1.0 Objective:
To guide bending personnel in the more rational selection of die molds, improve the service life of the molds, and reduce abnormal wear and tear.
2.0 Function:
To shorten the time required for selecting bending die molds, enhance production efficiency, and lower costs.
3.0 Scope of Application:
Sheet metal bending operations.
4.0 Content:
4.1 Commonly used top punch include: 88° straight punch (R1), 30° acute punch/straight acute punch (R1/R0.5), 88° gooseneck punch (R1), 88° straight gooseneck punch (R1/R0.5), flattening punch, and specialized upper die molds.
4.2 Commonly used lower die for bending include: single/double V lower molds with angles of 30° and 88°, V4, V6, V7, V8, V10, V12, V16, and V25 (mm).
4.3 The selection of bending die is generally based on the arrangement of the bending blade sequence after reviewing the drawings.
4.4 Selecting the upper die according to the angle:
4.4.1 When the processing angle is greater than or equal to 88°, use an upper die with an angle less than 88° (e.g., straight blade, sharp blade/straight sharp blade, curved blade, straight curved blade, etc.).
4.4.2 When the processing angle is less than 88°, use a 30° upper die (e.g., sharp blade/straight sharp blade).
4.4.3 When it is necessary to press a dead edge, use a sharp blade/straight sharp blade to form an acute angle (generally 30°), and then use a flattening mold to flatten the pressed edge.
4.4.4 When the plate thickness exceeds 3mm, avoid using sharp blades/straight sharp blades to prevent tool damage.
4.5 When it is necessary to process a U-shape based on the external shape requirements.
When b-a ≥ 5mm, you can choose from acute punch (straight sharp blade), straight punch (straight blade), straight gooseneck punch (straight curved blade), or gooseneck punch (curved blade).
When 1mm < b-a < 5mm, you can choose from straight gooseneck punch (straight curved blade) or gooseneck punch (curved blade). When b-a < 1mm, you can choose gooseneck punch (curved blade).
Note: Both a and b > 6mm and 100mm > a, b are internal dimensions. When you need to process a Z-shape, you typically choose from straight punch (straight blade), acute punch (sharp blade/straight sharp blade), straight gooseneck punch (straight curved blade), and gooseneck punch (curved blade).
4.6 Lower die selection:
4.6.1 The size of the V-groove is generally chosen based on six times the thickness of the plate.
4.6.2 Select the lower die according to the angle: when the angle is greater than or equal to 88°, you can choose from 88° or 30° lower dies; when the angle is less than 88°, choose a 30° lower die (measure the effective height of the upper die mold: the distance from the upper die mold to the blade edge on the force-receiving surface of the upper die clamp).
4.7 When splicing upper and lower dies, the following points should be considered:
4.7.1 Do not mix molds with different heights during selection, as this may cause poor angles, damage to the die molds, or even cause work-related accidents.
4.7.2 When selecting an upper die mold for a hemming door panel, consider product processing quality and ease of handling, generally leaving a gap of 3-6mm at both ends (if necessary, consider using an “edge blade”).
4.7.3 Avoid using damaged molds for product processing to prevent poor appearance, and inspect the linearity and flatness of the upper die mold’s cutting edge after installation.
4.7.4 When avoiding positions, be aware of appearance quality issues such as indentation at the avoidance point and insufficient angles.
4.8 Die mold selection under abnormal conditions:
4.8.1 For pressing lines, choose a pressure-resistant sharp blade for the upper die mold and a flat, aligned lower die mold with no steps between upper and lower die molds.
4.8.2 When processing U-shapes, if the inner dimension of the opening is less than 6mm, first use a curved blade to bend the opening larger than the second blade size, then press flat to ensure the dimension or use a specialized mold for shaping.
4.8.3 When processing products with specific requirements for the internal R radius, consider a matching R-radius upper die mold in advance when selecting the upper die mold (e.g., internal R radius requirements of R0.3, R1, R4, R8, or R10).
4.8.4 When bending 6mm with a 2.0mm plate thickness, choose an 88° V8 lower die mold; when bending 10mm with a 3.0mm plate thickness, choose an 88° V12 lower die mold to prevent workpieces from slipping and becoming unprocessable due to excessively small processing dimensions.
4.8.5 When processing round steel, use specialized die molds and have a dedicated operator.
4.9 When selecting top punch/bottom die molds, try to avoid splicing to prevent splicing marks and maintain a good product appearance.
4.10 When calibrating top/bottom die molds, use molds that are greater than or equal to 300mm for calibration. Do not use spliced small molds or molds smaller than 300mm for calibration. For molds over 1m in length, the length difference between the top and bottom die molds should not exceed 20%.
4.11 Before installing the die mold, make sure to check whether the machine’s limited travel is greater than the total height of the top/bottom die molds to prevent mold damage and work-related accidents.
4.12 Check whether the mold is locked before calibration, and check the mold’s tightness again after calibration.
4.13 Do not place unused die molds on the equipment to prevent molds from falling, causing damage or injury.
4.14 After using the die mold, promptly return it to the designated mold rack and place it neatly.
4.15 Do not install two different height die molds on the equipment at the same time.
4.16 The workshop should regularly maintain and service the die molds and clearly mark them.
