Tesouras Guilhotina: Análise e Otimização de Desempenho Mecânico

Guillotine Shears: Analysis and Optimization of Mechanical Performance

1. Introduction

The guillotine shear offers greater efficiency, precision and reliability compared to the swing beam shear, as it eliminates play in the structure and allows you to adjust the shear angle.

However, when cutting wide, heavy sheets or thin, high-strength sheets, the guillotine may face challenges such as machine deformation that affects cutting accuracy.

Most research in this field focuses on the impact of shear parameters on accuracy, control system design and automation, or simulation of the shear process using discrete points.

However, there is limited research on mechanical property analysis and structural optimization of guillotine shears.

This article aims to fill this gap by analyzing the static and dynamic characteristics of the machine tool and simulating the sheet metal shearing process. Through this analysis, continuous shear data is obtained and an optimization scheme is proposed.

two . Static analysis

A structural model of a 6 x 3200 NC guillotine is shown in Figure 1. During operation, the anti-recoil device, driven by the roller screw, adjusts the cutting length. The pressing cylinder is then compressed by the shear plate.

Once the cutting parameters such as blade clearance and cutting angle are set, the hydraulic cylinders at both ends drive the upper and lower blades to move and complete the plate cutting process.

In the simulation analysis, the transition thread and the threaded hole are disregarded and a simplified three-dimensional model is imported into finite element analysis software. The two sides of the upper tool holder are fixed with restraints and the bonding contact is established to simulate the welding and thread clamping of the upper parts of the tool holder.

6×3200 NC Guillotine Structural Model

Fig. 1 Structural model of 6 × 3200 NC guillotine

According to Norsali's formula:

f1

In the formula:

  • σb – Resistance limit of the sheet to be cut;
  • δs – Ductility of the sheet to be cut;
  • h – Thickness of the sheet to be cut;
  • α – Shear angle;
  • x、y、z – The bending force coefficient, the relative value of the lateral clearance of the cutting edge and the pressing coefficient.

The vertical shear force (P1) is calculated to be 212.8 kN using formula (1), while the horizontal shear force (P2) is estimated to be 30% of the vertical shear force, or 63.8 kN. Both vertical and horizontal shear forces are applied to the top tower and solved using ANSYS Workbench.

The deformation in each direction at the beginning, middle and end of shear is compared and analyzed. As seen in Table 1, the deformation of the upper carriage in the Y direction is greater, and the deformation in the X and Z directions can be considered negligible in comparison.

The initial and final positions of the deformation in the Y direction are approximately equal and much smaller than the intermediate position. During the shearing process, the deformation of the upper tool holder has a concave trend.

Table 1 Maximum equivalent stress and maximum deformation in the X, Y and Z directions of the upper tool holder

Shear position Maximum equivalent voltage
/MPa 		Maximum deformation in the X direction
/mm 		Maximum deformation in the Y direction
/mm 		Maximum deformation in the Z direction
/mm
Start 137.7 0.020 0.141 0.074
Quite 135.3 0.090 0.183 0.650
End 137.2 0.013 0.151 0.085

Figures 2 and 3 show the maximum equivalent stress in the medium and the maximum strain in the Y direction, respectively.

Fig. 2 Maximum equivalent voltage of the upper tool holder

Fig. 2 Maximum equivalent voltage of the upper tool holder

Fig. 3 Maximum deformation of the upper tool holder in the Y direction

Fig. 3 Maximum deformation of the upper tool holder in the Y direction

Analyzing Table 1 and Figures 2 and 3, it can be determined that the equivalent stress of the upper tool holder is greater at the beginning of the shearing process. This stress is located in the position of the hydraulic cylinder and has a value of 137.7 MPa, which is lower than the yield limit of 235 MPa for the upper support of the tool.

In the middle of the shearing process, the maximum deformation of the upper tool holder in the Y direction is observed at the rear support plate B, with a size of 1.183 mm. Meanwhile, the deformation of the blade in the Y direction is 0.346mm, which is less than 1mm and meets the necessary requirements.

3 . Transient dynamic analysis

In dynamic simulation, a slider is placed at the initial position of the upper blade and is constantly subjected to shear force with a specified speed. The movement of the slider is used to simulate the plate shearing process.

Since the slider transmits only shear force, it has been adjusted to have frictionless contact with the upper blade. During sheet metal cutting, the contact between the upper blade and the sheet to be cut is illustrated in Figure 4. The contact length(s) is 8:1.

f2

Fig. 4 Cutting diagram

Fig. 4 Cutting diagram

To simplify the calculation, it is assumed that the shear force is uniformly distributed over a rectangular area with the length(s) and width

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