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Finished Part Perfection With No Die Shimming

May/June, 2011

If you own a press brake that is eight feet long 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 and often accounts for up to 50 percent 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.

ENTER WILA WAVE TECHNOLOGY

Several years ago, Wila BV of the Netherlands 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 in the bed 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. The more ram deflection that occurred, the more the crown in the center of the crowning system was increased to compensate for it.

While this design worked, it was flawed, as 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 to the other would cause a noticeable change in the bend angle at the point where the wedges adjoined within the unit. This is most noticeable on parts made of thinner materials.

Realizing that this problem couldn’t be overcome when crowning systems relied on adjustable stacks of mechanical wedges, Wila invented what is known today as opposing wave technology, or simply put, 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 using a 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. They are 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 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, as most bending is done in the center of the machine, which can cause this area 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 in. 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, parts will be consistently accurate from end to end with no angular deviation in between.

CHOOSE YOUR DRIVE SYSTEM

Most Wila Crowning Systems are available with CNC-drive motors for customers that demand the latest technology and maximum productivity. With CNC driven Wila Crowning Systems, the press brake operator only needs 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 very popular with owners of new press brakes and as retrofits to existing machines. The digital readout makes it possible to read the crown position, record it in the notes section of the control or on the routing slip that accompanies the part through the shop for ultra-fast setups with parts that repeat.

Our 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 and counter clockwise 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 setup.

HYDRAULIC OR MANUAL DIE CLAMPING

If you make a lot of tooling changes and minimizing non-value added time is important to you, you’ll be happy to know that Wila Crowning Systems are available with hydraulic die clamping using a series of pins that run the full length of the unit for ultra-fast set-up times.

When activated, the hydraulic clamping pins extend to engage the tang on the die and apply approximately 725 psi 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.

Wila Crowning Systems are also available with manual die clamping using a series of set screws that are spaced at 1 in. intervals over the full length of the various models. Like our crowning systems with hydraulic die clamping, Wila Crowning Systems with manual die clamping are able to clamp individual die segments as small as 0.590 in. at any location along the full length of the crowning system.

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 used. Wila Crowning Systems come with 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 four-way dies.

Regardless of the application, Wila has a crowning system that is perfectly suited for your needs. For example, we offer them in lengths up to 60 ft. and in widths up to 24 in. to accommodate large, high-tonnage-capacity press brakes with wide beds, applications involving heavy plate forming and dies with extra-large V-openings. Wila Crowning Systems are also available for tandem press brakes.

Wila Crowning Systems are available with aluminum cover strips that come with an integrated scale, making it possible to locate die segments in specific locations and to repeat tooling set-ups with a high degree of accuracy. Our state of the art NSCR II Crowning System includes CNC-machined, deep hardened working surfaces to provide maximum durability and long-term accuracy retention.

Wila Crowning Systems are available with multiple mounting systems, including a bolt-down base that makes it possible to bolt them directly to the bed of a new press brake. They can also be purchased with a base that has T-slots that can be located in exactly the same position as the mounting bolts in the bed of the press brake. In addition, they can be provided with a flat base so that they can be mounted between clamps that are located on the front and back of the machine’s bed. They can also be provided with a standard tang for mounting on North-American-style press brakes with a slot in the bed with set-screws.

Wila isn’t the only source for precision crowning systems. While we offer the widest range and actually sell more than all other manufacturers combined, the fact is that many of our global press brake partners offer very high quality crowning systems with their press brakes. Some actually include Wila Crowning Systems with their machines or Wila Crowning System components, while others include their own crowning systems.