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.
2. Mold specifications
(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) Template thickness
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. The main templates of continuous die include punch fixing plate, pressing plate and concave die. According to the precision and output of stamping products, the processing equipment and methods of the die and the maintenance mode of the die, its structural design has the following three forms: (1) block type, (2) yoke type and (3) insert type.
1. Integral 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 fit between the yoke plate structure and the stopper parts is medium fit or 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 make the groove part of the yoke plate closely combined with the stopper part, the corners of the groove part should be machined with gaps. If the corner of the groove part of the yoke plate cannot be machined with clearance, the stop part should be machined with clearance.
(3) The internal shape of block parts should be considered at the same time, and 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: A. Fix them with locking screws, B. Fix them with keys, C. Fix them with U-shaped keys, D. Fix them with shoulders, and E. Fix them with upper 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), comprehensive processing machine, coordinate boring machine, coordinate grinding machine, wire cutting machine and EDM machine. 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: a. fix it with screws, b. fix it with shoulders, c. fix it with toe blocks, and d. press the upper half with plates. Press fit is also used to fix the female die insert. 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 assembling and disassembling the insert: The machining accuracy of the insert and its holes requires high assembly operation. In order to adjust the assembly even if there is a slight dimensional error, it is suggested to consider the countermeasures in advance. There are five specific considerations in the processing of the insert: a. Setting the press-in lead-in part B. Adjusting the press-in state and correct position of the insert with a gasket C. Setting the press-out hole D on the bottom surface of the insert. Using screws with the same size to facilitate locking and loosening E. To prevent errors in the assembly direction, we should
design
Unit 1.
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 die is installed on the punch, the blade is directly joined without using the guide device.
(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 combination of punch and 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 blanking plate and the 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 punching plate and the die fixing plate. So as to correctly maintain the positional relationship of each plate to protect the punch.
2. Guide post and guide sleeve unit
There are two kinds of mould guiding modes and accessories with guide posts and guide sleeve units: (a) external guiding mode (mould base type or main guiding mode) and (b) internal guiding mode (or auxiliary guiding mode). 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: generally used in molds with low precision requirements, 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 is rapidly popularized. 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 die device (round)
(1). Punch unit: According to its shape (shoulder type and straight type), length and maintenance convenience, the round punch unit should match the blank holder guide sleeve unit.
(2) Die unit: circular die unit, also known as die guide sleeve unit, can be divided into block type and separated type. According to the production quantity, service life and the rationality of product or chip stamping, the combined series of female die units are: (a) directly processing the female die shape by using the template, (b) having two inclined avoidance parts, (c) using the back plate or not, and (d) irregular female die.
4. Compression bolt and spring device
(1). Pressure plate bolt unit: The types of pressure plate bolts are: (a). External thread type, (b). Casing type, (c). Internal thread type. In order to keep the blank holder parallel at the specified position, the clamping ways of the blank holder bolt (shoulder contact part) are: (a) the cavity supporting surface of the die holder, (b) the top surface of the punch holder plate, and (c) the top surface of the punch holder plate.
(2) Compression spring unit: The compression spring unit of movable platen can be roughly divided into: (a) single-use type and (b) combined type with compression bolt.
When selecting the blanking spring device, it is best to consider the following points before making a decision:
(a) 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).
(b) Whether it is necessary to adjust the initial spring compression (pre-compression) or load.
(c) Consider the ease of mold assembly or maintenance.
(d) Consider the relationship with the length of the punch or compression bolt.
(e) Consider safety (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 get the correct feed 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 in the form of a pressure plate, so it is necessary to pay attention to the rigidity and guiding form of the pressure plate, because the amount of the guide pin protruding from the pressure plate is required to reach a certain level, and it is easy to bring processed materials when the mold 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. Guide device
(1), shape punching (blanking) or continuous stamping. In order to guide the width direction of the processed material and get the correct feed spacing, the material guide unit is used.
(2) The guide devices in the width direction of the strip are: (a) fixed plate guide pin type, (b) movable guide pin type, (c) plate tunnel guide type (single plate), (d) plate guide type (consisting of two pieces) and (e) lifting pin guide type (movable, fixed and fixed).
(3) There are two kinds of start-stop guide devices: (1), slider type, (2) and moving pin type. Its main function is to position the material in 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 are: (a) fixed stop pin, (b) movable stop pin, (c) trimming stop mode, (d) hook stop mechanism and (e) automatic stop mechanism.
(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 position positioning and guiding mechanism has the following forms: (a). Fixed pin guide type (blank shape), (b). Fixed pin guide type (using blank hole), (c). Guide plate (for large parts), (d). Guide plate (integrated), (e).
7. Lifting and ejecting device
(1). Lifting pin unit: Its main function is to lift the strip onto the female die during continuous stamping (the position height is called the feeding height, so as to achieve the purpose of smooth feeding. Its forms are: (1). The lifting pin type (circular, purely for lifting) is the most common lifting pin device. (b) Lifting pin type (round with guide pin holes) can prevent the material from bearing the deformation of the guide pin and make the guide pin work. (c) Both the lifting pin type and the guide pin type have the function of guiding materials, and this lifting pin type is most commonly used for guiding materials of continuous dies. (d) If necessary, the lifting pin type (square) shall be equipped with air blowing holes. (e) Lifting and guiding pin type (square).
(2) Ejection unit: In the process of automatic stamping, it is necessary to prevent stamping products or chips from jumping on the surface of the mold 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 female die in each stamping process. There are two positions for installing the ejection unit: (a) the mold with reverse configuration is installed on the upper mold part, and (b) the mold with forward configuration is installed 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. Precautions for use are as follows: (a) The fixed pin hole should be a through hole. If it is not possible, consider the design method of easy disassembly with screws. (b) The length of the fixing pin should be moderate and should not be longer than necessary. (c) Necessary escape parts shall be provided for the fixed pin holes. (d) When it is placed in the upper mold part, a mechanism to prevent it from falling should be designed to prevent it from falling. (e) When one side is press-fitted and the other side is slide-fitted, the fixing pin hole on the sliding side is slightly larger than the fixing pin. (f) The number of fixing pins should be two, and the same size should be selected as far as possible.
9. Blind plate device
One of the most important points of the blank holder unit is that the surface of the blank holder and the surface of the die have correct parallelism, and the buffer pressure needs to be balanced.
10. Misdelivery detection device
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) Install a detection pin in the upper mold, and when it deviates from the hole of the strip, it will contact the strip for detection. (b) The detection pin is installed in the lower die, and when a part of the strip contacts the detection pin, the detection pin is detected.
1 1. Waste cutting device
In the process of continuous stamping, the strip (waste) will leave the die one after another, and there are two ways to deal with it: (a) take up the wire with a winder, and (b) refine it with a die-cutting device. The latter has two ways: (a) using a special waste cutting machine (installed outside the punching machine), and (b) installing a cutting unit in the final project of the continuous die.
12. Height stop unit
The main function of the height stop unit is to correctly determine the position of the lower dead center of the upper die. It has the following two forms: (a) frequent contact during stamping, (b) only contact during assembly, and no contact 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. 1. Standard parts and specifications
The following matters should be considered in the selection method of mold standard specifications: (a) When the content of the specifications used is not limited, it is best to use the highest level. (2). In principle, the standard number is adopted. (c) If the standard parts of the mold do not have this size, the closest size shall be used for processing.
2. Punch design
Punch can be roughly divided into three parts according to its function: (1) Cutting edge tip of machining material (irregular, square, round and so on. ). (b) Contact part with the punch fixing plate (irregular, square, circular and other cross-sectional shapes of the fixing part or handle part). (c) Connecting part (middle part) between the blade and the handle.
From (a) the length of the cutting edge, (b) the grinding direction of the cutting edge, and (c) the fixing method of the punch and the shape of the handle, the design criteria of each part of the punch are briefly described.
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 1.5 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 material guide hole is designed according to the thickness of the material, and the tip shape of the guide pin can be roughly divided into two types: a. cannonball shape and b. 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. Die design
(1). Stamping die design
The main items to be considered in the shape design of stamping die are: a. the shape of die life and escape angle, b. the cutting angle of die, and c. the parting of die.
(a) 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.
(b) Shear angle of the female die: In order to reduce the punching force when stamping the shape, the female die can design a shear angle. When the shear angle is large, the punching force will be greatly reduced, but it is easy to cause warping and deformation of the product.
(c) Division of the female die: the female die must be finished by forming and grinding. Because it is concave, the grinding tool is not easy to enter, so it must be divided.
(2) Design of bending die
In the design of bending die, in order to prevent springback and excessive bending, the shape of U-shaped bending die 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 die should be small, about 1-2 times the thickness of the plate. Generally, most of the drawing parts of the drawing dies used for the upper cylinder and the square cylinder are straight. In order to prevent burns, damage the lubricating oil film and reduce the jacking force, it is suggested to have an escape part (step or push-pull) below the straight part. Especially in the case of necking, it is necessary to have as few straight segments as possible.
6. Side pressing countermeasures of punch press
It is the best ideal state that the punch bears equal loads on the left and right sides in the stamping process (that is, the side pressure is zero). When the punch bears lateral pressure, the upper die and the lower die will deviate laterally, resulting in the gap between the dies becoming larger or smaller (uneven gap), and it is impossible to obtain good precision stamping. There are several ways to deal with the side pressure of the punch: (a) changing the machining direction; (b) Products processed unilaterally (stamping, bending, drawing, etc.). ) to be arranged in two rows; And (c) the punch or die is equipped with a lateral pressure stop, and the side of the cutting edge is equipped with a guide device (especially for cutting and breaking).
7. Design of back pressure plate
During stamping, the main working parts (punch, blank holder and 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 die sleeve) should be used in two ways: partial use and full use.
Mold design software
Modern industry has developed rapidly, and it is basically designed and processed by computer, with the accuracy of 0.002 ~ 0.438+0. The world of mold design is endless. If you can use computer to carry out aided design, your opponent will fall behind you invisibly. Commonly used mold design software includes AUTOCAD Pro/E UG SW CImatron, Mi Xiong, etc. Design is the key step and initial link of mold production, which controls the whole process of mold production, so design also has a great influence on the service life of mold. The design mainly affects the service life of stamping die from the following two aspects.
(1) Accuracy of mold guide mechanism. Accurate and reliable guidance has a great influence on reducing the wear of die working parts and avoiding the biting of punch and die, especially for blanking die, compound die and multi-position progressive die with no gap and small gap. In order to improve the service life of the die, it is necessary to correctly select the guide form and determine the accuracy of the guide mechanism according to the requirements of process properties and parts accuracy.
(2) Geometric parameters of the cutting edge of the die (punch and die). The shape, fit clearance and fillet radius of punch and die have great influence not only on the forming of stamping parts, but also on the wear and life of the die. For example, the fit clearance of die directly affects the quality of blanking parts and the life of die. If the precision requirement is high, a smaller gap value should be selected in the design; On the contrary, the gap can be appropriately increased to improve the service life of the die.