Paperboard Thickness Tolerance

[dgerharter]

We run a variety of heavier (80# and up) paper and paperboard, and we have recently had some print quality complaints that our pressmen want to attribute (at least in part) to bad paper.

Does anyone have practical information regarding the standard variation in paperboard thickness? I can certainly understand a tolerance for what can be called "12 point", but how much variation within a roll or lot should be expected? We sheet our own stock and thus have the opportunity to measure the thickness at several points across the web and during the sheeting run.

Before I take this any further, I would like to know what this fine group thinks. How much variation is too much? What are the likely signs of overly inconsistent paper thicknesses?

Thanks for sharing your wealth of knowledge!

dgerharter

 

[gordo]

Specifications for paper thickness (let alone paperboard) or any other criteria? You must be joking!

Not much of an answer but that's been my experience - even during discussions with members of TAPPI (Here's their website - just try and find a meaningful specification TAPPI)

gordo

 

[Packin'JP]

industry acceptance is +/- 1 point.
BUT, it always seems to be on the minus side. We order .020 we get .019

It's a shame you don't get what we pay for. I can never understand for the life of me why and how they get away with it.
If board mics more than 1 point we will refuse it, or ask for credit as if we would have purchased that caliber board.

 

[dgerharter]

Gordo - I know, I know... perhaps wishful thinking that we could get a specification that we could actually hold them to...

What I'm really interested in is if anyone can tell me how much variation they have historically experienced.

Packin'JP - The key issue for me isn't so much that paper specified as 12-point is actually 11.5-point, but how much variation within that roll might we expect?

As you all know, print quality and color consistency can be affected by caliper variation and the resulting change in impression - and because our customers are getting pickier and pickier about quality, we as a provider have to do a better job of managing our raw materials and suppliers. If a supplier provides me with a product which creates or even just contributes to incidents of "nonconformance" (by my customer's definition), I need to be able to hold them to at least the same level of accountability that my customers are holding me. I have recently begun to get formal requests for Root Cause Analysis/Preventative Action Plans or other ISO mandated vendor responses for issues which could be resolved by a phone call in days gone by.

Make sense? How can we as printers communicate this issue up and down the client/vendor ladder in a way that put the responsibility where it belongs? Or am I way off base here?

 

[dabob]

As it happens . . . one of my paper salesmen was just here and I asked him . . . his answer for 12 pt was plus or minus .001 inch - but have your salesman get you in touch with the mill rep and see what he says . . . stock run to "caliper" will be truer than run to basis weight . . .

 

[Colt]

Yes, I was told "+/- 1 pt." recently as well. We ordered paper that was rated at 4.9 pt. but got 4.5 pt instead. Our client didn't have to mic. the paper to notice a 9% difference (?) in color.

 

[dgerharter]

As it happens . . . one of my paper salesmen was just here and I asked him . . . his answer for 12 pt was plus or minus .001 inch - but have your salesman get you in touch with the mill rep and see what he says . . . stock run to "caliper" will be truer than run to basis weight . . .

I've already asked a mill rep, and he doesn't care to respond, other than to say the same thing your guy did - +/- .001 up to 20 point, then +/- 5% for thicker papers. So am I to take it that within a roll (or sheet, or however you buy your paper) you can have a variance of +/- .001"? That means if we specify 12 point, we should expect thicknesses from .011 to .013 across the same sheet of paper? That's a 18% total variation, on a product's primary specification. Imagine if we could spec a 18% variance in color! Then I would never have to write another corrective action again!

I'm not a pressman, but with customer expectations so high and press tolerances so tight nowadays (we can adjust the impression amount on our KBA 162 in .0001 increments) it seems that a variation across a sheet of .002" has the potential for larger problems.

Anyone care to comment? How much color variation is exhibited with a .002" variance in paper thickness? How can you even set impression if you have no idea what the thickest, thinnest or average calipers are in a stack of paper? Any ideas how a test might be devised to measure this?

 

[Colt]

Thought maybe you would appreciate a before and after show-n-tell:

See attached photo of same paper/different lots on a light table. Left side is 4.9 pt and the right is 4.5 pt.

 

[dgerharter]

Thanks for the photo, Colt, but when I mentioned a color variation I meant the color we print, not the color of the stock itself.
Because dot gain is influenced (in part) by impression, if the thickness of the paper varies considerably across the sheet, shouldn't we be able to measure the relationship between caliper variation and color consistency? That is, assuming the only variable in flux is the caliper...

 

[Colt]

Gotcha, dgerhalter.

Wouldn't it be great if you could the uneven sheets as uneven packing.

 

[dabob]

I've already asked a mill rep, and he doesn't care to respond, other than to say the same thing your guy did - +/- .001 up to 20 point, then +/- 5% for thicker papers. So am I to take it that within a roll (or sheet, or however you buy your paper) you can have a variance of +/- .001"? That means if we specify 12 point, we should expect thicknesses from .011 to .013 across the same sheet of paper? That's a 18% total variation, on a product's primary specification. Imagine if we could spec a 18% variance in color! Then I would never have to write another corrective action again!

I'm not a pressman, but with customer expectations so high and press tolerances so tight nowadays (we can adjust the impression amount on our KBA 162 in .0001 increments) it seems that a variation across a sheet of .002" has the potential for larger problems.

Anyone care to comment? How much color variation is exhibited with a .002" variance in paper thickness? How can you even set impression if you have no idea what the thickest, thinnest or average calipers are in a stack of paper? Any ideas how a test might be devised to measure this?

I'd file a mill claim, if the paper is responsible for a defect because its out of spec they will usually back it up - but you need to document the issues and keep records . . the same sales rep that told me the spec. also related this,

He had recently filed his biggest mill claim - $60,000 - it was a political postcard job and the sheet varied in caliper and the post office wanted to charge an additional $100,000 for postage due the difference. They reprinted it for less than the additional postage and the mill paid the claim for the reprint