1. General Principles:
1. The cross-section of a bent part will undergo changes in the bending deformation zone. The smaller the ratio of the bending radius to the plate thickness, the greater the change in the cross-sectional shape.
2. The bending curve of the bent part is best perpendicular to the direction of the grain. It is preferable to use the smooth surface of the blank as the outer surface of the bent part to reduce surface tearing.
3. Bending processes will result in springback. The larger the ratio of the bending radius to the plate thickness, the greater the springback.
2. Selection of Bending Radius:
1. The bending radius of the bent part should be selected appropriately, neither too large nor too small. The minimum bending radius should only be used when necessary in the structure.
3. Process Requirements:
1. The length, width, and thickness of the material, as well as the direction of the grain, should meet the requirements of the drawings. The surface of the sheet metal should be clean.
2. Select suitable tooling according to the requirements of the drawings and the chosen material.
3. Check the working condition of the bending machine and perform maintenance before processing.
4. Clean and lubricate the bending surface of the tooling before and during the bending process.
4. Process Quality:
4.1 Appearance:
4.1.1 Non-machined surfaces should be kept clean. If the raw material has a surface protective film that does not affect the machining or part accuracy, it should be retained. The degree of surface scratches should not exceed the specified limit for heavy scratches, and for export products, it should not exceed the specified limit for light scratches.
4.1.2 Surface indentations, which are periodic or non-periodic concave impressions on the sheet metal surface, should be ≤ 5 × 10/m according to the length of the processed sheet metal.
4.1.3 There should be no obvious tensile cracks on the bent surface.
4.1.4 There should be no edge cracking on the bending angle. When unavoidable bending cracks exist, appropriate-sized process holes should be created at the cracked edges.
5. Dimensions:
5.1 The linear dimensions and tolerances of structural components and the relative positions of various openings and slots should meet the requirements of the drawings. If tolerances are not specified, they should meet the requirements of tolerance grade m.
5.2 The diagonal dimensions should meet the following requirements, while satisfying the linear dimensions, geometric dimensioning and tolerancing requirements:
a. When the diagonal length ≤ 550mm, the difference between the diagonals should not exceed 1.5mm.
b. When the diagonal length > 550mm, the difference between the diagonals should not exceed 3mm.
6. Shape:
6.1 Straightness, flatness, and perpendicularity should meet the requirements of tolerance grade L if tolerances are not specified.
6.2 The tolerance value for parallelism is equal to the given dimension tolerance value or the larger value between the tolerance values of straightness and flatness if not specified.
6.3 Other requirements are specified in the drawings or process documents.
7. Inspection:
7.1 First-piece inspection must be conducted before processing multiple sheet metal bending parts.
7.2 Visual inspection should meet the requirements stated in 4.1.
7.3 Dimensional inspection of the bent parts should meet the requirements stated in 4.2.
7.4 Shape inspection of the bent parts should meet the requirements stated in 4.3.
7.5 Bent parts that have undergone rework or repair should be re-inspected according to the inspection procedure, and the quality indicators should not be lowered.
7.6 Other quality requirements should be inspected and judged according to the provisions in the drawings and process documents.
8. Safety:
8.1 Overloading bending should be avoided as much as possible.
8.2 The bending force of the workpiece should not exceed the nominal force.
8.4 The opening size of the V-groove in the lower die of the bending workpiece should be greater than 6-8 times the thickness of the plate.
8.5 Operators should wear protective gloves during operation.
8.6 The gap between the upper and lower dies of the bending machine must be adjusted uniformly, and the gap can be 1mm larger than the plate thickness.
8.7 Tools and measuring instruments should not be placed on the bending machine dies or the worktable.
8.8 The workpieces should be handled with care to avoid dragging or dropping. The maximum height of stacked materials on-site should not exceed 1m.
1. The cross-section of a bent part will undergo changes in the bending deformation zone. The smaller the ratio of the bending radius to the plate thickness, the greater the change in the cross-sectional shape.
2. The bending curve of the bent part is best perpendicular to the direction of the grain. It is preferable to use the smooth surface of the blank as the outer surface of the bent part to reduce surface tearing.
3. Bending processes will result in springback. The larger the ratio of the bending radius to the plate thickness, the greater the springback.
2. Selection of Bending Radius:
1. The bending radius of the bent part should be selected appropriately, neither too large nor too small. The minimum bending radius should only be used when necessary in the structure.
3. Process Requirements:
1. The length, width, and thickness of the material, as well as the direction of the grain, should meet the requirements of the drawings. The surface of the sheet metal should be clean.
2. Select suitable tooling according to the requirements of the drawings and the chosen material.
3. Check the working condition of the bending machine and perform maintenance before processing.
4. Clean and lubricate the bending surface of the tooling before and during the bending process.
4. Process Quality:
4.1 Appearance:
4.1.1 Non-machined surfaces should be kept clean. If the raw material has a surface protective film that does not affect the machining or part accuracy, it should be retained. The degree of surface scratches should not exceed the specified limit for heavy scratches, and for export products, it should not exceed the specified limit for light scratches.
4.1.2 Surface indentations, which are periodic or non-periodic concave impressions on the sheet metal surface, should be ≤ 5 × 10/m according to the length of the processed sheet metal.
4.1.3 There should be no obvious tensile cracks on the bent surface.
4.1.4 There should be no edge cracking on the bending angle. When unavoidable bending cracks exist, appropriate-sized process holes should be created at the cracked edges.
5. Dimensions:
5.1 The linear dimensions and tolerances of structural components and the relative positions of various openings and slots should meet the requirements of the drawings. If tolerances are not specified, they should meet the requirements of tolerance grade m.
5.2 The diagonal dimensions should meet the following requirements, while satisfying the linear dimensions, geometric dimensioning and tolerancing requirements:
a. When the diagonal length ≤ 550mm, the difference between the diagonals should not exceed 1.5mm.
b. When the diagonal length > 550mm, the difference between the diagonals should not exceed 3mm.
6. Shape:
6.1 Straightness, flatness, and perpendicularity should meet the requirements of tolerance grade L if tolerances are not specified.
6.2 The tolerance value for parallelism is equal to the given dimension tolerance value or the larger value between the tolerance values of straightness and flatness if not specified.
6.3 Other requirements are specified in the drawings or process documents.
7. Inspection:
7.1 First-piece inspection must be conducted before processing multiple sheet metal bending parts.
7.2 Visual inspection should meet the requirements stated in 4.1.
7.3 Dimensional inspection of the bent parts should meet the requirements stated in 4.2.
7.4 Shape inspection of the bent parts should meet the requirements stated in 4.3.
7.5 Bent parts that have undergone rework or repair should be re-inspected according to the inspection procedure, and the quality indicators should not be lowered.
7.6 Other quality requirements should be inspected and judged according to the provisions in the drawings and process documents.
8. Safety:
8.1 Overloading bending should be avoided as much as possible.
8.2 The bending force of the workpiece should not exceed the nominal force.
8.4 The opening size of the V-groove in the lower die of the bending workpiece should be greater than 6-8 times the thickness of the plate.
8.5 Operators should wear protective gloves during operation.
8.6 The gap between the upper and lower dies of the bending machine must be adjusted uniformly, and the gap can be 1mm larger than the plate thickness.
8.7 Tools and measuring instruments should not be placed on the bending machine dies or the worktable.
8.8 The workpieces should be handled with care to avoid dragging or dropping. The maximum height of stacked materials on-site should not exceed 1m.
