WILA Press brake tooling is the main process equipment for sheet metal processing and forming. With the development of construction machinery, automobiles, ships, aerospace, electrical appliances, building decoration, and other industries, domestic and foreign sheet metal processing companies have adopted the accuracy and shape of sheet metal products.
The complexity requirements are getting higher and higher. And the surface quality requirements of sheet metal parts are getting higher and higher. Especially for the bending of stainless steel plates and aluminum plates, which require no scratches.
In order to avoid indentation on the surface of the workpiece during bending machine processing. In the experiment, the surface of the sheet metal part needs to analyze from the bending method of the sheet metal part.
The Defects of Traditional Bending
The following figure shows the lower die structure under the traditional bending method. This structure usually has V-shaped grooves with different opening sizes, which uses to bend plates of different thicknesses. Under the action of the bending force during bending, the plate moves along the edge of the V-shaped notch of the lower die.
And which squeezed and slidingly rubbed by the bending force, so that the surface of the formed sheet metal part has obvious indentation and strain defects.
The width of the defect belt is about 0.414 times that of the V-shaped notch, which seriously affects the appearance quality of the product.
To solve the above-mentioned defects in traditional bending, it is necessary to overcome the movement of the plate during the bending process. And the friction and extrusion force formed by the V-shaped groove of the lower die on the plate.
The competition in the sheet metal processing industry is becoming more and more fierce. If companies want to remain invincible, they must continuously improve their processing technology. In some bending applications such as precision stainless steel, aluminum alloy, aerospace parts, and copper plates. Users no longer meet with the functionality of the product and have higher requirements for its manufacture ability and aesthetics.
The traditional bending process is more likely to cause damage to the surface of the workpiece, and an obvious indentation or scratch will form on the surface in contact with the mold, which cannot remove, resulting in scrapped parts. Therefore, the user’s demand for seamless bending is becoming stronger and stronger. In this paper, five ways to reduce indentation are based on mold parameters (V opening size, shoulder fillet R-value), WILA non-marking indentation film, WILA non-metallic material V groove, WILA rotor mold, and WILA roller Multi-V mold. Introduce WILA’s non-marking bending solution in detail.
Influence of Lower Mold Parameters on Bending Indentation
- Influence of V opening size
When bending metal sheets of different thicknesses, the opening size of the lower mold V selected is different. Under the conditions of the same plate thickness and the same upper mold, the larger the size of the V opening, according to the principle of three-force balance, the smaller the pressure between the metal sheet and the shoulder of the V opening, the smaller the friction and the indentation. The depth also naturally reduces, so need to use a slightly larger V-opening lower mold.
- The influence of the R value of the shoulder fillet
The R-value of the rounded corner of the V opening shoulder is different, and the friction caused to the plate during the bending and forming process of the plate is different. The larger the R angle of the shoulder of the V opening, the smaller the pressure between the plate and the shoulder of the V opening, and the lighter the indentation, and vice versa. The figure below is the indentation test chart of WILA on the same plate with different R values (Ra<Rb). Obviously, the bending indentation of Ra is obviously more than the bending indentation of Rb, so it recommends choosing a lower mold with a slightly larger shoulder fillet.
From the perspective of friction, it is possible to achieve seamless bending by avoiding direct contact between the upper and lower molds and the plate and using urethane to separate the upper and lower molds from the plate. There are three models of WILA urethane: K-003, K-004, and K-005. The following figure lists the relevant parameters of WILA urethane. The urethane mainly acts as a buffer between the workpiece and the shoulder of the lower mold and reduces the coefficient of friction, offsets the pressure between the mold and the plate, thereby preventing the workpiece from producing indentation during bending.
The urethane has the advantages of low cost and convenient use. When using, only the urethane places on the lower mold. The picture below shows that the non-marking indentation film which uses for the bending test. The test results show that the use of the non-marking indentation film can effectively avoid bending and indentation.
WILA Non-metallic Material V Groove
From the perspective of friction, it can change the V-groove shoulder to a non-metallic material that is softer than the sheet, such as polyurethane, nylon, etc., while ensuring the originally required extrusion effect. As shown in the figure, WILA currently has a polyurethane elastomer V-groove K-001/5, which can use in conjunction with the standard mold OZU-016/327.
WILA’s unique INZU series V-groove which makes of high-strength nylon material and used in conjunction with an extended mold. It usually uses for bending aluminum plates with a thickness of 0.4~0.5mm under specific occasions, and the effect is better.
WILA Rotor Mould
The WILA rotary-wing mold changes the traditional V-opening structure of the lower mold. The inclined surfaces on both sides of the V-opening set as a reversible mechanism.
When the upper mold presses the plate, the reversing mechanism on both sides of the lower mold which replaces by the pressure of the upper mold. The apex of the upper die turns inward. So that the sheet can bend into shape. There are three types of WILA rotor molds, which can bend plates with a thickness of ≤5mm, as shown in the figure.
Thanks to the most stringent tolerance standards, the CNC deep hardening technology of the contact surface. And the rotatable V port, it is easy to use the rotor mold to produce parts. The indentation will happen on the surface during bending.
Advantages of Rotor Mold
- Holes and grooves are without deformation in the area close to the bending center line.
- Reduce the indentation on the surface when bending the part.
- A very small bend fillet can get.
- The rotor and the contact surface is hard to ensure a long service life and accuracy.
- The rotor is easy to disassemble and assemble, which is convenient for cleaning and maintenance.
- Strict tolerance requirements during mold processing ensure the ultimate accuracy during bending operations.
- The compact die size design ensures the greatest bending freedom.
- The same mold can bend a variety of thickness plates.
- It can use in combination with some customized lower molds for 90° bending.
The WILA rotor mold which equipped with a tension spring and a flap structure. It can realize the bending of parts with shorter flanges and beveled edges through the built-in replaceable rotating V port. The figure below shows that the rotor mold OZU-WRB-301 and the lower mold OZU-051 use for the bending test.
The plate which makes of ordinary steel with a thickness of 1mm, and the upper mold uses the same BIU-021 upper mold.
The test results show that the use Compared with the conventional lower mold OZU-051, the rotor mold can avoid bending and indentation more effectively.
WILA Roller Type Adjustable V Mold And Multi-V Mold
Also based on the principle of reducing the friction coefficient of the friction pair between the plate and the lower mold V opening.
The sliding friction pair between the plate and the lower mold V opening shoulder convert into a rolling friction pair. Thereby greatly reducing the friction force on the plate and effectively avoiding occurrences of bending creasing.
At present, this process has been widely used in the mold industry. In the WILA program, there is a roller-type adjustable Multi-V lower mold to match it.
The mold is equipped with hardened rollers with a low friction coefficient, which can greatly reduce the external creases of the bending parts. And at the same time reduce the bending force by about 10% to 30% compared with the traditional lower mold.
HARSLE Company also sells the WILA type press brake tooling, if you have a request, you can choose in our tooling division.
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