Sheet Metal Bending
Sheet metal bending is a forming process where a force is applied to a piece of sheet metal, causing it to form a desired angle and radius. When bending sheet metal, especially when using spring materials, there are several things to consider:
Bend Radius(K-factor) of Sheet Metal Bending
The first term to consider is the bend radius (neutral axis). The common term for this is the “K-factor.” Although there is a plethora of information on the internet, we will briefly discuss the spring aspect of sheet metal bending.
The inside radius is the distance from the bend axis to the inside surface of the material, between the bend lines. When specifying a radius on a drawing, most commercial, as well as government drawings specify the inside radius. This inside radius is easily measured with precision measuring equipment. With most annealed (soft) metals, a radius as low as 1/8 of the material thickness can be achieved. As a general rule, most full-hard/spring-tempered materials must have a minimum inside bend radius the same as the material thickness. This, however, isn’t always the case. One of the many variances from this rule is high carbon steel. Also known as ANSI 1074/1075, ANSI 1095, high carbon spring steel can be purchased in the annealed state, formed to a tight radius, then heat-treated to spring temper. These same materials can be purchased pre-tempered (black scaleless/blue-tempered). However, in no way, can these pre-tempered materials hold a radius as tight as the material thickness without fracturing.
Peninsula Spring has over 4 decades of hands-on experience with sheet metal bending. We understand that the sheet metal not only need to be formed without fracturing, but the integrity of the material grain structure must remain intact so that the springs will perform reliably.
Bend Lines in Sheet Metal Parts
A second, equally important term to consider when bending sheet metal, is the “bend-line”, or “fold-line.” In almost all cases, the bend line MUST be perpendicular to the material grain structure. This minimizes the chance of fracture or cycle fatigue. Many drawings require multiple bends, both parallel and perpendicular, to the grain structure. Peninsula Spring can help you determine which direction the grain structure should be facing as well as the proper bend radii by considering several variables including the material type, the spring function, and the application.
Springback When Bending Sheet Metal
Another term to consider when bending sheet metal is the residual stresses in the material. These stresses will cause the sheet to “spring-back” slightly after forming. Due to this elastic recovery, it is necessary to over-bend the sheet metal a certain amount so that the part to achieve the desired bend radius and bend angle.
Stress Relieving of Bent Sheet Metal Parts
When dealing with springs, these same residual stresses may cause the sheet metal to unbend when in use. For this reason, parts often need to undergo a stress-relief process. Peninsula Spring has the engineering experience to know when and how this crucial process must be performed. And, just like the above-mentioned spring back, when the stress-relief process is performed, there is some movement back to toward the unformed state. It is important to know how far to over-bend the sheet metal so that it returns to the desired angle after the stress relief process has been completed.
Contact Peninsula Spring For Your Sheet Metal Bending Needs
Please contact Peninsula Spring today or to Request a Quote for all your precision sheet metal bending needs. When you see how we can save you time, money and unnecessary headaches, you’ll be glad you contacted us first!