Stretch film snapping on the wrapping line is a costly issue for FMCG manufacturers.
- Snapping causes production downtime. Although each isolated event may only cause a short period of downtime, if it is happening frequently this can equate to a serios loss of production time each day.
- Snapping also causes increased wastage. Operators often discard rolls that are causing them issues without fully utilising them. This is why it is not uncommon for wrappers to have a stack of half used rolls next to each wrapping machine.
What causes snapping?
Snapping is most commonly caused by incorrect film to machine/load pairing.
There are three different places that a stretch film is likely to snap:
- Snapping on sharp edges or obtrusions on the pallet. This is often caused by a film that does not have the puncture resistance to cope with an awkward load.
- Snapping on the edges (uniform, smooth edges) of the pallet as the film is applied. This is often caused by too much wrapping tension (lay on tension).
- Snapping at the pre-stretch rollers in the film carriage. This is caused by a film which does not have the pre-stretch capabilities to match the machine gearing or pre-stretch settings.
How can you solve snapping?
- Reduce the wrapping speed.
By reducing the wrapping speed, the strain on the film is lessened which will reduce the likelihood of snapping. Wrapping machines and stretch films perform better at slower speeds as they have more time to adjust to changes in the pallet such as edges. However, it is an unpopular solution with operators and line managers as it will slow down production.
- Reducing the wrapping speed will slow down the speed of production.
- Reducing the pre-stretch.
Reducing the pre-stretch ratio will prevent snapping in the film carriage. By leaving more stretch in the film, it will also decrease the chance of snapping on obtrusions or edges.
- It is not always easy to change the pre-stretch ratio. The pre-stretch ratio cannot be changed on a fixed gear machine without replacing the gear set.
- Reducing the pre-stretch will increase the amount of film used to wrap each pallet. This will reduce efficiency and lead to a rise in cost per pallet and plastic waste.
- Reducing the wrapping tension.
Reducing the wrapping tension (also known as lay on tension) will leave more ‘give’ in the film. This will reduce the likelihood of snapping on obtrusions or edges.
- As with reducing the pre-stretch, reducing the lay on tension will increase the amount of film used to wrap each pallet.
- Increasing the thickness of the film.
Thicker stretch films usually have higher puncture resistance. This means that they are less likely snap on sharp edges or obtrusions.
- This should be avoided if at all possible as it is not a sustainable option because it will increase both the cost per pallet and the plastic waste.
- Ensure the right film is being used.
Stretch film is not a ‘one size fits all’ solution. In order to maximise efficiency and prevent snapping, the right film for both the wrapping machine and the load has to be used. For example, different machines have different pre-stretch capabilities and therefore it is important to ensure the film’s pre-stretch capability matches the machine’s.
- Nano films have a higher puncture resistance and performance than traditional films. This makes them well suited for wrapping awkward loads.
- Ensure the film’s pre-stretch capability is matched to the machine’s. Using a film with a lower pre-stretch capability that the machine is running at will result in snapping.
- Use cardboard corners.
Cardboard corners help to dull sharp pallet edges and therefore reduce the risk of the film snapping.
- They add additional cost to each pallet.
- Cardboard corners will not fit to every pallet and therefore their usefulness is limited.
- Check the film matches the specification.
A common cause of snapping is films that do not match the supplier specification. For example, the actual film pre-stretch capability does not match what is on the specification and therefore the machine is set up wrong causing snapping. It is also important to check the consistency of the film. For example, check that the film is a consistent thickness (it is not uncommon for the thickness of the film to vary wildly throughout the roll).
- Check the film is a consistent thickness and quality.
- Check your film performs as stated on the spec sheet (e.g. does it’s actual pre-stretch capability match the specified).
- Has the supplier recently change the film to recycled content? Due to imperfections caused by the recycled materials, this can often be a cause of snapping. The solution to this is either to revert to a virgin film or re-evaluate whether this particular recycled content film is right for the job.
- Ensure that rolls are not getting damaged.
Rolls of stretch film can be easily damaged. Dropping the roll, for example, can cause damage to the edge of the film which weakens it and increases the risk of snapping.
- Ensure pallets of stretch film are stored in a place where they won’t get damaged.
- Make it as easy as possible for operators to load new rolls to prevent damage during this process.