Filter cloth characteristics have to be designed for the filtration mode and the particle size by choosing the correct fibre fineness. Fibre forms with special cross sections and the finest fibres increase the efficiency of depth filtration by increasing the total fibre surface. A good strength ratio in longitudinal and cross direction can be achieved with card and crosslapper. The productions starts with the fibre preparation where the desired blend of fibre types is chosen and where the fibre balls are opened into single flocks. After opening and blending in the fibre preparation phase (DiloTemafa), the fibres are fed to a dosing opener (DON) which further opens and transports them under control to the card feeder. This results in an even flow of fibres between fibre prepration and web forming. The card feeder (MultiFeed) turns the fibre flocks into a very uniform compact flock mat. A belt weigher or a radioactive gauge keep the weight of the flock mat constant. In the card (MultiCard) the fibres are opened and blended and a web is created.
Stitch density of the needle loom, penetration depth and weight control the filtration efficiency. By needling together different layers (combinations of needlefelt, spunbond, meltblown webs) a density gradient can be achieved. Often reinforcing scrims are integrated into the needlefelt. The HyperTex installation allows the economic feeding of variable density scrims inline. In a HyperTex installation a yarn layer of Messrs. ONTEC is inline. This yarn layer creates the scrim on or between two preneedled felts. Needling from both sides follows. This process saves the separate step of scrim production, is highly productive and flexible in regard to fibre types and mesh size.