Chapa-Tipos de Desplegados
Aprovechamos el documento explicativo de AutoPOL para mostrar los distintos tipos de cálculos de desplegado que se usan y de esta forma saber de dónde sale la famosa formula de que usa en su parte final el logaritmo de la relación entre Radio interior y Espesor (como no tiene Norma DIN). Y tener claro que es una curva doble o simple.
La función de desplegado de Auto POL es capaz de crear el desplegado de una chapa de cualquier geometría desarrollo de patrón plano de todos los tipos de geometría 3D que sea de una solo superficie curva. Para una sola superficie curva, debe ser posible establecer una generatriz de la superficie, desde cualquier punto de la superficie. Por el contrario una doble geometría curva no puede ser desplegada.
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Geometrías de curvatura doble que no pueden desplegarse.
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Double curved, revolved solid. |
Double curved, lofted surface |
Double curved, swept solid. |
Geometrías de curvatura simple que pueden desplegarse.
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Single curved, lofted solid. |
Single curved, ruled surface. |
Single curved, swept solid. |
Durante el proceso de plegado el material se estira su lado exterior y es comprimido en su cara interna. La línea neutral, donde hay compresión ni elongación, no puede calcularse sólo geométricamente. Para calcular una longitud correcta de un desplegado para un determinado radio, es necesario utilizar un factor de compensación de plegado.
En Verde operaciones que ya son desplegadas por Autodesk Inventor desde la Versión 2011 en amarillo operaciones que aun siendo desplegados no obtienen resultados correctos y en rojo operaciones que no se pueden desplegar en la actualidad
K-factores de archivo
Estos valores son experimentales. Los valores del factor k dependen del ángulo de plegado y la relación entre el radio interior y el espesor. AutoPOL proporciona un fichero de material que contiene valores que generan precisa en la mayoría de los casos. Sin embargo, los valores del factor k dependen de muchos parámetros diferentes.
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30-180 |
Bend Angle |
0.5-10 |
Ratio calculated from Inner radius / Sheet thickness |
OK |
Exit and accept changes |
Cancel |
Exit and ignore changes |
The dialog box above contains the k-factors.
Note: The k-factor values are in the range of 0.00 – 1.00 and typed as percent (%) values in this table.
Interpolation is used by the unfolding function to calculate the K-factor for bend angles and Ri/t ratio values, which are not found exactly in the table. For example:
Inner radius Ri =0.5 Sheet thickness t=0.7 and Bend angle=45°
gives a K-factor=0.801 with calculation as shown below.
Ri/t = 0.5/0.7 = 0.7142
Bend angle = 30° K-factor = 0.8 + (0.7142-0.5) * (0.88-0.8) / (1.0-0.5) = 0.8342
Bend angle = 60° K-factor = 0.73 + (0.7142-0.5) * (0.82-0.73) / (1.0-0.5) = 0.7686
Bend angle = 45° K-factor = 0.8342 – (0.8342-0.7686) / (60-30) * (45-30) = 0.801
DIN 6935
Calculates the K-factor according to DIN 6935 standard.
The formula shown below is used.
K = 0.65 + 0.5 * Lg(Ri/t) |
(for Ri/t < 5) |
K = 1 |
(for Ri/t >= 5) |
Constant
Uses a constant K-factor regardless of bend angle, inner radius or sheet thickness.
Note: The K-factor values are in the range of 0.00 – 1.00 and typed as percent (%) value.
None
No calculation regarding to the sheet thickness or K-factor bend compensation is applied. The actual surface is unfolded. Normally used to generate a flat pattern, which will be used as a template.
Examples – Calculation of unfolding length
General Formulas: L = l1 + l2 + lb l1 = L1 – t – Ri l2 = L2 – t – Ri lb = p * Rn * v / 180 Rn = Ri + t * k / 2 K-factor DIN 6935: k=0.65+0.5*Lg(Ri/t) for Ri/t<5 k=1 for Ri/t>=5
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Example: K-factor from file: k = 0,72 (from table, Ri / t = 1 and v = 120°) Rn = 2 + 2 * 0,72 / 2 = 2,72 lb = p * 2,72 * 120 / 180 = 5,69 L = 70 + 50 + 5,69 = 125,69 K-factor DIN 6935: k = 0.65+0.5*Lg (Ri/t)=0.65 Rn = 2 + 2 * 0,65 / 2 = 2,65 lb = p * 2,65 * 120 / 180 = 5,55 L = 70 + 50 + 5,55 = 125,55 |
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Cilindro a Desplegar |
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Unfolding of the outside, L = F*100 using None opti |
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Unfolding of the inside, L = F*90 using None option |
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Unfolding of the cylinder, L = F*95 (Thickness=5) using K-factor method. (k=1) |
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