The stamping process is a processing method to obtain a certain size, shape, and performance of the workpiece by applying an external force to the blank through the die to produce plastic deformation or separation.
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The stamping process has a wide range of applications. Since the processing is usually carried out at room temperature, it can process both metal sheets and bars, as well as a variety of non-metallic materials.
Stamping process analysis is the comprehensive determination of the best stamping process through all aspects of parameters.
The processability of the stamped part is directly related to the quality and cost of the product. A good stamping process is simple and easy to process, which saves raw materials and extends the service life of the tooling. At the same time, the product quality is stable.
Under the condition of production volume, the parts can be manufactured with high quality and low cost, and the production efficiency can be very good. When considering the processability of the stamped parts, the following principles should be followed in general.
(1) Simplify the production process as much as possible, consider the least and simplest stamping process to complete the whole part processing, and improve labor productivity.
(2) Ensure the stability of product quality and reduce the scrap rate.
(3) Simplify the die structure as much as possible to prolong the service life of the die.
(4) To improve the utilization rate of metal materials and reduce the variety of materials used.
(5) Conducive to the generality and interchangeability of products.
(6) The design of the parts should be convenient for stamping operation and conducive to mechanization and automation of production.
The central part of the yoke-type template is machined into a groove to assemble the block. The structure depends on the application requirements, the groove part can be formed by another template.
The advantages of this yoke-type formwork structure are: easy processing of the groove, adjustable width of the groove, good processing accuracy, etc.; however, low rigidity is its disadvantage.
The design considerations of yoke-type formwork are as follows.&#;
(1) The yoke plate and the block part of the embedding adopt the middle fit or light fit, if the strong pressure fit is adopted, the yoke plate will be changed.&#;
(2) The yoke plate also has the function of holding the block parts, so it must be rigid enough to bear the side and surface pressure of the block parts. If the corner of the groove part of the yoke plate cannot be made into a clearance process, the block part must be made into a clearance process.&#;
(3) The division of the block part should also consider its internal shape and the datum must be clearly defined. In order not to produce deformation when stamping, the shape of each block part should also be paid attention to.&#;
(4) When the yoke plate is assembled with many block parts, the accumulated error in the processing of each block part will cause the pitch to change.&#;
(5) The block parts adopt the die structure of a side-by-side combination because the block parts will bear the side pressure during the punching process to make the gap between the block parts or cause the block parts to be tilted. This phenomenon is an important reason for bad stamping size, chip blocking, and other bad stampings, so there must be adequate countermeasures.&#;
(6) Depending on the size and shape of the block parts in the yoke plate, there are the following five methods of fixing: fixed by locking screws, fixed by keys, fixed by shaped keys, fixed by shoulders, and fixed by pressing parts (such as guide plates).
This type of template is called inserted structure. The accumulated tolerance of this structure is small, has high rigidity, and good reproducibility of accuracy when decomposition and assembly.
Because of the advantages of easy mechanical processing, processing accuracy is determined by the working machine, and the final adjustment is less, the inserted template structure has become the mainstream of precision stamping dies, but its disadvantage is that it requires high precision hole processing machine.
When this template structure is adopted for continuous stamping dies, the empty station is designed to make the template have high rigidity requirements. The precautions of the inserted template structure are as follows.&#;
(1) The processing of embedded holes.
The template embedded hole processing using a vertical milling machine (or jig milling machine) integrated processing machine, jig boring machine, jig grinding machine, wire-cutting discharge machine, etc. When using the wire-cutting and electrical discharge machine for the processing reference of the embedded holes, the wire-cutting process is carried out twice or more to improve processing accuracy.&#;
(2) Fixing method of embedded parts.
The deciding factors of the fixing method of embedded parts are not to change the accuracy of its processing, the ease of assembling and disassembling, and the possibility of adjustment.
Embedded parts of the following four fixed methods: fixed by screws, fixed by the shoulder, fixed by the toe block, and the upper part of the plate to press.
The method of fixing the embedded parts of the mother template is also used to press into the fit, which should avoid the result of relaxation due to the thermal expansion of the process, and should be designed to prevent rotation when processing irregular holes using a round mold sleeve embedded parts.&#;
(3) Considerations of insert assembly and decomposition.
Inserts and their cavities are processed with high accuracy to be assembled.
In order to get even a slight dimensional error that can be adjusted when assembling, it is advisable to consider in advance to solve the countermeasures, the specific considerations of the embedded parts processing are the following five items.
There is a press-in part to adjust the press-in state and correct position of the insert with a spacer, and there is a hole for press-out on the bottom of the insert, and the same size of the screw should be used for locking and loosening when locking with a screw.
The die alignment unit is also known as the die edge parts of the alignment guide device. In order to maintain the alignment of the upper and lower die and shorten its preparation time, according to the product precision and production quantity, and other requirements, the die alignment unit mainly has the following five kinds:
The die installed in the punching machine directly to its edge parts of the cooperation, without using the guide device.&#;
This device is the most standard structure, the guide device is installed in the upper die base and lower die base, not through each template, generally known as the die base type.&#;
- External guide and internal guide type (a):
This device is the most commonly used structure for continuous dies, and the internal guide is installed between the punch fixing plate and the press plate. The punch and the mother die are aligned using the fixing pin and the external guide. Another function of the internal guide is to prevent the plate from tilting and to protect the small punches.&#;
- External guide and internal guide type (2):
This type of device is the structure of high precision high speed continuous die, the internal guide device through the punch fixing plate, press plate, mother die fixing plate, and so on. The inner guide device itself also has the die edge parts to close and protect the role of a small punch. The main function of the outer guide is to decompose and install the die in the punching machine to get a smooth purpose.&#;
This structure does not use the outer guide device, the inner guide device through the punch fixing plate, pressure plate, and mother die fixing plate, etc., to correctly maintain the position of each plate relationship to protect the punch.
Punch according to its function can be roughly divided into three major parts.
The apex of the edge of the processed material (cutting edge, the shape of irregular, square, round, etc.).
The contact part with the fixed plate of the punch (fixed part or shank, with irregular, square, or round cross-sectional shape, etc.).
The link between the cutting edge and the shank (middle part).&#;&#;
The design criteria for each part of the punch are briefly described in terms of the cutting edge length, the grinding direction of the cutting edge, the fixing method of the punch, and the shape of the shank.&#;&#;
(1) Cutting edge length
The design of the cutting edge length of the stage-type punch should take into consideration that no lateral bending will occur during processing, and the clearance with the moving part of the plate should be appropriate. The relationship between the press plate and the cutting edge of the punch is guided and unguided, and the length of the straight section of the cutting edge will be different.&#;&#;
(2) Grinding direction of cutting edge
The grinding direction of the cutting edge can be parallel to the shaft (up-cutting process) or perpendicular to the shaft (crossing process).
In the case of the convex shape of the cutting edge, the crossing process can be used, and in the case of the concave and convex shape, the up-cutting process or the crossing process can be used.&#;
(3) Fixing the method of punch and shape of the shank
The shank of the punch is roughly divided into two types: straight section type and shoulder type. The factors for the selection of the fixing method are the accuracy of the product and the die, the processing machinery and processing method of the punch and the punch fixing plate, and the maintenance method.&#;&#;
(4) Shank size and precision
The size and precision of the shank of the punch will have different requirements according to the fixing method of the punch.&#;&#;
(5) Adjustment method of punch length
In order to maintain a balance with the punch length of other works such as bending and drawing, and to maintain the design length of the punch, it is necessary to adjust the length of the punch.&#;&#;
(6) Design of punch to match the stamping process
In order to achieve the safety of the quality of the stamped products and the absence of defective products during mass production, it is necessary to consider the following matters to the dies.
The grinding direction of punch processing should be the same, and the surface should be polished.
To prevent the floating of the punching chips, the punch can be equipped with an ejector pin or an air hole.
To reduce the punching force, the punch head should be beveled, and the small punch near the large punch head should be shorter to reduce the impact.&#;&#;
(7) Punch design with processing method
The shape of the punch is absolutely related to the difficulty of processing, when it is too close to the fixed plate of the punch, the processing of the punch becomes difficult, and the punch should be divided at this time.
(1) Design of punching die
The design of the shape of the die should take into consideration: the shape of the die life and escape angle, the shearing angle of the die, and the division of the die.
The shape of die life and escape angle: this design is very important, if the design is not correct, it will cause the breakage of the punch, the blockage or floating of the chip, the occurrence of burr, and other bad press processing phenomena.&#;&#;
The shear angle of the master dies: In order to reduce the punching force when punching the shape, the master die can be designed with a shear angle, which will reduce the punching force when the shear angle is large, but will easily cause the recoil and deformation of the product.&#;&#;
The division of the master die: the master die must be applied to forming and grinding and other finishing processes, because it is a concave shape, grinding tools are not easy to enter, so it must be divided.
(2) Design of bending master die
The design of the master die for the bending process, in order to prevent the occurrence of rebound and excessive bending, the shape of the part of the master die for the U-shaped bending process is the combination of double R and straight part (slope of 30 degrees), and it is best to approximate the shape of R. The shape of the R part should be polished after forming and grinding or NC electric discharge processing.
(3) Design of lead die
The shape of the corner part and the shape of the escape angle of the die is a very important design matters. The shape and characteristics of the corner part and the escape angle are as follows: The R angle of the die is easier to draw when the value of the die is large, but it also produces wrinkles on the surface of the drawn product and the thickness of the sidewall of the drawn product is larger than the thickness of the plate.
The R-value of the master die should be small, about 1-2 times the plate thickness, and most of the upper cylinders and square cylinders of the master die are made into straight sections to prevent burning, destruction of lubricating oil film and reduce the ejection force, etc. The lower part of the straight section should be designed with an escape section (stage shape or push-out shape). Especially in the case of shrinkage processing, it is necessary to have as few straight sections as possible.
(1) Machining workshop to process large parts according to drawings, technology, and technical requirements.
(2) The assembly workshop processes small parts according to drawings, drawings, and process requirements.
(3) Assembling workshop according to the drawings, technology requirements scribing, drilling, assembling panel (fixed seat) on the bottom, fastening, sent to the machine shop.
(4) Machine shop according to the drawings, technology, and technical requirements of rough (semi-finishing) processing parts surface, contour, hole, edge, etc.
(5) Clamp workshop according to the drawings, technology, and requirements for parts trimming, disassembly, scribing, drilling, etc.
(6) Assembly workshop according to the drawings, technology, and technical requirements of secondary processing of small parts (empty knife, back knife, etc.).
(7) Machine shop according to the drawings, technology, and technical requirements for finishing parts surface, contour (only the local extension mold);.
(8) Clamping workshop to be parts of the secondary processing is completed, check whether the parts are not processed and unqualified, such as parts have been fully processed and qualified, and can be sent to heat treatment.
(9) Heat treatment
According to the process requirements for the overall heat treatment and surface heat treatment (heat treatment contains: quenching, annealing, normalizing, tempering, blackening treatment, bluing treatment, carburizing quenching, nitriding quenching, salt bath, effective treatment, surface flame quenching, etc.). Its role is to make the parts of the HRC value to the standard required by the mold.
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(10) Clamp adjusting workshop will heat treatment qualified parts together with the drawings sent to the assembly workshop, the finishing of parts.
(11) Assembly workshop according to the drawings, technology, and technical requirements for the finishing of parts (flat grinding, round grinding, electrical machining, etc.).
(12) Clamping workshop according to the drawings, technology, and technical requirements, the second assembly of the panel (fixed seat), fastening, sent to the machine shop.
(13) Machine shop according to the drawings, technology, and technical requirements of finishing parts (surface, hole, edge, etc.) after passing, sent to the clamping workshop.
(14) Clamping workshop according to the drawings, technology, and technical requirements to repair the surface, contour, edge, installation of accessories, etc., until the requirements of the drawings, complete the assembly of the mold.
(15) Clamp workshop to clean the mold, brush anti-rust oil, paint, nail the label, and do all the factory work and mold perfection work.
(16) Assembly
Assembly is the combination of processed parts together to form a complete pair of molds. In this process, only the processed parts are fastened, or into the positioning pins, and other pure assembly operations are rare. Generally are in the process of assembly and adjustment of certain manual repairs or mechanical processing.
(17) Clamping workshop to debug the mold, and repair, until the transfer of qualified product process parts, including pre-acceptance, mold rectification, and customer&#;s final acceptance;
(18) Clamping workshop to clean the mold, brush anti-rust oil, paint, nail the label, and do other factory work and mold perfection.
Assembly is an important part of the clamp adjustment. The assembly of the mold and the general clamp assembly is very different.
General clamp assembly only needs to be installed in accordance with the assembly diagram, generally regarded as static assembly, while most of the mold assembly belongs to the dynamic assembly, generally considering the working condition of the press and heat treatment after the deformation.
The following are some common types.
(1) Die base guide plate installation
Find the relative position of the guide plate by pressing it against the face of the mountain, find the center point of the hole with a sample punch, and then drill and tap the hole. In addition, check the rate of the guide plate and the mounting surface.
After the installation of the guide plate, check the clearance between the upper and lower die base guide plate, the clearance of the outer guide plate is within 10 courses, and the inner guide plate is within 8 courses.
(2) Installation of the slanting part of the lifting die
The crane is divided into 3 parts: mounting slot, sliding part, and driving seat. Their benchmark is the mounting slot, the sliding part is standardized by the mounting slot, and the driving seat is standardized by the CNC and sliding part.
The convex die of the slant die (hanging die) is coarsely referenced to the CNC, and then the side clearance is adjusted on the press.
The effective contact surface of the guide plate on the inclined die (hanging die) and the mounting surface should be more than 80%.
The side clearance of the guide plate is 3 (below 500) or less; above 500 is 5 or less.
The clearance of the upper guide plate is within 2 (below 500); above 500 is within 3, and the flexibility of movement between them should be ensured at the same time.
(3) Installation of trim die block
The installation of the trimming block is the installation and local adjustment after the rough machining and quenching in the assembly workshop. Firstly, make an adjustment to the surface and cavity, including the trimming of the surface and gap and the trimming of the gap between the blocks.
If there is a cushioned surface, the cushion surface will be used as the benchmark, and if there is no cushion surface, the position of several inserts will be determined, usually diagonally. Then finish machining.
(4) Positioning of punching die convex die (punching pin)
Since the side clearance of the convex and concave dies is only 3 channels, there are errors in both CNC point finding and manual drilling and tapping (especially the latter), so it is difficult to locate them precisely, and the only way to locate them manually, in this case, is in the dynamic situation of the press.
The general method: for cylindrical type, find one point in the CNC machine; for non-cylindrical type, find two points in the CNC machine for drilling and tapping to rough positioning.
For precise positioning, put putty on the convex die, apply red-dan powder on the relative concave die, find the precise position by the press, and finally use the positioning pin to locate.
(5) Assembly of scrap cutter
The assembly of the scrap cutter is somewhat similar to that of the punching die. Since the scrap knife changes after the trimming model surface and cavity adjustment, and sometimes it is very large, it is positioned purely by hand.
First, put the die on the press, put the scrap knife against the cavity, find out the position of the scrap knife with a scribing needle, and then find out the precise position after drilling and tapping.
The above (4) and (5) are used to achieve the requirement by having a 1.5 pass margin between the screw and the hole.
Adjustment is the most important part of the clamping process, adjustment is to enable the mold to process a qualified part, can enhance the performance of the mold, and service life, and provides some accurate parameters for the debugging process, adjustment, and assembly are often carried out at the same time.
Before adjustment, one should first master the type of mold, structure, the shape of the parts, and relative reference frame. Adjustment is divided into static adjustment and dynamic adjustment.
Static adjustment mainly includes the adjustment of research rate and surface roughness. Dynamic adjustment includes the adjustment of various guide pillars, guide bushings, and guide plate clearance; the adjustment of the grinding rate of the guide plate, slanting cage (hanging cage), and the mounting surface and the cleaning surface.
Adjustment of the gap between the trimmer cavity and the press ring, and adjustment of the gap between the inserts.
Adjustment of all die movement strokes; commissioning of press pressure.
Adjustment of various inlays and scrap knives.
Rounding the transition surface of the drawing dies, punching and releasing material, etc.
The impact of various factors on the mold.
(1) The influence of the research rate
The poor research rate of the drawing die and plastic dies will produce defects of uneven thickness of parts, pulling cracks or wrinkles or inaccurate size of parts; the defects of the trimming die, plastic die, and punching die will produce defects of misalignment, strain and pulling crack of parts.
(2) The impact of roughness
It is easy to cause scratches on the surface of the parts; especially for the drawing die, if the surface roughness is too high, it will cause high resistance to drawing, resulting in strains or cracks in the parts.
The surface roughness of the drawing die should reach 0.8 or even higher for the drawing inlay and transition inflection point.
(3) The impact of the gap between the standard parts
If the gap is too small, it will cause strain on the surface of the standard parts; if the gap is too large, it will cause the relatively moving part with larger misalignment, and it will affect the service life of the mold.
(4) Influence of drawing die pressure
If the pressure is too large, it will cause the pulling crack or thinning of the parts, too small, resulting in pulling wrinkles. For double-action press, if the external pressure is too large, it will cause the pulling of the situation.
Many factors affecting the parts failed, and the cause of the cause can only be comprehensive analysis to exclude one by one, mainly by the accumulation of experience.
In the adjustment of the research, the rate must pay attention to the benchmark of the mold. General convex die as the benchmark, the benchmark can only be surface roughness and burr repair, do not allow for grinding or change of surface.
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