Question from Kevin: Our maintenance department keeps postponing work on our stretch wrappers because they have higher priorities and feel the wrapper maintenance isn’t really needed. What happens if the wrappers aren’t serviced regularly?
Hi Kevin,
Happy Holidays to you, and thanks for sending in your question.
Would it surprise you to know you’re not alone? Stretch wrapper maintenance is frequently overlooked. Although wrappers contain moving and rotating components subject to wear, the consequences of that wear are often more subtle than with upstream equipment in your process. When upstream equipment doesn’t perform properly, quality control may detect product weights that are out of tolerance, misalignment can cause conveyor jams, or equipment malfunction could halt production altogether. When that happens, alarms sound, lights flash, and maintenance teams rush in.
Wrappers, on the other hand, usually receive attention only when they fail completely and bring production to a halt. I’m reminded of the old Maytag commercials where the repairman never had any work to do. I am here to tell you that those commercials were entirely a work of fiction. In reality, most plant maintenance departments are understaffed, overworked, and underappreciated. They are lucky if they can just keep all the machines operating, sometimes with nothing more than bailing wire and duct tape. In most companies, downtime is at a premium, so the actual “squeaky wheel” gets the grease and everything else gets pushed out.
Now that we understand the reality, let’s answer your question.
The purpose of wrapping a pallet is to prevent load failures during shipment. To accomplish this, there must be a clearly defined load containment standard in place. This standard specifies the wrap pattern, the number of wraps, the film weight, and the amount of unitizing force the stretch wrap applies around the load (force-to-load). In practical terms, it’s the “recipe” entered into the wrapper to meet your containment standard.
Before the film is applied to the load, it is stretched between two rollers in the pre-stretch carriage. It is further stretched as it leaves the carriage and as the load is being wrapped. Achieving a consistent stretch percentage is critical to meeting your target load containment. As the film stretches, its elasticity decreases and it becomes stiffer, requiring more force to stretch further. If there is insufficient stretch, then the film will allow the contents of the load to move during shipment. This excess movement leads to load failures.
When a wrapper is not properly maintained, both the pre-stretch and applied tension (defining the total amount the film is stretched) will diminish. The longer it operates without maintenance, the more it will degrade. The challenge is that wrapper wear isn’t immediately obvious, unlike wear on upstream equipment. As a result, issues often go unnoticed until you have load failures, your film usage spikes, or both!
The most significant wear occurs within the pre-stretch carriage, where the film is being stretched 200% to 300%. Worn components, such as belts, cogged pulleys, chains, sprockets, and keyways will reduce the speed differential between the infeed and outfeed rollers. The speed differential determines how much the film is stretched. In addition, the roller surface has a rough texture, which helps to grip the film as it’s being stretched. This surface will wear down over time, reducing its grip on the film.
Idler rollers route the film around the driven pre-stretch rollers and the greater the amount of wrap, the higher the grip, which provides higher achievable pre-stretch. When web breaks occur, the film can wrap around these idler rollers and must be cut off. If operators aren’t careful, knife blades can gouge the aluminum roller damaging it and creating sharp edges that can cause even more web breaks. These gouges can easily be removed with emery cloth if they are detected early. However, repeated web breaks often lead the maintenance crew to “work around” the problem by adjusting the position of the idlers. This reduces the amount of wrap around the pre-stretch rollers, which lowers film stretch, and most importantly, compromises load containment.
We understand the challenges your maintenance team face and offer a couple solutions.
First, we have a nationwide footprint of highly qualified Field Service Engineers who perform periodic audits and inspections to ensure your equipment runs at its peak performance. They can repair or replace worn components and make precise adjustments to ensure you are wrapping pallets that meet your load containment standard. This also allows your in-house maintenance team to focus on other critical equipment, making downtime more productive.
Second, we offer a sophisticated monitoring system that accurately measures all the parameters that affect your cost per pallet and load containment (including pre-stretch). The system alerts you immediately when something changes, such as machine component wear. This proactive visibility is part of the value we provide. We know you have enough on your plate, and when it comes to stretch wrapping a pallet, we can give you peace of mind.
Thanks for asking!
