How To: Buying a Press Brake

From mechanical to hydraulic, and then on to hybrid and electric, press brakes have evolved significantly over the last 100 years. “Accuracy is all that matters,” and “more tonnage for your money” are just a few sales slogans you will hear when shopping for a new brake for your job shop or production floor. Use this “How To Buying a Press Brake” guide to know what you’re looking for before you begin shopping for your next press brake.

Important factors to consider when purchasing your next press brake include the material you wish to bend, the flanges and other bends you wish to make, your operator experience and braking knowledge, operating costs, speed, and how much you are able to invest in your new machine.

There are three main brake styles in the market today. The press brake most commonly found on production floors is that which utilizes hydraulic power exclusively, via large hydraulic pistons, to provide the pressing power. Next you will find electric press brakes, which utilize ball-screw or pulley systems to drive the ram. Finally, hybrid press brakes combine the hydraulic pistons with electric (servo) motors.

It is important to ensure that your new press brake will be wide enough to fit the materials you wish to bend. Do you need a 10’ brake, or do you need 10’ between the columns? The main support columns, located on either end of the press, are typically C-shaped and have a throat for inserting materials into the entire length of the brake, but this throat depth can vary by machine and manufacturer. Here at KRRASS, we offer brakes 3 – 20’ wide. Typically, it is better to invest in a machine which allows the majority of your materials to fit between these columns unencumbered by the throat’s max depth of insertion. Once you know what length of brake you need, you can go on to determine what tonnage machine you will need.

The tonnage necessary to bend your material is based on its inherent properties including elasticity, yield, and thickness. The thicker or harder your material is the more tonnage you will need to form it. Standard tonnage charts, can be used to simply match your material thickness with the size of your die (typically a V) to determine the tonnage needed per linear foot of material based on the desired bend radius. Multiply this number by the width of your material in feet and you will get to total tonnage needed.

The tonnage necessary to bend your material is based on its inherent properties including elasticity, yield, and thickness. The thicker or harder your material is the more tonnage you will need to form it. Standard tonnage charts, can be used to simply match your material thickness with the size of your die (typically a V) to determine the tonnage needed per linear foot of material based on the desired bend radius. Multiply this number by the width of your material in feet and you will get to total tonnage needed. When braking harder materials, such as stainless steel, add 50% of additional tonnage; and when braking softer materials, such as aluminum, deduct 50% of the total. KRRASS offers brakes with tonnage ranging from 44 to 440 tons of pressure.

When buying a press brake, you will also want to ensure you will have enough daylight to allow the material to be maneuvered between the upper and lower tooling, between bends or at the end of the bend cycle. However, as the daylight increases, so can your cycle times. Most brakes increase the speed at which the ram travels toward the material, and then slows the travel speed during the actual braking.

The most basic style of brake has only one axis control, the vertical, known as Y, which controls how deeply the ram pushes the top tooling into the bottom die. The KRRASS MB8 hydraulic workshop press brakes offer this single axis control, which is manually adjusted on the side of the machine column. The KRRASS MB8 CNC press brakes are available with up to 10 axis CNC control.

Adding a back-gauge when buying a press brake, controls the length of your bend leg or flange. The most basic back-gauges are manually adjusted while CNC back-gauges are powered and adjust according to the requirements determined by the bending program. How many axes you will need to control (and how they are adjusted) depends on the complexity of your desired final product and the skill of your operator. Control over the X axis (flat, horizontal), allows the operator to control the flange length by setting the depth at which the material is inserted into the brake. This can also be split into X1 and X2, allowing one end of the material to be inserted farther than the other resulting in an asymmetrical flange.

Control over the height of the back-gauge, is realized by adding an R axis control. This allows the backgauge to be aligned to the edge of the material for a second bend.

The amount of variation in your material width det