Loose Cores: Why do they occur and what steps can we take to fix?

Posted by Chase Corp Editor on Oct 15, 2019 1:00:00 PM
Chase Corp Editor
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How to avoid loose cores in binded tapes

Loose cores are an issue that can arise from time to time.  Primarily they can occur on tape products that are wound in a “pancake,” or flat configuration.  It is less likely to find loose cores in a traverse wound tape, but it is possible.  Unfortunately, this situation can occur, even if many precautions are made in production.

Based on supplying these products to the industry for over 60 years, we have found that this is one of the few problems that have proven very difficult to totally eliminate. We have performed extensive investigation and problem solving through our long-standing and well-established quality process, yet still encounter loose cores from time to time.

Over the years, we have identified a few causes of loose cores. Major contributors are tape tension, humidity, core construction, storage and usage, and general handling of the pads.

Variations in tape tension as the tape is being wound onto the core can create problems. As the pad diameter increases, our process provides for “variable” tape tensions in order to maintain a constant tension throughout the pad formation.  If the tension is too great, you will crush a cardboard core. Too light, and you have a loose pad, not just at the core, but throughout the pad, which is unacceptable.  The “potential cause” could be a machine set-up issue or a machine maintenance issue. Being aware of and recognizing this as a potential cause, we take all steps to prevent this from happening in our manufacturing process through operator training and machine maintenance, but it can still occur from time to time.

Related article: What Causes Loose Cores & How to Avoid Them

Core construction can also be a contributor to loose cores. Plain cardboard core constructions are subject to fluctuations in ambient humidity. If we produce pads in the summer, in a humid atmosphere, the core absorbs some level of moisture. If the pad is not used by a customer until later in the year, perhaps in December when humidity levels are lower, the core can contract and result in a loose core situation.  To combat this potential cause, we have evaluated the use of phenolic coated cores to prevent moisture from ingress into the cardboard. These tend to be more costly than standard cores. Over time we have tested and sourced an upgraded cardboard core that has improved resistance to water ingress. Another option is to use plastic cores, which do not absorb any moisture, but are not easily removed from the machine.  Over the years we have found that customers prefer some variation of a cardboard core due to the way the tape is used in their processes. Usually multiple pads are loaded onto the machine, and when one runs out, the next one is in place to continue the process. The empty cardboard cores can easily be cut off the machine to allow access to the next pad to be used and so on.

We do have the ability to provide plastic cores, but it is not a typical customer request.

If a customer is located in a geographic area where humidity is high or low, depending on the season, this can be a factor that affects the cores.  Based on this variable, the length of time that the product is in storage, and when it is used, may create a loose core.  Sometimes we see loose core customer complaints due to products being stored for an extended period of time from our ship date.  Using the product in a timely fashion vs. longer storage conditions may minimize the variation in moisture that the core picks up or loses, thereby decreasing the probability of a loose core.  Storage in a controlled environment may also help prevent variations in moisture in the cores.  We highly recommend materials not be stored in an area that is subject to cold temperatures.  This will increase the likelihood of loose cores.

Lastly, but important in preventing loose cores once in a customer’s plant, is the way the customer physically handles the pads of material when using them. We highly encourage that instructions be given to the operators and others handling pads that they lift and handle them from the outer edges, not from the cores.  Lifting the pad by the core is not the recommended method of handling and can result in pulling the core out of the material that is wound around it, since the whole weight of the pad is focused at the core and inner windings of the pad.

Despite being a recurring problem over the years, loose cores do not constitute a major quality problem for Chase Corporation.  In truth, we have a very low rejection rate for all our shipped products, even for loose cores, but as noted above, it has been difficult to eliminate them.

If you do encounter a loose core problem, let us know right away.  You can be sure that we will resolve the problem to your satisfaction. 

As a suggested fix should you receive a shipment and experience some loose cardboard cores and need to process the tape before it can be replaced, you may want to try a few drops of water on the core to see if there is enough moisture uptake in the core to improve tightness, or move the pad to a humid environment for a few days to absorb some moisture and improve the looseness in the core.  

The bottom line is that this is a historical problem about which we are aware and take all prevention measures. There are some variables, however, that are out of our control, which is why we haven’t been able to eliminate the issue.  We appreciate your understanding should this happen to be a reason for a customer complaint in the future, but you can be sure we will address it and rectify it promptly.

Topics: Loose Cores