Does Speed Matter When Shearing Sheet Metal?

Shearing Process

• Metal shear blades never touch because there is a gap between the two. Metal is placed on a table with the section to be cut off hanging over the end between the blades. Hold-down feet keep the sheet of metal in place. The top blade pushes down on the metal, bending it over the bottom blade. This roll over affect continues until the metal fractures and breaks off.

Laws of Motion

• For every action there is an equal and opposite reaction. Therefore, if an object is at rest it will stay at rest until a force is applied. Force is a change in momentum and there are two forces acting on metal during the shearing process. The force of the blade pulls the metal forward as it pushes through the sheet of steel. A slower cut creates a greater stress on the metal for a longer time reducing the effectiveness of the cut.

Energy

• Energy is a property of an object and does not change. Faster blade speeds coming down onto the metal as it cuts have higher energy levels than slower speeds. As mentioned before, when the strength of the metal is overpowered it breaks. When the cutting blade has more energy produced by speed, it will overcome the metals tensile strength. The result will be a more even-shaped cut.

Force VS. Energy

• As the front of the metal is being pushed down by the blade a counter force is pushing up on the hold down feet releasing the holding power on the metal. The metal pulls forward creating a curved cut. When the blade moves faster the metal cuts easier. Less force is pushing up on the hold down feet and the metal stays in place giving an accurate cut. A balance of energy versus force is produced by the speed of the blade.