RU2456131C1 - Method of strips cutting - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building and may be used for producing metal structures. Proposed method comprises gripping workpiece by disc blades, pulling it into gap between disc blades by friction forces and cutting it into preset width strip by shear forces. Metal of workpiece is subjected to simultaneous deformation by shearing with the help of disc blades. First pair of blades deforms workpiece metal by 5-10% to ensure prop pressure at inlet of second pair of blades and stable grip of metal by second pair of blades. Second pair of blades performs primary deformation of workpiece in the limits of 70.0-80.0% of initial workpiece thickness. Third pair of blades performs kinematic intensive effects on workpiece to create stretch strain at outlet of disc blades so that final deformation making 100% of initial thickness is performed. Then, strip is detached from workpiece. In cutting, strip outer edge position is adjusted with respect to lower disc blade cutting edge by rule. Third pair of blades features larger peripheral speed.

EFFECT: stable cutting irrespective of fouling and lubrication.

2 dwg, 1 ex

Description

The invention relates to mechanical engineering and can be used in the manufacture of metal structures.

A known method of cutting strips with an inclined knife, while the resistance to cutting is exerted not by the entire cross-sectional area of the sheet, but only some small part of the sheet in the form of a triangle. The cut is carried out due to the reciprocating movement of the knife (see Korolev A.A. Design and calculation of machines of rolling mill mechanisms. M., Metallurgy, 1969, pp. 263-264, Fig. 127, b).

A significant disadvantage of the described method is low productivity and high energy costs.

A technique for cutting a strip (prototype) is also known in the art, in which a workpiece (sheet) is captured by circular knives, pulled into the gap between the circular knives, and the workpiece (sheet) is cut by shifting to strips of a given width (see ibid., P. 273 -274).

The disadvantage of the described method of cutting the strip is that the conditions for trapping metal by circular knives depends on the coefficient of friction of the surface of the circular knives on the metal of the workpiece (see ibid., P. 275), if oil (grease) enters the surface of the cut sheet, this leads to slipping jamming the strip in the knives, and thus, a decrease in productivity. In addition, for stable cutting of the workpiece (sheet) accounts for from 50 to 100 thicknesses of the workpiece sheet. With a sheet blank thickness of 2.0 to 6 mm, the nominal diameter of circular knives will be 200 to 600 mm, and the manufacture of such knives from stainless steel is very difficult and expensive.

An object of the invention is to develop a method of cutting the strip, ensuring the stability of the cutting process, regardless of the presence of dirt and grease on the surface of the workpiece (sheet), and allowing the manufacture of knives of small diameter.

The stated technical problem is solved due to the fact that the metal of the cut workpiece is subjected to simultaneous deformation of cutting by pairs of circular knives with increasing intensity and kinematic interaction of the foci of deformation of the cut metal, and the first pair of knives deforms the metal of the cut workpiece by 5-10% and provides back pressure at the input a second pair of knives, as well as a stable metal pickup by a second pair of knives, where the main deformation of cutting the workpiece is carried out within 70.0-80.0% of the initial the initial thickness of the cut workpiece, while the third pair of knives acts more kinematically on the cut workpiece, since it has a 5-10% higher peripheral speed, resulting in tensile stresses at the exit of the second pair of circular knives, while the final pair of circular knives the deformation of the cut, which is 100% of the initial thickness of the workpiece, and the strip is separated from the cut workpiece, and during the cutting process, the position of the outer edge of the strip relative to ezhuschey lower circular knife edge ruler.

The invention is illustrated in the figure, on which:

figure 1 - sequence of operations when cutting strips of the proposed method;

figure 2 - sequence of deformation of the workpiece with circular knives.

The strip cutting method includes (Fig. 1) simultaneous finding of the cut workpiece 1 in pairs of circular knives 2, 3, 4 with increasing deformation intensity and kinematic interaction of the deformation centers of the cut metal 5, 6, 7, while the deformation of the cut workpiece 1 by the first pair of knives 2 is from 5.0 to 10.0% of the original workpiece 1, that is, from h ₀ to a thickness of h ₁ , and creating a backwater pressure 8 at the entrance to the second pair of knives 3, where 70 to 80% of the original thickness ho of the cut workpiece is deformed 1, the thickness h ₀ to h _2, etc. than backwater voltage does not exceed σ yield strength _t of the material of the billet 1, wherein the diameters D ₁ of the first pair of knives 2 are equal to the diameter D ₂ of the second pair of knives 3 have the same peripheral speed, i.e. V ₁ = V _2, and carry equal kinematic effect on the cut workpiece 1, and at the exit from the second pair of 3 knives, tensile stresses 9 do not exceed the yield strength σ _{t of the} material of the cut workpiece 1, while the third pair of knives 4 acts kinematically more intensively on the cut strip 1, having a larger circumference of 5-10% speed V ₃ than the peripheral speed V _{2 of the} second pair of knives 3, and the peripheral speed V _{1 of the} first pair of knives 2, which is achieved by the fact that the diameter D _{3 of the} third pair of knives 4 is 5-10% than D ₂ and D ₁ . This ensures that at the exit from the second pair of knives 3, the presence of tensile stresses 9, and in the third pair of knives 4, 100% deformation of the initial workpiece 1, that is, the complete separation of the cut workpiece 1 and the receipt of the finished product of strip 10, in the process of deformation of the cut workpiece 1 is carried out. three consecutive pairs of knives 2, 3, 4 (figure 2) the width of the cut "in" is kept constant relative to the cutting edge 11 of the lower knife 4 of each pair of knives 2, 3, 4 and the ruler 12.

Example

The cut workpiece with a thickness of h ₀ = 5 mm is captured by the first pair of knives and is deformed by 10%, i.e., the cutting depth in this pair of knives will be Δh = 0.5 mm. Considering the worst case scenario, that the surface of the workpiece is contaminated with grease, the angle of capture by knives will be α≈0.06 rad. According to the formula Δh = R · α ² known in the theory of metal forming, with a sufficient degree of accuracy, knowing Δh = 0.5 mm and α≈0.06 rad, we determine the diameter of the first pair of knives D ₁ = 140 mm. When the workpiece is deformed less than 5%, the friction force reserve in the metal cutting center sharply decreases and, accordingly, back-up stresses when the metal is put into the second pair of knives, the pushing force decreases and the cutting process becomes unstable.

In the second pair of knives, the diameter of which is 140 mm and equal to the diameter of the first pair of knives 140 mm, the cut workpiece is deformed by 80% of the initial thickness h ₀ = 5 mm, that is, Δh = 4 mm. When the workpiece is deformed less than 60% of the initial thickness, the load on the third pair of knives increases significantly, which leads to their increased wear. Compression and a stable process of cutting with knives of a small diameter of 140 mm is ensured by the back pressure created by the first pair of knives, however, separation of the strip from the cut workpiece does not occur in the second pair of knives.

The final cutting of the workpiece is carried out by a third pair of knives, the diameter of which is 10% larger than the diameter of the disk knives of the first and second pair and is 1251 mm. If the diameter of the third pair of circular knives is more than 10%, the tensile stresses at the outlet of the second pair of knives will exceed the yield strength, which will lead to plastic deformation of the metal and a change in the geometric dimensions of the strip. When the diameter of the third pair of circular knives is exceeded by less than 5%, the tensile stresses at the outlet of the second pair of circular knives become minimal, and this leads to warping of the cut strip. The larger diameter of the knives of the third pair provides greater peripheral speed and has a greater kinematic effect on the strip, which creates a tensile stress at the exit of the second pair of knives, ensuring the stability of the metal cutting process in them and reduces the contact stress of cutting in the third pair of knives, increasing their resistance. The ruler keeps the workpiece from lateral movement during cutting and obtaining a strip width with tolerance deviations in accordance with the requirements of the standard.

The proposed method of cutting the strip allows you to distribute the compression of cutting the workpiece between three pairs of knives, and this made it possible to produce circular knives with a diameter of 140 mm, while for cutting according to the known method for one pass of the workpiece (sheet) with a thickness of 5 mm in accordance with the literature recommendation (see Korolev AA Design and calculation of machines and mechanisms of rolling mills. M., Metallurgy, 1969, p. 275) the diameter of circular knives is necessary for a stable cutting process within 250-500 mm. The practice of cutting metal with circular knives shows that high stresses that occur when cutting cold metal lead to their rapid wear and require regrinding in diameter to restore the cutting edge of the circular knife, the removal in diameter is usually 2-3 mm, that is, twenty to thirty regrinding knives are no longer suitable for further exploitation. At the same time, the manufacture of circular knives from special steel with a diameter of 250-500 mm requires special technologies and high material costs. This significantly inhibits the application in engineering of technology for cutting steel sheets into strips with circular knives, which allows two to three times to reduce cutting forces and save up to 70% energy compared to cutting a sheet on a guillotine.

Used for the implementation of the proposed method, circular knives with a diameter of up to 150 mm can be made in almost any forge workshop and their cost is ten times less than the cost of knives with a diameter of more than 250 mm. These advantages of the proposed method can ensure its widespread use in mechanical engineering and other areas related to metal processing.

Claims (1)

A method of cutting a strip, including gripping a cut workpiece with circular knives, pulling it into the gap between the circular knives due to friction forces, cutting the workpiece into a strip of a given width due to a shift, characterized in that the metal of the cut workpiece is subjected to simultaneous deformation of cutting by three pairs of circular knives with increasing the intensity and kinematic interaction of the deformation zones of the cut metal, and the first pair of knives deform the metal of the cut workpiece by 5-10% and provide stress and at the entrance to the second pair of knives and stable metal capture by the second pair of knives, in which the main deformation of cutting the workpiece is carried out within 70.0-80.0% of the initial thickness of the cut workpiece, with the last third pair of knives having 5- 10% greater peripheral speed, kinematically more intensively affect the workpiece being cut, create tensile stresses at the exit of the second pair of circular knives, perform the final deformation of the cut, which is 100% of the original thickness of the workpiece, and TVOC is separated from the workpiece being cut, the cutting process is controlled in position the outer edges of the strip relative to the cutting edge of the lower circular knife ruler.

Images