Injection mold_ How to maintain injection mold

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Issuing time:2021-03-17 16:06Author:TianShiDa medical technologyLink:http://www.sztianshida.com/

Injection mold_ How to maintain injection mold


With the rapid development of China's economy, the application of injection molding in all walks of life is more mature. Many plastic parts of products need to be used in injection molding. The quality and service life of injection moulds have a great impact on the production cost of enterprises. Therefore, it is very important to improve the quality and maintenance of injection molding and improve the service life of injection moulds, So what factors will affect the quality of injection molding and how to maintain the injection mold?


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Injection mould


The quality of injection molding mould will be affected from raw materials, design, processing technology and other aspects, which are shown in the following aspects:


1. mould steel


Steel is the decisive factor of mould quality, and selecting reasonable steel is the most important. The criteria for selecting steel are:


① Requirements for injection molding data


Different plastics should choose different steel, such as the requirements for high polishing, corrosion resistance and so on;


② Price


The steel properties can be used well, not the more expensive, the better; considering the cost factors of the mold, the die steel should be selected and the die life corresponding data should be selected to prevent unnecessary waste; the life of P20 data is about 300000; 2738 data is no problem in 500000, h13/2344 is usually over 800000-1 million, which can be selected according to the situation;


③ Exterior treatment


The appearance treatment of the mold is also very important. Nitriding can enhance the hardness of steel surface, extend the die life, electroplating can be used to modify the mold steel, and electroplating can be used to enhance and improve the function of steel for some plastic parts requiring high brightness and corrosion resistance.


2. structural design


The mature die structure not only takes into account the characteristics of product data, shortening rate, forming temperature, elastic tensile deformation coefficient, but also the cooling water path and opening and closing die speed. Reasonable mold structure can extend die life and ensure smooth production of mold, improve efficiency and reduce cost.


3. mold processing


Sharp tools make good work. The organization of die technology is particularly important. Reasonable process organization can accelerate the production cycle, shorten the processing time, and save cost. And more importantly, accurate and reasonable processing can ensure the mold in the production process of stability and extended life. Some machining errors may lead to die Burning and welding, no matter how good the welding is, it is a loss to the mold; other poor processing may also affect the mold action, reduce the die life, resulting in the die in the production process of crack and even break.


4. standard parts


The lowest piece of wood is the one that determines the capacity of the bucket. We all understand this, but we often don't notice when we do it. The same is true for the mold. Although the standard parts are not directly involved in the forming, they control the operation of the whole die. Good standard parts should be wear-resistant, hard enough, high precision, and should not be deformed. Different brands of standard parts have a great price difference, so do not kill the mold, kill to kill, your mold from running straight to the public.


5. collision (flying mode)


The experience of die fitters is the key to the collision. The most technical work seems to be a simple job. The first thing to look at is this Kung Fu. The flat die is the simplest, fractal surface only need no flying edge break difference is basically OK. It is very difficult to mold car parts, not only fractal surface is irregular, but also often contains multiple sliders and top blocks. Through the collision, other problems of the mold can be improved and improved together, so it is a comprehensive operation.


6. polishing / leather


Polishing of the mould is the final link of the mold production. Polishing is directly reflected on the plastic, so it's the most decent job. Polishing can also help and compensate the mold movement, especially for demoulding is very meaningful. Often some mold production is not smooth because of the light is not in place, resistance is too large, demoulding difficult, even top white, top crack, etc.


7. mold device


The mold device is just like the assembly machine. Every part, every screw can not make mistakes, otherwise the result will be quite serious, light will lead to the product defects, affect the production, and the heavy will completely harm the mold, forming a void. So the life of the device must be very detailed. In the process of the device, pay attention to the cleaning of the mould, especially the water path and screw hole. The iron chips in the mould must be blown clean.


8. the warm runner is still the cold channel


This actually has the least influence on the quality of the mold, because the warm runner is generally designated by the customer, especially some major customers. Foreign famous brands are very good at quality or after-sales service, so there will be no problem in quality. Only some domestic heating channels are of great difference in quality. In order to save money, a small enterprise is competing for the advantage of price. It is easy to use some unreliable heating and conducting accessories. The first problem of cold runner is how to ensure the balance of injection molding, the size of gate, injection pressure and so on.


9. cooling water


Anyone who has had a mold experience knows how important cooling is to a mold. Because of the increase of price and human compensation, it is impossible to imagine the profit of a second injection cycle without cutting the injection cycle when mass production of products. But the acceleration of production cycle will be the rise of mold temperature, if not useful control, it will make the mold because of too hot to form, even lead to die deformation failure void. So excellent water design is particularly important, including the layout density, diameter, link between water routes and so on.


Maintenance of injection mold


Mold maintenance is the first in the production process of maintenance and maintenance. The mold is like a car, if it is not necessary and maintenance is not necessary for a long time, it may cause the mold to be discarded. So every time after the use of the mold to carry out comprehensive maintenance, especially the forming part of the rust prevention, the first action of the anti rust parts. Because the mold needs water in the production process, it may sleep on the mold during the device or disassembly process, so make sure the mold is dry and then brush another layer of oil for maintenance.


Injection mold_ How to maintain injection mold


1、 The use of injection molding


The mould creates value in use, but also loses its own value gradually in use. Therefore, the operator must pay great attention to the use of the mold, and generally pay attention to the following problems.


(1) Before use, check whether there are impurities and dirt in all parts of the mold. For the remaining plastic and impurities in the mold, wipe and remove the adhesive with cotton yarn and use copper knife to wipe out the adhesive materials with strong adhesion.


(2) The reasonable selection of the locking force, the product molding does not produce flying edge as the standard, can not think that the higher the better, that will increase the power consumption, and also easy to damage the transmission parts.


(3) All transmission parts should be well lubricated, so they must be kept lubricated.


(4) It is not allowed to hit any part of the mold with the heavy objects such as Lang tou, so as to avoid deformation or damage of the mold.


2、 Maintenance of injection molding

(1) Maintenance of cooling water channel


The cooling water channel is used to cool and solidify the plastic parts in the cavity by cooling water, which has a great influence on the forming process of the plastic parts.


1. The harm of cooling water channel blockage


In the long-term work, the surface of cooling water channel is easy to deposit scale, dirt, corrosion, etc. they will reduce the circulation area of cooling water channel, and greatly reduce the heat exchange between cooling water in the mold, so that the cooling effect is greatly reduced and the harm is very great.


2. Check for blockage of cooling water channel


The increase of sediment on the surface of cooling water channel will cause local blockage of the channel, which can be used to judge the internal condition of cooling water channel by measuring the flow rate of cooling water. When measuring, a pressure control valve can be installed between the mold and the cooling water channel. Under the same conditions, the pressure drop of cooling water through the mold can be measured. Thus, the blocking condition of cooling water channel can be distinguished. If the blockage reaches a certain extent, it is necessary to clean it in time.


3. Cleaning of cooling water channel


Because the design of cooling water channel is related to the shape of cavity, its shape is tortuous and inconvenient to be disassembled. Therefore, it is impossible to clean it by mechanical method, only cleaning agent can be used for washing, and the attached dirt can be removed under the strong impulse of the cleaning agent. There are many cleaning agents used, which can be used.


(2) Maintenance of unloading mold of injection mold


After the injection mold completes the given production task, it needs to be removed from the injection molding machine. During disassembly, the residual plastics shall be carefully removed and different cleaning methods shall be adopted according to different properties of different plastics. Soap water can be used to remove residual plastic and other deposits in the mold, and then air dry the mold. If there is rust on the surface of the cavity, it shall be cleaned, polished, protected with lubricant, and stored in storage.


3、 The trouble of injection mold and its elimination


In the process of working, there will always be some faults in the injection molding process. They will bring adverse effects on the quality, productivity and mold of the products. The following will be described.


(1) Die deformation and its elimination


Die deformation refers to the excessive elastic deformation or plastic deformation of the mold in the work project, which makes the mold not working normally or the quality of the products is unqualified. The reasons and the elimination methods are as follows.


1. Insufficient rigidity


In injection molding, the mold will be subjected to huge pressure holding pressure. If the mold has permanent deformation, the mold will not be used. However, even within the elastic limit, the deformation can be recovered. The solidification molding during deformation will make the mold open difficult or even open. In this case, it is impossible to reconstruct the mold from the structure, but it can reduce the injection pressure properly or to add the frame to the outside to strengthen the rigidity. Although it is not good-looking, it can be used.


2. Misalignment of die assembly


If the die is not assembled properly, such as the bad alignment of the die, the die closing and its joint are not correctly aligned, which makes the melt filling die unbalanced, which may cause the deformation or dislocation of the mold. In this regard, the mould should be reassembled, for the imbalance of filling mold, sometimes the method of modifying gate can be used to correct.


(2) Cavity damage and its elimination


Cavity is the place where plastic parts are formed. Its damage will directly affect the product quality. Cavity damage is hard damage on the surface of the cavity, which causes scratches, pits, cracks and other defects on the surface. The causes and the elimination methods of these damages are as follows.


1. Hard damage cavity


Sometimes it is difficult to take the plastic parts after the mold is opened, so it is easy to hurt the cavity by using hard tools such as the lifting gear. In addition, after the mold is opened, the hard objects such as spanner and hammer are accidentally dropped into the cavity, which causes damage to the mold cavity.


2. Improper operation


If the plastic parts are not taken out, the mold is closed, especially in the automatic forming, the cured plastic parts are easy to damage the cavity and mold.


3. Repair of damage


After the cavity damage, it is difficult to continue to work without repair. There are several methods to repair the cavity.


(1) Welding. Welding is a common repair method, and the most commonly used welding method is gas welding. If welding with electricity, because of the high temperature, the mold is easy to deform or even crack. Repair by electric welding. Preheat the mold and heat treatment after welding.


(2) Inserts. For damage with small area and deep depth, insert repair can be added. Generally, insert parts are driven after drilling. When drilling, pay attention not to drill through cooling water channel and screw hole. The fit between the insert and the cavity shall be close, and then polished and smooth after installation.


(3) Electroplating. For the defects with a depth less than 0.5mm, the method of electroplating is better to repair, and copper and chromium can be plated.


(4) Knock. For the cavity with soft material, a blind hole can be drilled on the back of the damaged part, and then the bottom of the blind hole can be knocked to make the damage protrude; or the concave part can be raised by knocking 3mm away from the damaged part, and then the raised part shall be ground, ground and polished.


(3) Rust of mould and its elimination


Injection molding is made of tool steel, which is made of corrosive gas and water which lead to rust. The plastic parts made by rust mould will produce quality problems, so they need to be eliminated.


1. Gas from melt decomposition


Some raw materials will produce volatile gas after heating, and many raw materials will also produce volatile gases when they are overheated. These gases are corrosive. They are diffused around the machine. When the mold is not working, they will corrode the mold. In this regard, when the machine stops working, the mold shall be wiped with soft cloth and the mold shall be closed. If it is not used for a long time, rust inhibitor shall be sprayed in the mold cavity, and butter shall be applied to close the mold and the gate shall be blocked.


2. Cooling water in the mold


The mould is cooled by cooling water to wake up, so the water and gas around the machine are more. If the mold is cooled to dew point, the moisture in the air will form water beads on the surface of the mold, and it will easily rust if it is not wiped out in time. Especially after the die stops working, condensate will be produced soon. Therefore, do not stop forming easily, even if it is to stop, also shut down the cooling water, and wipe the mold dry.


3. Carbide produced during forming


After the mold works for a long time, carbide is precipitated and decomposed in the forming material, which often causes the mold to wear, corrode or rust. If carbide is found to be formed, it should be wiped off and cleaned with dry cloth immediately.


In conclusion, in order to make the production cost of the whole enterprise in the injection mold lower, we must work together in the quality of injection mold and the maintenance of the later stage, so as to improve the service life of the whole injection mold, so as to reduce the product cost and enhance the market competitiveness of the whole body.


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