If you own a press brake that is eight feet (2.5 meters) in length or longer, the odds are very good that your press brake operators are shimming dies to eliminate the inconsistent bend angles caused by deflection in the ram and bed of the machine. This is a very tedious and time consuming process that often accounts for up to 50% of the average non-value added time spent on a press brake. In short, it costs a lot of money, generates a lot of scrap, and robs you of precious productivity.
Several years ago, Wila recognized that the deflection that occurs in the ram and bed of most press brakes could be overcome with the introduction of what has since come to be known as a crowning system. Mounted on the bed (lower beam) of the machine, early designs often included stacks of mechanical wedges that could be increased or decreased in height, predominantly in the center of the machine. This made it possible to increase or decrease the curve in the crowning system to match the natural curve that was the result of deflection in the ram when the machine came under a load.
While this design worked, it was flawed in that the stacks of mechanical wedges created a staircase effect. If one stack of wedges was increased in height, the stack of wedges next to it had to be increased to a similar height or the drop-off from one stack of wedges to the other would cause a noticeable change in the bend angle at the point where the stacks of wedges adjoined within the unit. This is most noticeable on parts made of thinner materials.
Wila engineers came up with a solution, called “opposing wave technology,” or as we call it, “The Wila Wave®.” With Wila Wave technology, a long rectangular bar with precision waves machined into the top surface is placed at the bottom of the unit with the waves facing up. This bar is driven left to right along the full length of the unit via a manual hand crank or a CNC motor under an opposing bar that has the same precision waves machined into it. On both the top and bottom bars, the waves are taller in the center of the unit, where the press brake experiences the most deflection, and shorter toward the ends of the unit where the press brake is at its strongest and most rigid point.
As the opposing points of contact are waves as opposed to mechanical wedges, the slightest change in the pitch of the waves will change the overall crown position providing extremely accurate results and virtually infinite control.
Localized adjustments provide fine tuning
Because of their length, the ram and bed of even the most accurate press brakes are often milled to finish as opposed to being precision ground. Consequently, they will frequently have small peaks and valleys that can lead to slight inaccuracies on finished parts. This is especially common to press brakes that have been in service for several years, due to the fact that most bending is done in the center of the machine, which can cause this area of the machine to take a set. This must be compensated for if the machine is to produce consistently accurate bends along the full length of the parts being bent.
All Wila Crowning Systems come with localized adjustments every 8” (200mm) to enable the press brake operator to adjust for these slight inaccuracies in the press brake and the natural distortion that occurs in the machine when it comes under a load and is in a plastic state. They also make it possible to adjust the crowning system to compensate for wear on specific punch and die combinations, which can be extremely beneficial for those applications where the tooling will only rarely be changed, or when less durable non-hardened tooling will be utilized. Either way, the end result is parts that are consistently accurate from end to end with very little or no angular deviation in between.
The optional CNC version has one drive motor, located on the end of the system.
Alternative drive systems
Most Wila Crowning Systems are available with CNC drive motors. With CNC, the press brake operator needs only to enter the pertinent programming data into the machine’s control, and the combination of the independent control axis and the CNC motor will automatically set the crown to the proper position prior to each bend.
Wila also provides crowning systems with manual hand cranks that have digital readouts. These units are less expensive than the CNC controlled units and are therefore very popular with new press brake buyers and as retrofits to existing machines. The digital readout makes it possible to read the crown position and record it in the notes section of the control or on the routing slip that accompanies the part through the shop for ultra-fast set-ups with parts that repeat.
Wila’s lowest cost crowning system is driven by a large Allen type wrench that is inserted into the right front face of the unit. This wrench is turned clockwise or counter clockwise, whichever is required, to obtain the proper crown position. A vernier scale is located on the front of the crowning system where the wrench engages the unit to make it easy to locate specific crown positions.
Regardless of which drive system you select, the central crown in all Wila Crowning Systems is set from a single point, making them extremely fast to set-up.
Wila’s Standard Pro Crowning System with manual hand crank features a digital readout, an aluminum cover strip with scale, and localized adjustments every 8 in. (200mm)
Hydraulic or manual die clamping
If you make a lot of tooling changes, our systems are available with hydraulic die clamping, via a series of pins that run the full length of the unit. When activated, the hydraulic clamping pins extend to engage the tang on the die and apply approximately 725 psi (50 bar) of pressure to provide safe and secure die clamping. Being hydraulically driven, the clamping pins can also compensate for minor variations in the tang dimension on the die to provide for secure clamping of even low quality tooling.
The option is manual die clamping, via a series of set screws that are spaced at 1-in. (25mm) intervals over the full length of our New Standard Premium models. These have set screws every 1” (25mm) in the center 39.370” (1,000mm) of the unit, with additional set-screws on 3.937” (100mm) centers from there to both ends. Like our crowning systems with hydraulic die clamping, manual die clamping is able to clamp individual die segments as small as .590” (15mm) at any location along the full length of the crowning system.
A 4-way die mounted on Crowning System, using standard 4-way die brackets provided by Wila.
Accepts all die styles
Obviously, any plans that you have for adding a crowning system to a new or existing press brake must take into account the type of dies that you are going to use. Our system has a standard slot that will accommodate all Wila New Standard, Wila American Style, and all other lines of conventional American style tooling. Wila also provides lower holders and adapters to make it possible to use our full line of Multi-V Dies, European style 2V Dies, Hemming Dies, custom Hemming Tables. Channel Dies, and 4-way Dies.
Systems are available in lengths up to 60 ft. (20 meters), and in widths up to 24 in. (610mm). Standard units come with tonnage capacities starting at 68 tons per foot (200 tons per meter), while HD Heavy Duty units come with tonnage capacities up to 269 tons per foot (800 tons per meter) to accommodate large, high tonnage capacity press brakes with wide beds, applications involving heavy plate forming, and dies with extra-large V-openings. They are also available for tandem press brakes.
While Wila Crowning Systems with CNC motors are normally sold with new press brakes, manually operated units are easily installed on new press brakes and retrofitted to existing press brakes in which the die holder is bolted to the bed of the machine, and press brakes that have a slot in the bed with set-screws. The entire process of installing a Wila Crowning System and fine tuning it to the deflection characteristics of the press brake normally require approximately one to two hours.
The payoff
Well over a decade of research has proven that Wila Crowning Systems consistently provide a reduction in the amount of time required to shim dies by 80-90%. This is true even when crowning systems with manual die clamping and manual adjustment of the central crown are utilized.
This doesn’t take into account the added capability to efficiently produce parts in short production runs. It also does not account for the reduction in the cost of scrap and assembly time made possible by the greater accuracy and finished part quality that they provide.
While Wila offers the widest range of crowning systems and actually sells more crowning systems than all other manufacturers combined, our global press brake partners also offer high quality crowning systems with their press brakes. Many of them include Wila Crowning Systems with their machines or Wila Crowning System components, while others include their own crowning systems.
