For the production of silicon steel sheets (矽钢片), in the past, general molds were used on ordinary punching machines; as the demand for silicon steel sheets became larger and higher, the precision was higher and higher, and the traditional production methods could not meet the requirements; some enterprises would The introduction of high-speed punching and carbide molds to produce silicon steel sheets. Molds are consumables, and imported molds are expensive and have a long lead time. Since 1997, after several years of efforts, from imitation, digestion, absorption, and improvement, we have developed a series of carbide molds for high-speed punching: standard EI film molds from EI*24 to EI*105, Standard electric meter molds, motor stator and rotor molds, etc. The mold performance is equivalent to that of imported molds. The highest speed is 400 times/minute and the life is 100 million times. The precision of punching (especially flatness) is better than that of imported molds, and it has achieved good economic and social benefits.
Carbide materials are small in size, expensive, high in hardness, difficult to process, and molds are used for high-speed punching, which must reach high speed. Therefore, mold design and manufacturing are different from ordinary material molds on ordinary punching machines, and must be taken seriously.
2 Punch sheet layout design Punch sheet layout is an important part of mold design. The layout not only determines whether it can punch out the punching film, but also determines the material utilization rate and high-speed productivity.
Non-standard EI punching film is a non-standard EI film to be punched, and one piece of E film corresponds to one piece of I. The more common layout is as shown, the material utilization rate is only 74%. For large-scale production, the material utilization rate is slightly improved. The economic benefits are significant, so we should maximize the material utilization rate. Then there is no material utilization ratio higher than this layout, carefully analyze the EI film drawings, add and subtract the relevant size, carry out the mobile combination arrangement, the two E pieces are staggered, as shown, the material utilization rate reaches 85%. Compared with the two, the material utilization rate is improved by *1:20*2-the layout scheme is 11%, and the mold is basically the same in terms of size, shape and number of convex and concave molds, processing difficulty, etc. No increase, and the economic benefits of the punch film manufacturers have been significantly improved.
In the layout design, it is also considered to facilitate the extraction of the punch. Imagine that the speed of four hundred times per minute, four films (two pieces of EI film), if they can not be smoothly taken out, all of them are scattered, and by manual division, it is impossible to be alone. The high-speed punching machine (operating punching, loading, and punching all in one package) must therefore allow the punching film to be smoothly taken out through the lead frame.
It can be used to solve the problem of positioning the stopper by adjusting the feeder feeding advancement and pressing device to the appropriate degree. A better solution should be as shown, according to the mold designed for such layout and station, the punched punch is flat; therefore, the design is scientific and reasonable, and the reliability is also high.
3 guiding and positioning design 4 convex and concave die design guiding and positioning mainly have three forms: guide nail, square guide, jaw stop. The three methods are applicable to different situations and should be selected according to different requirements. However, the positioning of the guide nail and the square guide head has higher requirements on the feeding step of the feeder, and the speed is not up. Therefore, the positioning of the jaw block should be selected as much as possible. Here mainly talk about the positioning design of the seesaw block.
In the layout drawing, the non-standard film to be punched is two pieces of U-piece corresponding to one piece of the piece, and the feeding step direction is provided with a seesaw stopper positioning device (guided nail for standby). In this way, the position blocked by the stopper on the strip is not the position assumed: while the punch is rushing downward, the stopper section of the raft is lifted up, and the automatic feeder stops feeding; When the punching piece falls and the punch is lifted up, the block section of the seesaw is pressed down to the strip, and the feeder starts to feed forward. After the block is pressed to the strip, the strip continues to advance, when the strip is When the first blanking hole passes, the gear passes through the blanking hole and is pressed onto the concave die surface. When the left side of the blanking hole is pressed against the stopper, the feeder stops feeding; after the punch reaches the upper limit, it goes down. When the block section of the seesaw starts to lift, the next cycle begins. Therefore, it is impossible for the stopper to always settle in the right drop hole at the second station to determine the feed step size; if the spare guide pin is used for positioning, the punch has no high position of the stopper, and the production efficiency is low. In fact, only hard alloy materials require high hardness, are difficult to process, and are expensive. For the larger punches, the welded structure is mostly used, that is, the cemented carbide is embedded in the edge of the punch, and the electric spark, wire cutting or grinding machine is processed after welding; for the small punch, the whole is made of cemented carbide material; Most of the molds are inlaid with a mosaic structure; the concave molds are inlaid with a mosaic structure, which can be used to spell out right angles (sometimes the radius of the wire cutting wire with a large radius of the die cavity is not allowed), and once a cavity is damaged, only Replace the insert again.
In the selection of the material of the convex and concave molds, it seems that the convex mold is better than the hardness of the concave mold, so that the convex mold is not easily broken. However, for a punch with a sharp corner, such a material is easy to wear, and in order to ensure the dimensional accuracy of the punch, only the worn portion of the punch can be worn away. In order to solve the problem of convex wear and wear, improve the life of the mold, change the previous idea of ​​selecting the convex and concave mold, and at the same time improve the punching resistance of the punch by designing the punch to be stepped, sheathed, or designed to be in a floating state. Practice has proved that such a design is feasible and improves the life of the mold.
5 The main measures to improve the precision of the punching film have many influences on the dimensional accuracy and flatness of the punching piece. The punching piece is slightly modified, and the position is adjusted to the fourth working position. 5 bshi* body properties have an impact, mold design also has an important impact on precision, good mold design can reduce the impact of the material properties of the punching material, and if the punching material performance is good, it can make up for the lack of mold design. Here we mainly introduce how to improve the precision of the die by improving the die design.
In the case of as much as possible, the multi-purpose spring-loaded discharge plate is used, and the fixed discharge plate is used less, which can significantly improve the flatness of the punch: for the fixed discharge plate, the strip can smoothly pass through the mold, and the strip There is a gap between the die surface and the discharge plate. When the punch is punched down, the strip is in a floating state, that is to say, the strip is not pressed down on the concave surface and is pressed downward; The working principle of the elastic type unloading plate is not the same. When the punch is punched down, the elastic type unloading plate presses the strip tightly on the plane of the concave template, which is of course easier than when the strip is not pressed. The punching, and also the re-leveling of the strip (although the strip has been leveled before entering the mold) is particularly effective in eliminating the deformation caused by the stripping of the strip after passing the previous station.
In order to improve the flatness of the punching sheet, other measures can be taken: determining a reasonable draft curve, so that the die can not only accommodate the punching sheet, but also not to deform the punching sheet; when the punching knife edge is changed, the change is made. Generally, the plane of the punching die edge is parallel with the plane of the die to form a slight angle with it, or to be ground into a circular arc surface.
In order to improve the dimensional accuracy of the punching chip, the following aspects must also be paid attention to: designing a reasonable guiding and positioning device, improving the guiding positioning accuracy, thereby improving the precision of the punching die; designing a reasonable die structure, in general, the die cavity inner cavity product The film can reach more than 20 pieces (the thickness varies with the depth of the die and the thickness of the die). The tension is quite large. The design must ensure that the die does not open and deform; according to the material properties and thickness of the die, the gap of the die is determined. According to the condition of the machine tool equipment, the mold structure is reasonably designed. If the machine tool equipment does not meet the required machining precision, it can be designed to be adjusted. After the adjustment is in place, take a reasonable and reliable positioning and fixing method; to facilitate the mold maintenance, ensure disassembly and assembly. Before and after consistency, such as the mold often removes the sharpening mouth, try to use the tapered pin and use less cylindrical pins.
6 mold processing problems The processing of cemented carbide molds has some special requirements. The design of the mold can only be based on the existing processing equipment, so there are some special solutions in the processing. For the welding of cemented carbide, in order to improve the compactness of the weld and the reliability of the welding, the following measures are taken: improving the surface roughness of the weld and, if possible, grinding the machine; preheating before welding, and aging after welding Processing; such as the processing of convex and concave molds, due to the limitations of the equipment, in addition to the partial rectangular punch, circular punch or splicing die, the state after processing of the AGIE1000 slow wire cutting machine is the final state, after cutting the surface Roughness does not meet the requirements, generally need to cut four times: after the first cutting, the punch is still connected with the base metal, leaving the connecting part about two to three millimeters (to be cut four times before cutting) from the second At the beginning of the cutting, the wire cutting wire is located in the slit that has been cut: under normal circumstances, the wire cutting wire is pressed against the edge of the punch to perform single-sided cutting; if the gap is changed, especially smaller, even smaller than the diameter of the wire cutting wire, Then the cutting situation is different, no longer single-sided cutting, which will inevitably affect the processing precision of the punch. To improve the machining accuracy of the punch, it is necessary to ensure that the gap after cutting does not change or change little. Obviously, the pre-punctured wire cut closure (remaining material closure) is better than the open cut. In practice, considering the material utilization and less threading, there are many open-cut cutting. In the processing, the problem of over-discounting of the punch in the height direction is easy to occur; using the pre-punching hole to close the cutting, the basic The problem of oversize of the punch in the height direction does not occur.
7 Conclusion In the development of hard alloy molds for high-speed punching, there are many practical problems. The above are just some experiences. I hope to communicate with peers and improve the level of mold development.
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