1. Ordinary Blade Arc
1. Select 0.2R ordinary upper and lower dies based on the mold selection criteria, calculate the arc length, determine the number of bends required to complete the arc based on the arc length and material thickness, calculate the bending angle for each fold based on the arc angle and number of folds, and then perform the bending. However, since the arc forming process is achieved by bending with several or even dozens of blades, the size range of the bending arc is limited by the tooling.
The general processing range is as follows:
1) Forming a 90-degree arc: Forming an arc larger than R12.
2) Forming an arc exceeding 120 degrees: Any arc larger than the tool's limit can be processed.
2. Processing considerations
The choice of tooling depends on the processing method, for example, the width of the V-groove should be determined based on the feed rate.
2. R-die Folding Arc (Round Bar and Arc Blade Folding Arc)
Form the arc with the inherent R-angle of the tooling. When selecting the die, if the arc is smaller than R12, the upper and lower dies of the processing specification can be selected for one-time forming. Since the R-die is a standard die and its size is limited, the size of the processed arc is also limited.
The existing standard die specifications are as follows:
1) R-angle for ordinary blades: R3.0.
2) Round bar specifications: R3.0, R4.0, R5.0, R6.0, R8.0, R10, R12. If the required R is not within the range of standard die specifications, the R can be increased by feeding at the outer circumference of the R-die. If an arc larger than R12 requires multiple bends, the processing conditions are the same as for ordinary blades.
One advantage of R-shaped arcs is that they compensate for the shortcomings of ordinary blade arcs. The bending appearance is smooth, the effect is good, and it can process products with strict appearance requirements.
3. Processing considerations
1) When bending R-die arcs, attention should be paid to selecting the die based on the die selection criteria. However, when processing a 90-degree arc, due to the springback of the processed sheet, the machining of a 90-degree arc with the lower die at 90 degrees may not meet the requirements. Manual pushing is required during processing to ensure the bending angle. Therefore, when the lower die is set at 88 degrees, the 88-degree lower die should be used as a priority when processing a 90-degree arc.
2) When processing arcs, it is necessary to use inspection fixtures for dimensional inspection to ensure the appearance dimensions of the processed parts.
3) When processing corner arcs, easy dies or manual processing are generally used.
4) Using R-type dies (round bar and arc blades)
The standard width of the V-groove for the lower die in arc folding is as follows:
(1) When bending a 90-degree arc, the width of the V-groove for the lower die should be: V > 2(R + T).
(2) When bending a 135-degree arc, the width of the V-groove for the lower die should be: V > 1.5(R + T).
4. Types of Arc Processing
1) Forming a 1/4-circle folding blade:
Workpiece radius (r) = Folding blade radius + shim.
2) When the workpiece has a large R-angle, use folding blades to process multiple times until the desired arc angle is achieved.
3) Processing a 2/4-circle arc:
Folding blade R + shim + 30-degree lower die + shaping = Workpiece processed R; Rod + washer = Workpiece processed R.
4) Processing a 3/4-circle arc:
(1) When the workpiece is long, use folding blades to process one by one (suitable for larger R-angles).
(2) When the workpiece is narrow, use ear blades for processing (suitable for larger R-angles).
(3) Special method of processing: Using rolling dies.
