Training on the wedge mechanism of automotive stamping dies

■ I. Definition of a Wedge Mechanism

■ II. Composition of a Wedge Mechanism

■ III. Classification and Characteristics of Commonly Used Wedge Mechanisms in Dies

■ 1. Forward-Mounting Wedge Mechanism

■ 2. Lifting Wedge Mechanism

■ 3. Roller Wedge Mechanism

■ 4. Reverse Wedge Mechanism

I. Definition of a Wedge Mechanism

■ Wedge Mechanism

■ A wedge mechanism is a mechanical mechanism that transforms vertical motion into horizontal or inclined motion through the combined use of a wedge and a slider. The wedge, also called the active wedge, acts as the force-applying body during operation. The slider is the working wedge, the force-receiving body. Auxiliary devices include a reverse block, guide plate, pressure plate, wear-resistant plate, spring, screw, etc., which serve to attach to the die, guide, and balance forces.

■ A wedge mechanism allows stamping processes that cannot be performed in the stroke direction of the press, or several stamping operations in different directions, to be completed in one stroke of the press.

II. Composition of Wedge Mechanisms

■ Composition of Wedge Mechanisms

III. Classification and Characteristics of Commonly Used Wedge Mechanisms in Molds

■ Classification and Characteristics of Commonly Used Wedges in Cover Part Molds:

■ 1. Forward-Mounting Wedge

■ 2. Lifting Wedge

■ 3. Roller Wedge

■ 4. Reverse Wedge, etc.

■ Characteristics of Commonly Used Wedges in Cover Part Molds:

■ 1. Easy to install on stamping dies

■ 2. Lubricant-filled guide surfaces effectively prevent adhesion, eliminating the need for additional lubrication

■ 3. After completing one stroke, the forced reset block and spring safely reset the mechanism

■ 4. New models feature a compact design, reducing installation area

■ 5. Unique structure with high strength and durability

■ 6. Accurate, smooth, and noiseless transmission during operation, featuring self-locking, labor-saving, high speed ratio, and easy modification of component movement direction and mode.

III. 1. Forward-Mounting Wedge Mechanism

■ The standard wedge mechanism, also called a regular wedge mechanism, typically involves a slider attached to the lower die, simplifying design and movement. However, in some cases, when the slider is attached to the lower die, it can hinder workpiece feeding and removal, or affect other die functions. In such cases, a suspended wedge mechanism should be considered.

■ When the die is closed, the closed height of the wedge mechanism must not be lower than the closing height specified in the standard parts (SANKYO, PUNCH) to avoid over-travel and damage to the mechanism.

■ The working surface of the slider can be fitted with punching punches, trimming cutters, flanging cutters, etc.

■ Example: In Figure A735, a standard wedge is used for upward flanging.

III. 2. Suspended Wedge
Precautions for Punching Dies

Punching is generally combined with blanking, trimming, and flanging; there are also standalone punching dies.

When the punching angle is greater than 15° and the wedge cannot meet the punching requirements, a pull wedge punching method is used, as shown in the figure below:

II. Structural Dimensions of Punching Dies

1. 1. The common value for A is 15mm, and the minimum value is 10mm. When 10 > A ≥ 5, the interference machining symbol should be noted in the design. For special needs, the design must specify this, and Amin ≥ 3mm should be ensured.

2. The common value for the blank holder B of the punch seat is 10mm, and the minimum value is 5mm. It can be appropriately increased while meeting the requirements of seat strength and casting processability.

3. The diameter of the punch through the hole is φD + 4.

4. The bottom surface of the punched area must be firmly pressed.

5. The blank holder of the pressure plate profile should minimize machining and lapping while meeting the blank holder requirements.

Plane Section III. Structural Dimensions of Side Punching Die

1. The structural dimensions of the side punch are shown in the right figure:

2. The side trimming or side punch insert and punch on the wedge should be shown in the figure after retraction to check for interference, ensuring that the punch or insert does not interfere with the pressure plate during operation and removal. 3. For simple punching die end guidance, guide pillars are sufficient. If there is significant lateral force caused by side punching, guide pillars plus guide plates should be used.

IV. Structure for Reducing Machining on Punch Surface

1. As shown in the right figure: The punch design should reduce the machining area by 15mm around the circumference and 10mm for the blanking edge. (See the shaded area in the figure)

2. When the punch has sufficient screw positions, the punch seat can also have its machining area appropriately reduced.

V. Setting the Size of Scrap Hole

B=(A+3) or more

VI. Setting the Punching Clearance

1. Set the cutting edge clearance value according to the material thickness.

1) Round the clearance values ​​on both sides to two decimal places.

VII. Determining the Punching Diameter and Selecting Standard Parts

1. 1. The size of the hole is equal to the hole diameter plus 75% of the tolerance. For example, if the tolerance of a hole with a diameter of φ10 is +0.1, then the hole diameter of the punch should be φ10 + 0.08 = φ10.08. If the material thickness is 1mm, the clearance between the two sides of the punching should be 0.14mm, then the hole diameter of the die should be φ10.08 + 0.14 = 10.22mm.

2. For front punching, a punch with a centering element but without an ejector should be used. For standard round hole parts, the SPAS-C series is generally selected. For side punching, a punch without a centering element but with an ejector should be used. For standard round hole parts, the SJAS series is generally selected. In principle, the punch diameter should be L = 90mm. In all cases, standard punches, dies, and fixing plates are preferred.

3. For punches with locating pins, locating pin holes should be made on the punch holder, with dimensions as shown in the diagram below. Note: For punches with both centering and ejector functions, the locating pin diameter is φ10 when D is greater than 32.

4. Currently, punching die manufacturers generally require a backing plate under the fixed plate. For round punches, the fixed plate should be CP-AP; for non-round punches, the fixed plate should be CP-FP to prevent rotation.

5. The die sleeve generally uses the EKSD series with locating pin stop, as shown in the diagram below.

6. Punches with a diameter less than or equal to φ8mm should use quick-change punches, including side punches. For convenient maintenance and replacement of punches, a window should be opened at the corresponding pressure plate. As shown in the diagram below. Note: Quick-change punches are also used for front punching. For side punching punches with centering but no ejector, a punch without centering and with ejector should be used.

VIII. Regarding wedge punching

1. For side punching or side trimming, a V-shaped guide plate type wedge must be used for easy assembly.

2. The side-cutting or side-punching inserts and punches on the wedge must be shown in the drawing after retraction to check for interference, ensuring that the punch or insert does not interfere with the pressure plate during operation and removal.

3. Non-standard side-punching punches should be equipped with spring-loaded ejector pins to facilitate waste discharge.

IX. Positive Punching Conditions

1. To ensure the accuracy of the product hole diameter and prevent punching burrs, the angle of the inclined surface and the punching diameter are limited.

2. Structural Settings

As shown in Figure 1 above: When θ < 15°, the end of the punching punch is made flat, with a minimum cutting depth of 2mm.

As shown in Figure 2 above: When θ > 15°, the end of the punch follows the shape and a 2-3mm flat surface is made, with a cutting depth of 2mm.
X. Calculation of Adding Shims to the Punching Punch

1. The compressive stress on the bearing surface of the punching punch is calculated using the following formula:

P Punching force (kg);

F Punching punch bearing surface area (mm²);

D Punching punch bearing surface diameter (mm);

If the calculated compressive stress is greater than the allowable stress of the base plate, a quenched shim should be added; if it is less, no shim is needed.

2. Parameter table for whether to add shims to the base plate

XI. Handling of scrap from front punching

XII. Handling of scrap from side punching small holes

1. In side punching dies, there is often a situation where the space behind the die is very small, causing the scrap to fall vertically, which is easy to cause blockage. The following methods are usually used to prevent this:

1) Use a chip remover as shown in Figures a) and b);

2) When intersecting with the vertical punching position, increase the vertical discharge hole as shown in Figure c);

3) Minimize the wall thickness below the side punch as much as possible as shown in Figure d);

4) The structural dimensions for scrap discharge from the rear are shown in Figure e) D=d+(1.0-2.0)

XIII. Regarding the fixing plate:

1. When punching multiple holes, the fixing plates should be arranged as centrally as possible to facilitate the placement of the pressure plate ribs.

2. When two punches are close together, interference may occur due to interference between the fixing plates. A portion of the end of the fixing plate can be trimmed off, but care must be taken to ensure strength, as shown in the diagram above. If the strength of the fixing plate cannot be guaranteed, a non-standard fixing plate should be made, as shown in the diagram below. If there is a non-standard punch on the fixing plate, an anti-rotation clamping platform should be made.

3. When the punch is a non-standard punch, and the punch is a straight rod type without a clamping platform, a backing plate should be placed under the fixing plate, and screws should be added on the reverse side to fix the punch in place to prevent the punch from being pulled out during punching. Additionally, for punches with straight surfaces, a 5mm mounting platform can be made.

4. When punching relatively large holes, the punch can be made as a single piece and directly fixed to the die base.

XIV. Regarding Die Fittings:

1. Use standard die fittings whenever possible. When there are no other working operations around the punching hole, the die fitting can be directly inserted into the casting. If the material thickness is relatively thick, pay attention to the material thickness direction. When there is a large surface drop at the die fitting's cutting edge, use a die with an extended cutting edge.

2. If the punching hole is too close to the trimming cutting edge to insert a die fitting, directly create the hole on the insert. The minimum distance between the hole and the trimming cutting edge should be 5mm. For holes directly created on the insert, the hole size must be accurate, and the punching clearance must also be included. Programmers directly machine these holes based on the 3D drawing.

3. When the die fitting is inserted into a Cr12MoV insert, a 45# soft sleeve should be inserted outside the die fitting. This avoids direct impact and facilitates assembly and adjustment. If the hole is too close to the edge, inserting a soft sleeve will affect the strength of the insert; in this case, the soft sleeve should not be inserted.

4. The specific dimensions of the soft sleeve are as follows: The single-sided thickness of the soft sleeve is specified as 4mm. The outer diameter tolerance is m6 to fit the hole, and the inner diameter tolerance is H7 to fit the die sleeve. The height is consistent with the height of the die sleeve, and it also needs to have a φ4 anti-rotation pin. Note that the position of the anti-rotation pin of the die sleeve should be staggered, preferably by 90° in angle, as shown in the figure below:

XV. About the Scrap Box

1. Punching scrap is generally collected in a scrap box. If the scrap is large, it is slid out using a scrap slide.

2. The structural dimensions and fixing method of the scrap box are shown in the figure below: A support plate should be made under the scrap box.

XVI. Representation of Punches with the Same Hole Diameter in a 3D Drawing

1. Punches with the same hole diameter are colored the same color at the ends for easier viewing, as shown in the figure below:

All punches with red ends have a hole diameter of φ14.1;

All punches with yellow ends have a hole diameter of φ9.1;