Factors affecting THE STRAIGHTENING PROCESS
WHAT IS STRAIGHTENING?
Straightening is the apparent elimination and removal of stresses induced into the material to be straightened during its manufacture due to force and torque related influences. This applies to wire straightening, tube straightening, cable straightening, strip and flatwire straightening and profile shape straightening.
AN ANALYSIS OF THE MANUFACTURING PROCESS RELATING TO THE MATERIAL TO BE STRAIGHTENED:
The smaller the force and torque related influences, the easier the straightening process.
- Overhead take-off
- Static spooling
- Improper product guidance
- Frequent changes in direction
- Poorly located straightening processes
- The wrong tools
- Spooling and coiling
- Directional changes and guidance
Corrective measures applicable to unavoidable stresses:
- Verified straightening
- Controlled directional changes
- Maintenance of constant curvature
- Uniformly consistent bending direction
IT FOLLOWS THAT ATTENTION SHOULD BE GIVEN TO:
- Staying on the centerline (i.e., avoiding deflection in the material path and directional changes). Maintain a straight path through drawing with axial and radial spool movement.
- Maintenance of bend direction and curvature when spooling and guiding (seefigure 2) i.e., do not bend the material to be straightened “back over” (see figure 1).
- Maintenance of constant initial curvature and constant torsion or helix i.e. by choosing a suitable straightener such as a helix straightener or killing-pulley set (see figure 3-5)
THE ANALYSIS OF THE MATERIAL TO BE STRAIGHTENED
A correct analysis of the material is a prerequisite if a verified straightening process is to be constructed. ISO 6931 provides information regarding the long neglected torsion test.
- Check the range of initial curvature (see figures 3 and 4) taking into account different spool diameters (min./max.)
- the torsion (helix)
- radial displacement (figure 5)
- axial displacement (figure 6)