FEATURE NEWS:
Straightening units and systems for drawing machines
As a part of wire, bar and cable production, the drawing process plays an indispensable role. In each drawing machine, straightening units and systems are essential components. As an example, the straightening process after the last die is used to guide the process material, to bend it in a specific way and to reduce inherent stress. Drawing professionals often talk of normal straightening and killing. Various roll configurations are used to achieve the different straightening effects. During killing, the straightening rolls in the infeed area are set very close and this close setting normally causes a residual curvature which corresponds to the capstan diameter. Killing can be used to achieve a maximum reduction of inherent stress. Minimal inherent stress enhances optimal bending and twisting characteristics as well as a balanced relationship between the limit of elongation Rp and tensile strength Rm.
It is common practice in the industry to use the drawing die for straightening the wire. The German company Witels Apparate-Maschinen Albert GmbH believes that this method cannot compete with the traditional roll straightening process. Many studies have shown that the die-based method has disadvantages both for the work piece and for the tool. The primary disadvantages for the work piece or process material are non-uniform distribution of tension and variations in material structure across the diameter. This results in a level of finished product quality that makes handling difficult in downstream processes, causing repeated problems. It has, for example, a negative impact on the dimensional accuracy of finished products (springs, bent parts, etc.). With this in mind and based on an analysis of drawing trials, the recommended method is to place a straightening process between the drawing die and the capstan. This process has an influence on internal properties as well as on curvature and helix. It allows the drawing die to revert to its primary purpose, namely diameter reduction.
Specific straightening units and systems are designed for use on drawing machines. Design details depend on the process material, the final product to be produced and the technical parameters of the drawing process such as drawing speed. Robust, long-lasting straightening systems with integrated deflection roll are typically used after final diameter reduction. To allow a purely elastic deflection of the process material, the deflection rolls are designed to have sufficient diameter. High-speed straightening rolls, which are sealed for protection against contamination, are available as an option on straightening systems. These rolls are coated to prevent wear at the infeed point and also feature axial positioning. The wire path can be adjusted in a number of ways to allow precise adaptation to the geometric characteristics of the individual machine.
Company: |
Witels-Albert GmbH |
Country: |
Germany |
Fax: |
+49 30 723 988-88 |
Email: |
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Website: |
www.witels-albert.com |