Does This Roll Contain Quality Web?

I was listening to a podcast about blind people learning to 'see' through echo-location. They make a clicking noise with their tongues and listen for the echo, forming a picture of distance, shape, and hardness of objects near them. Over time, they get quite good at this and can go on hikes by themselves, even ride a bike(!). (See Invisibilia podcast's "How To Become Batman.")

Measuring roll hardness is a little like this. When you start with this new sensing method (roll hardness or echo-location) you have to crash into and trip over things a few times until you know what the feedback is telling you. The more you do it, the more you know when your new sense is telling your something clearly or something mysterious.

The falling and crashing is important. For roll and web quality, roll hardness data alone has limited value. No one can tell you with only roll hardness data that the ideal average hardness is '70' or the hardness range must be between '60' and '80.' If they know your exact product and roll geometry and have experience correlating roll hardness to process waste (wrinkles, telescoping, etc.), then they may have some valuable recommendations, but you will have to form this correlation for your product and process. You have to learn to use this new sensing method and test it in the real world to find if it is helpful.

Measuring roll hardness is also like trying to figure out what is in a wrapped package. When you get a mysterious package or present, you'd like to know what is inside. The only true way to find out is to remove the wrapping, open the box, and see what it is, but sometimes we try to guess what is inside without opening it. You look at the dimensions of the box. You lift it to see how heavy it is and if it is heavier on one end than the other. You shake it to see what it sounds like, maybe even smell it. You may even pull back a little bit of wrapping paper to see if the outside of the box says what is inside.

With all this information, sometimes you can tell you are getting some clothing, a book, or a new LEGO set, but other times you still don't have much clue what to expect.

Roll hardness is like this. You are trying to guess what is in the wound roll's package without opening it.Roll hardness will never beat actually running the material, but over time, you can find it is a reasonable predictor. You can certainly know the difference between a package containing clothing, a book, or LEGOs. And you can do it without opening the box.

When 'opening the box' or unwinding and running the roll is expensive in terms of machine and operator time, raw materials, and even lost profits, then learning to use roll hardness as a predictor of roll and web quality can be a valuable practice.

Tim Walker

To learn more about me or TJWalker+Assoc., visit: www.webhandling.com or read my "Web Lines" columns at www.pffc-online.com/web-lines.


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