The basis of any high quality metal wire cloth is an exactly formed wire. That is why for decades PACO has kept extremely close ties with some of the world’s best wire manufacturers. This ensures the best possible starting point for the demands that PACO places on its own processing and finishing as well as the specific requirements of each individual customer.
Wire is drawn by pulling wire rods that are initially relatively thick (diameter approx. 5 – 6.3 mm) a number of times through draw plates that decrease the diameter in tiny increments. Between the drawing stages, the wire is annealed to re-crystallize it. This helps ensure that the wire retains the physical properties demanded by PACO throughout the multiple-stage drawing process. The wire sizes used by PACO go down to a fineness of 0.016 mm (16/1000 mm). The particular challenge to the wirepuller is to produce a wire that is within a close tolerance of the specified wire diameter from the first to the last meter of the wire – throughout a length of a number of kilometres!
All wires used by PACO undergo an intensive quality assurance process before they are released for the next stage in the production procedure.
The characteristics and qualities of PACO metal wire cloth are as varied as the applications and demands of our customers. The majority are made of stainless steel wires of the grades 1.4301, 1.4401, 1.4541, 1.4571 and 1.4550 – to name just a few.
However, wires made of copper, brass, tin bronze, nickel, monel, aluminium or high-performance alloys such as inconel, incoloy or hastelloy have also been used. The diameters of the metal wires range from 0.016 to 1.4 mm, whereby PACO wire processing continues to explore developments at both ends of the spectrum.
The “linen weave“ is the most common type of weave. Its advantage is in its simplicity that provides both tightness of weave and high precision. Each shute wire passes alternately over and under each warp wire so that they fix each other.
The plain weave guarantees an extremely accurate width of opening compared to other similarly fine weaves, providing advantages for applications ranging from filtration through sieving to screen printing.
The twilled weave is characterised by the filling threads being alternately woven over one and then under two or more threads, thereby producing a diagonal pattern with an inherent elasticity. This method of weave can relate to either warp or weft threads, thereby giving a large variety of different twills. In conjunction with PACO’s precision weaving technology, even the standard twilled weaves provide good weave stability. Twilled weaves are used for sieve and filter products.
The additional name “DUPLEX“ indicates a particular characteristic of the modified plain dutch weave: instead of only one thick warp wire, two parallel running thinner warp wires are used. As with other plain dutch weaves, the weft wires are arranged as close together to each other as possible. The resulting geometry enables the cloth to be extremely flat so that it is predestined for filtration applications such as filter plates as well as pressure and vacuum filters. Its reputation in these areas is enhanced by extremely good flow characteristics with low loss of pressure, vastly superior contaminant retention than straight-forward plain dutch weaves and ease of cleaning or regeneration.
Also available is the plain dutch weave type TRIPLEX with three warp wires and specific capacities.
The origin of the plain dutch weaves is braiding, where separate strands of a material – e.g. a yarn – are interwoven. A flexible approach to the way that the threads can cross provides a variety of cloths that differ in appearance and structure. With the plain dutch weave SPW, the weft wires are very close together so that a so-called zero-mesh structure is formed. The warp wires are thicker and arranged wider apart. This provides a high inherent stability with a relatively small mesh size. The plain dutch weave SPW is extensively used for filtering as it possesses excellent filtering characteristics and can be easily cleaned of the filtrate.
This type of weave is very similar to the normal SPW but has relatively thin shute wires resulting in a much higher mesh count in the weft direction. Due to the much higher number of openings provided by the triangle formed by the weft wire going above and below the warp wire, this weave has a much higher free open area resulting in better flow rates – consequently, the name highflow. A further advantage is the considerably higher contaminant trapping capabilities. With free open area of 28 – 42 %, depending on specifications, the PACO HF has an unrivalled leading position among the filters with a similar mesh count.
With the dutch twilled weave, the weft wires are arranged as close together as possible completely covering the warp wires. Through the combination of twill and dutch weaves, this weave has double the number of weft wires than a plain dutch weave. As with SPW, twilled dutch weaves can also be woven with multiple warp wires laying parallel with one another. This weave ensures that there is little variation in the screen openings so that solid particles can be accurately separated. The trade-off is that DTW meshes have a higher flow resistance than other fabrics. The filter will clog quicker than other weaves, thereby further reducing the flow rate.
In contrast to conventional twilled weaves, the weft wires are not arranged close together but are positioned at a given distance from each other. On one hand, this means that the accuracy of the retention is not as good as a classic twilled weave. On the other hand, higher flow rates are possible, there is a low loss of pressure and the filter can be easily regenerated. The surface of the cloth is smooth on both sides, meaning that it can be easily cleaned.
The characteristic of this weave is that the warp wires are thin and arranged as close as possible to each other. The weft wires are thicker, consequently, the “reverse“ in the name. Depending on the required flow rate and flow resistance, the weft wires can be arranged either close together or widely spaced. The type of mesh can be made in a way that spherical particles can be retained at the surface rather than inside. In most standard RDW meshes, the narrow part of the mesh is determined by the arced triangle formed by two warp wires and the weft wire. The RDW weave is available in “heavy” and “light” versions, whereby the latter have a filter related free open area of 25 – 38%.
A further construction in the family of the reversible weaves is the so-called reverse dutch twilled weave RDTW. The warp wires are very similar to the warp wires in a RDW construction. The weft wires are woven in a twilled construction. With this design, the warp wires are formed in such a way that they are not so heavily stressed, meaning that the construction is particularly suitable for applications that are subject to an inherently higher mechanical stress.