Which press brake is best?

I’ve even spent a fortune on new tooling—tooling that doesn’t match our stock tooling. Just to keep production up, we will need to purchase additional adapters to accommodate all of our legacy tooling.

What should I have known before I spent all this money on a press brake and tooling? While you can’t help me with this purchase now, you can, I hope, prevent other shop owners in my position from making the same mistakes that I just made.

Answer: I am asked that question a lot, and even with plenty of experience answering it, I find the question by nature to be subjective. There is no “absolute best” press brake. There is, however, an absolute best press brake for you, and that really is the heart of your question.

Look at Your Operation, Not the Numbers

You’re pretty sure you need a new press brake. You’ve budgeted for the purchase, but what’s your return on the investment?

You have dozens of drive system types and styles to choose from. Which drive system is best? How much technology do you really need? To make a wise choice, you need a solid understanding of the different types of machines and their niche in the industry.

This is not an attempt to promote one type or style over another; it is meant to give you a basic description of the different styles of press brakes, tooling, and methods. This will allow you to make an unbiased comparison.

Mechanical

The mechanical press brake’s basic design comes from the early 1920s. A flywheel provides the power—as much as 150 percent of the rated tonnage. Because of its design, a mechanical brake isn’t a realistic option for air bending in any production operation. Instead, these machines are mainly used for operations in which the inside radius is stamped at less than material thickness (coining) or at 20 percent above the material thickness (bottoming). For more details on the differences among air forming, bottom bending, and coining, see “Bending Basics: How the inside radius forms,” available at www.thefabricator.com.

This can be an adequate machine if you are making an occasional truck bumper or a hundred fence posts. However, precision work will take a craftsman, extra setup pieces, and a lot of production time. And because each bend angle requires a unique tool, you will need to handle the part multiple times as you work your way through the bends.

This machine is best suited for American planed tooling. It would be somewhat of a waste of effort to adapt precision-ground tooling as any precision gained from the tooling would be lost to the errors in the machine and drive systems.

Crude backgauging systems were and still are common, though computer numerical control (CNC) was not an option or truly available when most mechanical brakes were being manufactured. Many have tried retrofitting CNCs to mechanical brakes, but this has never seemed to work out well.

Not many mechanical press brakes are being made anymore, and for good reason: They are dangerous. While it is possible to install safety guarding, the guarding itself is functionally inadequate. Modern safety guarding retrofitted to one of these press brakes is somewhat akin to adding a state-of-the-art automatic, electric, antilock braking system to a Model T Ford.

For instance, in order for a light curtain to work, it would need to be placed approximately the same distance from the pinch point as where the operator needs to work. This means that the first time you’re not looking, the operator will disable the curtain.

Hydra- or Hydromechanical

This style was an early adaption of hydraulics to the press brake. In this design, motion from hydraulic oil pressure turns a hydraulic motor, which provides motion to the ram. This in turn provides full power at any point in the ram stroke.

Unlike the mechanicals, which provide full power only at bottom dead center of the stroke, the hydromechanical press brake is able to return to the open position from any point. Simple NCs control the backgauge, and some early versions had ram-axis control available.

These brakes are designed for American-style tooling. You can use adapters for European tooling, but you will lose a substantial amount of open height—that is, the working area between the ram and the bed.

Single-cylinder Hydraulic: The Bell Crank

The bell crank-style machine has a single hydraulic cylinder running parallel to the ram and bed. A change in angle of the linkage causes motion in the ram, a mechanism not unlike those used in older drum-style car brakes.

These machines aren’t very accurate when it comes to bend angles. However, because of the way the mechanism operates, the machine can produce high tonnage loads. You often find these brakes in heavy bending applications such as structural components for bridges and buildings. These brakes are designed for heavy-gauge applications and American-style planed tooling. They also generally have only the simplest numerical controls (NCs).

Internal-Stop (Stroke-Limited) Hydraulic

This press brake’s drive system, in simple terms, has “hard” stops—solid but adjustable limits within the hydraulic cylinder. While this improves repeatability over the mechanical press brake, the machine itself operates in a similar fashion.

When compared to the mechanical brake, this machine offers shorter setup times and requires less tryout material, but it’s still not very fast or efficient. Like the mechanical brake, the internal-stop hydraulic has no fixed reference point for ram axes control. You simply need to bend a test piece based on a best-guess depth of penetration into the die space, and then make adjustments to the penetration depth from there. Still, once the ram depth is tuned in, the control can be turned over to the NC, giving the operator control of both the ram and backgauge positioning.

These machines are designed for American-style tooling and, with adapters, can be used with European-style tooling, though again with a substantial loss in the open height.

CNC Hydraulic and Hybrid

These machines are driven by standard hydraulic systems, drawing from a shared oil reservoir or by closed individual systems working independently. The hydraulic pumps can be straightforward or “servo-over-hydraulic,” combining the accuracy of an electric press brake with the power of a hydraulic system.

Fixed reference points and high repeatability are the key phrases here. Of course, this comes at a price when compared to the previous two machine styles. Nonetheless, these machines offer quick setups and consistent bend angles, especially for air forming, the bending method preferred for these machines. While you can bottom-bend with them, you won’t be making the best use of the technology. You should also avoid coining, which can damage the press brake and tooling, not to mention the operator.

These systems have CNCs with multiple axes of control, each with high repeatability. The brakes can, depending on the manufacturer, be designed for use with all three tooling styles: American, European, and New Standard.

Electric

Fast and efficient, these press brakes have electric motors that drive the ram. To produce motion, motors can be attached directly to the drive screw or by way of a timing belt.

Electric motors will need to improve some before 300- to 500-ton machines make it to market. In the meantime, some press brake manufacturers have added a series of pulleys as a force multiplier. This mechanism also reduces the need for a crowning or antideflection device.

These machines are specifically designed for precision-ground tooling. Like using precision tooling in a mechanical press brake, using planed tooling will not give you the accuracy these press brakes are designed to achieve. These machines have CNCs that have precise control over multiple axes.

Controllers

Do you need CNCs with all the bells and whistles, or are you just aligning the punch to a scribe line? The choice really is yours. What are your production needs? If they include high-precision one-off parts or small-volume production runs, then a controller with a lot of options may be your best choice.

Before you purchase a machine with more than basic dual-axis control, consider your operators or, at the very least, your lead or setup people. Do they really understand what the functions are for? Consider the dwell function. Sure, it causes the ram to pause at the bottom of the stroke for a short period of time, but the question is: What, when, where, and how do I apply these functions? When picking a controller package, consider the cost of additional functions and how likely it is operators will use those functions.

Will you be purchasing new tooling? This may not be like the planed American tooling you already have, but rather precision-ground tooling, with which it’s implied that operators will be air forming.

Does this mean your staff will need to learn an entirely new way of doing things? Are they going to accept it willingly or will they pine for the old ways? I’m not trying to deter shop owners from making the leap; I’m just making an observation. It will be hard to justify the cost of the press brake if your operators opt for the old one they are familiar with.

What’s Next? Tooling

Before you can choose a new press brake, you need to understand the tooling. Picking the right press brake is as much about your tooling style and forming method choices as anything else. I would argue the type, style, and application of tooling is the most important part of your decision—but you’ll have to wait until next month for that part of the story.