wire straighteners, feeders, guides and accessories

Oxford, MD 21654 USA
Phone: 410.228.8383
Fax: 410-228-1813

Exclusive stocking office for North, South and Central America

Spring Wire Straightening

The way the spring wire straightening process is designed is reflected in a straightening system defined by a combination of straightening units designed to create constant material characteristics through adaptation to the changing characteristics of the feed material. Every straightening unit and every straightening system has a specific straightening range which is fixed by the spacing and the diameter of the straightening rolls. The straightening range D thus has limits for the minimal and maximal cross-sectional dimensions of material to be straightened. For round wires, for example, the relevant parameters are the minimal wire diameter dmin and the maximal wire diameter dmax
Equation 1:

Once the straightening range is fixed with due consideration to the material's cross-sectional dimensions, the next step is todecide on the number of straightening rolls.

Given the difficulty of establishing the number of rolls by mathematical means, using a knowledge base consisting of the linguistic terms (membership functions) of the input and output variables; a rule base; and the inference and “defuzzifying” mechanisms. The knowledge which is channeled into the fuzzy system (Figure 1) is the result of empirically established and verbally formulated rules, and is also based on the results of putting the virtual simulation of the straightening process to actual use.


Via the rule base, consisting of 25 rules, the input variables Dr and Rp are linked to the output variable n (representing the number of straightening rolls). A sharply defined value for the input variable "radius of curvature range Dr" can be calculated with Equation 2. The variables rmax and rmin are the maximal and minimal radius of curvature determined with Equation 2.

Equation 2:                                                                                                          


The membership functions of the input variable yield point Rp are laid down in Figure 2. The fuzziness is particularly evident in the overlapping of the variable sets. For example, an elongation limit Rp = 800 MPa at 33 % (degree of membership m = 0.33) is assigned to the set “very small” and at 67 % (degree of membership m = 0.67) to the set “small” .



Use of a suitable inference mechanism and a specific “defuzzifying” method yields a specific conversion characteristic as shown in Figure 3. It can be used at any time to generate a sharply defined output variable for a set of sharply defined input variables. The Table presents derived values of n (the number of straightening rolls) for a number of discrete values of the input variables Rp (yield point) and Dr (radius of curvature range).

The way that straightening rolls are positioned must also be considered. After all, It is the position of each straightening that affects bending operations and the residual curvature.

WITELS-ALBERT has developed straighteners with a variety of automation levels. In conventional straightening systems, simple tools are used to position the rolls. Another option is to adjust elements equipped with a position gauge or vernier scale. Yet, advanced straightening technology featuring a high degree of automation, e.g. semi-automatic straightening units and systems (Figure 4) or automatic roll actuators (Figure 5) can position straightening rolls with reproducible high precision within a very short time. Software is a key component of each of the systems mentioned above. Whatever degree of automation is required, WITELS-ALBERT uses our proprietary SimDATA program (Figure 6) to determine the roll adjustment values.








Table: Values for the number of straightening rolls n calculated with fuzzy logic

Range of initial curvature radius

Dr [mm]

Yield point


Rp [MPa]

Number of straightening rolls

n [ - ]
















Witels Albert supplies a variety of straightener accessories for ease of set-up and “repeatability” of settings. For example: quick opening/closing options, roller position indicators, locking levers, entry/exit guide pulleys, guide dies, micrometer adjustment, guards, and Witels Albert proprietary software packages that allow for automatic or semi-automatic positioning of rollers and other components.

In addition, our wide range of range of raw material handling products includes wire straighteners, tube straighteners, wire guides, tube guides, tube feeders and wire feeders or drive units, cable straighteners, strip straighteners, flatwire straighteners, custom built feeding machines, straightening rolls , preformers or preform heads , sleeve rolls for high speed and high temperature applications, computerized wire straightener and tube straightener adjustment systems, and Witels Albert proprietary software packages that allow for automatic or semi-automatic positioning of rollers and other components.

WITELS ALBERT USA - 208 E. Pier St. - Oxford, MD 21654 - Phone 1-410-228-8383 - Fax 1-410-228-1813 - info@witels-albert-usa.com