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Bending stainless steel presents a unique set of challenges compared to working with softer materials like mild steel or aluminum. Its strong nature, work-hardening characteristic, and springback characteristic require a considerate method of tooling choice. Selecting the appropriate press brake tooling is not only a matter of producing a bend, but a matter of producing a precise bend, a surface quality and long time life of your tools. This guide will take you through the imperative considerations.
Understanding the Material Characteristics
It is imperative to know what is different about stainless steel before choosing your tooling. It has high level of yield strength and is difficult to bend as compared to mild steel. More importantly, it hardens very fast as it is bent. This serves to make the material more brittle and hard at the exact bend point. Also, stainless steel has the great tendency to spring, trying to get to its initial position after bending. These characteristics require that your tooling is strong enough to get over.
Selecting the Appropriate Tool Steel
The material used in your punches and dies are most critical. Normal tool steel will wear out easily and is also subject to galling, where some material of the stainless workpiece sticks to the tool face and creates scratches and defects.
For repetitive, high-volume bending of stainless steel, it is highly advisable to invest in hardened and ground tool steel. The Tools that are produced using this material have superior wear resistance and life. In order to obtain a good result and virtual absence of the phenomenon of galling, it is best to imagine the tools that have a mirror finish. It has an ultra-smooth surface and decreases friction and material pick up to maintain the original stainless steel surface on your parts.
The Correct Die Opening
V- die width is a fundamental computation. The standard common rule of thumb is to multiply the material thickness by eight to determine the appropriate die opening for stainless steel. An example is that a 1-inch die opening would typically be required where the sheet is 10-gauge (approximately 0.135 inches).
Excessive tonnage, higher cracking and faster tool wear can be met when using a die that is too narrow. An excessively wide die may cause unwanted springback and more difficult attainment of an accurate angle. It also may raise the chances of developing an unwanted large bend radius. Always always look at tonnage charts so you know the amount of force your press brake can exert on your given combination of material and die width.
Accounting for Springback and Bend Radius
The opponent of bend accuracy in the stainless steel is springback. To resist it, you should bend the material more than the desired angle, foreseeing the extent of the spring-back tendency. The amount of springback increases with the material's tensile strength.
Selection of tooling is also a factor that determines the inside bend radius that you are able to attain. In general rule, punch nose radius must be a bit small than the intended inside bend radius. Nevertheless, the substance will automatically create a radius depending on the die opening. When air bending is involved, the inside radius is usually cut at 15 to 20 percent of the die opening. The knowledge of this association is essential in obtaining your desired part specifications.
Final Considerations for Success
There are also some minor tips that will make the difference besides the primary factors. You should always clean your tools and remove any dirt or debris which may be impressed on the soft stainless surface. A higher durometer urethane pad on your die may protect the bottom of the part against scratching. To achieve the best quality bends on difficult parts, a consultation with a tooling specialist can be a valuable guide depending on the application you make of it. All it takes is a little attention to your tooling to learn to bend stainless steel to make a component that is strong and precise and has a visual finish to it.
