Shirtboards slightly crowned: How much warpage is acceptable on your platens?

[Itsa Little CrOoked]

No, don't tell me yours are PERFECT. They aren't. "Perfect" only exists in the theoretical, but I'll bet yours are flatter than mine. "Too flat to measure" any warpage is an acceptable answer, but plus or minus how much??....That really is my question.

I have a Hopkins (International??) 6/4 Manual Press. I print almost every day, and am entering my 4th year, full time.  I want to switch to all Newmans and need to fine tune my press.  My everyday platens are Action Engineering 16 X 18 X 1/4" Aluminum plate with a simple radius on all 4 corners.  They are crowned a few thousandths, left to right from the printers perspective. Front to back, not so much.

READ ON....

I straightened these ailing shirtboards a while back on a hydraulic press, a feat deemed difficult, and most likely futile, by the folks at Action, but I specialize in quirky repairs. (I also straightened 17 nearly crushed MZX tubes by yanking out the end caps with a dent puller, and ramming a homemade die through while hammering with various dent tools:  A sheet metal dolly of sorts--utilized daily by auto body technicians everywhere. Don Newman was dumbstruck by my story. Buy your used Newmans with caution....But that's another story!)

Anyhow, the GREATLY improved, flatter shirtboards worked nicely for a couple of years, but now have me thinking they aren't flat enough for 35 to 40 Newtons. Plus, they aren't even as flat as they were---post repair. Action Engineering was dead right about that part. 

Prior to my Hydraulic Pressing Excursion, the margins measured....oh.....35 thousands low, making a large image difficult to print. After straightening, they were flat enough that warpage was hard measure with my farmboy tooling. I use a 2' long aluminum spirit level and feeler gauges to verify my .030" to .035" crowning problem. After said hydraulic press work, no crown was measurable, at least with the silicone sheeting in place.  I could have stripped it off, but no thanks.  The backs can be measured via the same process, but not as well.  There is a CNC'd plate affixed to the platen backs to recieve the clamp, and that interferes.

I certainly can afford new platens better now than when we started in business, but I don't really wanna cough up 7 or 8 hundred if I don't actually need to.  (It may be my only option.)

Anyhow, HOW MUCH PLATEN WARP IS TOO MUCH for retensionables? I can press them flatter again, but they probably won't stay flat beyond 2 years under flash...that's my experience. They are probably 10 to15 thousandths out of spec.

Sorry this is so long winded. Anybody care to weigh in?

Thanks!
Stan

PS:  A crisp. new dollar bill is about 0.004" in thickness.

[alan802]

I've seen brand new pallets that were about 1.5 mm lower in the middle than on the outside and I would have sent those back.  I'm having a hard time visualizing 10-15 thousandths of an inch right now without any of my tools, but 1/32" out of true flat would be fine for 40 newton screens because I don't think your manual press is capable of holding the screen any flatter front to back side to side than that, no matter how great a manual it is. 

[blue moon]

this is the advantage of the honeycomb aluminum. I have used the dial indicator to level the press and our plattens are with a thousand or two (even after printing for few years). They do get nicked a little easier than solid aluminum, but nothing that causes any issues with the prints.

As far as what is OK, our press is within about 10-15 thousands of an inch. That's in relation to the squeegee travel. I've printed a freshly glued platten once and pulled it out of level to where it was out about 1/16th (about 60/1000th) and for the most part it was OK. As Alan said, 1/32nd (about 30/1000th) will probably be OK.

pierre

[Screened Gear]

This is what I like about this board. We have people that are just happy to be able to make a screen and print a one color design, then we have you guys. You guys talk about 1000ths of a inch as a concern. I think the levelness of the pallet (at that point) is really not as much of a concern as many other aspects of the process.

[ScreenFoo]

I guess it all depends on how many variables you have nailed down, right?   

Our auto platen *rubber* has low and high spots that are in the range of 15-20 mils--for most work they're great, but since the spots are random, process and sim process occasionally suffers, as well as one hits being difficult.

Although Pierre's making me think I should just rip that crap off, zero them out again, and try the platens bare for a season...

[Screened Gear]

I guess it all depends on how many variables you have nailed down, right?   

Our auto platen *rubber* has low and high spots that are in the range of 15-20 mils--for most work they're great, but since the spots are random, process and sim process occasionally suffers, as well as one hits being difficult.

Although Pierre's making me think I should just rip that crap off, zero them out again, and try the platens bare for a season...

Screenfoo,

You have a MHM with rubber? Or are they solid pallets with rubber?

[blue moon]

I guess it all depends on how many variables you have nailed down, right?   

Our auto platen *rubber* has low and high spots that are in the range of 15-20 mils--for most work they're great, but since the spots are random, process and sim process occasionally suffers, as well as one hits being difficult.

Although Pierre's making me think I should just rip that crap off, zero them out again, and try the platens bare for a season...

interesting, I often think how nice and forgiving it would be to have the rubber on our plattens! Hmmm . . .

pierre

[alan802]

I think you should put rubber on them Pierre, just give it a try that way you won't ever have that question in your mind that you could be doing something better. 

[ScreenFoo]

M&R, solid platens.  (but with plenty of OC adjustment room)
Alan's right on that Pierre--you never know what you might be missing till you try it. (hence my wondering    )

The only reason I debate is that I've jigged up weird loads and pocket prints with glass for many years--especially for doing one hits, and even with thin material and little give, I get excellent results with it.

I guess it depends on how you do it--soft platens with hard squeegees, or hard platens with soft squeegees or medium for both? 
Anyone who's done the neoprene cover for printing seams or zippers with a hard squeegee has probably had this debate, right?

One of the zillions of variables I often wonder about...

[Screened Gear]

M&R, solid platens.  (but with plenty of OC adjustment room)
Alan's right on that Pierre--you never know what you might be missing till you try it. (hence my wondering    )

The only reason I debate is that I've jigged up weird loads and pocket prints with glass for many years--especially for doing one hits, and even with thin material and little give, I get excellent results with it.

I guess it depends on how you do it--soft platens with hard squeegees, or hard platens with soft squeegees or medium for both? 
Anyone who's done the neoprene cover for printing seams or zippers with a hard squeegee has probably had this debate, right?

One of the zillions of variables I often wonder about...

That just explained alot. I am alway wondering why I have to use softer squeegees then others. I never thought about the pallets playing a roll in it. Atleast now I know the answer.

[tonypep]

If you want to see whether you platens are crowned or warped squeeze a little motor oil on them and place a sheet of glass on top....now you will see the deficiencies.

[Action1]

I guess it all depends on how many variables you have nailed down, right?   

Our auto platen *rubber* has low and high spots that are in the range of 15-20 mils--for most work they're great, but since the spots are random, process and sim process occasionally suffers, as well as one hits being difficult.

Although Pierre's making me think I should just rip that crap off, zero them out again, and try the platens bare for a season...

interesting, I often think how nice and forgiving it would be to have the rubber on our plattens! Hmmm . . .

pierre

Pierre:

We would happily send you a piece of the rubber to try on a pallet at no charge. The advantages of the rubber are numerous. If you do search on this site for soft top pallet rubber - you will find a great deal of information on the subject. The vast majority of people who have used pallets with and without rubber - prefer the rubber surface.

Erik

[Frog]

If you want to see whether you platens are crowned or warped squeeze a little motor oil on them and place a sheet of glass on top....now you will see the deficiencies.

So that's where those spots on my white shirts come from!

[RICK STEFANICK]

its all relative. how do your prints look? are you getting consistant pressure. are your screens toooo tight? what durometer squeegie are you using? whats the average print size? do narrower prints print better than wider? how hot are you running your flash? are you tacking enough? are you getting deflection?  bottom line is: pefectly true is great but are they effecting your quality and ability to do your jobs? if not keep your money.

[ScreenFoo]

I'm not disagreeing with you, by any means, Erik.  In fact, your suggestion sounds like a great idea--Pierre has all the gear to give an excellent opinion on transfer and dot gain improvements.