chasing my tail...squeegee angles, pressures, and stroke speeds

[alan802]

It won't put excessive pressure on the pallet or substrate if you use the air pressure regulators to set your pressure.  If your squeegee blade is touching the pallet then what do you have to use to regulate how much pressure is being applied?  Your air pressure regulator.  My squeegee blades are going to touch the mesh just hard enough to overcome the mesh tension and off contact with the pressure I set it at.  Just because they'll technically travel further without opposite force doesn't mean I'm applying any added pressure than if I used the squeegee distance to regulate pressure along with the air pressure.  Look, either way can work, but I prefer to only have to change one setting instead of two to get the exact same results.

Foo, not very hard at all, but what does that have to do with transfering a thick, tacky ink through a woven mesh with tiny tunnels along with tension and off contact?  The transfer is technically a capillary action but there are many outside forces/variables to overcome right?  I wish screen printing were done with the forces needed to get ink on your finger, that would be great.

[Du Manchu]

It looks like I kicked a beehive with this post.  Thanks for all of the input.  I absorbed and took what I could back to the print job today and had much better results.  Below are some changes and observations regarding my inability to get a good print with one stroke (black on white)

*Stencil was too thin.  Went up to a 160 screen, coated, dried, and recoated and got a nice thick stencil.
*I messed with the squeegee depth and off contact  extensively, but could not get a good print to save my life with one stroke. Finally, I just added squeegee depth to the point of deflecting the pallet and hit it twice, which was screenprinters123 advise (and former owner of the press)..."to  just get the job out the door".  However, I can only assume that a double hit of black on white is ridiculous.  I'll be revisiting this on some other jobs this week, so I's still open to new suggestions.   I am guessing that the static frames tensions (lack of)  aren't helping my situation either???

Thanks for the clarification Alan802.  I can wrap my brain around cranking the barrels down and and work on mastering the pressures only for now.   

[Screened Gear]

Stay with it. It is not easy in the beginning. I consider myself really good at problem solving and it took me a long time to figure my press out. I had high expectations of my press. I was a really good manual printer so when my auto was not printing perfect it pissed me off. I made changes and it did nothing. I couldn't get enough ink on the shirt. I tried everyone's settings and some did a little better but still looked like crap. I had no experience with an auto so it was all new. I was so frustrated that I stopped messing with it in the first month and just printing jobs on my manual to get them out the door. It sat for weeks. I finally had a large job that I had to use the auto for. I talked to some great guys that have the same press and worked out enough of the bugs to get it printing well. Not great but acceptable for me. Latter I figured out I was printing with way to much pressure and printing too slow. I made those adjustments and it was like a light switch. Everything started working. I still have issues but I can figure them out in mins now. Good luck.

[ScreenFoo]

It won't put excessive pressure on the pallet or substrate if you use the air pressure regulators to set your pressure.  If your squeegee blade is touching the pallet then what do you have to use to regulate how much pressure is being applied?  Your air pressure regulator.  My squeegee blades are going to touch the mesh just hard enough to overcome the mesh tension and off contact with the pressure I set it at.  Just because they'll technically travel further without opposite force doesn't mean I'm applying any added pressure than if I used the squeegee distance to regulate pressure along with the air pressure.  Look, either way can work, but I prefer to only have to change one setting instead of two to get the exact same results.

Foo, not very hard at all, but what does that have to do with transfering a thick, tacky ink through a woven mesh with tiny tunnels along with tension and off contact?  The transfer is technically a capillary action but there are many outside forces/variables to overcome right?  I wish screen printing were done with the forces needed to get ink on your finger, that would be great.

True, the force required is far higher to load and print the stencil with thick tacky ink, but you want that extra force is to overcome the viscosity of the ink, not to transfer unneeded force to the platen, right?   What I was getting at was that if you are 'filling' the stencil properly, all you need to do is get the ink to touch the substrate, and shear the ink properly, and the layer of ink will be on top of the shirt, instead of in your stencil. 
If you were to achieve a good print with no platen pressure on textiles, you'd still have to crank it up or you wouldn't get a very good mechanical bond with the fibers of the shirt--and with a thick tacky ink, you'll need more extra pressure to penetrate the fibers of the garment for that bond.

I'm trying to bounce the ideas around because I ignored all the theory to start, not realizing how much easier everything can be if you identify and control all the variables you can--Jon's story sounds quite familiar to me.  When I started automatic printing it was with people who were well convinced they knew how to print on an auto properly--they got results, but when they didn't get lucky, they used 'band-aid' solutions, reducing ink, adding excessive pressure, double stroking, etc.  With any luck, Dewey won't waste as many years as some of us have. 
(BTW, I don't know about kicking beehives, hopefully no one's getting stung.  It's more like rattling cages    )



   

[Du Manchu]

Long day(and night) on a 3 color, 40 piece job!  Thank goodness I sold my manual press before I printed my first job on the auto, because I would have certainly resorted to it this week!   Below is what I learned:

*the big revelation: soft screen require much more off contact! (I was focusing on the setting my predecessors used, but realized they were 100% roller frame shop.  My statics  frames are probably half the tension.

*Thick inks need to be reduced

*Barrels up, adjust pressure, don't sweat the pallet defection.  (although I still feel as though I am printing with too much pressure, as the squeegees is rolling under a good bit......work on that later)

*Slowed my stroke speeds on some half tones, which I could not hit twice due to muddy-ing it up.

*Rookie mistake...Thin, cheap 5oz tees print differently than 6oz.  (without thinking, I keep pulling and mixing 5 & 6oz. scrap shirts for test prints, when in reality, the final shirt would have printed fine at some settings)

*Rookie mistake...one had better take the extra time at the washout both and make sure the half tones are good and clear.  (still not totally sure if the better choice for a larger area of halftone is a 196 or 160 screen.  Reburned and went down to 160, and had success. 

Heading to the shop now for a 450pc white on navy job.  Hoping and praying for a productive day!

Thanks to all for the advise and support.

Dewey

[Printficient]

Long day(and night) on a 3 color, 40 piece job!  Thank goodness I sold my manual press before I printed my first job on the auto, because I would have certainly resorted to it this week!   Below is what I learned:

*the big revelation: soft screen require much more off contact! (I was focusing on the setting my predecessors used, but realized they were 100% roller frame shop.  My statics  frames are probably half the tension.

*Thick inks need to be reduced

*Barrels up, adjust pressure, don't sweat the pallet defection.  (although I still feel as though I am printing with too much pressure, as the squeegees is rolling under a good bit......work on that later)

*Slowed my stroke speeds on some half tones, which I could not hit twice due to muddy-ing it up.

*Rookie mistake...Thin, cheap 5oz tees print differently than 6oz.  (without thinking, I keep pulling and mixing 5 & 6oz. scrap shirts for test prints, when in reality, the final shirt would have printed fine at some settings)

*Rookie mistake...one had better take the extra time at the washout both and make sure the half tones are good and clear.  (still not totally sure if the better choice for a larger area of halftone is a 196 or 160 screen.  Reburned and went down to 160, and had success. 

Heading to the shop now for a 450pc white on navy job.  Hoping and praying for a productive day!

Thanks to all for the advise and support.

Dewey

In reference to screen selection for your halftones, the formula is line count x 3.5-5.  example: 45lpi x 3.5= 157.5 or a 160.  This would be the hardest mesh count to hold the dot.  45lpi x 5= 225 or a 230.  This would be the easiest mesh count to hold the dot.  Most use 4.5 as the multiplier.  One other thing regardless of the mesh count, holding a consistent dot of 10% or lower is very difficult.  I recommend a tonal range of 20%-100%.

[tonypep]

That last part is untrue. A reasonably skilled shop should easily hold a 5%. Many can capture 3%. If you can't get below 20% you're going to get  pretty crappy results. For discharge halftones we are holding right at 5% consistently without even trying.

[alan802]

We can hold a 5% with crappy pure photopolymer emulsion.  We don't use dual cure very often but I'm sure if we can hold 5% with PP then we can do better with a dual cure.

[tonypep]

Correct Alan. FYI we use a diazo due to all the DC printing. Slower but awesomer.

[ScreenFoo]

Dewey--Good to hear you got good some good results.  With the thicker inks, and more off contact, another thing to try would be pushing the floodbar down further--as long as the index doesn't bump the platens up and hit it (read: split screen) you can sometimes get much better results with the floodbar pushing into the screen a good bit.

As far as % goes, I've heard of people holding 5% without a vacuum--although I'm inferring we're all talking about the standard 45-60LPI that goes on in most shops. 

If we were talking 5% at 100 LPI, that would be pretty amazing to consistently hold. 
If I'm not mistaken, a little number crunching places that (with a round dot for sake of EASY math) right around 35 microns...