Roll covering.

Rubber roll manufacturer Hefner specializes in the covering of rolls in various sizes, shapes, colors, profiles and elastomer qualities. With the Covermatic KH 110 N, a fully automatic roll covering system, Hefner is said to more than double its production capacity.

To date, Hefner covered its rolls with calendered sheets according to the winding principle. Benefits gained from the Covermatic system are said to include shorter manufacturing times and reduced personnel and material requirements, along with better roll quality. The manufacturing time of individual rolls has been reduced by a factor of eight to ten, for example, with manpower savings of 50-60%.

The Covermatic KH 110 N roll coveting system consists of a cold-feed rubber processing extruder of the GE 90 KS series, which is used as a feed extruder, and a Covermatic extrusion die. The Hefner package also included a roll core feeder, a roll take-off unit and the PLC control system. The Covermatic system has a covering capacity of about 7 kg/min, and is designed for rolls with core diameters ranging from 5 mm to 110 mm, lengths of between 100 mm and 10,000 mm and layer thicknesses of 2 mm to 40 mm.

The covering speed achieved by Hefner with the Covermatic system is said to be significantly higher than with the winding methods used in the past. This is because the Covermatic allows the rubber to be applied directly to the roll core in a single operation. The conventional winding process requires the calendered sheets to be applied successively, and this takes much longer and causes more scrap, according to the company. Moreover, the relatively expensive production of calendered sheets before the actual roll coveting process is no longer necessary, as the rubber strips can be processed directly in the Covermatic feed extruder.

Another major benefit said to be provided by the Covermatic system is the excellent covering precision. The fully-automatic, high-precision roll core feeder ensures that the radial runout of the covered rolls is as little as 0.5 to 1.0 ram, compared to about 2 to 3 mm with the winding process.

The transition zone between the feed extruder and the Covermatic enables in-line degassing or straining of the coveting material. This is said to ensure a homogeneous and untextured surface of the covered rolls without any air inclusions.

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