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What You Should Know About The Basic Knowledge of Bending Tooling


Estimated reading time: 9 minutes

bending tooling,
the selection of bending tooling, customized tools

Types of Upper And Lower Dies of Bending Machine

  1. The common types of bending machine upper die (also known as a bending tool) are r = 0.2 and R = 0.6, and the tool angles are 88 ° and 90 °. The figure below shows the bending upper die of 88 °.
the bending upper die of 88 °
What You Should Know About The Basic Knowledge of Bending Tooling 7

The upper die of the bending machine has two types: integral type (Length of integral upper die (mm): 835) and split type (Length of split upper die (mm): 10, 15, 20, 40, 50, 100, 200, 400).

2. Common V-groove sizes of lower die (also known as V-groove) of bending machine include V4, V5, V6, V7, V8, V10, V12, V16 and v25. (For example, “V5” indicates that the V-groove finish is 5mm) there are two common V-groove angles: 88 ° and 90 °, and the common lower die types of bending machines are shown in the figure below.

 the common lower die
single V 85-degree single V90 degree      double V90 degree      double V88 degree   flattening die

The lower die of the bending machine can also be divided into two types: integral upper die (Length of integral upper die (mm): 835) and split upper die(Length of split upper die (mm): 10, 15, 20, 40, 50, 100, 200, 400).

How to Select a Bending Die During Bending?

1. Select the applicable mold according to the shape, size, and internal R angle marked on the process drawing after forming the workpiece.

2. Fully consider the possible abnormalities in the forming process, such as pig’s mouth, rivet, die, machine, workpiece folding collision, etc.

3. Selection of V-groove when bending the workpiece

According to different material thicknesses, the selection of V-groove is also different

When t ≤ 4mm, V slot = t * 6 times; When t ≥ 4mm, V slot = t * 8 times.

4. Note: during 90 ° bending, the minimum width of the “V” groove shall not be less than 4T, otherwise the die may be damaged or the workpiece may be scrapped.

5. If the folding size is too small and a “V” grooveless then 4T must be used, first fold an appropriate obtuse angle, and then fold it by 90 ° with a large “V” groove.

6. Thoroughly clean the tool die and machine tool die base to ensure that there is no dust and hard objects;

7. Take out the center of the machine tool with the upper and lower molds with a length of at least 300mm, and pay attention to the appropriate pressure to avoid crushing the mold.

8. Replace the appropriate mold required for this processing, clamp up and down in place, and lock the fastening screw/splint.

9. The mold shall be clamped in the center of the machine tool as far as possible to ensure the sustainable and stable operation of the machine tool.

How to Use The Bending Machine Die Safely And Correctly?

The safety operation procedures for bending machine molds mainly include the following contents:

1. Check the coincidence degree and firmness of the upper and lower molds, whether the positioning device is correct, whether it can be used normally, and whether there are other problems. It can be used only after there are no problems, otherwise, it cannot be used.

2. The position of the die on the workbench shall be placed in the middle.

3. The commissioning of the mold shall be carried out when the equipment is powered off and stopped.

4. For the stamping of the die, the upper and lower die bases shall be pressed to prevent the die from being damaged.

5. It is strictly prohibited to punch at one end alone.

6. Before changing settings, check whether you can make changes.

7. The loading and unloading of molds shall be carried out when the equipment stops running.

8 . The safety device and safety protection cover shall not be adjusted without authorization to avoid problems.

9. The mold shall be inspected frequently to see if it is damaged or damaged. If so, it shall be repaired or replaced.

What Are The Specific Types of Mold Bending? How to Calculate The Expansion Value?

The specific implementation method will be in the following aspects:

1. The definitions of two algorithms of bending compensation and bending deduction, and their corresponding relationship with the actual sheet metal geometry.

2. How does the bending deduction correspond to the bending compensation? How can users who adopt the bending deduction algorithm easily convert their data to the bending compensation algorithm?

3. Definition of K factor, how to use K factor in practice, including the applicable range of K factor value for different material types.

Bending Compensation Method

The bending compensation algorithm describes the unfolded length (LT) of the part as the sum of each length after the part is flattened, plus the length of the flattened bending area. The length of the flattened bend area is expressed as the bend compensation value (BA). Therefore, the length of the whole part is expressed as equation (1):

LT = D1 + D2 + BA (1)

The bending area (shown in light yellow in the figure) is the area that is theoretically deformed during bending. In short, to determine the geometric dimensions of the unfolded parts, let’s think as follows:

1. Cut the bending area from the best part

2. Lay the remaining two flat sections on a table

3. Calculate the length of the bending area after its flattening

4. Bond the flattened bending area between the two flat parts, and the result is the unfolded part we need.

bending tooling
What You Should Know About The Basic Knowledge of Bending Tooling 8

K-factor Method

The K-factor is an independent value that describes how sheet metal bends /unfold under a wide range of geometric parameters. It is also an independent value used to calculate bending compensation (BA) in a wide range of cases such as various material thickness, bending radius/bending angle, etc. Figure 5 will be used to help us understand the detailed definition of the K-factor.

bending tooling
What You Should Know About The Basic Knowledge of Bending Tooling 9

We can be sure that there is a neutral layer or axis in the material thickness of the sheet metal part. The sheet metal material in the neutral layer in the bending area is neither stretched nor compressed, that is, the only place that does not deform in the bending area. Figs. 4 and 5 show the junction of the pink region and the blue region. During bending, the pink area is compressed and the blue area extends. If the neutral sheet metal layer is not deformed, the length of the neutral layer arc in the bending area is the same in its bending and flattening states. Therefore, BA (bending compensation) should be equal to the length of the arc of the neutral layer in the bending area of the sheet metal part. The arc is shown in green in Fig. 4. The position of the neutral layer of sheet metal depends on the properties of a specific material, such as ductility. It is assumed that the distance between the neutral sheet metal layer and the surface is “t”, that is, the depth from the sheet metal part surface to the thickness direction into the sheet metal material is t. Therefore, the radius of the arc of the neutral sheet metal layer can be expressed as (R + T) Using this expression and bending angle, the length (BA) of the neutral layer arc can be expressed as:

BA = Pi(R+T)A/180

To simplify the definition of sheet metal neutral layer and consider the thickness applicable to all materials, the concept of the K-factor is introduced. The specific definition is: K-factor is the ratio of the thickness of the neutral layer of the sheet metal to the overall thickness of the sheet metal part material, that is:

K = t/T

Therefore, the value of K will always be between 0 and 1. If a k-factor is 0.25, it means that the neutral layer is located at 25% of the thickness of the part sheet metal material. Similarly, if it is 0.5, it means that the neutral layer is located at 50% of the whole thickness, and so on. Combining the above two equations, we can get the following equation (8):

BA = Pi(R+K*T)A/180 (8)

This equation is the calculation formula that can be found in the Solid Works manual and online help. Several of these values, such as a, R and T, are determined by the actual geometry. So back to the original question, where does the K-factor come from? Similarly, the answer is from the old sources, i.e. sheet metal material suppliers, test data, experience, manuals, etc. However, in some cases, the given value may not be obvious may not be fully expressed in the form of equation (8), but in any case, even if the expression is not the same, we can always find the relationship between them.

For example, if the neutral axis (layer) is described in some manuals or literature as “positioned at 0.445x material thickness from the sheet metal surface”, it is obvious that this can be understood that the K factor is 0.445, that is, k = 0.445. In this way, if the value of K is substituted into equation (8), the following formula can be obtained:

BA = A (0.01745R + 0.00778T)

If equation (8) is modified by another method, the constant in equation (8) is calculated, and all variables are retained, the following can be obtained:

BA = A (0.01745 R + 0.01745 K*T)

Comparing the above two equations, we can easily get: 0.01745xk = 0.00778. It is also easy to calculate k = 0.445.

After careful study, it is known that the Solid Works system also provides the bending compensation algorithm for the following specific materials when the bending angle is 90 degrees. The specific calculation formula is as follows:

Soft brass or soft copper material: Ba = (0.55 * t) + (1.57 * r)

Semi-hard copper or brass, mild steel and aluminum: Ba = (0.64 * t) + (1.57 * r)

Bronze, hard copper, cold-rolled steel and spring steel: Ba = (0.71 * t) + (1.57 * r)

2 thoughts on “What You Should Know About The Basic Knowledge of Bending Tooling

  1. Avatar of Sophia Sophia says:

    Hi, can you make the toolings according to the drawing?

    1. Avatar of designer designer says:

      Yes, you can send the drawings to my email , my email is

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