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With the rapid development of China's economy, the application of injection moulds in all walks of life is becoming more and more mature, many plastic parts of products need to use injection moulds, and the quality and service life of injection moulds have a greater impact on the production cost of enterprises, so it is particularly important to improve the quality and maintenance of injection moulds to improve the service life of injection moulds. So what factors will affect the quality of the injection mold and how to maintain the injection mold?
Injection mold from raw materials, design, processing technology and other aspects will affect the final injection mold quality, specific performance in the following aspects:
1. Mold steel
Steel is the decisive factor of mold quality, and the selection of reasonable steel is the most important thing. The criteria for selecting steel are:
① Requirements for injection molding information Different plastics should use different steels, such as high polishing requirements, corrosion resistance requirements, and so on;
② Price Steel can be used, not the more expensive the better; Considering the cost factor of the mold, the mold steel should be selected and the corresponding information of the mold life to prevent unnecessary waste; Generally, the life of P20 data is about 300,000; 2738 data is no problem in 500,000, H13/2344 is usually more than 800,000 to 1 million, can be selected according to the situation;
③ Exterior treatment The appearance of the mold is also very important. Nitriding can enhance the outer hardness of steel and extend the die life. Electroplating can be a useful modification of the mold steel, and some plastic parts that require high brightness and corrosion resistance can be used to enhance and improve the function of the steel.
2. Structural design
Mature mold structure not only takes into account the characteristics of product data, shortening rate, forming temperature, elastic tensile deformation coefficient, etc., but also takes into account the cooling water, the speed of opening and closing mold. Reasonable mold structure can extend the life of the mold and ensure the smooth production of the mold, improve efficiency and reduce costs.
3. Mold processing
If a worker wants to do a good job, he must first sharpen his tools. The organization of mold process is particularly important, and reasonable process organization can speed up the production cycle, shorten the processing time, and save costs. And more importantly, accurate and reasonable processing can ensure the stability and extended life of the mold in the production process. Some processing mistakes will lead to mold welding, no matter how good the welding is, it is a loss to the mold; Other processing is not good and may affect the mold action, reduce the life of the mold, resulting in the mold in the production process to crack or even break.
4. Standard parts
The lowest piece of wood determines the volume of the bucket. We all understand this truth, but we often don't notice it when we do it. The mold is the same, although the standard parts do not directly participate in the molding, they control the operation of the entire mold. Good standard parts should be wear-resistant, hard enough, high precision, not deformation. The difference between the standard parts of different brands is very large, so do not blindly fight the price of mold, kill to kill, your mold from running straight down to the public.
5. Contact (flying mold)
On the touch is the experience of the mold fitter, the seemingly simple work is the most technical content of the operation. This is the first thing to look at the messy mold. The plate mold is the simplest, and the fractal surface only needs no flash break difference. Like car parts mold is very troublesome, not only the fractal surface is more irregular, and often contains multiple sliders and top blocks. Together with the touch can also improve and perfect other problems of the mold, so it is a comprehensive operation.
6. Polish/leather grain
The polishing of the mold is the final part of the production of the mold. Polishing is directly reflected on the plastic, so this is a most decent job. Polishing can also help and make up for the effect of mold action, especially for demoulding is very meaningful. Often, the production of some molds is not smooth because the lighting is not in place, the resistance is too large, the demoulding is difficult, and even the top white, the top crack.
7. Mold device
The mold device is like the assembly machine, every part, every screw can not make mistakes, otherwise the result will be quite serious, light will lead to product shortcomings, affect production, heavy will completely harm the mold, the formation of scrap. So the work of the device must be very detailed. In the process of the device, pay special attention to the cleaning operation of the mold, especially the water and screw holes, and be sure to blow clean the iron filings inside.
8. Warm runner is still cold runner
This actually has the least impact on the quality of the mold, because the warm runner is generally designated by the customer, especially some large customers. Foreign well-known brands do very well in quality or after-sales service, so there is generally no problem in quality. Only some domestic heating channels are very different in quality. A single small business in order to save costs, to compete for price advantages, with some unreliable heating and conduction accessories, simple problems. The main problem of the cold runner is how to ensure the balance of the injection, the size of the gate, the injection pressure and so on.
9. Cool waterways
Anyone who has had mold experience knows how important cooling is to a mold. Because of the increase in prices and human compensation, it is impossible to imagine the profits brought by the injection molding cycle without cutting one second when the products are produced in large quantities. However, the acceleration of the production cycle will be accompanied by the rise of the mold temperature, if not useful control, it will make the mold because it is too hot to form, and even lead to mold deformation failure. Therefore, excellent waterway design is particularly important, including the layout density, diameter, links between each other and so on.
Injection mold maintenance
Mold maintenance is primarily maintenance and maintenance in the production process. Mold is like a car, if a long time without maintenance may lead to mold obsolescence. Therefore, every time the mold is used, it is necessary to carry out comprehensive maintenance, especially the rust prevention of the forming part and the rust prevention of the main moving parts. Because the mold needs to receive water during the production process, it may sleep on the mold during the device or disassembly process, so we must ensure that the mold is dry, and then brush a layer of oil for maintenance.
First, the use of injection molds
The mold creates value in use, but it also gradually loses its own value in use, therefore, the operator must attach great importance to the use of the mold, and the following issues should be paid attention to in general.
(1) Before use, check whether there are impurities and dirt in each part of the mold. The remaining plastics and impurities in the mold should be scrubbed and removed with cotton yarn, and the adhesive material with strong adhesion should be scraped with a copper knife.
(2) Reasonable choice of clamping force, to the product molding does not produce flash, can not think that the higher the better, which will increase power consumption, but also easy to damage the transmission parts.
(3) The transmission parts should be well lubricated, therefore, it is necessary to maintain the lubrication of these parts.
(4) It is not allowed to use first class heavy objects to hit any parts in the mold, so as not to cause deformation or even damage to the mold.
Two, injection mold maintenance
(1) Maintenance of cooling waterways
The function of the cooling water channel is to cool and solidify the plastic parts in the cavity through the cooling water, which has a great influence on the molding process of the plastic parts.
1, the harm of cooling water channel blockage
In the long-term working process, the surface of the cooling water channel is easy to deposit scale, dirt, rust, etc., which will reduce the circulation area of the cooling water channel, and greatly reduce the heat exchange of the cooling water between the mold, so that the cooling effect is greatly reduced, and the harm is very great.
2, cooling water channel blockage inspection
The increase of sediment on the surface of the cooling water channel will cause local blockage of the water channel, which can be judged by measuring the flow rate of the cooling water. When measuring, a pressure control valve can be installed between the mold and the cooling water channel to determine the pressure drop of the cooling water through the mold under the same conditions. Thus, the blockage of the cooling channel can be judged. If the blockage to a certain extent, it is necessary to clean up in time.
3, cooling water channel cleaning
Because the design of the cooling water channel is related to the shape of the cavity, its shape is twists and turns, and it is inconvenient to open, therefore, it can not be cleaned by mechanical method, and can only be washed by cleaning agent, and the attached dirt can be removed under the strong impulse of cleaning agent. There are a variety of cleaning agents used, you can choose to use.
(2) Maintenance of injection mold unloading
After the injection mold completes the given production task, it needs to be removed from the injection machine. When disassembling, the residual plastic should be carefully removed, and different cleaning methods should be used according to the different properties of different plastics. Generally, soapy water can be used to remove residual plastic and other deposits in the mold, and then the mold is air-dried. If there are rust spots on the surface of the cavity, it should be removed, polished, and then coated with lubricant protection, and then stored in the warehouse.
Third, the fault of injection mold and its elimination
Injection mold in the working process, there will always be more or less some failures, they have adverse effects on product quality, productivity, mold, etc., will be discussed below.
(1) Mold deformation and elimination
Mold deformation refers to the excessive elastic deformation or plastic deformation of the mold in the work project, so that the mold can not work normally or the quality of the product is unqualified, the reasons and elimination methods are as follows.
1, insufficient rigidity
In injection molding, the mold should be subjected to a huge pressure holding, this pressure if the mold has a permanent deformation, the mold will not be able to use, but even within the elastic limit, the deformation of the mold can be restored, and the curing molding at the time of deformation will make the opening of the mold difficult, or even cannot be opened. In this case, it is impossible to transform the mold structurally, but the injection pressure can be appropriately reduced, or the frame can be added from the outside to enhance the rigidity, although it is not good-looking, but it is also used.
2, mold assembly misalignment
If the mold is improperly assembled, such as poor alignment of the mold, the mold closing and its joint are not accurately aligned, which makes the melt filling unbalanced, easy to cause the mold deformation or dislocation. In this regard, the mold should be reassembled, and the imbalance of the filling mold can sometimes be corrected by modifying the gate method.
(2) Cavity damage and its elimination
Cavity is the place of molding plastic parts, its damage will directly affect the quality of the product, cavity damage is the hard injury on the surface of the cavity, so that the surface has scratches, pits, cracks and other defects, the causes of these damages and their elimination methods are as follows.
1. Hard objects damage the cavity
Sometimes it is difficult to take plastic parts after opening the mold, and it is forced to take them with hard tools such as the screwdriver, which is easy to damage the cavity. In addition, after opening the mold, hard objects such as wrenches and hammers are accidentally dropped into the cavity, resulting in cavity damage.
2, improper operation
If the mold is closed before the plastic part is removed, especially in the automatic molding, the cured plastic part is easy to damage the cavity and mold.
3. Repair of damage
After the cavity is damaged, it is difficult to continue to work without repair. The repair methods for the cavity are as follows.
(1) Welding. Welding is a common repair method, the most commonly used welding method is gas welding. If electric welding is used, due to the high temperature, the mold is easy to deformation, or even cracking, using electric welding repair, preheating the mold, and heat treatment after welding.
(2) Insert. For the damage of small area and deep depth, insert can be added to repair, generally after drilling into the insert, when drilling, be careful not to drill through the cooling water channel and screw holes. The insert and the cavity should be closely matched, and then polished and smooth after installation.
(3) Electroplating. For defects with a depth of less than 0.5mm, it is better to repair them by electroplating, which can be plated with copper or chromium.
(4) Tapping. 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 protrusion; Or knock at a place 3mm away from the damage to make the concave convex, and then smooth, grind, and polish the convex part.
(3) mold rust and elimination
The injection mold is made of tool steel. In the work, it encounters corrosive gases, water and other substances that cause rust. The plastic parts made from rusty molds will have quality problems, so they need to be eliminated.
1. Gas produced by melt decomposition
Some raw materials will produce volatile gases after heating, many raw materials also produce volatile gases when overheating, these gases are more corrosive, they diffuse around the machine, when the mold does not work, they will corrode the mold. In this regard, when the machine stops working, use a soft cloth to wipe the mold and close the mold. If not used for a long time, the mold cavity should be sprayed with anti-rust agent, and butter should be applied when the mold is closed and the gate should be blocked.
2. Cooling water in the mold
There is more cooling water in the mold to wake up the cooling, so there is more water around the machine. If the mold is cooled to the dew point, the moisture in the air will form water beads on the surface of the mold, and it is easy to rust if it is not erased in time. Especially after the mold stops working, condensate will soon be produced. Therefore, do not easily stop the molding, even if you want to stop, you should also turn off the cooling water, and dry the mold.
3. Carbides produced during molding
After the mold works for a long time, carbides are precipitated and decomposed in the forming material, which often makes the mold wear, corrosion or rust. In this regard, if carbides are found, they should be wiped off and wiped off immediately with a dry cloth.
To sum up, in order to reduce the production cost of the entire enterprise in the injection mold, it is necessary to work hard in the quality of the injection mold and later maintenance, improve the service life of the entire injection mold, so as to achieve product cost reduction and enhance the overall market competitiveness.
