The phenomenon of floating material is a common and undesirable phenomenon in metal stamping dies. The reasons for the floating material are various, so the solution is also diverse. Some of the scraps are caused by poor mold design, some are caused by poor raw materials, and some are caused by stamping operators. When you need to make an effective and fast solution, you should carefully study its type and cause. Here are the experiences and experiences of the monks in the design of metal
Molds. Please share your opinions with friends.
First, the type of floating material Today, I will talk about the types of floating materials. For floating materials, I divide them into three types according to their size and formation factors.
1. The phenomenon of rising waste Waste refers to the part that is detached from the product during a single die cutting (forming) process. The size is generally the same as the shape of the lower die. Its area and hazard are the largest among the three phenomena. When this phenomenon occurs, it may cause the punch or the blade to crack or even break, which may cause the positive needle of the product to break, and may cause cracks in the template.
2, the phenomenon of rising debris Waste is the non-integrated product or non-integrated waste produced in a single process. Its size is relatively small, like the burrs (burrs) of the product fall off; punching waste filaments. When this happens, it is reflected in the appearance of scratches, scratches, pits or dents in the product. This situation is mainly caused by bad products, but this situation is the most common and relatively concealed in mold production.
3. The phenomenon of waste powder rising Waste toner refers to fine dust that is generated by friction between the punch and the product in a single process. This phenomenon is generally difficult to detect in the early stages of the eye, and it is easy to distinguish when the head and the color change occur when the degree of accumulation is increased. When the waste powder reaches a certain level, it is easy to cause the punch to break or the mold to be broken. Most likely to occur in brass-based and aluminum substrates.
Second, the reason for floating material 1. The floating material of the scrap The reason for the rising of the scrap is to first analyze the source of the force. The scrap is generally the same shape as the punch or the lower die. Therefore, the scrap should have a certain friction in the insert of the mold, from the principle of punching. After the cut-off, the scrap will recover the structure due to the plasticity or elastic deformation of the material. In other words, the actual shape in the unconstrained shape should be larger than the shape of the lower die edge, which is why when the waste is taken out from the insert. After that, it is no longer easy to refill the waste into the mold. If the waste is raised, there should be a upward force and greater than the sum of the friction and tension. This force may come from two directions. One is the tension or elasticity of the scrap material itself. Since the scrap is flexed (in a nutshell) during the punching process, when the punch is detached from it, its internal Tension will have a rebounding force, perhaps downwards or upwards; second, external forces, this force also has two aspects, the punch surface and raw materials (and waste) when the punch and the die are cut away. ) closely fits in
Together with the lower mold to form a closed space to create a vacuum state, when the punch rises, destroying this vacuum state, so the effect of the negative pressure of the air induces the waste and the punch to rise together to produce the phenomenon of rising waste; Secondly, in the general stamping process, there is a phenomenon of waste overlap in the lower die. When the latest piece of scrap is added, the internal force (rebound force) of the other scrap itself will also cause the new scrap to rise. Therefore, when the stamping speed is very low, and there is no waste accumulation phenomenon, the floating material phenomenon of the waste type rarely occurs. This is also one of its reasons.
2, the waste material rising up How is waste generated? There are several situations, one is the detachment of the burrs (or hairs) of the product or waste; the other is the small scraps caused by the scratches or bruises of the punches or other parts of the mold and the raw materials. Because the punch does not have a corresponding structure when it needs to make excessive effects on the raw materials; the third is because the raw material has been surface treated before the stamping, and the surface treatment layer and the material itself still have a certain non-structural fusion phenomenon. The edge of the material is separated and peeled off; another is due to the unreasonable design of the mold, there are secondary die-cutting (re-cut) or too small scrap cutting, generally the width of the punching should not be less than 1/3 of the thickness of the material. Too small a cutting waste is easily detached from the bulk waste or forms a waste due to hardening.
3. Reasons for the rise of waste toner Waste toner is caused by structural reasons of raw materials. It has been said that aluminum-based and brass-based materials are prone to such a situation. There is no way for raw materials, and the reason for this is that the surface of the punch or the inlet has roughness, that is, the surface has pits at a certain degree of magnification. When the punch or the incoming contact is in contact with the raw material, the raw material (like a shovel and iron) is rubbed to produce waste toner.
Third, the countermeasures for floating materials Through the above two phenomena and the cause of formation, it is possible to analyze the countermeasures of the mold. First explain the method of each kind of waste floating material.
A. The floating material caused by the improper design of the discharge material
This type of floating material is most likely to occur during the discharge process, and most of them produce a relatively simple die cut shape. Such as square, smaller side shaped waste.
At this time, it is generally necessary to deliberately make process gaps during design, such as trapezoids and dovetails. The simple punching shape is complicated, and the friction of the scrap is increased to prevent the scrap from rebounding and vacuum suction.
B, the punching hole itself is simple in shape
Such as round holes, square holes, etc. In this case, the reasons for the formation of waste materials are changed. One is to change the direction of rebound, and the other is to reduce the vacuum area. Common methods are as follows: 1. Grinding the punch into a single bevel or a double bevel, so that the material can be deformed to reduce the rebound force inside and outside the material, and the vacuum area is reduced. 2. It is also possible to grind a small boss in the center of the circular punch when punching the hole. The effect is the same as that of the bevel, but this method is more effective for the hole. 3. When the cut edge is three or two sides, the punch is not required to be cut to make a certain step, so that when punching, a little bending action can be made to make the waste downward deformation is beneficial to the waste. material. 4. Make the corrugated or rough surface of the punched surface of the punch. It can be processed with a file or electric grinder to increase the amount of air and reduce the amount of vacuum.
C. For all punched shapes that are likely or produce floating material
The above B methods (mostly bench-fitted) sometimes do not completely solve the problem, and should be resolved from the design considerations.
1. Punching the punch into the top needle The top needle and the spring are added to the punch which is prone to floating material, and the top needle is used to push the waste into the lower mold when the mold is divided. This method is suitable for occasions where the punching shape is relatively large and the raw material is relatively thick.
2. The lower die and the punch are made into sharp corner pits. That is, the normal step size of itself should be equal to the punching off the shape surface, but deliberately forming a concave pit such as a triangle on the punching shape surface near the feeding end and the other cutting edge is designed according to the normal edge, so that the punching is performed in one step. When you need to cut off the edge, there will be a small triangular protrusion due to the pit, which is larger than (actually beyond) another cut edge, so that the corresponding punch is rounded and does not form a punch. The effect is that the extra triangle edge will be pulled into the lower mold and strongly resist the lower mold to increase the friction to prevent rebound or resist vacuum suction.
3. The lower die is inserted into the sub-hole as a symmetric pressing point. Usually, when designing the mold insert, it will match the punch equal clearance, and in order to prevent the floating material, one pair or two pairs of symmetrical points in the lower mold are smaller than the punching gap by 1/2 or so, so that the punching is performed. In the case of scrap, the scrap is stuck in the lower mold due to the small gap stamping. This grammar can be done by discharge plus tumor or wire cutting.
4, the lower mold into a straight shape This method is more suitable for thin materials. Generally, when designing the mold insert (knife edge), there will be a straight edge of 3-5 mm. In this method, there is no straight edge to directly make the 8-15' slope, so the scrap is the smaller the gap, and the larger the gap is, the easier it is to rebound upwards.
5, the lower mold into the sub-use of 3mm cut away from the remaining part of the straight edge by the discharge method to increase the blanking part so that the waste does not accumulate, lengthen the length of the punching punch. Each punch cuts the waste into the blanking area, making it impossible for the scrap to float upward. 6. The punch is equipped with a blow hole and a blowing device as if a thimble is added. Since the air blowing device can control the blowing time in conjunction with the punching machine, it can be applied to a thinner material, which is unmatched by the thimble anti-floating material. 7. Lower die or lower die pad plus blowing groove This kind of method is similar to the principle of punch blowing. The specific method is to make the air passage in the lower mold pad, and then drill the downward 45 hole through the blank hole in the blank hole that needs to be blown, and the air passage. It is not compatible with the blanking hole (remember this point), and when the air is blown down, a negative pressure space is formed to suck the waste. This method is suitable for thin materials.
8, using external suction to absorb waste The method is to add a lower die auxiliary plate under the lower mold base to make all the drop holes of all possible and even the punching portions into a large blank frame on the auxiliary plate, and weld a funnel-like material tube, and then use The industrial suction device is connected to the material pipe. All the waste is sucked into the industrial suction device by the suction of the suction device; what waste waste is passed in and the insurance is reliable. Ha ha.
9, ultra-thin material below 0.10 simple shape anti-floating Due to the small punching gap of the extremely thin material, some of the above methods for preventing the waste material from floating are not very suitable, such as the ejector top material, the lower mold for bumping, the industrial suction device and the like.
For this kind of material, it is generally designed to make the lower mold into 8-12' without straight body, and then test the test which is easy to jump. Then remove the mold, use a long thin thimble plus diamond powder (diamond paste) carefully to make a few symmetrical rough points in the lower mold. This method works well, but requires a high level of fitter.
The waste material is mainly caused by unreasonable design or the material itself.
Unreasonable design: Try to avoid heavy cutting and overcutting during the blanking process. Since the metal molds are generally designed with CAD, there are some semi-processes that have not taken care of the previous processes when doing some processes.
