Calcular fórmulas e gráficos de dedução de curvatura

Calculate curvature deduction formulas and graphs

1. What is curvature deduction?

The curvature deduction is commonly called the “withdrawal value”. It is a simple algorithm used to explain the sheet metal bending process.

What is curvature deduction

The bend deduction method states that the flat length (L) of a part is equal to the sum of the lengths of the two flat parts extending to the “cusp” (the point where the two flat parts virtually intersect) minus the deduction of bending (DB).

2. Calculate curvature deduction

    3. Curvature deduction formula

    How to calculate the bending deduction coefficient in sheet metal manufacturing?

    Flexure allowance in sheet metal fabrication is a term used when defining Solidworks parameters and is also a formula used for many years in sheet metal fabrication shops. Let's take a look at the calculation formula in Solidworks.

    Lt = A + B – BD

    Where:

    • Lt is the total unfolded length
    • A and B are as shown in the figure
    • BD is the flexion deduction value.

    Bend deduction in Solidworks is only used for calculating 90-degree bends in sheet metal.

    However, it can also be used for the calculation of unfolding of sheet metal other than 90 degrees, but the bending deduction value for bending other than 90 degrees must be used according to the bending coefficient table.

    Each manufacturer has a different table and there may be errors. Some sheet metal plants may not use bends other than 90 degrees frequently.

    Today, I will mainly share the flexion deduction calculation method for 90-degree flexion that I am familiar with.

    Today, I will share the calculation method for deduction of 90 degree flexion flexion that I am familiar with.

    There are approximately three algorithms for calculating flexion deductions:

    1. 1.7 times the thickness of the material.

    Sheet metal factories generally use 1.7 times the material thickness as bending deduction, which is the simplest calculation method for sheet metal unfolding.

    However, it is not very accurate. If the accuracy requirement is not high in sheet metal processing, it can be used directly.

    Different materials can also have different values; aluminum plates can be calculated based on 1.6 times the material thickness, while stainless steel plates can be calculated based on 1.8 times the material thickness.

    1. Bending deduction = 2 times material thickness + 1/3 material thickness.

    This bending deduction calculation formula has been summarized by the sheet metal manufacturing industry for a long time and is also an approximate calculation method.

    The theoretical explanation of this calculation formula is: Sheet unfolding = Length A + Length B – 2 times the thickness of the material + 1/3 of the thickness of the material's elongation coefficient.

    The calculation begins by adding the lengths of the shortest straight line and the elongation factor. It is believed that sheet metal will stretch during the bending process.

    1. Bending deduction = 2 times the material thickness – (0.72t-0.075V-0.01).

    This formula is derived from an online newspaper article. Its characteristic is to consider the influence of the width of the lower die on the deduction of bending.

    Test data is derived from experiments on carbon steel plates and the accuracy of using other materials is unknown. I used this formula for the unfolded calculation of an aluminum plate folded once with a slot width of 4 times the material thickness, and the resulting numerical value was relatively accurate. This formula is very accurate for unfolded calculation of carbon steel plates.

    Explanation: t is the actual thickness of the sheet metal, and the nominal thickness should not be used for calculation. The above two methods have approximate calculations and are not strict in thickness requirements. This formula needs to be calculated based on the actual thickness measured by the calipers.

    V is the width of the groove in the lower die during bending. Generally, 6 to 8 times the material thickness is considered the groove width. The actual amount used is calculated according to actual usage, for example: using 10 lower folds for 1.5.

    There are many methods for calculating bending deductions, including formulas based on neutral layer theory. This formula is not conducive to the actual processing of sheet metal, so it is not mentioned here.

    The above three methods are the most practical and simple bending or unfolding calculation methods, suitable for sheet metal factories.

    4. Curvature deduction chart

    (1) Sheet Metal Material Bending Deduction Table

    V Matrix width
    w    		 radius of curvature T 30° 45° 60° 90° 120° 150° 180° Outer layer with 90° double fold Minimum bend size H Minimum Z Curve Size (Z)
    8.0 12.0 R1 0.6 0.2 0.5 0.9 1.0 0.7 0.2 0.3 1.9 6.0 10.0
    0.8 0.3 0.6 1.0 1.6 0.8 0.3 0.4 2.2
    1 0.3 0.7 1.1 1.7 0.9 0.3 0.5 2.5
    1.2 0.4 0.8 1.3 2.2 1.1 0.4 0.6 2.8
    R2 0.6 0.2 0.5 0.9 1.6 0.7 0.2 0.3 1.9
    0.8 0.3 0.6 1.2 1.8 0.8 0.3 0.4 2.2
    1 0.3 0.7 1.2 2.0 0.9 0.3 0.5 2.5
    1.2 0.4 0.8 1.4 2.3 1.1 0.4 0.6 2.8
    10.0 14.0 R1 1.5 0.7 1.2 1.6 2.5 1.3 0.5 0.7 3.2 7.0 11.0
    R2 1.5 0.6 1.0 1.5 2.7 1.3 0.5 0.7 3.5
    12.0 16.0 R1 two 0.6 1.3 2.0 3.4 1.7 0.6 0.9 4.4 8.5 13.0
    R2 two 0.9 1.4 2.0 3.6 1.7 0.6 0.9 4.5
    16.0 26.0 R1 2.5 0.7 1.5 2.4 4.3 2.2 0.8 1.1 5.6 12.0 20.0
    3 0.8 1.7 2.8 5.1 2.8 0.8 1.3 5.8
    R2 2.5 0.8 1.6 2.5 4.8 2.3 0.9 1.1 6.2
    3 1.0 2.0 3.0 5.2 2.8 1.0 1.3 6.4
    22.0 32.5 R1 4 1.0 2.4 3.5 6.5 3.3 1.1 16.0 26.0
    R2 4 1.2 2.6 4.0 6.8 3.5 1.1
    32.0 50.0 R1 5 1.2 3.2 4.8 8.6 4.6 1.4 24.0 38.0
    6 1.5 3.5 4.5 9.5 5.0 1.8
    R2 5 1.5 3.4 5.0 8.8 4.5 1.6
    6 1.8 3.8 5.5 9.8 5.2 2.0

    Explanation:

    • T: Material thickness;
      V: Bottom width of the die slot;
      W: Bottom width of the matrix;
      α: Internal angle after bending;
      H: Minimum distance from the bending center of the die to the edge of the material;
      Z: Minimum Z fold size.
    • Unfolding formula: L = A + B – K; (A, B: External dimensions of the part; K: Material flexion coefficient);
    • Expanded size of flattened steel sheet: L = A + B – 0.45T;
    • Expanded size of pressed steps: L = A + B – 0.3T;
    • Minimum Z-fold size: Z = W/2 + 2T + 1;
    • The deduction coefficients for cold-rolled steel sheet, aluminum-zinc coated sheet, stainless steel sheet, electrolytic sheet and aluminum sheet are the same;
    • According to the current conditions of the company's upper die, the upper die bending coefficient R1 is suitable for cold-rolled steel sheet, aluminum-zinc coated sheet and stainless steel sheet; The upper die bending coefficient R2 is suitable for aluminum plates, copper plates, electrolytic plates, etc.

    (2) Mild steel curvature deduction chart

    Formula 0.2t 0.4t 0.6t 0.8t 1.0t 1.2t 1.4t 1.6t
    Angle 155-165° 145-155° 135-145° 125-135° 115-125° 105-115° 95-105° 85-95°
    Thickness

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