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Labor outlays required for the fabrication of structures formed from strips and shapes, and also their quality depend primarily on the perfection of the equipment employed. Such strip defects as longitudinal distortions of the blanks, and their nonrectilinearity are prevalent during the cutting of blanks on inclined-throat shears.
The method of straightening by stretching is the most productive straightening for rolled products of limited length (cut rolled product),which provides good quality. The rolled product (strips, tubes, shapes) is secured by the ends in grips, one of which is stationary, and the other is displaced in the longitudinal direction under a tensioning load, created, for example, by the hydraulic unit of a tension machine, as a result of which the rolled product is tensioned in its plastic zone. Deformation of the blank is monitored via the displacement of the moveable grip [i]. This method of straightening the rolled product has a significant disadvantage, since in each specific case, it is necessary to calculate the displacement of the movable grip, which depends on the degree of waviness on the rolled product, its length, and material. Where it is easy to account for the length and material of the blank, it is extremely difficult to determine the degree of its waviness, and is almost impossible with an adequate degree of accuracy. This leads to a reduction in the quality of straightening.
The All-Union Scientific-Research Institute of Projects and Technology for Chemical Engineering has studied and developed a method of straightening rolled products by stretching [2] with automated monitoring of the straightening process, for which it is necessary to account only for the article's material (Fig. 1).
One end of the rolled product being straightened 6 is secured by stationary grip 7, and the second by movable grip 1; a measured section of constant length (for example, 100mm), which is adopted as the measurement base le1 is marked off (where the waviness is smaller). Measurement apparatus 2 with scale mechanism 3, which is coupled with adjustable stop 5, is set on this base. The apparatus has sensitive element 4 (for example, a limit switch). The approximate value of reference standard εre is determined from the equation
δ/εre≤Pr ( 1 )
(here, Pr is a characteristic of the rolled product, and δ is the throw of the switch in mm)
εre=le1PrK ( 2 )
(here, K is the scale factor). Aligning standard εa is determined from the equation
εa = εre－δ （3）
and the height of support 5 is adjusted according to this standard. The values obtained for εre and εa are used hereinafter to straighten all articles formed from a given material, irrespective of their length and waviness.
Adjustable stop 5 is set at a distance εa from the limit switch, and, in turn, is given the reference standard εre = εa + δfrom which the elongation of the measurement baseΔle1 will be compared in the process of straightening the rolled product. In this case, Δl = Prle1K.
*The measurements were made for specimen deformations equal to 0, 1, 2, and 3%, respectively.