How to Measure Paper considering Variation and Humidity

#1
Paper is a critical component of our product with the variation and humidity of the paper being key inputs into our setup. There are some assumptions made during the setup but if the assumptions are wrong, the process is not optimal.

We are looking for ideas on how best measure a huge roll of paper for thickness of individual sheets as well as its humidity. Any ideas?
 
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Marc

Hunkered Down for the Duration
Staff member
Admin
#2
I can't personally help, but you might want to let people here know what your dimensions, variance and tolerances are.
 
#3
Paper used in electrical power application (as part of bushing condenser). The problem is the thickness of the paper and its moisture content impacts the winding process around the conductor. Even variation inside the specification causes waste by having the operator dial the process in for every roll entering the winder.

I would normally say measure by weight of the roll and calculate the paper thickness; however, the paper isn't necessarily dry. Not to mention, the cardboard tube in the center will have variation and same problem with moisture content changing its weight..
 

howste

Thaumaturge
Super Moderator
#4
#5
Thanks for the feedback. I'll take a look. I finally dug through a few layers of specifications and found the paper spec. One of our options is: .100 mm +/- .005 mm. the rolls are 120mm ID and 1000mm OD (max)...weight is 2700kg. The challenge is measuring a single sheet of paper to that level of accuracy. We are investigating taking a core and measuring multiple layers with some simple math.
 

normzone

Trusted Information Resource
#6
Well, I don't envy you this one. It's all very doable in theory, but it brings new meaning to the phrase " Well, it looks simple on paper, but ... "

:popcorn:
 
#8
Are you wanting to measure the paper thickness as it's being wound up on this roll? Is this heavy weight paper?

We make a thin-walled product in some of our processes-- I have considered measuring the thickness with air gaging as the material moves over a mill roller in the calendaring machine (36" wide). I considered using a series of ports across this web to get several measurement points (using calipers, only the edges could be measured). I haven't moved forward with it, because current methods seem to be sufficient, given the application and tolerances.

Of course a solution like this isn't portable/hand-held, but if you're looking to measure the product as it is being wound, you might look at it. My concept isn't perfect-- the variation in the roll itself and its orientation is going to add into the measurement error. Porosity of the paper might be a challenge, too, using air.
 

David-D

Involved In Discussions
#9
What is your underlying concern on the paper thickness? Is it roll-to-roll variation or within-roll variation? If the paper is consistent within a roll, but you're concerned about how this roll's thickness will affect performance/manufacturing, then your problem is "easier" in that you only need to measure at the outside and you can stack multiple layers, measure together, and divide (using a micrometer). Hopefully you can then adjust your process parameters accordingly (or control your input requirement more tightly). If you're concerned about variation within the paper roll, that's more difficult, especially since I assume you're feeding it at high speeds and don't want to stop periodically to measure (and change you're tension, etc).

If you need fast in-process measurement, that's going to be tough - perhaps some sort of laser micrometer? Perhaps some sort of laser and detector to measure attenuation thru the paper?

Good luck,

David
 

David-D

Involved In Discussions
#10
So I just did some quick math and you said your spec tolerance is +/- 0.005 mm which would equate to a bit tighter than +/-0.0002 inches. That means for a single sheet, it is asking a lot (too much) from a standard micrometer which might be +/-0.0001" and completely invalidates calipers. I'd also assessume that measurement area and force probably affect good measurements. You might want to see of there is an "official" industry standard on how to do the measurement and if it is specified for a single sheet or multiple at once.

David
 
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