Press brake is a machine to bend metal sheets and plates for specific needs in metal fabrication. These machines are the ones that are used for metal bending the sheets at specific angles for curved and angular use of those metal sheets.
The angles that a press machine can bend your metals are predetermined. Usually, two different C-frames form each side of a press brake. The sides are connected to the table below and on a flexible or movable beam at its top. The bottom side of the machine stays mounted on the table and the top tool stays mounted on the upper beam.
Types of Press Brake Machine
There are 2 major types of press brake machines available for use, Mechanical and Hydraulic.
Mechanical: In a mechanical press brake, a big flywheel spins at high velocity. Once the operator engages the clutch via pneumatic, the flywheel is mated to the crankshaft with which the Ram is attached. Then the crankshaft spins the ram up and down. This is how mechanical press brake machine functions.
The advantages of this type of mechanical press brake is that they are electronically simpler. The mechanical ones are perfect for punching application because the shock of the punching materials is equally distributed, thanks to the machine’s design.
The main disadvantage of the mechanical ones is that the ram needs to complete a full stroke or cycle and usually can’t be reversed while the process of bending is happening. And to operate a mechanical press brake, a heavily skilled operator is a must.
Hydraulic: In these press brakes, hydraulic pressure is passed from the cylinders to force machine’s ram down. The hydraulic controls of machine, ram accuracy of the press brake are more precise than mechanical brakes. The number of cylinders controlling the press brake varies machine to machine.
The hydraulic ones utilize the electrohydraulic control, which is based on linear control systems and measurements. This provides precise and reliable operation in metal sheet work. However, hydraulic press brakes are comparatively expensive but they are safer than the mechanical ones.
Applications of Press Brake Machine
Shaping, bending, and curving metal sheet with press brake is a kind of art, which is vastly dependent on the operator and his skills. That’s why its application may vary for two different operators. But here are some basic universal application of Press brake machine:
Sheet metal bending: It’s obvious that press brake machines will be used for sheet bending the most. The resultant product can be used in different manufacturing industries.
Home appliances: Press brake machines can be useful for making the structure for different home appliances.
Vehicles: The structural bodies of a car, bus, train, etc. have many curves and angles. It is important that the angles are précised and that’s why press brakes are used in the vehicle industry.
Heavy Industrial Machine: Many industries have gigantic machines with a bulky cover body. These are shaped with press brake machines for saving time and effort.
Press Brake Tooling
To ensure that the Press brake works properly each time when you punch and select a dye, it is important to check the tooling tolerance. But for the best and smooth result, using correct die is the most important thing. Here are some common dies to choose from.
- Curling Dies: This die is used for coiling or curling metal sheet edges.
- Multiple bend dies: These dies are made for specific shapes. They can form multiple bends in 1 motion, depending on your project requirement.
- Offset dies: For “Z” shaped two-angled formation, offsets dies are suitable.
- Seaming dies: For creating seams in metal tubes and sheet, seaming dies are used.
- Acute-Angle dies: These dies are used for specifically right angle and acute angle. But they can form obtuse angles in the metal sheet.
- V-Dies: For “V’ shaped angles, V-dies are used in a press brake.
- Gooseneck dies: These dies are used for clearing flanges.
- Rocker type dies: They can bend metal by moving back and forth or up and down.
Types of Bending
Two major categories of bending sheet metals are described below.
Bottom Bending: It is a simple operation of the punch or tool that is mounted in the ram of press brakes. In this type of bending, the workpiece is forced down in the bottom of dies, which is mounted to the bed over the press brake. Typically, the tools is forced slightly closer to its die than sheet’s thickness. The overbending “coins” the metal and uniformly “seats’ the bend.
The advantage of this bending is that the accuracy of bending depends mostly on the tools itself, rather than largely on the press brake.
Air bending: Air bending is a simple process of pressing down material into the die, just enough to achieve your desired angle. The material isn’t pressed up to the bottom of die, which leaves an air gap.
It is preferred between the two different bending types because in this method, the die needs to change only when the thickness of material is changed. But the main disadvantage of air bending is that the bending accuracy vastly depends on material thickness.
How can Press Brake Machine achieve high precision?
Precision bending came a long way in recent decades. What was considered “precision” in the 80s wouldn’t even pass the muster nowadays.
Although today’s press brake machines are far more advanced than the ones in early 2000s, the precision is not quite there that one would have expected. Here are few variables that can be the reason why the precision is not up to mark.
- Total time the material is held under the load
- Ram repeatability of machine
- Deflection of side housing
- Ambient & oil temperature
- Deflection of ram and bed
- Response time of filling valves of hydraulic machines
- Wear of the die and punch
- Proper alignment and seating of the tooling
- Dimensional tolerance of die, die holder, and the punch
- Spring back
- Material’s protective coating
- Surface hardness
- Material thickness
- Gain direction of the metal during formation
- Homogeneity of material, especially their yield strength
To achieve higher precision:
Proper tooling is a must. No matter how accurate the press machine is, if the tooling isn’t done properly, maximum precision can’t be expected. That’s why the press brake machine you are about to use, must be equipped with proper tooling.
Skilled operator should be recruited. Although it is true that nowadays, the press brake machines are smarter and even a low skilled operator can get the job done, it’s wise to have someone around the machine who is well aware of what he’s doing.
Ram repeatability. Ram repeatability is an important factor to consider if you want higher precision. So, it’s important to keep that on the mind.
Although a press brake might seem a simple machinery for your factory, but like most of the machines in stainless steel fabrication,
aluminium fabrication or steel fabrication, it’s much more complicated than you’d think. That’s why it is important to know how it works and what type of press brake or which type of bending is suitable for you. Remember, in order to achieve high precision, there is no alternative to caring about even the smallest detail of the machine, whether it is laser cutting machine, Metal bending press brake or metal rolling machine.