Hagan asks:
We recently had a customer contact us in reference to issues in their automatic food packing line which they think may be related to the boxes. They are concerned that the finished surface of some of the outer liners is too porous and causing the suction grippers to lose their grasp of the sheet. They also referred to the boxes causing jams as being “fuzzy”. Their second concern is that occasionally their inline metal detectors are rejecting boxes for metal shavings. This happens after the product has been loaded into the box. Therefore, the package and the contents are rejected and dumped.
We don’t test for smoothness in-house, but we have contacted our paper supplier and asked for them the to provide test results for the rolls in question. Below are the results they provided.
| Roll | Smoothness | Porosity | |
| A | 374 | 18 | |
| B | 370 | 19 | |
| C | 345 | 22 | |
| D | 345 | 22 | |
| E | 339 | 28 | |
| F | 375 | 18 | |
| G | 356 | 25 | |
| H | 376 | 18 | |
| I | 381 | 14 | |
| J | 381 | 12 | |
| K | 381 | 12 | |
| L | 368 | 15 | |
| M | 345 | 23 | |
| N | 365 | 18 | |
| O | 378 | 13 | |
| P | 362 | 18 |
The porosity range between 12 and 28 seems to be quite a difference, but the supplier says that’s within TAPPI standards. We don’t have a good benchmark. With your vast background in the paper industry, do you believe the data provided above is in fact satisfactory results for both categories?
As far as porosity goes that does seem to be a bit of a variance between Roll ‘J’ and Roll ‘E’. The porosity does, as we would expect, coincide with the smoothness. The smoother the paper the lower we expect to see the porosity. The plant I was responsible for typically ran an average of 350 smoothness and a minimum of 16 for porosity. Even with the range of your examples, they do seem to be in tolerance.
The smoother the liner the better the grasp the suction cups are going to have. I would think it would take a rather porous liner to allow enough vacuum loss to lose the grip. However, I don’t know what that number may be. As well, it would make sense that a surface which may be “fuzzy” could lead to vacuum loss and loss of grip before the box was completely open.
Occasionally we hear of a bit of metal finding its way into the paper. End users, especially food and pharmaceuticals, take this very seriously. I assume at the customer’s plant there are no metal detectors prior to final inspection. It’s unfortunate that it’s not being found until the product has already been packed. At that point the paper/box has been through so many operations that it is possible the metal could have been introduced to the paper nearly anywhere, the paper mill, shipping, converting, storage and even the packing process itself. You mentioned [in and off-line conversation] that your supplier, as well as your own operation, was looking into the metal issue, reviewing operational and maintenance logs, and samples would be sent out for analysis. That sounds like a very good action plan and hopefully it will result in identifying the source. Please follow up and let us know what results you receive.
This points out how important it is to maintain good operational, maintenance, and service records of our operations. Not only can it help us prevent or reduce unscheduled and/or unnecessary downtime, but it can also help diagnose quality issues and sometimes help us pinpoint the source of the issue. Ralph
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