Joining methods for conveyor belts and power transmission belts
People often ask why we use different joining methods for different conveyor belt types. In this blog, I explain the various ways to join a belt. The most common joining methods we use at Habasit are:
Quickmelt fusion joint
This easy and fast fusion joint method is used for belts that consist almost entirely of thermoplastic material. The belt ends are cut to length at a certain angle, fixed together in a guide rail, then hot pressed to fuse the materials. We use this method where small pulley diameters are present, and operating temperatures are no higher than 80 °C/176 °F. Quickmelt is typically used for round belts, elastic machine tapes and monolithic belts. The quality of the joint can be easily assessed by visual inspection, and thermoplastic material can be melted repeatedly.
Flexproof fusion joint
If there are fusible layers and fabrics, including at least one layer of thermoplastic material in the belt construction, we use a finger joint for this easy and fast fusion joint method. The belt ends are cut in a finger pattern, matched together, then hot pressed. With this kind of joint, the weld length is decisive for the tensile strength.
- For power transmission belts with a polyester traction layer, we use long narrow fingers
- Standard conveyor belts use mid-length fingers
- Machine tapes use short fingers
Provided the joining procedure is properly done, at room temperature a Flexproof joint offers over 70% of the tensile force of the original belt. High flexibility over the joint allows a smaller minimum pulley diameter. This fusion joint can be used for operating temperatures up to 80 °C/176 °F. Higher operating temperatures are possible, however the joint will deteriorate faster at these higher temperatures due to its variation in thermal history compared to the rest of the belt. The quality of the joint is easily assessed by visual inspection, and thermoplastic material can be melted repeatedly.
Stepflex fusion joint
This joining method is mainly used for PVC belts, which have a guide on the running side of the belt, or are used in contaminated conditions. The belt is split into a lower and upper part, and a finger is punched in both parts that is staggered in a longitudinal direction. The bond is fused together by a meltable intermediate layer.
Due to this overlap / staggered joint technique, the fingers are more resilient from localized pressure forces from below / above the belt and so the weld provides a higher penetration resistance.
Thermofix bonded joint
Thermofix is a bonded joining method used for conveyor belts and power transmission belts with different material combinations of non-thermoplastics, e.g. rubber or silicone with polyamide, where high resiliency and/or shock resistance is needed. It is suitable for operating temperatures up to 100 °C/212 °F, but not where small pulley diameters are involved. If a Nylon (polyamide) layer is present, it is combined into a whole using a chemical bonding method.
The ends of the belt are skived to a wedge shape, one end of the belt from the top, the other from the underside, and bonded together using an adhesive system, heat and pressure. This is a very strong welding method, and provided the joining procedure is properly done, at room temperature the Thermofix method offers over 70% of the tensile force of the original belt. Due to the use of different adhesives and welding times, careful craftsmanship is required, and it is time consuming. After the heating procedure the joint is irreversible, and the quality of the joint cannot be assessed visually. The joint has good resistance against lateral forces and dirt on pulleys.
Mechanical fasteners join or fasten two objects together mechanically. They are used in places where conveyor belts must be changed regularly or for applications where the belt needs to be replaced quickly. However, the mechanical fastener is a vulnerable part of the belt and may have openings where dirt can enter, so this is not a preferred solution for many applications.
Which joining method is used on which belt?
For details, visit our Product Data Sheet Portal and look for the belt’s Joining Data Sheet. For further support, please contact us for personal support or leave a comment under this article.