Reproducibility of straightening roller positions

  • documentation
  • repetition of adjustments
  • reproducibility of straightening roll positions

All straightening results, including the final curvatures of the material to be straightened, ultimately depend on the correct positions of the straightening rolls. It is vital, therefore, for the straightening process to display constant reproducibility.

In addition to being a precondition for constant results, reproducibility also minimizes unnecessary line stoppage times and it wastes less material during repeat set-ups. High speed and continuous availability also play a major role in minimizing costs.

Existing possibilities of achieving reproducibility differ in their use of reference points on the adjustable elements of a straightener and in the methods used to determine actual positions.

The most commonly used possibilities are:

             1)      Engraved veneer scales
             2)      Dial gauges
             3)      Scales
             4)      Screws; hex screws, slotted screws etc.
             5)      Knurled screws
             6)      Micrometer screws
             7)      Veneer scales on buttons
             8)      Collar screws with veneer scales
             9)      Machine knobs/tapered machine handles
           10)      Handwheels
           11)      Geared motors / stepping motors
           12)      Hydraulic / pneumatic cylinders
           13)      Automatic roll positioners

A solution is chosen which best meets the demands of local conditions and technical handling criteria. A combination of two of the above options is also possible, in which case the functions are divided into adjustment and position measurement.

Whatever option is selected it should not be forgotten that continuous documentation of the adjustment values is essential if reproducibility is to be achieved as planned.

Roll-type straightener

  • adjustment
  • double straightener
  • drag-type gripper bench
  • drag-type straightener
  • drag-type straightening set
  • pre-straightening device
  • roll unit
  • roll-type straightener
  • roll-type straightening device
  • rope straightener
  • sickle straightener
  • single straightener
  • straightening rotor
  • straightener
  • straightening device
  • straightening machine
  • straightening mechanism
  • strip straightener
  • wire bending unit
  • wire straightener
  • wire straightening device

Using a roll-type straightener it is possible to change a process material's unidimensional initial curvatures, i.e. initial curvatures in one plane, so that defined final curvatures remain after the straightening process. The bending tools of such a roll-type straightener are straightening rolls arranged in two parallel, mutually offset rows. When the rolls are accordingly adjusted, the process material is subjected to alternating bends as it passes through the straightener. The number and magnitude of these alternating bends must be such that the initial curves are changed in defined manner over the complete length of the product to be straightened.

To straighten a product over its complete length it has to be transported relative to the straightener.
For this purpose, straightening machines are equipped with driven rolls. By contrast, the rolls on a straightener are not driven, i.e. additional devices such as drive units, pull-in units, drivers or the like are required to transport the product to be straightened.

In other words, a straightening machine has technical elements for transporting as well as straightening the product, whereas a straightener has only elements for straightening it. By this definition it is possible to use straighteners in straightening machines.

Straighteners can be classified in terms of their degree of automation. WITELS-ALBERT offers products for conventional straightening, semi-automatic straightening, and straightening with automatic roll positioners. Automatic straightening is currently the subject of intensive research.
Each sector should have a matching straightener with specific features that can be adapted to the cross section to be straightened and to the properties of the process material.

Roller crosses/guides

  • guiding
  • roll crosses/roll guides
  • roll material

Roller crosses/guides are used in the processing of endless material between the spool or coil, straightener, pull-off unit or processing machine. Their function is to guide and support the product to be processed.

The number and the arrangement of the roller crosses/guides in the material flow system are selected so that

  • sagging of the material is prevented,
  • sharp edges and deflections with small radii do not damage the surface of the material,
  • the endless material enters the next apparatus or machine in central position.

The diversity of roll guides results in a wide range of different applications. Which roll guide is selected will depend on the particular requirements. Roll guides are available as rigid and adjustable types. Adjustable roll guides are used when dimensions change and when exact positioning of the material is essential.

Centrally adjustable roll guides are suitable for a range of dimensions. The center of the material is retained even when dimensions change. The material itself does not have to be adjusted for it to enter the line centrally.

Some roll guides are designed to completely enclose the material while they guide it. Others are open on one side for better insertion of the material.

Roll diameter, roll material and clear widths depend on the dimensions and geometry of the material.
Burnished and hardened steel rolls are used e.g. for firm materials. Softer rolls made of PETP can be used for sensitive surfaces. The following basic types of roll are available:

  • with chromium-plating
  • hardened (up to 64 HRC)
  • with rubber coating
  • with ceramic coating
  • rolls made of PETP, PVC or polyamide

Rotary straightening

  • alternate bending
  • rotary straightening
  • straightening
  • wire straightening

Unlike the roll straightening process, rotary straightening subjects the process material to alternating bends with a revolving bending axis.

The number of alternate bends depends on the speed of the product to be straightened and the number of rotations made by the spinner. Straightening blocks, straightening cheeks or straightening rolls are among the straightening tools used.

Rotary straightening is mainly performed in the production of rods or bars which permit a certain spring back of the material from the bending and torsion as the result of being cut to length.

It is sometimes wrongly assumed that two counter rotating straightening spinners neutralize the unwelcome stresses induced by torsion.

In view of the surface damage and sometimes severe impact on material parameters caused by the more aggressive forming of the product in the rotary straightening process, preference is being given more and more often to roll-type straighteners as the gentler alternative.