Squeegee angle and pushing (vs pulling)

[Gilligan]

So I was reading Sunny's list of things "required" to get a great print and this got me thinking.

16.  Very high shearing force is needed to cause matte-down and a smooth surface

17.  High shear is ONLY possible with high stroke speed

18.  High speed is ONLY possible with minimum angle [or broadcasting and wet artifacts occur]

This discussion was mainly centered around automatics which of course "pull" the squeegee.  We print manually and therefor we push the squeegee.  So how does the squeegee angle relate when you switch?

My thoughts are that if you hold the squeegee up to nearly upright (like this --> /  )  then the actual angle where it translates to a pull stroke is pretty much the opposite.  It's like almost dragging the squeegee horizontally if pulling.  So one would need to push would a lot of angle to get the equivalent of a pull stroke that is nearly 90 degrees to the screen.

Issues I would think could arise is that now you are pushing the mesh laterally too much which could cause distortion?

I'm sure I'm off on some (most) of my line of thinking... could someone with a better theoretical understanding of all of this set the record straight for me.

[Printficient]

On the first press I ran (a Challenger in 1988-1991) the press ran the flood stroke toward the inside and the print stroke toward the inside (pulling) to you manual printers.  Now most auto's do that in reverse.  That is to say , flood to the outside and print to the inside (pushing).  As to the points listed they are print neutral. That is to say, that they are meant to be guidelines for either manual or automatic printing. When I manually printed, I pushed the squeegee.  Anytime I could on an automatic press, I printed so that the print stroke ended toward the outside of the press not the middle. This made for easier cleanup when you were breaking down the press.

[Inkworks]

I think I know what you're getting at Gil. When pulling a squeegee, deflection decreases pressure and angle of attack. When pushing, deflection increases pressure and decreases angle of attack. When pushing, laying the squeegee flatter increases the shearing ability, when pulling laying the squeegee flatter decreases the shearing ability.

I think the main reason that auto's don't print with a negative angle like pushing on a manual, is that squeegee deflection increases pressure and could be catastrophic if there isn't enough clearance to the platen as there really isn't any room to give.

[Gilligan]

I think I know what you're getting at Gil. When pulling a squeegee, deflection decreases pressure and angle of attack. When pushing, deflection increases pressure and decreases angle of attack. When pushing, laying the squeegee flatter increases the shearing ability, when pulling laying the squeegee flatter decreases the shearing ability.

I think the main reason that auto's don't print with a negative angle like pushing on a manual, is that squeegee deflection increases pressure and could be catastrophic if there isn't enough clearance to the platen as there really isn't any room to give.

Right.  Things are changed by pushing in the manner that you described and how does that effect what your angles should be to achieve what Sunny was talking about?

I wasn't trying to understand why autos don't push... I get that on various levels.  My question is how do you achieve the same "effective" angle when pushing.  What correlates to 10 degrees from vertical when pulling while you push?

Sunny, I wouldn't say that autos "push" just because the direction of the flow, it's more about the angle of the dangle.  They are moving the squeegee away from you but they are "dragging" the blade behind them vs pushing it in front of the holder.  Effectively pulling the squeegee towards the middle vs pushing it.

[Inkworks]

Just look at the leading edge of the squeegee whether pushing or pulling, and consider deflection. The squeegee angle is independent of the squeegee handle angle due to deflection. To get 45degrees pulling with a soft squeegee you may need the handle at almost vertical.


I pulled squeegees manually for 5+ years before I saw someone pushing and it was an eye opening experience. I can't remember the last time we pulled for a job. It's way harder on your body. Just like the first time I saw someone loading with the stack of shirts print side down.... D'oh I'd been doing it wrong for 5 years!

Auto's don't push because there is nowhere for the squeegee to go if it starts deflecting, it would immediately start applying more pressure, which would cause more deflection, which would cause more pressure.... until something gave. Think pole-vaulting.

[Gilligan]

So I should be looking at the squeegee in the "opposite" direction when thinking about our angle.

Look at the bottom of the blade like you would the side of the blade when pulling?  So holding  the squeegee at 45 degrees or even more horizontal would be acceptable?

[Binkspot]

I think you are thinking to much about this.

I have found the thicker inks, whites and poly's hold the squeegee more upright. Thinner inks you can go beyond 45 and still get a nice print. It's more of what feels better and produces the best results. As the day goes by if you start out pushing with the squeegee more upright as the day goes by and fatigue sets in the angle will change.

You are less likely to distort images with thinner inks, less pressure. Thick you can distort pushing or pulling depending how hard you are working it. Pushing too hard and steep angle you will start pushing the ink under the edge of the stencil causing a ghost image.

[Frog]

I think you are thinking to much about this.

I agree. I think that fifteen minutes of actual squeegee pushing and/or pulling could teach more than a lot of theory.

[Gilligan]

I think you are thinking to much about this.

I have found the thicker inks, whites and poly's hold the squeegee more upright. Thinner inks you can go beyond 45 and still get a nice print. It's more of what feels better and produces the best results. As the day goes by if you start out pushing with the squeegee more upright as the day goes by and fatigue sets in the angle will change.

You are less likely to distort images with thinner inks, less pressure. Thick you can distort pushing or pulling depending how hard you are working it. Pushing too hard and steep angle you will start pushing the ink under the edge of the stencil causing a ghost image.

I agree... BUT there is sound science behind it all.  If I knew that exactly 15.6 degrees and 15" per second was optimal then that is a target to shoot for BUT more to the point is that is an interesting topic of discussion.

One of the reasons I am seeking this "solid" information out is because my guy has a hard time remembering to ease up since we switched to rollers (high tension) screens.  He will THINK he's using light pressure but in reality it isn't.

If we have some semi-specifics to talk about then it's easier for him to understand what he "should" be doing optimally and he can see the differences in what he's doing.  Plus we may never think to keep trying something "too" extreme when that might actually be the way we should be trying harder at getting it right.  VS, well, that didn't seem right, don't do that again.

[Frog]

One of the reasons I am seeking this "solid" information out is because my guy has a hard time remembering to ease up since we switched to rollers (high tension) screens.  He will THINK he's using light pressure but in reality it isn't.

The simplest way to illustrate too much pressure probably is ink coming through the shirt. That gives him something more concrete to verify. Look at the inside.

[Gilligan]

That's what is telling him he's using too much... it's just hard for him to lighten up as much as is needed.

[Binkspot]

Again too much thought being put into this. It is more of a feel thing. You need to print the first shirt, look at the image and adjust accordingly to obtain the desired results. The key thing to remember is your not trying to mash the ink through the screen and into the garment but shear the ink off so the ink in the stencil remains on the garment. IMO it is more important to be able to trouble shoot and make adjustments on the fly then worry if you are using the perfect angle, speed, etc.

There is no exact science to screen printing, way too many variables. If there was an exact science anyone could read a book and do every job perfectly, there would not be a need for forums like this. I am a firm believer you should remove as many variables as possible but there will always be some and not to be afraid to try alternative methods. Manual or auto printing you will always be tweaking something, no way to avoid it. Every job, ink, screen, squeegee, garment, firm/light flood, etc will print differently. Do you use the same pressure, speed, angle, etc printing regular Wilflex cyan and Wilflex process cyan? Probably not, how about black ink as opposed to silver shimmer. Are all your screens, stencils, inks, squeegee's, ink temps, garment, mood, physical ability, etc exactly alike everyday, no so you need to adjust accordingly.

Take this as an example, 12 dark garments, 3 color with an under base. Set up and register the job. Under base a 70/30 mix of white and UB grey, nice full coverage and smooth, slow firm push stroke almost vertical. The green and blue dial right in, fast light push stroke almost 45 degree angle (late in the day getting lazy). The red is real close, a hair of under base is peaking out at the top with a fast light push again almost 45 degrees. So instead trying to play with reg you use a firm slower pull stroke to fill it in and the job comes out perfect. Lets take this a step further you set up the job, the phone rings so you ask someone else to run it for you and he/she prints a little different. Because they print a little different the green is now out a little so instead of push, push, push, pull they are doing push, pull, push, pull or maybe UB flash UB flash then top colors because they can not get the under base in one hit. All that matters here is the printers knew how to correct the problems and produce a nice looking product. Although the printing is generally the same everyone does it a little different. All the shops I have visited I watch how they are printing and try to apply their ideas to my shop, some work some don't but the desired end result is all anyone is looking for.

I know you are trying to come up with a "Standard" for printing but IMO you should be concerned with the printer being able to trouble shoot issues and be able to correct them.

[Gilligan]

I'm with you Brian.

When I meant "exact science" I meant that given if you KNEW all those variables there would be an exact "formula" to print that screen.  No, we will never know all those variables and won't even come close to controlling many of them to that level of needing to know to print by that formula... just overall understanding would help in us getting there, or even just trying things we might think of as "wrong".

You have to know the rules before you can break the rules, otherwise you are just winging it and will never be able to get very good or do something "right" (repetitively).

He has been experimenting and he's been watching a lot of videos in his down time.  We are about to do a year end review with him so we can reinforce this positive behavior and hopefully keep him on track.  He's been showing more initiative around the shop, so we'll bring that up as well and probably give him a small bump in pay and explain that it is because of that and see how that motivates him some more.

I've always personally thought it would be a bad idea to really lean the squeegee over when printing... but that is due to low tension frames and understanding how much that will push that stencil out of registration and cause ghosting.  But now we are getting a wave effect of ink rolling through the stencil that is causing ghosting.

Shifting to higher tension hasn't really solved our problems in a way, it's shifted them to different problems but the symptoms look very much the same so it's been hard to trouble shoot and it's kind of one of those things we you really need to stop and start all over from the beginning with a different understanding/approach to printing so we can see what is doing what to what as opposed to what we "know" was causing that problem before.