The engineering project technology of China's mold industry still started late, and there is a big gap with developed countries. In recent years, China's mold industry has absorbed advanced experience, advanced technology and high-level talents from foreign mold manufacturing by introducing foreign capital, and the design and manufacturing level of China's molds has been greatly improved. Let me tell you something about the basics of mold design. Interested friends may wish to have a look.

1. According to the structure, stamping dies can be divided into three categories: simplex dies, compound dies and continuous dies.

The first two kinds need more manpower and are not economical. Continuous dies can be produced in large quantities with high efficiency. Similarly, to design a set of high-speed precision continuous dies, you should also check the products you produce (including all stamping products). In the design of continuous die, attention should be paid to module spacing, parts processing accuracy, assembly accuracy, fit accuracy and interference, so as to achieve the purpose of automatic batch production of continuous die.

Second, the concept of unit design:

The overall structure of stamping die can be divided into * * * parts and parts that vary from product to product. * * * Common parts can be standardized or normalized, which varies from product to product. Some parts are difficult to standardize.

Third, the template composition and specifications:

1, composition of the template

The structure of stamping die can be divided into two categories according to the type, structure and difference of die: forward configuration structure and reverse configuration structure. The former is the most commonly used structure, while the latter is mainly used for drawing dies or special dies.

The main work includes:

(1) Digital drawing transforms 3D product and mold models into 2D engineering drawings for routine processing;

(2) Digital Design of Mould According to the product model and design intention, the related three-dimensional solid model of mould is established;

(3) Digital Analysis and Simulation of Mould According to the product forming process conditions, structural analysis, thermal analysis, fatigue analysis and mould motion analysis are carried out for the mould parts;

(4) The product molding process simulates injection molding and stamping molding;

(5) Customize the standard parts and standard design process suitable for the company's mold design;

(6) Mold production management.

2, the specifications of the mold

(1) Die dimensions and locking screws

The size of the template should be larger than the working area, and the standard template size should be selected. The position of the template locking screw is related to the mold type and template size. Among them, locking screws are most commonly used in the four corners of a single engineering mold, and the most standard working areas can be widely used. Long dies and continuous dies are most often arranged at the corners and middle positions and fixed with locking screws.

② the thickness of the template

The selection of template thickness is absolutely related to the structure of the die, the type of stamping, the working force of stamping and the precision of stamping. It is difficult to determine the thickness of the die according to theoretical calculation, which is generally obtained through experience. The types of mold thickness used in the design should be as few as possible, and the mold height and clamping height should be standardized to facilitate procurement and inventory management.

Fourth, the template design:

The main templates of continuous die are punch fixing plate, pressing plate and mother template. Its structural design has three forms: block type, yoke type and insert type according to the precision and output of stamping products, the processing equipment and methods of dies and the maintenance methods of dies.

1, block type

Integral formwork is also called integral structure type, and its processing shape must be closed. Integral formwork is mainly used for molds with simple structure or low precision, and its processing mode is mainly cutting (no heat treatment is needed). After heat treatment, the template must be processed by wire cutting or electric discharge and ground again. When the template size is long (continuous die), two or more pieces will be used for one main body.

2. Yoke type

The central part of the yoke template is machined into a groove shape to assemble the block. Its structure depends on the application requirements, and the groove part can be composed of other templates. The advantages of this yoke template structure are: the groove is easy to machine, the width of the groove is adjustable and the machining accuracy is good; But low rigidity is its disadvantage.

The design considerations of the yoke template are as follows:

(1) The yoke plate structure and the stopper parts are matched with a medium fit or a light fit. If a forced fit is adopted, the yoke plate will be replaced.

(2) The yoke plate also has the function of supporting the block, and it must have enough rigidity to bear the lateral pressure and surface pressure of the block. In addition, in order to closely combine the groove of the yoke plate with the block member, the corners of the groove member are machined to avoid. If the corner of the groove part of the yoke plate cannot be machined to be detached, the block part must be machined to be detached.

(3) At the same time, considering the internal shape of the block parts, the datum plane must be defined. In order to avoid deformation during stamping, we should also pay attention to the shape of each part.

(4) When the yoke plate is assembled by many pieces, the pitch will change due to the accumulated error in the processing of each piece. The solution is to design the middle block part in an adjustable way.

(5) Block parts adopt side-by-side combined die structure, because block parts will bear lateral pressure in the stamping process, resulting in gaps between block parts or inclined block parts. This phenomenon is an important reason for poor stamping, such as poor stamping size and chip blockage, so adequate countermeasures must be taken.

(6) According to the size and shape, there are five ways to fix the stopper parts in the yoke plate: locking screws, keys, keys, shoulders, and pressing on pressing parts (such as guide plates).

3. Mosaic

A circular or square concave part is processed in the template, and a block part is embedded in the template. This template is called embedded structure, which has the advantages of small accumulated tolerance, high rigidity and good reproducibility of disassembly and assembly accuracy. Embedded template structure has become the mainstream of precision stamping die because of its advantages of easy machining, machining accuracy determined by machining machine tools and few final adjustment items, but its disadvantage is that it needs high-precision hole machining machine tools.

When the continuous stamping die adopts this template structure, the empty station is designed to make the template have higher rigidity requirements. Precautions for embedded formwork structure are as follows:

(1) Processing of embedded holes: The embedded holes of the template are processed by vertical milling machine (or coordinate milling machine), coordinate boring machine, coordinate grinding machine, WEDM machine, etc. When WEDM is used as the machining benchmark of embedded holes, it is necessary to perform WEDM twice or more to improve its machining accuracy.

(2) Fixing method of embedded parts: The determining factors of fixing method of embedded parts include machining accuracy, difficulty of assembly and disassembly, possibility of adjustment, etc. There are four ways to fix the insert: screw fixation, shoulder fixation and toe block fixation, and the upper part of the insert is pressed with a plate. Press fit is also used to fix the insert of the main template. At this time, the relaxation result caused by thermal expansion should be avoided, and the anti-rotation method should be designed when machining irregular holes with circular die sleeve inserts.

(3) Consideration of the assembly and disassembly of the insert: The machining accuracy of the insert and its hole requires the assembly operation. In order to adjust even a small dimensional error during assembly, it is suggested to consider countermeasures in advance. There are five specific points for attention in the processing of embedded parts: there is a press-in lead-in part, the press-in state and correct position of embedded parts are adjusted with gaskets, and there is a hole for press-out on the bottom surface of embedded parts. When locking screws, screws of the same size should be used to facilitate locking and loosening. In order to prevent the error of assembly direction, chamfering should be designed to prevent stupidity.

V. Unit design:

1, mold calibration device

The mold alignment unit is also called the matching guide device of the mold blade. In order to ensure the alignment between the upper die and the lower die and shorten its preparation time, according to the requirements of product precision and production quantity, there are mainly five types of die alignment units:

(1) Non-guide type: When the punching die is installed on the punching machine, it does not use the guide device and directly cooperates with its blade.

(2) Externally guided type: This device is the most standard structure. The guide device is installed on the upper die frame and the lower die frame without passing through the template, so it is generally called die frame type.

(3) Combination of external guide and internal guide (1): This device is the most commonly used structure of continuous die, and the internal guide device is installed between the punch fixing plate and the blanking plate. The engagement between the punch and the die uses a fixed pin and an external guide device. Another function of the internal guide device is to prevent the platen from tilting and protect the fine punch.

(4) Combination of external guide and internal guide (2): The device is a high-precision and high-speed continuous die structure, and the internal guide device penetrates the punch fixing plate, the pressure plate and the female die fixing plate. The inner guide device itself also has the functions of aligning the die blade and protecting the fine punch. The main function of the external guide device is to decompose the die and make it smooth when it is installed in the punch.

(5) Inner guide type: This structure does not use the outer guide device, and the inner guide device passes through the punch fixing plate, the blanking plate and the die fixing plate. So as to correctly maintain the positional relationship of each plate to protect the punch.

2. Injection guide and guide sleeve unit

There are two kinds of mold guide modes and accessories: external guide type (mold base type or leading type) and internal guide type (or auxiliary guide type). In addition, in order to meet the requirements of precision mould, it is very necessary to use the combination of outer guide rail and inner guide rail.

(1) external guide type: it is generally used in molds that do not require high precision, and most of them are sold as a unit with the mold base. The main function is to cooperate with the blade when installing the die on the punch, and there is almost no dynamic precision maintenance during stamping.

(2) Internal guide type: Due to the development of mold processing machinery, it has been rapidly popularized recently. The main function is not only to align the blade when the die is installed in the punch, but also to maintain dynamic accuracy in stamping.

(3) Combination of external guide and internal guide: a pair of molds use both external guide and internal guide devices.

3. Punch and master die unit (round)

(1) Punch unit: According to its shape (shoulder type and straight type) and length, as well as the convenience of maintenance, the use of punch unit should match the platen guide sleeve unit.

(2) Mother die unit: circular mother die unit, also known as mother die guide sleeve unit, has two forms: one-piece and split. According to the production quantity, service life and the rationality of product or chip stamping, the combination series of master die unit includes: directly processing the shape of master die with template, having two-stage oblique angle avoidance part, using back plate or not, and having anti-rotation design for irregular master die shape.

4. Compression bolt and spring device

(1) Pressure plate bolt unit: The types of pressure plate bolts are: external thread type, sleeve type and internal thread type. In order to keep the blank holder parallel at the specified position, the stopping methods of the blank holder bolt (shoulder contact part) are: the supporting surface of the die seat cavity, the top surface of the punch seat plate and the top surface of the punch seat plate.

(2) Compression spring unit: The compression spring unit of movable platen can be roughly divided into single-use type and combined type with compression bolt.

When selecting the blanking spring device, it is best to consider the following points before making a decision:

Ensure the free length of the spring and the necessary compression (the spring with large compression should be placed in the cavity of the blank holder);

Whether it is necessary to adjust the initial spring compression (pre-compression) or load;

Consider the ease of mold assembly or maintenance;

Consider the relationship with the length of punch or blanking bolt;

Consider safety (to prevent the spring from flying out when it breaks).

5. Guide pin unit (positioning of feeding direction)

(1) guide pin unit: the main function of the guide pin is to obtain the correct feeding pitch during continuous stamping. There are two types of guiding devices for stamping dies: indirect (the guiding pin is used alone) and direct (the guiding pin is installed inside the punch).

(2) The assembly method of the guide pin is the same as that of the punching punch (installed on the punch fixing plate). It is limited by the punch fixing plate through the spring.

(3) The guide pin is additionally installed on the pressure plate, so it is necessary to pay attention to the rigidity and guide form of the pressure plate because the guide pin is required to extend from the pressure plate to a certain extent, and the processed material is easy to be taken away when the die rises.

(4) The guide pin unit has a direct-acting type and is installed in the punching machine. It is mainly used for contour punching (blanking processing) or trimming processing of the drawing project, and its position positioning is based on the hole of the product and the inner diameter of the drawing part.

6. Material guide device

(1) In the process of shape punching (blanking) or continuous punching, the material guide unit is used to guide the width direction of the processed material and get the correct feed spacing.

(2) The guide devices in the width direction of the material belt include: fixed plate guide pin type, movable guide pin type, plate tunnel guide type (single plate), plate guide type (consisting of two pieces) and lifting pin guide type (movable, fixed and both).

(3) There are two kinds of start-stop guide devices: slider type and movable pin type, which are mainly used to position the material at the initial starting position of the mold.

(4) Feed stop device, which can correctly determine the feed pitch, is mainly used for manual feed. Its forms include: fixed stop pin, movable stop pin, trimming stop die, hook stop mechanism and automatic stop mechanism. Mould man magazine wechat is the first wechat platform in mould industry.

(5) Side-pushing material guide mechanism, which can prevent the material from snaking due to the difference between the width of the material strip and the width of the material guide.

(6) The blank positioning and guiding mechanism has the following forms: fixed pin guiding type (using blank shape); Fixed pin guide type (using the hole of blank); Guide plate (for large parts); Guide plate (integrated); Guide plate (split type).

7. Lifting and ejecting device

(1) Lift pin unit: Its main function is to lift the strip to the female die during the continuous stamping process (the height of this position is called the feeding height, so as to achieve the purpose of smooth feeding. Its forms are: lifting pin type (circular, purely for lifting), which is the most common lifting pin unit; Lifting pin type (round, with guide pin hole) can prevent the material from bearing the deformation of the guide pin and make the guide pin work; Both ejector pin type and guide pin type have the function of guiding materials, and this ejector pin type is most commonly used for guiding materials of continuous dies; When necessary, the lifting pin type (square) is equipped with air blowing holes; Lifting guide pin type (square).

(2) Ejection unit: During automatic stamping, it is necessary to prevent the punched products or chips from jumping on the surface of the master mold, so as to avoid mold damage and the generation of bad stamping parts.

(3) Ejection unit: The main function of the ejection unit is to eject the product or waste from the master mold in each stamping process. The ejection unit has two installation positions: the reverse configuration mold is installed on the upper mold part; The in-line mold is arranged on the lower mold part.

8. Fixing pin device

The shape and size of the fixed pin unit are designed according to the requirements of standard specifications. Matters needing attention in use: the fixed pin hole should be a through hole, if it is not possible, the design method of convenient disassembly with screws should be considered; The length of the fixing pin should be appropriate and not exceed the necessary length; Necessary avoidance part for fixing pin holes; When put into the upper mold part, a mechanism to prevent it from falling should be designed to prevent it from falling; When one side is press-fitted and the other side is slip-fitted, the fixed pin hole on the sliding side is slightly larger than the fixed pin; The number of fixing pins should be two, and the same size should be selected as far as possible.

9. Blind plate device

The key point of the blank holder unit is that the surface of the blank holder and the surface of the main die have correct parallelism, and the buffer pressure needs to be balanced.

10, error detection unit

When punching with a continuous die, the die must be designed with an error detection unit to detect whether the change of the feed pitch exceeds its reference and stop the operation of the punch. The error detection unit is installed in the mold. According to its detection mode, there are two installation forms: a detection pin is installed in the upper mold, and when it deviates from the hole of the strip, it will contact the strip for detection; The detection pin is installed in the lower die and can be detected when a part of the strip comes into contact with the detection pin. Recently, the detection method using contact mode will change, and the examples of using proximity switches will increase.

It is a standard testing device to install a testing pin in the upper die. Because it is detected near the bottom dead center, there is a time deviation from the beginning of detection to the stop of the punch, so it is difficult to completely achieve the effect of error prevention. The detection device installed in the lower die can directly detect the material after the feeding action is completed. This method has always been concerned.

1 1, waste cutting unit

In the process of continuous stamping, the strip (waste) will leave the die one after another, and there are two treatment methods: winding with a winder; It is refined by using a die-cutting device. The latter has two ways: using a special waste cutting machine (located outside the punching machine); A cutting unit installed in the final project of a continuous die.

12, height stop device

The main function of the height stop unit is to correctly determine the position of the lower dead center of the upper die, which has the following two forms: frequent contact during stamping; Contact only during assembly, but not during stamping. In addition, in order to prevent the contact between the upper die and the lower die during transportation and storage, it is best to put a gasket between the upper die and the lower die. When the accuracy requirement is unnecessary, the use standard can be screw adjustment type.

Design of main mould parts of intransitive verbs;

1, standard parts and specifications

The selection method of mold standard specifications should consider the following matters: when the content of the specifications used is not limited, it is best to use the highest level; In principle, the standard number is adopted; When the standard parts of the mold do not have such a size, the closest size should be used for processing.

2. Punch design

Punch can be roughly divided into three parts according to its function: the cutting edge tip of machining material (cutting edge, its shape is irregular, square, round and so on. ); The part in contact with that fix plate of the punch (the fixed part or the handle part with irregular cross-sectional shape, square, circle, etc.). ); The connecting part (middle part) between the blade and the handle.

The design criteria of each part of the punch are briefly described from the aspects of the length of the cutting edge, the grinding direction of the cutting edge, the fixing mode of the punch and the shape of the handle.

(1) Edge length: The design of the edge length of the grading punch should consider that it will not produce lateral bending during machining, and the clearance with the moving part of the blank holder should be appropriate. Whether the relationship between the blanking plate and the cutting edge of the punch is guided or unguided, the linear length of the cutting edge will be different.

(2) Grinding direction of the cutting edge: There are two grinding directions of the cutting edge: parallel to the axis (upward machining) and perpendicular to the axis (through machining). In order to improve the wear resistance and flame resistance of punch, the former should be adopted. When the cutting edge is convex, cross machining can be adopted, and when the cutting edge is concave and convex, upward cutting and cross machining can be adopted.

(3) Fixing method of punch and shape of handle: The handle of punch can be roughly divided into straight section type and shoulder type, and the selection factors of its fixing method include the accuracy of products and dies, the processing machinery and methods of punch and punch fixing plate, and the maintenance methods.

(4) Size and accuracy of the handle: The size and accuracy of the punch handle will have different requirements with the fixing method of the punch.

(5) Adjustment method of punch length: The length of punching punch is shortened due to regrinding, so it is necessary to adjust the length of punch to keep balance with the length of punch in other projects (bending, drawing, etc.). ) and keep the design length of the punch.

(6) Punch design for stamping: In order to achieve the quality and safety of stamping products and the generation of defective products in mass production, the following matters need to be considered in the mold: the grinding direction of punching holes should be consistent, and the surface should be polished; In order to prevent chips from floating up, ejector pins or processing air holes can be installed on the punch; In order to reduce the punching force, the punching punch should be chamfered, and the small punch near the big punch should be shorter to reduce the impact force.

(7) The punch design of collaborative machining method: The shape design of punch is absolutely related to the machining difficulty. If it is too close, it becomes difficult to process the punch fixing plate, so the punch should be separated (closed).

3. Design of punch fixing plate

The thickness of the punch fixing plate is related to the size of the die and load, which is generally 30~40% of the punch length, and the length of the punch guide part should be higher than 1 and 5 times the punch diameter.

4. Design of guide pin (punch)

The gap between the diameter of the guide part of the guide pin (punch) and the guide hole is designed according to the thickness of the material, and the tip shape of the guide pin can be roughly divided into cannonball shape and conical shape (push-pull shape).

(1) Shell shape is the most common form, and there are also standard parts on the market.

(2) The cone has a certain angle, which is very suitable for high-speed stamping of small parts. The decisive factors of push-pull angle are stamping stroke, workpiece material, pilot hole size and machining speed. When the push-pull angle is large, it is easier to correct the position of the processed material, but the length of the push-pull part will become longer. The connection between push-pull parts and cylindrical parts should be smooth.

5. Master mold design

Design of (1) stamping die

The main items that should be considered in the shape design of blanking die are: the life of die and the shape of escape angle, the cutting angle of die and the parting of die. Master of Mold Design WeChat: mujuren

Die life and shape of escape angle: This design is very important. If the design is not correct, it will lead to punch damage, chip blockage or floating and burr.

Shear angle of the female die: In order to reduce the punching force of the female die when stamping the shape, the shear angle can be designed. When the shear angle is large, the punching force will be greatly reduced, but it is easy to cause the product to warp and deform.

Division of master mold: The master mold must be finished by molding and polishing. Because it is concave, the grinding tool is not easy to enter, so it must be divided.

(2) The design of bending female die

In the design of the master die for bending, in order to prevent springback and excessive bending, the part shape of the master die for U-shaped bending is a combination of double R and straight line (slope is 30 degrees), and it is best to approximate R shape. The shape of r parts should be polished after form grinding or NC discharge machining.

(3) Design of drawing die

The corner shape and escape angle shape of drawing die are very important design matters. The shape and characteristics of the corner and escape angle are as follows: when the R angle of the drawing die is large, it is easy to draw, but it also causes the surface of the drawn product to wrinkle, and the thickness of the side wall of the drawn product is greater than the thickness of the plate. When it is difficult to stretch the thick plate and eject it, the r value of the master die should be small, which is about 1-2 times of the thickness of the plate. Generally, the drawing parts of the drawing die for the upper cylinder and the square cylinder are mostly made into straight sections. In order to prevent burning, damage the lubricating oil film and reduce the jacking force, it is suggested to have an escape part (step or push-pull shape) under the straight section. Especially in the case of necking, it is necessary to have as few straight segments as possible.

6, punch side pressure countermeasures

It is the best ideal state that the punch bears equal load on the left and right sides (that is, the side pressure is zero) during stamping. When the punch bears lateral pressure, the upper die and the lower die will deviate laterally, resulting in a larger or smaller die gap (uneven gap), and it is impossible to obtain good precision stamping. The countermeasures of punch side pressure are: changing the processing direction and adopting two rows of arrangement (stamping, bending, drawing, etc.) for products processed on one side. ), install a side pressure stop on the punch or female die, and install a guide part on the cutting edge side (especially for cutting and breaking).

7. Design of blanking plate

The function of blanking plate is to peel off the material attached to the punch and guide the fine punch. According to different functions, its design content is also very different. The thickness and selection criteria of blank holder are as follows according to the product design: movable blank holder and fixed blank holder.

The gap between the blank holder and the punch should be less than half of the gap of the die (especially the precision continuous die). When designing the blank holder, we must pay attention to the following items: 1, the gap between the blank holder and the punch and the length of the punch guide rail; 2. Installation standard of auxiliary guide post and blank holder and design of avoiding part of blank holder; 3. During stamping, the movable blank holder ring should be prevented from tilting.

8. Design of back pressure plate

During stamping, the main working parts (punch, blank holder and main die) will bear surface pressure. When the punch pressure is higher than the surface pressure, the back pressure plate (especially the back of the punch and the female die sleeve) should be used. There are two ways to use the back pressure plate: partial use and full use.

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