What is a press brake and why do I need one?

Press brakes are fabrication machines used for bending sheet metal. The material is placed over a V-shaped die and pressed into from above by a punch.

The material is placed over a V-shaped die and pressed into from above by a punch.
Punch pressing down into the die

These machines can bend simple and complex parts, and they are used in a variety of industries ranging from automotive and aircraft to housing and cabinets.

Whenever there is a need for bending metal panels, a press brake is essential, which makes them very common in job shops and machine shops.

What size press brake should I buy?
The most important factors when purchasing a press brake are the tonnage and bending length. These specifications are determined by the size and thickness of the material you will bend.

Knowing your application in advance and planning accordingly will help you to make the best decision.

CNC Press BrakeTonnage
The press brake’s bending force, known as tonnage, determines how much pressure can be applied by the punch during a bend. Higher tonnage allows for bending thicker and harder metals, and lower tonnage is most appropriate for thinner metals.

Bending length
The bending length of a press brake is the maximum possible length of a metal sheet which can be bent.

If you have a very small press brake with 4′ bending length, you won’t be able to bend a 6′ piece of sheet metal because it would be too long. You want to get a press brake with a bending length that is slightly larger than the length of sheets you will be bending.

Why are the tonnage and length so important?
These factors are important because every press brake has a concentrated load limit which is calculated in tons per inch, in the center of the press. Using the wrong tonnage can damage the press ram, the die or the working part, and in the worst case, could ruin the machine.

Figuring out the press brake’s load limit can be done with some fairly basic math. Here is a hypothetical scenario: You take the number of inches between the side columns, multiply it by .6 and then divide that number into the tonnage.

So if you had 10.6′ between the columns on a 350 ton press brake, you would take the number of inches (10.6 x 12″ = 127.2″) times .6 (which is 76.32) and divide that into the tonnage. 350 / 76.32 = 4.58, so that press brake’s load limit would be 4.58 tons per inch. Then if you chose to bend a 5′ sheet on that press, you would want to use a press power of 275, because (5 x 12″ = 60) x 4.58 = 275 tons.

This scenario would change for different kinds of metal and different kinds of machines. There are many different equations to use for determining press power. Thefabricator.com has a great article explaining press brake tonnage limits in much more depth.

These kind of calculations are typically available in a chart on the machine or in the operation manual. However a press brake operator should be aware of what he or she is bending and calculate the proper press power to use, to avoid using too little or too much, which can damage the machine.

So which press brake should I buy?
One of the most common types of press brakes is hydraulic, and when paired with a CNC control, it is known to reduce job setup time and greatly increase efficiency. CNC hydraulic press brakes can come in a wide variety of tonnages and sizes.

We sell press brakes ranging from 3′ up to 20′ in length, with press power from 44 tons up to 440 tons.

For very small applications, you might go with our 3′ x 44 ton model, the MB8 1600/50 CNC hydraulic press brake. For a larger application you might go as large as our 20′ x 440 ton model, the MB8 400ton/6000mm  CNC. All of our hydraulic press brakes come with an automatic backgauge and a DELEM control.

The bending length and tonnage needed when purchasing a press brake are determined by application and what size and thickness of metal you are bending.
KRRASS has press brake experts that are happy to walk you through it and help figure out what machine is best for your situation.

Let us know how we can help you