Free Sheet Metal Bending Force Calculator
Quickly calculate the required tonnage and V-die opening for your sheet metal bending projects. Compatible with mild steel, stainless steel, and aluminum.
Bending Force Calculation Formula
Understanding Sheet Metal Bending Parameters
Whether you are operating a CNC press brake or calculating required tonnage for a new machinery investment, understanding the core bending variables is essential for precision fabrication. Here is a breakdown of the key parameters used in our tonnage calculator:
- $F$ (Bending Force / Tonnage): Often referred to as press brake tonnage, this is the total amount of pressure required to successfully bend your material. It is usually measured in tons (t) or kilonewtons (kN). Exceeding your machine's maximum tonnage capacity can damage both the press brake and the tooling.
- $S$ (Sheet Thickness): The physical thickness of the metal plate you are bending (measured in mm). The required bending force increases exponentially with the square of the material thickness ($S^2$).
- $V$ (V-Die Opening): The width of the V-shaped groove on your bottom die. Choosing the correct V-opening is critical. As a rule of thumb, the V-opening should be 6 to 8 times the sheet thickness. A wider V-opening requires less bending force but will result in a larger internal bend radius.
- $L$ (Bending Length): The total length of the bend line along the sheet metal. The tonnage required is directly proportional to this length—the longer the bend, the more force you need.
- $Ri$ (Internal Radius): Also known as the inside bend radius, this is the natural curve formed on the inside of the bent metal. In standard air bending (which accounts for 90% of press brake work), the $Ri$ is primarily determined by the V-die opening, typically forming at about 1/6th of the $V$ width.
- $B$ (Minimum Flange Length): The shortest edge, or lip, that you can safely bend. To prevent the material from slipping into the die, the flange must be long enough to bridge the V-die opening during the entire pressing cycle.
- Material Tensile Strength: Different metals yield differently. Mild steel is the standard baseline (Factor = 1.0). Aluminum is softer and requires less force, while stainless steel has a much higher ultimate tensile strength (UTS) and typically requires 50% more bending force than mild steel.
Frequently Asked Questions (FAQs) About Press Brake Bending Force
How do I choose the right V-die opening (V) for my sheet metal?
A: As a general rule of thumb in the sheet metal industry, for material thickness ($S$) up to 3mm, the V-opening should be 6 to 8 times the material thickness. For plates between 3mm and 10mm, use 10 to 12 times the thickness. Choosing a wider V-opening reduces the required bending force but increases the inside radius of the bend.
Does bending stainless steel require more tonnage than mild steel?
A: Yes, absolutely. Stainless steel has a much higher ultimate tensile strength (UTS) compared to standard mild steel. Typically, you will need about 50% more bending force to bend stainless steel of the same thickness and length. Always make sure your press brake has enough capacity before bending high-tensile materials.
Can I bend thicker materials if I use a larger V-die?
A: Yes, increasing the V-die opening distributes the bending force over a larger area, which lowers the required tonnage. However, this comes at a cost: a larger V-opening will result in a larger internal bend radius ($Ri$) and requires a longer minimum flange length. Never exceed the maximum rated tonnage of your KRRASS press brake or tooling.