Six basic knowledge of stamping die design
First, According to the structure, stamping dies can be divided into three categories: single engineering die, composite die, and continuous die.
The first two categories require more manpower, which is inconsistent with economic benefits, and continuous molds can be produced in large quantities with high efficiency. Similarly, designing a set of high-speed precision continuous dies should also be based on the products you produce (including all products processed by stamping). In designing continuous die, attention should be paid to the spacing between modules, part processing accuracy, assembly accuracy, coordination accuracy and interference, so as to achieve the purpose of automated continuous production of the continuous die.
Second, the concept of unitized design:
The overall structure of the stamping die can be divided into two parts: the common part and the part that varies according to the product. Common parts can be standardized or standardized, and parts that vary depending on the product are difficult to standardize.
Structure and specifications of the template:
1. The composition of the template
The structure of stamping dies will depend on the type and composition of the dies, and there are two major types, namely the collocation configuration and the reverse configuration. The former structure is the most commonly used structure, and the latter structure is mainly used to extend forming dies or cooperate with special dies. The main work he has done includes:
(1)Digital drawing-converting three-dimensional products and mold models into two-dimensional engineering drawings used in conventional processing;
(2) The digital design of the mold-based on the product model and design intent, establish a relevant three-dimensional solid model of the mold;
(3) Digital analysis and simulation of molds—Structural analysis, thermal analysis, fatigue analysis, and mold motion analysis of mold parts according to the product forming process conditions;
(4) Simulation of product forming process-injection molding and stamping;
(5) Customized to fit the company's mold design standard parts and standard design process;
(6) Die production management.
2. Specification of mold
(1) Mold size and locking screws
The size of the template should be larger than the work area and select the standard template size. The position of the template locking screw is related to the type of mold and the size of the template. Among them, the single engineering mold is most commonly configured with locking screws at the four corners, and the most standard form of the work area can be widely used. Long molds and continuous molds are most commonly located at the corners and in the middle using locking screws.
(2) The thickness of the template
The choice of the thickness of the template has an absolute relationship with the structure of the mold, the type of stamping process, the processing force of the stamping process, and the precision of the stamping process. It is difficult to determine the thickness of the mold based on theoretical calculations. Generally, it is obtained by experience. The thickness of the template used in the design should be as small as possible, and the mold height and clamping height should be standardized to facilitate procurement and inventory management.
Design of template:
The main templates of continuous molds are punch fixing plates, blanking plates, mother templates, etc. The structural design of the continuous mold has three forms according to the precision of the stamped products, the number of production, the processing equipment and methods of the mold, and the maintenance of the mold. Monolithic, yoke, embedded.
1, monolithic
The one-piece formwork is also called an integral structure, and its processing shape must be closed. The monolithic template is mainly used for simple structures or molds with low accuracy. The processing method is mainly cutting (no heat treatment is required). The template using heat treatment must be subjected to wire cutting or electrical discharge machining and grinding. When the template size is long (continuous mold), two or more integrated types will be used.
2.Yoke
The central part of the yoke template is processed into a groove shape to assemble a block. Its structure depends on the application requirements, and the groove portion can be formed by other templates. The advantages of this yoke type template structure are easy to groove processing, adjustable groove width, and good machining accuracy; but low rigidity is its disadvantage.
The design considerations of the yoke template are as follows:
(1) The fitting of the yoke plate structure part and the block part adopts a middle fit or a light fit. For example, a strong press fit will change the yoke plate.
(2) The yoke plate also has the holding function of the block-shaped parts. In order to withstand the side pressure and the surface pressure of the block-shaped parts, it must have sufficient rigidity. In addition, in order to obtain a tight combination of the yoke plate groove and the block-shaped part, the groove corner ridge of the yoke plate is made into clearance processing. If the yoke plate groove ridge cannot be made into clearance processing, the block part must be made into clearance processing.
(3) The division of block parts should take into account the internal shape, and the reference plane must be clear. In order to prevent deformation during press processing, attention should also be paid to the shape of each block-shaped part.
(4) When many pieces of block-shaped parts are assembled in the yoke plate, the pitch varies due to the cumulative processing error of each block-shaped part. The solution is that the middle block-shaped part is designed to be adjustable.
(5) The block structure adopts a side-by-side combination mold structure. Because the block parts will be subjected to side pressure during punching processing, a gap is created between the block parts or the block parts are inclined. This phenomenon is an important cause of poor punchings, such as poor punching size and blockage of punching chips. Therefore, sufficient countermeasures must be taken.
(6) There are five methods for fixing the massive parts in the yoke plate according to their size and shape: fixing with locking screws, fixing with keys, fixing with shape keys, fixing with shoulders, and more pressing parts (such as guides) Plate).
3. Embedded
Round or square recesses are processed in the template, and block-shaped parts are embedded and embedded in the template. This template is called an embedded structure. This structure has less cumulative tolerances, high rigidity, and reproducibility during decomposition and assembly. good. Due to its advantages such as easy machining, machining accuracy determined by the work machine, and few final adjustments, the inlay template structure has become the mainstream of precision stamping dies, but its disadvantage is that it requires a high-precision hole processing machine.
When the continuous stamping die adopts this template structure, in order to make the template have high rigidity requirements, the empty station is designed. The precautions for insert formwork construction are as follows:
(1) Embedded hole processing: The embedded hole processing of the template uses a vertical milling machine (or jig milling machine) integrated processing machine, jig boring machine, jig grinding machine, wire cutting electric discharge machine, etc. For machining standards for embedding holes, when using a wire-cut electrical discharge machine, in order to improve its machining accuracy, two or more wire-cut operations are performed.
(2) Fixing methods of inserts: The determinants of fixing methods of inserts include the accuracy of processing, the ease of assembly and disassembly, the possibility of adjustment, and so on. There are four ways to fix the inserts: screws, shoulders, toes, and the upper part of the inserts. The method of fixing the insert of the mother template also uses press-fitting. At this time, the loosening result due to processing thermal expansion should be avoided. When using the circular mold sleeve insert to process irregular holes, a rotation prevention method should be designed.
(3) Considerations for assembly and disassembly of inserts: The inserts and their cavities must be processed with high precision for assembly operations. In order to obtain adjustments during assembly even if there is a slight dimensional error, it is advisable to consider solutions in advance. The specific considerations for the processing of inserts include the following five items: a press-in introduction part is used to adjust the press-in of the insert with a spacer. The state and correct position, the bottom of the insert is provided with a hole for pressing out. When tightening with screws, screws of the same size should be used to facilitate locking and loosening. In order to prevent errors in the assembly direction, a dull chamfering process should be designed.
Continuous die design technology
V. Unitized Design:
1. Mold alignment unit
The mold alignment unit is also referred to as the butt guiding device of the mold blade. In order to ensure the alignment of the upper mold and the lower mold and shorten the preparation time, according to the requirements of product accuracy and production quantity, the mold alignment unit mainly has the following five types: (1) non-guided type: when the mold is installed on the punch Directly cooperate with its blades without using guides.
(2) Outer guide type: This type of device is the most standard structure. The guide device is installed in the upper mold base and the lower mold base. It does not pass through the templates and is generally called the mold base type.
(3) Combination of external and internal guidance
(A): This device is the most commonly used structure for continuous molds. An internal guide device is installed between the punch fixing plate and the blanking plate. The combination of the punch and the die uses a fixed pin and an outer guiding device. The other function of the inner guiding device is to prevent the pressure plate from tilting and to protect the small punch.
(4) Combination of external and internal guidance
(B): This device is a structure for the use of high-precision and high-speed continuous molds. The inner guide device runs through the punch fixing plate, the blanking plate and the master mold fixing plate. The inner guiding device itself also has the function of the die blade to engage and protect the small punch. The main function of the outer guide device is to achieve smoothness when the mold is disassembled and installed on the punch. (5) Inner guide type: This structure does not use an outer guide device. The inner guide device runs through the punch fixing plate, the blanking plate, the die fixing plate, etc., and maintains the positional relationship of each plate to protect it. shower.
2.Guide and guide sleeve unit
There are two types of guideways and accessories for the mold: guide injection and guide sleeve units: outer guide type (mold base type or main guide), inner guide type (or auxiliary guide). In addition to the requirements of precision molds, the combination of external and internal guidance is highly demanding.
(1) Outer guide type: Generally used in molds that do not require high precision, and are mostly sold as a unit with the mold base. The main role is to match the blades when the mold is installed on the punch, and there is almost no stamping. Dynamic accuracy is maintained.
(2) Internal guidance type: Due to the development of mold processing machines, it has been rapidly popularized recently. The main effect is that in addition to the cutting of the blades when the die is installed on the punch, it also has the effect of maintaining dynamic accuracy in stamping.
(3) Combination of external and internal guidance: a pair of molds use both external and internal guidance devices
3. Punch and master unit (round)
(1) Punch unit: According to the shape (shoulder type and straight type) of the round punch unit and the convenience of maintenance, the use of the punch unit should be matched with the blank guide unit.
(2) Female die unit: The circular female die unit is also called the female die guide bushing unit. Its form includes a monolithic and split type. According to the production quantity, service life and rationality of the product or chip, the female die unit The combination series includes: using a template to directly process the shape of the master mold, which has a two-segment beveled clearance. Whether to use a backplate, the shape of the irregular master mold must be designed to prevent rotation.
4. Pressure bolt and spring unit
(1) Pressure bolt unit: There are types of pressure plate bolts: external screw type, sleeve type, internal screw type. To keep the blanking plate parallel at the specified position, the method of stopping the blanking bolt (shoulder contact part): the bearing surface of the cavity of the die seat, the top surface of the punch fixing plate, and the top surface of the punch backplate.
(2) Material holding spring unit: The movable material holding spring unit can be roughly divided into single-use type, combined with the material holding bolt.
It is best to consider the following points when selecting the pressure spring unit:
Ensure the free length of the spring and the necessary compression amount (the spring with a large compression amount should be placed in the cavity of the pressure plate); Is it necessary to adjust the initial spring compression amount (pre-compression amount) or load?
Consider the ease of assembly or maintenance of the mold;
The relationship between the consideration and the length of the punch or press bolt;
Consider safety (to prevent flying out when the spring breaks).
5. Guide pin unit (positioning of the feeding direction of the bar)
(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 guide units for stamping dies: indirect type (guide pin is used separately) and direct type (guide 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 restrained by a punch fixing plate by a spring.
(3) The guide pin is separately installed in the form of the blanking plate. As the guide pin is required to protrude to the blanking plate to a certain amount and prevent the mold from rising, it is easy to bring the processed material. It is necessary to pay attention to the quote form.
(4) The guide pin unit has a direct type, which is installed in the punch. It is mainly used for cutting of the shape (cutting processing) or edge processing of the extension project. Its position is determined by using the product's hole and the inner diameter of the extension. .
6. Guide unit
(1) When die-cutting (cutting) or continuous punching, the guide unit is used to guide the width direction of the material to be processed and to obtain the correct feeding pitch.
(2) The guiding device in the width direction of the bar, the guiding methods are fixed plate guide pin type, movable guide pin type, plate tunnel guide type (single plate), plate guide type (two components) ), Lifting pin guide type (there are movable, fixed and both).
(3) The guidance devices for starting and stopping are of two types: slider type and movable pin type. The main function is to position the material in the initial starting position of the mold.
(4) The feeding stop device can correctly determine the feeding pitch. It is mainly used for manual feeding. Its forms are fixed stop pin, movable stop pin, side-cut stop method, hook stop mechanism, automatic stop mechanism.
(5) Side push-type guide mechanism, the material is pressed to one side during the stamping process, which can prevent the material from hunting due to the difference between the width of the strip and the width of the guide.
(6) Positioning guide mechanism for the blank position, its forms are fixed pin guide type (using the shape of the blank); fixed pin guide type (using the hole of the blank); guide plate (for large parts); Guide plate (integrated); Guide plate (split).
7. Lifting and jacking unit
(1) Lifting pin unit: its main function is to lift the bar to the master die during continuous stamping (the height of the position is called the feeding height and achieves the purpose of smooth feeding. Its form is: lifting pin type (round, For pure lifting), is the most common lifting pin unit; lifting pin type (round, with hole for guide pin), hole for guide pin to prevent the material from bearing the guide pin The deformation and the guide pin do work; the lifting and guiding pin types, with the guiding function, are most commonly used for continuous mold guides; this type of lifting pin type (square) can be set if required. There are air blow holes; lifting and guide pin type (square).
(2) Top material unit: It is necessary to prevent punched products or punches from jumping on the surface of the master die during automatic punching to avoid die damage and bad stamping parts.
(3) Ejection unit: The main function of the ejection unit is to eject the product or waste material from the mother mold each time it is punched. There are two installation sites for the ejection unit: the reverse configuration mold is set on the upper mold part; the collocation configuration mold is set on the lower mold part.
8. Fixed pin unit
The shape and size of the fixing pin unit are designed according to the requirements of standard specifications. The precautions when using it are: the fixing pinhole should be a through-hole. When it is not possible, consider a design method that is easy to remove with screws. It should not be longer than the necessary length; the fixing pin hole should have the necessary escape part; when it is placed on the upper mold part, a mechanism to prevent falling should be designed to prevent it from falling; The fixing pin holes on the side are slightly larger than the fixing pins; the number of fixing pins is based on two principles, and the same size should be selected as much as possible.
9. Pressure plate unit
The particularly important point of the blanking plate unit is that the blanking surface and the female mold surface have the correct parallelism and the buffer pressure needs to be balanced.
10. Failure detection unit
In the case of continuous die stamping, the die must be designed with an error detection unit to detect whether the change in the feed pitch exceeds its reference and stop the operation of the punch. The error detection unit is installed inside the mold. According to its detection method, there are two types of installation methods: a detection pin is installed in the upper mold. When it deviates from the hole of the bar, it will contact the bar to detect it. The detection pin is installed in the lower mold and is detected when a part of the bar is in contact with the detection pin. Recently, the detection method using the contact method will be changed, and the number of cases using the proximity switch is increasing.检 The detection pin installed in the upper mold is a standard detection device. Because it is detected near the bottom dead center, there is a time deviation from the detection start to the stop of the punch. It is difficult to completely achieve the error prevention effect. The detection device installed in the lower mold directly detects when the material feeding operation is completed. This method has been valued.
11. The waste cutting unit
During the continuous punching process, the strip (waste) will leave the mold one after another. There are two ways to deal with it: using a coiler to take it up; and using a mold cutting device to refine it. There are two methods of the latter: using a special waste cutting machine (located outside the stamping machine), and a cutting unit installed in the last process of the continuous mold.
12. Height stop block unit
The main function of the height stop block unit is to correctly determine the position of the bottom dead center of the upper mold. There are two forms: the method of frequent contact during stamping; the method of contact only during assembly; and the method of non-contact during stamping. In addition, when the mold is being transported and stored, in order to prevent contact between the upper mold and the lower mold, a spacer is preferably placed between the upper mold and the lower mold. When accuracy is not necessary, the standard for its use can be adjusted by screws.
Continuous die design technology
Design of main mold components:
1. Standard parts and specifications
The selection method of the standard specifications for the mold is best to consider the following: when the specifications used are not limited, the highest one is preferred; in principle, the standard number is used; when the standard parts of the mold do not have this size, the closest one is used for processing.
2. Punch design
The punch can be roughly divided into three parts according to its function:
The Cutting edge of cutting material (cutting edge, its shape is irregular, square, round, etc.);
The contact part with the punch fixing plate (fixed part or shank, the cross-sectional shape is irregular, square, round, etc.);
The connecting part (middle part) of the blade part and the handle part.
The design basis of each part of the punch is briefly described in terms of the length of the cutting edge, the grinding direction of the cutting edge, the method of fixing the punch, and the shape of the shank.
(1) Cutting edge length: The design of the cutting edge length of the stage punch should consider that no side-bending will occur during processing, and the clearance with the moving part of the pressure plate should be appropriate. The relationship between the blank and the cutting edge of the punch is guided and non-guided. The straight length of the cutting edge will be different.
(2) Grinding direction of the cutting edge part: There are two methods of grinding the cutting edge part parallel to the shaft part (up-cut processing) and perpendicular to the shaft part (pass-through processing). In order to improve the wear resistance of the punch and Burn resistance, the former should be used. When the shape of the cutting edge portion is convex, a through the process can be used, and when a concave and convex shape is used, a combination of up-cut processing or through the process can be used.
(3) Fixing method of punch and shape of shank: The shank of punch is roughly divided into two types: straight type and shoulder type. The choice of fixing methods includes the precision of products and molds, punch and punch. Processing machinery and processing methods of fixed plates, maintenance methods, etc.
(4) The size and accuracy of the shank: The size and accuracy of the shank of the punch will have different requirements depending on the fixing method of the punch.
(5) Adjusting method of punch length: The length of the punching punch is shortened by re-grinding. It is necessary to maintain balance with the punch length of other projects such as (bending, drawing, etc.) and maintain the design length of punch. Adjust the length of the punch.
(6) Punching design for stamping processing: In order to achieve the quality and safety of stamping products and no defective products during mass production, it is necessary to consider the following matters in the mold: the grinding direction of the punching process should be the same, and the surface should be polished. Treatment; To prevent the floating of punching chips, the ejector pin or air hole can be installed in the punch; To reduce the punching force, the punching punch is beveled, and there is a small punch near the large punch. Shorter to reduce impact.
(7) Punch design in accordance with the processing method: The shape design of the punch has an absolute relationship with the difficulty of processing. When it is too close, the processing of the punch fixing plate becomes difficult. At this time, the punch should be divided. (Adopt a combination).
3. Design of punch fixing plate
The thickness of the punch fixing plate is related to the size of the die and the load. Generally, it is 30 to 40% of the punch length, and the length of the punch guide should be higher than 1, 5 times the diameter of the punch.
4. Design of guide pin (punch)
The diameter of the guide pin (punch) and the gap between the material guide hole, its size and the amount of the protruding blank are designed according to the thickness of the material. The tip shape of the guide pin is roughly divided into two types: shell shape, Conical (push shape). (1) The shell shape is the most common form, and there are standard parts on the market. (2) The conical shape has a certain angle, which is very suitable for high-speed stamping of small parts. The determining factors of the pushing angle include the stamping stroke, the material of the workpiece, the size of the guide hole, and the processing speed. When the pushing angle is large, it is easier to correct the position of the material being processed, but the length of the pushing part will be longer. The connection between the pushing part and the cylindrical part should be smooth.
5. Design of the master mold
(1) Design of punching master die
The main items to be considered in the design of the shape of the blanking die are the life of the die and the shape of the escape angle, the cutting angle of the die, and the division of the die. Mold life and shape of the escape angle: This design is very important. If the design is incorrect, it will cause damage to the punch, blockage or floating of punching chips, and the occurrence of burrs. Cutting angle of the master mold: In order to reduce the punching force when the shape is punched, the master mold can be designed with a shear angle. When the shear angle is large, the reduction of the punching force is also large, but it is easy to cause the product to buckle and deform. Segmentation of the master mold: The master mold must be subjected to finishing such as forming and grinding. Because it is concave, the grinding tools are not easy to enter, so it must be divided.
(2) Design of bending master
The design of the master for bending processing, in order to prevent springback and excessive bending, the shape of the part of the master for U-shaped bending processing is a combination of double R and straight parts (inclination of 30 degrees), it is best to approximate R shape. The shape of the R part should be polished after forming grinding or NC electrical discharge machining.
(3) Design of the extension master
The shape of the corner of the extruded female mold and the shape of the escape angle are very important design matters. The shape and characteristics of the corner and the escaped female angle are as follows: When the R-value of the extension female mold is large, it is easier to extend the processing, but it also produces the surface of the extruded product. Wrinkle occurs, and the thickness of the sidewall of the extruded product is greater than the thickness of the plate. Where it is difficult to stretch thick plates and ejection, the R-value of the female mold should be small, about 1-2 times the thickness of the plate. Generally, most of the extensions of cylindrical and square tube female molds are made into straight segments to prevent For the purpose of burning, the destruction of the lubricating oil film and the reduction of the ejection force, there should be an escape section (stage or push) design under the straight section. Especially in the case of shrinkage processing, it is necessary to minimize this straight section.
6.Punch side countermeasures
When punching, it is best to receive the equal load on the left and right of the punch (that is, the side pressure is zero). When the punch is subjected to lateral pressure, the upper mold and the lower mold will be offset in the horizontal direction, causing part of the mold gap Larger or smaller (uneven gaps) and failing to obtain good precision stamping. The countermeasures for the side pressure of the punch are as follows: products with changing processing direction and single-sided processing (punch cutting, bending, extension, etc.) should adopt a two-row arrangement method, and the punch or die should be equipped with side pressure stoppers. The side of the blade is provided with a guide (particularly cutting and cutting processing).
7. Design of pressure plate
The function of the blanking plate has the function of peeling off the material attached to the punch and guiding the small punch, and its design content is greatly different depending on the function. The thickness and selection basis of the blanking plate is based on the product design in the following two types: movable blanking plate and fixed blanking plate.
The gap between the blank and the punch should be less than half of the gap between the mold (especially for precision continuous molds, this principle should be adhered to). When designing the blank, it varies according to different products. Attention must be paid to the following:
1). The gap between the pressure plate and the punch and the length of the punch guide,
2). The installation standard of the auxiliary guide column and the blanking plate and the design of the escape section of the blanking plate.
3). The countermeasures to prevent tilting of the movable blanking plate during stamping,
4). The dimensional relationship between the fixed guide plate and the guide pin hole of the press plate,
5). The relationship between the material guide of the fixed blanking plate and the width of the material being processed.
8. Design of backpressure plate
During the stamping process, the main functioning parts (punch, blanking plate, and master mold) will bear the surface pressure. When the punching pressure is higher than the surface pressure, a back pressure plate (especially the back of the punch and the die sleeve) should be used. There are two forms of use: partial use and full use.