Conveyor belts – from fiber to fabric
In today’s blog I discuss the conveyor belt manufacturing process – in particular the fabrics used.
Different textiles for the manufacturing of conveyor belts
Among other things, the properties of a conveyor belt depend on the textile used. Most textiles contain extruded filaments. These filaments could be twisted together to a yarn.
A fabric for example, can be produced from the yarn. A fabric is a right-angled weave of yarn (warp and weft). The warp threads run in the longitudinal direction while the weft threads run transversally. The manner in which these yarns are crossed is referred to as the weave. The weave has an influence on the belt properties, such as strength and noise behavior, etc.
A fleece, which is nonwoven, consists of filaments that are interconnected. These filaments can be joined through different processes (mechanical, thermal, or chemical). For example, a mechanical process bonds the filaments with the aid of needle boards. The nonwoven is formed on machines with rotating cylinders (cards) on which filaments are laid out for a fleece. Thereafter needling occurs, i.e. the bonding and compaction of the nonwoven. The objective of needling is to make a thinner textile fabric out of a voluminous, soft nonwoven. For this a needle board is moved up and down at a high stroke speed. During the needling process, an almost smooth or structured surface can be generated. The nonwoven will have a different influence on the belt property (flexural strength, coefficient of friction, etc.) depending on how intensively the nonwoven has been bonded, what filaments have been used, etc.
Yarn types used in conveyor belt fabrics
The distinction is made between three types of yarn: monofilament, multifilament, and staple fiber yarn. Monofilament is a man-made fiber and consists of one “thick” filament which is used mainly in the weft direction (transversal). A multifilament is also a man-made fiber; it is a thread that contains many individual filaments which are twisted together to form a yarn. Multifilaments are used in the warp (longitudinal) and weft (transversal) direction. Staple fiber yarns can be manufactured with man-made or natural fibers. In this regard, cut filaments are twisted together to a yarn.
Influence of the yarns on the conveyor belt properties
The yarn type that will be used in the fabric is selected depending on the requirements imposed on the conveyor belt. Usually a multifilament is used as the yarn type in the warp (longitudinal) direction. This offers the advantage of the belt being extremely flexible and thus able to be routed over small pulleys.
Another yarn type that is popular in the warp (longitudinal) direction is the staple fiber yarn, which is quite hairy compared to multifilament. The advantage offered by staple fiber yarns and fabrics is that fraying on the edges of the belt is quite minimal.
Monofilaments are mainly used in the weft direction (transverse). This results in higher rigidity and flatness of the belt. This is important in food production, for example, or for treadmill belts in the fitness industry.
Of course, besides the yarn type, the material is also crucial. For standard applications polyester is mainly used as the yarn, but in applications in which the belt needs no elongation, aramid is used as the warp material.
To generate additional properties, the weave is another crucial point for a fabric. The weave type (crossing of the yarns) can influence the strength of the belt, its noise behavior, the coefficient of friction, etc.
The finished fabric is coated
Finally the fabric is coated. Different materials (TPU, TPO, rubber, PVC, etc.) are used for the coating depending on the requirement. However in many industries uncoated fabric is also used, for example, in bakeries. In this area the cotton fabric without coating is used, because cotton offers excellent release properties and thus is suitable for transporting sticky dough.
The surface of the coated fabric can be embossed in different ways to create a certain structure that offers specific properties. A high-grip material makes it easier for the conveyor belt to pick up what is being carried on a surface moving at an angle. A waffle structure offers better release properties against sticky dough. Consequently, the different steps in the manufacturing process are very important to the properties that a conveyor belt will have when it is finished. It is important to make the right choices, so that the fabric will have the exact properties necessary to meet the demands and requirements of each application.
Habasit’s in-house production means control over the properties of the conveyor belt
At Habasit, we manufacture our own fabric in our own weaving mill, and thus we have extensive knowledge of the different types of belts. Habasit has the knowledge and competence necessary to find a solution based on your specific wishes and demands. People often say that it is what is on the inside that counts. We certainly agree – at least when it comes to conveyor belts!
Do you need help making the right choice? Contact us!
