at 55lpi on 330S mesh on the Vastex unit. Same thing with 3140 was holding 3%. BUT . . . . the exposure system was dialed in for the 3140 so changes in the RIP can be made to compensate for it. I am certain that with proper tools LED unit will expose 3%.

For anybody trying to see the calibrated 2% dot on a 305, it is not going to happen with ANY unit!!! As I understand, the physical limitation of the mesh is 3%. At that point the dots become too small to hold on. It would be possible to calculate the dot size and compare it to the opening size, but I'll take the expert's word on it. Anybody printing a 2% at 55lpi on a 305 and holding it is either not calibrated, on the wrong mesh or wrong lpi.

pierre

It's all relative to your specific device and setups. I'd guess that 90-95% of the industry produces printed apparel without a densitometer calibrated halftone LPI because of the cost to get one and the fact that they have been selling printed apparel without one for years. That doesn't mean what they print for halftone dots is truly correct, just well enough apparently.


Also, note that even with a densitometer, those calibrate (tone) accuracy and not size of dot accuracy. For example, an accurate calibrated 2% tone can still have a huge dot such as in a 20lpi. One mans 2% in a 55lpi is not the same as another. There will be people who can hold a 2% dot in a 55lpi on a 305 mesh (with their device). Of those, their dot is larger or closer to a 3% in another device.


RE: Abuffington on the digital Dmax (as it pertains to DIGITAL from DTS from what Iv'e seen). Our picoliters laid down over top each other to form that 2% dot can be made with varying options.


* 1, 2 or 3 head that contributes to Dmax
* You have the ink/output resolution 1200x1200, 1200x900, 1200x600 etc. that contribute to Dmax.
* print speed.
* Uni or Bi direction.
* INK TYPE. Ours is already very solid/opaque despite the other contributing factors above.


All of those contribute to an excellent Dmax. At the same time,  some of those can also contribute to additional gain at output. Therefore, we already build in a standard 80/60 curve at install for basic prints. Think 45lpi. As you go up in line count, you want to open those shadow tones up a little in your curve to compensate for gain in the shadow tones. as line counts go up, shadow tones get smaller and (closer) together.  Someone who has a 1 head that likes to print 65lpi, will have one curve adjustment while someone who has 3 heads printing 65lpi will have another gain adjustment.  This is yet one other reason why one curve for one shop does not work best for another shop.


These curves (without calibration) using a transmissive densitomotor are all just a (hypothesis) until you have them calibrated on press. We do not calibrate (using a transmissive densitomotor). We calibrate our machine for various print speeds/heads and confirm alignment etc.. Everything after that is up to the customers as each customers shop and gain is different.


Each imaging device (Wet film imagestter, Digital film, Laserwriter, DTS) comes with some form of image adjustment options internally but many printers are not designed or intended for single color B/W (solid) output with halftone conversions in mind. For those, you must get a RIP to do halftones. Those various rips output on their own a halftone dot sized by line count. They do not compensate by default for the TYPE of printer device it is coming out of.


The sharp sides (smoothness) of each dot or edge of the curve on the letter S, is determined by the devises output resolution. 300, 600, 1200, 2400 dpi etc.   While early on, for myself I had always preferred the Wet film imagestter at the highest rez I could get, it was not needed for apparel. 600-1200 dpi (output) rez is fine.


A very high line count (in the mid tones or 20-80%) is very beneficial. The finer you can hold the small dots, the better but there is a point where it is not feasible such as trying to hold 1,2 and 3% dots in production as some such as Pierre has indicated. Still, you should have a goal of holding the smallest as best you can and then the most important part is to (know what that is) so that you can prepare your art accordingly. High LPI produces a beautiful tone and blends verses chunky dots. The higher the lpi, the thinner the ink should be up to a point. Blends are easier to achieve but so should the other needed elements be in place such as mesh tension, high mesh, thinner EOM, proper printing methods etc.  This is why some may not be able to hold the 2% dot even if they had a machine that could give it to them. Many factors must fall in line.


As a theoretical comparison, back in the day, I was holding a 3% dot on 55lpi (using wet imagesetter film) at 2400dpi on a 305 mesh. The mesh brand was SATTI but I don't remember thread diameter. Compare that size to something of today from the typical digital film and that dot size might be similar to your 3% in a 70lpi and many would not be able to output it let alone hold it in the screen nor print it with your average inks.  Comparing again, the hardest case scenario considering 3 head and heavier ink coverage for fast production using DTS at it's average dpi output, the 3% 55lpi dot might fall close to your typical results of a digital film printer if not 4% without some form of compensation. This is why the need for a densitomotor exist.


It should be said, that the (size) of the 2-3% dot (based on output device) is not as important as can you hold it on press with your other variables. Having a goal of shooting for the smaller 2-3-4-5% dots and learning what is needed/how to get there to increase your ability to hold smaller dots (no matter the lpi) can only make you better than proving you are comfortable with the 7-10% dot. You are losing more art information somewhere on some of your jobs if not.

[blue moon]

We've successfully held the calibrated 4-5% dot at 55lpi on 330S mesh on the Vastex unit. Same thing with 3140 was holding 3%. BUT . . . . the exposure system was dialed in for the 3140 so changes in the RIP can be made to compensate for it. I am certain that with proper tools LED unit will expose 3%.

For anybody trying to see the calibrated 2% dot on a 305, it is not going to happen with ANY unit!!! As I understand, the physical limitation of the mesh is 3%. At that point the dots become too small to hold on. It would be possible to calculate the dot size and compare it to the opening size, but I'll take the expert's word on it. Anybody printing a 2% at 55lpi on a 305 and holding it is either not calibrated, on the wrong mesh or wrong lpi.

pierre

It's all relative to your specific device and setups. I'd guess that 90-95% of the industry produces printed apparel without a densitometer calibrated halftone LPI because of the cost to get one and the fact that they have been selling printed apparel without one for years. That doesn't mean what they print for halftone dots is truly correct, just well enough apparently.


Also, note that even with a densitometer, those calibrate (tone) accuracy and not size of dot accuracy. For example, an accurate calibrated 2% tone can still have a huge dot such as in a 20lpi. One mans 2% in a 55lpi is not the same as another. There will be people who can hold a 2% dot in a 55lpi on a 305 mesh (with their device). Of those, their dot is larger or closer to a 3% in another device.

the 20lpi was never part of this conversation!
if you take a look, you'll see that I SPECIFIED 55lpi and 2%. This creates a dot that has to be very specific in size and can be recreated anywhere in the world, by any piece of equipment and if it is 2% and 55lpi it will ALWAYS look the same!

Anybody can print any size they want and as long as the print and the printing works out OK, nobody needs a densitometer. Some ppl have a 2% dot in their art file, but when they actually develop the screens, it's 7%! They just held a 7% dot, not a 2% dot. BUT as soon as you start saying that you can hold a 2% dot at 55lpi, that means only one thing.

Also, holding a dot means (at least in my book based on what I was told) all the dots in that range have opened or cleared. By that definition, it is not possible to hold a 2% dot on the 305 as it is thinner then the mesh and will be lost when it lands on it.

pierre

[blue moon]

We've successfully held the calibrated 4-5% dot at 55lpi on 330S mesh on the Vastex unit. Same thing with 3140 was holding 3%. BUT . . . . the exposure system was dialed in for the 3140 so changes in the RIP can be made to compensate for it. I am certain that with proper tools LED unit will expose 3%.

For anybody trying to see the calibrated 2% dot on a 305, it is not going to happen with ANY unit!!! As I understand, the physical limitation of the mesh is 3%. At that point the dots become too small to hold on. It would be possible to calculate the dot size and compare it to the opening size, but I'll take the expert's word on it. Anybody printing a 2% at 55lpi on a 305 and holding it is either not calibrated, on the wrong mesh or wrong lpi.

pierre

Still, you should have a goal of holding the smallest as best you can and then the most important part is to (know what that is) so that you can prepare your art accordingly. High LPI produces a beautiful tone and blends verses chunky dots. The higher the lpi, the thinner the ink should be up to a point. Blends are easier to achieve but so should the other needed elements be in place such as mesh tension, high mesh, thinner EOM, proper printing methods etc.  This is why some may not be able to hold the 2% dot even if they had a machine that could give it to them. Many factors must fall in line.

THIS! Get your stuff calibrated and test to see what you can hold. With that knowledge, as Dan preaches, you will know exactly what you can and can not print and what will be the issues on the press. Calibration helps to have an intelligent conversation with another person allowing the dots to be compared (or we might be comparing apples to oranges). If you don't care to compare, work of your own system, but in the end it is much better to measure properly.

And the example I often cite is the need for 4% magenta in 4CP in order to print gold jewlery or medals. If you can't hold a 4% dot, your gold will be all yellow and not look right. So learn what your limitations are, drop down to 45lpi if you need to hold a 4% dot and print the gold medal order!

pierre

[jvanick]

Getting a densitometer, using it, calibrating our curves to our press, and learning what variables affect that curve during printing (which we're still learning, to be honest), has been huge to my quality of printing, and quality of knowing what it's going to look like at output vs on the screen.

We've done some single-screen discharge printing here recently that I would have said that I couldn't print done just 6 months ago... and now, while I wouldn't say easy-peasy, is certainly not only do-able, but makes some of our more cost-sensitive customers VEYR happy.

It's amazing what you learn when you start looking at the dots and realize that you don't really have to adjust the art to make it look great on press...

*staying out of the LED discussion, as when it really comes down to it, all I care about is solidly exposed screens... 18 seconds, 60 seconds or 75 seconds... it's still faster than I can image a screen, or rinse it out...  if you can image a screen faster than you can expose it, I guess then it might mater.

[alan802]

Got 3 more screens with Chromablue'ish emulsion, results aren't as good as I was hoping.  305's again, 15%EOM/R on the 30 & 7 second screen, 14% for the 15 second.  8 microns on two and 9 microns for the other.

30 SECONDS:                                         15 SECONDS:                         7 SECONDS:
Imagesetter-65lpi=31-97%                      Imagesetter-65lpi=28-97%      Imagesetter-65lpi=15-93%           
                  85lpi=53-96%                                        85lpi=48-90%                       85lpi=18-90%
                100lpi=71-94%                                       100lpi=62-87%                    100lpi=40-83%
Epson-65lpi=28-90%                                       Epson-65lpi=23-90%             Epson-65lpi=washout
          85lpi=44-85%                                                85lpi=36-81%                       85lpi=washout

I finally got to see MAJOR differences (there were many already but this was not so subtle) between the imagesetter film (great D-max, very good D-min) and our Epson film.  The 7 second exposure really showed how really good film can make the difference. The Epson section didn't hold up and half of it washed out without much effort.  I guess I could have babied it and held a lot of the detail but I'm trying to not do that with this test and spray them out just like it's any other screen. I sure wish I had a Techstyler the last few years.  But I can't wait to get even better exposures with CTS.