K-factor, bend allowance, and bend deduction are important values used to calculate the correct sheet metal flat length or flat pattern.
The length of the sheet in the bending state is different from the length of the flat pattern because the sheet metal will stretch and compress during bending on the prensa plegable.
En este artículo, hablaremos del factor K, de la tolerancia de curvatura y de la deducción de curvatura.
¿Qué es el factor K?
First, we need to understand the neutral axis. When sheet metal is bent, the bottom surface is compressed, and the top surface is stretched.
The neutral axis is located inside the metal where it will neither be compressed nor expanded, allowing it to maintain a constant length.
In flat sheet metal, the neutral axis is evenly located at half the thickness of the sheet metal, but it will move during bending.
The position change of the neutral axis is determined by various factors such as the material properties, thickness, bending angle, internal radius, and bending method of the plate.
Mathematically, the K-factor represents the ratio between the position of the neutral axis (t) and the plate thickness (T).
Donde t es la distancia de la superficie interior al eje neutro y T es el espesor del metal (Figura 1).
The K-factor is determined by the physical properties of the material, bending method, bending angle, and other factors.
It typically ranges between 0.30 and 0.50.
In precision sheet metal manufacturing, the K-factor is a crucial factor.
The K-factor is used to calculate the bending flat pattern, which is directly related to the length of the sheet metal stretched during bending.
It is the fundamental value for determining the bending allowance and bending deduction.
Since the ratio of the distance to the neutral axis to the plate thickness determines the position of the neutral axis in the metal plate, knowing the K-factor helps determine the position of the neutral axis after bending.
You can also determine the K-factor using the table below:
¿Qué es el subsidio de curvatura?
The Bend Allowance (BA) is the arc length of bending measured along the neutral axis of the metal plate since the length of the neutral axis does not change after bending.
Once the bend allowance is calculated, it should be added to the flat length to determine the required sheet metal length needed to form the desired workpiece.
Como se muestra en la siguiente figura:
Para calcular la longitud plana se utiliza la siguiente fórmula:
Longitud de la chapa = Longitud de la pata 1 +BA + Longitud de la pata 2
Fórmula de cálculo del subsidio de curvatura
Dónde:
A - Ángulo de curvatura
R - Radio interior
Factor K - K
T - Espesor del material
¿Qué es la deducción por flexión?
After bending, the flange length (i.e., the total length) is greater than the length of the sheet metal flat pattern.
Bend deduction is the length of material that we need to remove from the total length of the plate to obtain the correct flat pattern.
Fórmula de cálculo de la deducción de la curva:
De acuerdo con la figura anterior, la deducción de curvatura es la diferencia entre la tolerancia de curvatura y el doble del repliegue exterior.
Deducción por flexión = 2 × OSSB - BA
Fórmula de cálculo de la deducción de la curva:
Conclusión
The K-factor, bend allowance, and bend deduction are crucial factors to consider when designing and bending sheet metal parts.
By calculating these values, the material length and workpiece size can be determined, resulting in more accurate bending and reduced material waste.
For stable press brake performance, consider ADH's products, which can be found on our product page.
