Rules for perfect bags palletising

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Europack at Interpack 2023
March 9, 2023
palletising line for pet food bags
Palletising Pet Food bags
April 14, 2023
Logo Interpack 2023
Europack at Interpack 2023
March 9, 2023
palletising line for pet food bags
Palletising Pet Food bags
April 14, 2023
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Rules for perfect bags palletising

The bags tend to be a difficult product to palletise, as by nature of the products packed inside, they tend to deform if handled incorrectly, compromising the final quality of the pallet. There are several elements to take into consideration, but we can mainly summarise them in 2 macro-categories:

1. Type of packaged product (dusty, granular)

2. Type of bag / bagging technology

1). Let us start with the first category:

PALLETISING OF A POWDERY PRODUCT:

This type of product is mainly packed in valve or open-mouth bags. We are talking about products such as flour and pre-mixed chemicals (e.g. cement). In this case we prefer a belt conveyor over a roller conveyor (square rollers) and the use of a pressure roller. In addition, Europack's fork gripping heads for sacks are equipped with a special pusher and side bulkheads that allow for additional adjustable pressing once the bag has been placed on the pallet. This technology can form compact, homogeneous layers without protruding outside the pallet and with excellent vertical shape development.

PALLETISING A GRANULAR PRODUCT:

Most granular products are packaged in plastic bags formed from a tubular reel (VFFS). We are talking about pelleted products, such as wood pellets or animal feed, or in granules such as plastic granules or fertilisers. But also in polyethylene bags or raffia for food products such as grain. In this case it is advisable to handle the product inside the bag (in order to distribute it uniformly) by means of square roller conveyors and, if necessary, to carry out subsequent levelling by means of a roller. Also in this case, the Europack bag gripping heads are equipped with a special pusher for layer compaction, and the customisation of the jaw width ensures a high quality of bag handling.

2). Let us now move on to the analysis of bag types:

VALVE BAGS:

These are prefabricated bags with an internal or external valve that can be welded using ultrasound. They are usually paper bags and are used for packaging powdered or granular products (flour, premixed products, cereals, plastic granules, pellets, fertilisers, etc.). Thanks to the valve system, the bag can be filled with a multitude of equipment (manual, automatic or semi-automatic) and sealed once filled. This type of bag lends itself to automatic palletising because of the compactness achieved by the valve closure. The bag once filled is stable and compact and by means of a belt conveyor and a roller-pressor in the same, an excellent bag can be prepared for palletising. The layer will be flat and compact without any particular curvature as it grows in height.

OPEN-MOUTH BAGS:

Prefabricated open-mouth bags are among the most popular packaging in the world as they allow the consumer the possibility of opening and closing them several times. They are closed by means of an automatic or semi-automatic sewing machine, are usually made of paper or raffia depending on the product they contain and are mainly used to package animal feed, seeds, fertilisers. The automatic palletising of these products is mainly influenced by two factors: 1) the filling level of the bag; 2) the height of the seam. These two factors determine the level of compactness of the bag and the possibility for the product to move within it. In this case, the handling of the bag must be additionally precise to ensure optimum palletising quality. It must therefore be taken into account that the product is accumulated towards the feed side and must be adequately flattened, while keeping the bag mouth unloaded for possible overlapping during palletising. This latter necessity is due to the fact that usually the measurements of these bags do not fit precisely into a palletising scheme and the unloaded mouths need to be overlapped.

VFFS BAGS

Polyethylene bags formed from tubular reel differ mainly in that they are not prefabricated products but are directly formed from a reel of film. This is stretched, welded at the bottom forming the bag and once the latter is filled with product, it is then sealed in the upper mouth. It can contain any powdery or granular product (plastic granules, pet food). They are mainly used for packaging chemical products, such as granular fertilisers or plastic granules. The granular nature of these types of products requires careful flattening before being handled by a palletising robot, as explained above.

For bags that are more difficult to handle, the bag flattening station comes to our aid. This device is our best friend for handling any type of bag. It is a device consisting of two belt sections and gear motors that allows perfect bag compaction. Although more expensive than the solutions described above, it allows the handling of the most difficult products while offering a high level of pallet quality.


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