First and foremost, the industry terms “forming” and “bending” mean the same thing when used by manufacturing industries involved in sheet metal fabrication.
The process of sheet metal forming and bending consists of a punch (top tool), to press a workpiece into a die (lower tool) in order to create an angle. The machine used for this process is known as a press brake.
At FSM there are a number of sheet metal bending processes that we perform in-house, including Air bending and Die/bottom bending. We will go into a bit of detail about what each process entails below:
Air Bending
The punch presses the workpiece into the die taking care not to press it against the walls. The machine has a control mechanism to help calculate the desired angle, the path and press force based on the material being used, the required product properties and the tooling available.
The deeper the punch presses into the workpiece, the more acute the angle. Therefore, it is very important that clients are clear on what angles match their specification before forming as this process is referred to as a path-dependent method because each angle requires a defined path.
Die/Bottom Bending
The sheet metal is bent by pressing it into a V-shaped tool (die) with an upper tool, and it differs to air bending as there is no clearance between the die, workpiece and punch when the desired angle is created. This process requires a separate tool for each different angle and form as the punch and die must fit into each other exactly.
When the workpiece has been completely pressed in, the punch cannot move further down and the machine controls the press force until this predefined value has been reached. As the pressure on the workpiece increases, it takes on the shape of the punch and die, and the angle stabilises under high-pressure so that the spring back is eliminated.
How do we maintain quality at FSM
When die/bottom bending is carried out, we used bending foil which gets placed over the lower tool to prevent friction marks from forming on the workpiece. This helps maintain the aesthetics of the final piece for the customer’s satisfaction.
We have the TruTops Bend (BOOST) Trumpf software at our facility which our CAD engineers can use to program the press brake offline, thus reducing non-productive time and helps with controlling the operation to give the business more operator options and flexibility.
What is folding and hemming?
The edges of a sheet metal are often bent over completely, much like the edges of a box. This means the sides are then parallel to each other and this creates edge protection, as well as providing more stability.
Folds often come in handy as they allow for other components to be hooked onto the final product at a later stage. Folding and hemming occurs in two steps:
Step 1: The operator pre-bends an angle of 30°.
Step 2: The workpiece is reinserted and the angle is pressed shut.
This procedure is referred to as folding if a gap remains between the sides and otherwise hemming if the sides are pressed completely together as folding is path-dependent and hemming is a force-dependent process.
If you would like to discuss how our sheet metal bending service can assist you in your ongoing or upcoming project, please get in touch via our contact page where you can ask us a question and a member of the FSM team will get back to you, or you can get in touch directly.