Bending steel is defined as deforming steel around a straight axis. We use force to manipulate steel until it reaches a desired angle or shape. The difference between bending versus rolling depends on the radius. For larger radii, we call it rolling, and for smaller radii, we use bending. In this post, we’ll be focusing on bending plates.
The bend must always be performed perpendicular – or at most 45-degrees – to the grain lamination direction. This will increase bent resistance and reduce the risk of fractures.
A keen knowledge of Bending Direction can help protect sheet metal strength. When metal is rolled and stretched thinner and longer in a particular direction, it develops a natural “grain.” This grain has a significant impact on the nature and strength of the metal. Sheet metal fabricators must be able to identify the direction of the produced grain and counteract any defects that might develop if the metal is formed or rolled in the wrong direction. Working with the natural grain and natural ductility of the metal in the appropriate manner will help maintain its strength. In fact, the direction of the grain on a piece of rolled metal will have a direct impact on the type and degree of inside bend radius.
Ratios and proportions
The ratios and proportions of the Inside Bend Radius matter. Yes, contrary to belief, understanding the math is crucial to successful sheet metal bending or rolling. The minimum inside bend radius is directly proportionate to the thickness of the metal being formed. The thicker the material, the greater the radius. Calculating the proper inside bend radius is a key step in crafting a strong product every time. Every type of metal will have its own unique capabilities and ratios assigned for bending. Then, the next step is to identify which tool is the proper tool to complete the bend appropriately without compromising its structural integrity. It takes a highly-skilled, exceptionally trained fabricator to understand those unique specifications and produce optimal results every time.
- The curvature radius has an important impact on thickness variations. One bend with no inside radius could imply material fractures and we should always avoid this kind of bend. Below are two examples of how stretching from press compression relates to thickness reduction:
- If the radius equals the thickness of the steel plate, the stretching of the material due to the tightness of the bend causes the plate thickness to decrease up to 20%.
- If the radius equals up to 5 times the thickness, the material does not stretch nearly as much, and material thickness decreases by less than 5%.
The material tends to want to bend back to its original shape – this is commonly known as “spring back”. Every piece of material has to be evaluated and taken into consideration when bending. In some cases, the dies used to roll the material will bend the material further than the desired radius, but the over bend will be compensated by the material´s spring back.
Bending metal is ap skill. Anticipating how the metal will bend under pressure can be challenging. One thing is certain, however; metal is elastic. Yes, that’s right. Metal will tend to bend back toward its original shape when being bent. This is a fabrication problem that great formers will be able to overcome, however. By knowing exactly how much to over-bend the sheet or plate beyond the intended final radius, formers can compensate for the “spring back” of the metal, ensuring that the desired radius is reached in the end.