Dutch bending tools (often called hemming tools or flattening tools) are used to pre-bend the sheet and then press it closed. This technique is used, for example, to finish the sharp edges of the ends of a sheet or to reinforce the sheet and thus strengthen the bent product.
Depending on the available tonnage and the sheet to be bent (material type and thickness), the sheet can be pressed closed to a greater or lesser extent. The force table on the left lists the tonnages required for closing the sheet for mild steel 42kN/cm2 = 42 x 1450 = 60900 psi and for stainless steel 70 kN/cm2 = 70 x 1450 = 101500 psi. The values as indicated may deviate slightly in actual practice.
A variety of tools in the Wila program can be used to perform this bending operation. Hammer tools are used if hamms are some-times made, and are usually applied in combination with a 30 top and bottom tool. With reference to the transverse forces occurring when flattening the sheet, we advise that these tools be used on sheets that are no more than 2 mm / 14 gauge thick.
Using the New Standard top tool type BIU 051, for example, combined with bottom tool type OZU 081, a Dutch bending combination can be created that can be used for both pre-bending and flattening. An advantage is the fact that this tool can also be used for universal bending. Because the design of the configuration is centric, no sliding mechanism is required. Here too, we advise a maximum sheet thickness of 2 mm / 14 gauge.
The spring-action Dutch bending tool, consisting of a holder with a spring-action Dutch bending part, is another option. When combined with a 30 top tool, the sheet can be pre-bent and then hemmed. Because the V opening can be adjusted to suit the sheet thickness, short flange lengths can be bent. The range of products includes a number of standard designs, type DDU.
A variety of other designs are also available.
As a modern version of the spring-action Dutch bending tool, Wila offers the hydraulic Dutch bending tool. The pressing part is not operated by spring action (by which the inactive tool is always open), but is powered by hydraulic cylinders incorporated in the tool. The inactive tool is therefore in a closed position, and simultaneously serves as a tool holder. This means that the tool does not need to be removed from the machine after each use. Interchangeable tools can be placed in the Dutch bending part, making it possible to adjust the size of the V opening as desired.
Wila offers a modified hydraulic unit for this purpose, type D6.
The spring-action and hydraulic Dutch bending tools can be mounted on the machine in a number of ways:
separately on the press brakes table; in the clamping slot in the table or lower beam using a clamp holder. The clamp holder is bolted and normally attached at intervals of approximately 0,5 meter / 20. directly on the lower beam. In this case, there are two options: the lower beam is equipped with a pattern of holes, or the lower beam is equipped with threaded holes. In both cases, the hole pattern is available upon request. Here too, the hole pattern can be modified to suit the customers needs. Both models can be standardly equipped with additional M16 holes 200 mm / 7.87 center to center, so that support arms and such can be attached. Because of their universal application, in practice the hydraulic Dutch bending tools are often attached to the lower beam. The bottom tools used with the hydraulic Dutch bending tool can be clamped in the tool in one of two ways:
mechanically, using standard clamping bolts 100 mm / 3.94 center to center. This method is used for the types DD 005 and DD 006. hydraulically, using a hydraulic clamping bar A2. This variation is used for the types DD008 and DD009. The advantage of the hydraulic clamp A2 as compared to normal set screws is that the bottom tools can be clamped in a single motion via the central controls. This can be parallel-switched to a New Standard tool clamping system. A hydraulic unit Type HM6 can also be supplied. Moreover, this creates a continuous clamping line, meaning that even small segments can be clamped at any point of the clamping holder.