When designing sheet metal bending, we had discussions with experienced engineers to share insights into sheet metal bending. Consequently, a list of common mistakes and solutions to avoid these errors has been compiled.
Minimum Flange Length
As mentioned earlier, there is a minimum flange length. Refer to the bending force chart for guidance. Select die width based on thickness. If the flange you design is too short, it will "clumsily" fall into the gap, and you will not achieve the desired result.
Chamfer Faces
Chamfers must stop before the bottom of the detail.
If you are making a flange with one or two chamfered ends, the previous minimum flange length rule still applies. There must be enough space left for the chamfers to complete the proper bend; otherwise, the chamfers will appear deformed, and no one will be truly satisfied.
Distance of Hole to Bend
Nearby holes may deform.
If the holes are too close to the bend, they might deform. Round holes do not have issues of this nature, but your bolts might still not fit through. Again, refer to the bending force chart for the minimum flange dimensions and place the holes farther than the minimum distance.
Symmetry
Rectangular holes can be on both sides to avoid confusion.
There is a significant risk in manufacturing nearly symmetrical parts. If possible, make it symmetrical. If it is nearly symmetrical, the press brake operator might become confused. The result? Your part will bend in the wrong direction.
Symmetry cannot be guaranteed in all cases, but ensure that it is easily understood how it should be manufactured.
Rivet Nuts
Rivet nuts affect the way bending tools function.
If using rivet nuts near the bend line, it is well known that inserting them before bending ensures their applicability. After bending, the holes might deform. However, ensure that the nuts do not obstruct the tooling during bending.
Small Flanges on Large Parts
Small bends at the ends of large parts might pose difficulties.
It is best to avoid small flanges with large and heavy parts. This makes manufacturing very difficult and may require physical labor. However, this costs more than simple machining. Therefore, if possible, choosing an alternative solution is wiser.
Adjacent Bends
Refer to the bending force chart for the minimum flange length.
If continuous bending is to be included, check for feasibility. Problems arise when you cannot fit the already bent part onto the tooling. If the bends are facing the same direction (U-shaped bends), the general rule is to design the middle section longer than the flanges.
Keeping Bends in the Same Line
This part requires significant adjustments.
If there are multiple flanges in a continuous sequence, it is best to keep the bends on the same line. Considering this, you can minimize the number of operations. Otherwise, the operator needs to readjust the part for each bend, meaning more time and more money.
Bend Lines Parallel to the Side
This type of bend line leads to inaccurate results.
As the title suggests, for alignment, the bend lines must be parallel. If not, aligning the part becomes a headache, and the result might be unsatisfactory.
Bend Relief
Bend relief is necessary.
For optimal results, it is recommended not only to make a small laser-cut notch but also to actually cut a notch on the side that will become the flange, i.e., the protruding part of the bend. The width of this notch should be greater than the material thickness. This ensures that there will be no tearing or deformation at the final bend. Another good practice here is to include smaller radii at the bend relief, as they can also relieve material stress.
Bending Boxes
Subtle gaps ensure smooth operation.
When bending boxes, there should be small gaps between the flanges. Otherwise, the last bend will collide with the existing bend, disrupting the entire structure.
Check the Flatten Pattern
One thing to remember is to occasionally switch your CAD view to flat pattern mode. There are many benefits. First, if you are not used to flanges, you might encounter situations that cannot exist in flat pattern mode. What cannot exist in flat pattern mode cannot exist in any other way.
Measure the layout. Perhaps you can adjust the design for the best fit. If the dimensions are small, try to avoid using larger sheets of paper. If you are short by a few millimeters, perhaps two pieces can fit on the same sheet? It will reflect in the final quote.
The Empirical Rule of Minimum Bend Radius
Keep it simple. It's simpler than choosing an inner radius (ir) equal to the material thickness. This avoids future troubles, overthinking, and silly mistakes. Going below this value might land you in trouble. Larger radii only make some calculations more difficult.
Bend Direction
Perpendicular to the rolling bend.
The design direction of the bend should not be the same as the material rolling. This is especially important for aluminum. Of course, we all know that aluminum enclosures have four sides, which means the bending operation is opposite to what we recommend. Nevertheless, it is still best to avoid this situation. The result might be uneven surfaces or even fractures.
Although manufacturing engineers will pay attention to these things, it's best to be mindful yourself. It helps to explain the use of the material.
Hemming
Retain the inner radius (if possible).
If reinforcing the edge of a metal sheet, hemming is a good choice. Nevertheless, there are some recommendations. It's best to leave a small radius on the underside. Completely crushing the radius requires tremendous force and tonnage. Moreover, it puts the material at risk of cracking. On the other hand, retaining the radius can mitigate this risk.
Consider the Material
Standard 1...3mm thin structural steel can withstand almost any pressure. Beyond that, you need to do research. Some materials are more unpredictable in their handling. Getting good results depends on your knowledge and the assistance that production engineers can provide.
