Making a superior tannery felt

28 March 2004

Felts are used in a range tannery machines in both the wet-end and finishing. Huyck have been involved in the business for the past 30 years but have recently decided to increase their presence in the tanning sector. They have teamed-up with bService, an Italian company that have a long association of providing components such as felts to the international leather industry. The new co-operation will see bService cover a number of European, South East Asian and Latin American markets on behalf of Huyck. Huyck use their experience gained in a number of markets, including tanning, to provide a range of value-added, high performance products. In addition to supplying several major tanneries in Germany and Austria directly, they have also supplied 90% of tannery machinery manufacturers in Italy and the rest of the world with felts. The full range of tannery felts provided by Huyck is given in Table 1. They have recently developed a new finishing felt that has been impregnated with an anti-static ingredient. During the ironing and embossing process, fine dust and dirt is attracted to the leather surface as it becomes electrically charged by friction built up during embossing or ironing. 'We aim to add value to our products. All our felts have a guarantee that they will not contain metallic objects and the finishing felts include the anti-static compound developed in our laboratories', Horst Preisinger, director industrial textiles told Leather International. The anti-static material is added at the end of the manufacturing process, during the felt finishing step. Afterwards, the whole felt is passed through a metal detector before packing and shipping. 'To improve quality and performance, we sometimes ask customers to return old felts to us for assessment. We can then look at how each felt has performed during its working life', Preisinger added. Huyck attended Tanning Tech for the first time in October 2003 under their own name and aim to attend the Fimec fair in Brazil later this year. The move is part of their overall strategy to increase focus on the tanning sector and improve market share. 'We are able to use our knowledge and synergies from other industries such as pulp and paper to transfer ideas into other areas of our business including tannery felts', says Preisinger. 'We aim to provide tannery machinery makers and tanners with a high quality product and offer the best customer service', he added. Huyck Austria Huyck Austria are located in the town of Gloggnitz which is 80km south of the Austrian capital Vienna. Huyck have been making felts for a wide range of industries, under several different names, since 1874. The original business was formed in 1852, under the name of the Volpini Group, when they took over the yarn-spinning factory in Gloggnitz producing fez caps. The Austrian plant is the international headquarters and R&D centre for the international textiles division. Since 1999, they have been part of the Xerium Group of companies. The Dutch name Huyck has been used since 1974. The Gloggnitz site features some of the most modern and high-tech industrial textile making equipment in the world. A number of the larger looms and needling machines are impressive in terms of size and performance. Huyck certainly pride themselves on technology, efficiency and cleanliness. The 64,000 sq m of purpose built covered factory space is light, airy and pleasant to work in. The temperature and humidity are controlled in a number of the buildings to ensure consistent quality for the end product. Felt making process Depending on final application, a typical tannery felt (sleeve or belt) has to withstand water, chemicals, high pressures, friction and heat yet remain durable and maintain its shape. At Huyck, the company have split their operations into two groups, one for the production of paper felts and the other for the production of textile wires and threads, press felts and tannery felts. This article will concentrate on processes involved in making a tannery felt. A flow diagram of the felt making process is given in Figure 1. Simply put, the process begins with two processes using woven and non-woven fibres. These may be natural or synthetic or a blend of both. Natural woollen fibres are often used in the non-woven 'layer' fabric process. Synthetic fibres usually form the woven 'base' fabrics. Both are processed individually and then combined in a process called needling. 'In the past, tannery felts were made wholly from woollen fibres. Modern felts are constructed from a mixture of natural and man-made materials. The blend of different fabrics gives the customer better product consistency and improved durability compared with wool-only felts', says Engelbert Diabl, development and application manager. There is a perception in the tanning industry that natural only felts are the best. But successive research and development has proven that a blend of synthetic and natural fabrics make the best felts. In a typical tannery felt, between 10-50% of the final felt is made from natural fibres depending on the end use. Polyester and polyamide co-polymer blends provide most of the synthetic fabric layers. Woven fabrics A tannery felt is made up of several smaller layers of synthetic and natural materials. Many of the layers are woven together and then each of the layers is connected to another using a process known as needling. Synthetic threads such as polyester and polyamide are blended together on a loom to produce a single sheet. Several of these layers, known as 'base' fabrics, are produced using different blends. Each blend offers different physical properties to the end felt. 'The composition of each tannery felt is different depending on its end-use. 'For a typical felt, we may use fifteen different fibre blends and seven base fabrics', said Diabl. Huyck have six Sulzer weaving looms controlled by a single operator to produce base felts. Prior to weaving, the fibres are passed through a 'warp preparation' machine. It adds tension to the fibres so that they remain firm when formed into a fabric sheet. Each woven 'base' layer is then inspected for quality and rolled. Non-woven fabrics Woollen fibres can be woven or non-woven as seen in Figure 1. The non-woven material is carded to separate the fibre strands before being re-carded across two directions which run at right angles to one another (ie north to south and east to west). Each layer is laid on top of another in opposite directions to add strength across opposing directions on the final felt. The whole fabric is then passed through a needling machine to join the layers together. Typically 15-16 non-woven layers are needled together to produce a single layer fabric. Each needle is fitted with a serrated edge which grips the thread on the downward motion attaching it to an adjoining thread on the upward motion. Each needle passes up and down several times a second and each needle has several hooked barbs along the shaft. 14,000-20,000 needles can be fitted on each needling machine at Huyck. Huyck use 16-17 needle types. Finishing The base fabrics and the layer fabrics are joined together on another needle punching machine prior to finishing. Rollers compress and compact the felt to the required specifications. Sleeve rollers are wrapped up to 14 times to make sure that the final felt remains tight. The final multi-layered felt belt is then passed through a heated finishing roller. A solution is sprayed on to the felt surface, including the anti-static agent, to protect the felt and increase durability. The solution is a mixture of resins and thermoplastic compounds. It takes between four and six weeks for a single felt to be delivered once the order has been placed. This is dependent on factory demand at Huyck and the complexity of the felt required. A complex process The felt making process is very complex and what may look like a simple component on a tannery machine has undergone several steps. The process is both very mechanical and labour intensive. Huyck have invested several million euros on the latest equipment. Most of the larger pieces of equipment operate 24 hours a day, seven days a week. When Leather International visited the factory in Gloggnitz, Huyck announced that they would be ordering a new felt finishing machine, which will be installed later this year. The cost of the new machine is anticipated to be around €1 million. Huyck remain one of the largest and most modern felt manufacturers in the world.

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