Mold selection and maintenance
Mold selection is a very important part of the entire mold making process.
The selection of the mold needs to meet three principles. The mold meets the work requirements of wear resistance, toughness, etc. The mold meets the process requirements, and the mold should meet the economic applicability.
Conditional requirements
1, wear resistance
When the blank is plastically denatured in the mold cavity, it flows and slides along the surface of the cavity, causing severe friction between the surface of the cavity and the blank, which causes the mold to fail due to wear. Therefore, the wear resistance of the material is one of the most basic and important properties of the mold.
Hardness is a major factor affecting wear resistance. In general, the higher the hardness of the mold part, the smaller the wear amount, and the better the wear resistance. In addition, the wear resistance is also related to the type, quantity, shape, size and distribution of carbides in the material.
2. Strong toughness
Most of the working conditions of the mold are very bad, and some often suffer from a large impact load, resulting in brittle fracture. In order to prevent the mold parts from suddenly breaking during work, the mold must have high strength and toughness.
The toughness of the mold depends mainly on the carbon content, grain size and microstructure of the material.
3. Fatigue fracture performance
During the working process of the mold, under the long-term effect of the cyclic stress, fatigue fracture is often caused. The form has small energy multiple impact fatigue fracture, tensile fatigue fracture contact fatigue fracture and bending fatigue fracture.
The fatigue fracture properties of a mold depend mainly on its strength, toughness, hardness, and the amount of inclusions in the material.
4. High temperature performance
When the working temperature of the mold is higher, the hardness and strength are lowered, resulting in early wear of the mold or plastic deformation and failure. Therefore, the mold material should have high anti-tempering stability to ensure that the mold has high hardness and strength at the working temperature.
5. Resistance to cold and heat fatigue
Some molds are in a state of repeated heating and cooling during the working process, causing the surface of the cavity to be subjected to tensile and pressure-induced stresses, causing surface cracking and spalling, increasing friction, impeding plastic deformation, and reducing dimensional accuracy, thereby resulting in The mold failed. Hot and cold fatigue is one of the main forms of hot work die failure. It should have high resistance to cold and heat fatigue.
6. Corrosion resistance
Some molds, such as plastic molds, when working, due to the presence of chlorine, fluorine and other elements in the plastic, after the heat, the HCI, HF and other strong aggressive gases are resolved, eroding the surface of the mold cavity, increasing its surface roughness and aggravating wear and tear.
Process performance
Mold manufacturing generally involves several processes such as forging, cutting, and heat treatment. In order to ensure the quality of the mold and reduce the production cost, the material should have good forgeability, machinability, hardenability, hardenability and grindability; it should also have small oxidation, decarburization sensitivity and quenching. Deformation cracking tendency.
Forgeability
It has low hot forging deformation resistance, good plasticity, wide forging temperature range, low tendency for forging cracking and precipitation of reticulated carbides.
2. Annealing processability
The spheroidizing annealing temperature range is wide, the annealing hardness is low, the fluctuation range is small, and the spheroidization rate is high.
3. Machinability
Large cutting amount, low tool loss and low surface roughness.
4. Oxidation and decarburization sensitivity
When heated at high temperature, the anti-oxidation energy is good, the decarburization speed is slow, and it is not sensitive to the heating medium, and the tendency to produce pitting is small.
5. Hardenability
Uniform and high surface hardness after quenching.
6. Hardenability
After quenching, a deep hardened layer can be obtained, which can be hardened with a mild quenching medium.
7. Quenching deformation cracking tendency
The conventional quenching volume change is small, the shape is warped, the distortion is slight, and the abnormal deformation tendency is low. Conventional quench cracking has low sensitivity and is not sensitive to quenching temperature and workpiece shape.
8. Grindability
The relative loss of the grinding wheel is small, the maximum amount of grinding without the burn is large, and it is not sensitive to the quality of the grinding wheel and the cooling condition, and it is not easy to cause abrasion and grinding crack.
Performance
1. Low density: The low density of plastics is of great significance for reducing the weight and energy saving of mechanical equipment, especially for vehicles, ships, aircraft, and spacecraft.
2. Specific strength and specific stiffness: The absolute strength of plastic is not as high as that of metal, but the density of plastic is small, so the specific strength (σb/ρ) and specific stiffness (E/ρ) are quite high. In particular, reinforced plastics made of various high-strength fibrous, flake and powdered metals or non-metal fillers have higher specific strength and specific stiffness than metals.
3. Good chemical stability: Most plastics have good acid, alkali, salt, water and gas properties. Under normal conditions, they do not chemically react with these substances.
4. Electrical insulation, heat insulation and sound insulation performance are good.
5. Good wear resistance and self-lubricating property: plastic has small friction coefficient, good wear resistance, good self-lubricating property, high specific strength and low transmission noise. It can be used in liquid medium, semi-dry or even dry friction. Work effectively under conditions. It can be made into machine parts such as bearings, gears, cams and pulleys, which is very suitable for occasions where the speed is not high and the load is not large.
6. Strong bonding ability.
7. Good molding and coloring performance.
Economic requirements
In the selection of the mold, the principle of economy must be considered to reduce the manufacturing cost as much as possible. Therefore, under the premise of satisfying the performance of use, firstly, the price is lower, carbon steel can be used without alloy steel, and domestic materials can be used without imported materials.
In addition, the production and supply of the market should also be considered when selecting materials. The selected steel grades should be as small as possible and concentrated.
Repair
According to incomplete statistics, the annual consumption value of molds in the machining industry is five times the total value of various machine tools. It is conceivable that the mold market in the industries of machinery, metallurgy, light industry and electronics is so huge. Another example: in the metallurgical industry, the annual consumption of hot-rolled rolls is more than 300,000 tons, and the value of hot-rolled rolls accounts for more than 5% of steel production costs. The large consumption of molds not only directly increases the production cost, but also causes a large economic loss due to the frequent shutdown of a large number of production lines due to frequent mold changes.
The failure of the mold is actually scrapped due to the wear of the surface material of the surface, etc., and the processing cycle of the mold is very long and the processing cost is extremely high (especially the manufacturing cost of sophisticated molds or large molds is as high as several hundred thousand yuan or even millions. yuan). Therefore, it is undoubtedly an economically significant method to carry out surface strengthening on a specific part of the mold that is actually subjected to wear and to greatly extend and improve the service life of the tool. In addition, most of the molds are scrapped due to the thin surface of the material. Therefore, it is only necessary to repair the surface of the mold and the key parts of the key metal parts, and the surface of the mold is actually subjected to wear during the repair process. The surface is coated with a layer of high hardness and high wear-resistant metal layer, which can "turn waste into treasure", not only the mold is repaired, but the service life of the repaired mold will be greatly improved compared with the original mold, and the economic benefit is huge (for example : Repairing a large shaft of a power plant motor, including various preparation times, can also be used in a micro-beam cold welder for several days, but it can create millions of dollars in economic benefits).
The mold repairing machine is a high-tech equipment for repairing the surface wear and processing defects of the mold. The principle of the mold repairing machine is to use the principle of high-frequency electric spark discharge to weld the workpiece without thermal surfacing to repair the surface defects and wear of the metal mold. The main feature is that the heat affected area is small, the mold will not deform after deformation, and will not anneal. No stress concentration, no cracks, to ensure the integrity of the mold; it can also be used to strengthen the surface of the mold workpiece to achieve the wear resistance, heat resistance, corrosion resistance of the mold.
The mold repairing machine strengthens the long life of the mold and has good economic benefits. Various metal-based alloys such as iron-based alloys (carbon steel, alloy steel, cast iron), nickel-based alloys, and other metal materials can be used for surface strengthening and repair, and the service life can be greatly improved.
Applications: Machinery, automotive, light industry, home appliances, petroleum, chemical, electric power and other industrial equipment manufacturing departments and use departments, aviation engine key wear parts, hot extrusion molds, warm extrusion film, hot forging, rolling steel rolling Guides, rolls, automotive engine camshafts and other parts and molds
maintenance
1: After the mold is used for a long time, the cutting edge must be sharpened. After grinding, the cutting edge surface must be demagnetized, and it cannot be magnetic, otherwise it will easily block the material. The mold manufacturer must make detailed records, count its use, care (lubrication, cleaning, rust prevention) and damage, and thus find out which parts and components have been damaged and the degree of wear and tear to provide information for discovering and solving problems. And the molding process parameters of the mold, the materials used in the product, in order to shorten the test time of the mold and improve the production efficiency. The various properties of the mold should be tested under the normal operation of the injection molding machine and the mold, and the size of the final molded plastic part should be measured. Through this information, the existing state of the mold can be determined, and the cavity, the core, the cooling system and the cavity can be found. The damage of the parting surface, etc., according to the information provided by the plastic parts, can determine the damage state of the mold and maintenance measures.
2: Springs and other elastic parts are most vulnerable to damage during use, and usually breakage and deformation occur. The method adopted is to replace. In the process of replacement, we must pay attention to the specifications and models of the spring. The specifications and models of the spring are confirmed by the color, outer diameter and length. Only when all three items are the same can be replaced. The spring is preferably of the quality of the inlet.
3: During the use of the mold, the punch is prone to breakage, bending and smashing, and the punching sleeve is generally smashed. Damage to the punch and sleeve is generally replaced with parts of the same specification. The parameters of the punch mainly include the working part size, the mounting part size, and the length size.
4: Fasten the parts and check whether the fastening parts are loose or damaged. The method is to find the parts with the same specifications for replacement.
5: Pressing parts such as pressure plate, superior glue, etc., unloading parts such as stripping plate, pneumatic top material, etc. During maintenance, check the accessories of each part and whether there is any damage, repair the damaged part, check the pneumatic top material for air leakage, and take measures for the specific situation. Replace if the air tube is damaged. It is necessary to carry out key tracking and inspection on several important parts of the mold: the function of the ejection and guiding parts is to ensure the opening and closing movement of the mold and the ejection of the plastic parts. If any part is stuck due to damage, it will lead to production stoppage, so it should be kept frequently. Lubricate the thimble and guide post of the mold (use the most suitable lubricant), and regularly check the thimble, guide post, etc. for deformation and surface damage. Once found, replace it in time; after completing a production cycle, work on the mold surface. , sports, guide parts coated with professional anti-rust oil, especially the protection of the elastic strength of the bearing parts with gears, rack and die and the spring mold to ensure that it is always in the best working condition; as the production time continues The cooling channel is easy to deposit scale, rust, sludge and algae, so that the cooling passage section becomes smaller, the cooling passage becomes narrower, the heat exchange rate between the coolant and the mold is greatly reduced, and the production cost of the enterprise is increased, so the flow path is cleaned. Attention should be paid to it; for hot runner molds, the maintenance of the heating and control system is beneficial to prevent production failures, so it is especially important.
Cause of loss
1) The problem of the material of the main working parts of the mold is improperly selected. The material performance is poor, not wear-resistant; the mold steel is not refined, and has a large number of smelting defects; the convex and concave mold, the forging blank forging process is not perfect, and there are hidden dangers of heat treatment.
2) The problem of mold structure design, the die structure is unreasonable. The slender punch has no design reinforcement device, the discharge port is not smooth, and the unloading force is too large, so that the punch is subjected to the alternating load.
3) The molding process is not perfect, mainly in the poor quality of the convex and concave die forging blanks, the heat treatment technology and the process have problems, causing the convex and concave die to be impervious, and there are soft spots and uneven hardness. Sometimes microcracks or even cracks occur, the polishing is not in place, and the surface roughness value is too large.
4) Unlubricated or lubricated but not effective,
Company Profile:
Luoyang Yujie Industry&Trade Co, Ltd established in 2004, is a professional manufacturer engaged in the research, development, production, sale and service of large non-standard machinery parts such as: gears, shafts, sprockets,bearings,bearing housings, minning machinery parts, rollers, sleeves,steel spools, welding parts, etc.We manufacture and supply all models of CNC machining centers, such as VMC 850, VMC 650, VMC and 1060, etc. Our machinery parts are extensively applied in such industries as mining, petroleum, cement, steel mill, power plant, sugar factory, precision molding industries, aerospace ,military project and some other fields.
We are located in Jianxi Industrial Park, Luoyang, Henan Province, China with convenient transportation access. Dedicated to strict quality control and thoughtful customer service, our experienced staff members and professional engineers are always available to discuss your requirements and ensure full customer satisfaction. In recent years, our company has introduced a series of advanced equipment including 2m, 3m, 4m, 6m CNC Gantry boring and milling machine , 1.6m,5m large CNC vertical lathe, 5m, 8m, 10m,12m Horizontal lathe,large size CNC Machining center, Large size CNC floor boring machine and some other advanced equipments. Selling well in all cities and provinces around China, our products are also exported to clients in such countries and regions as Germany, Spain, Russia, USA and other countries . We also welcome OEM and ODM orders. Whether selecting a current product from our catalog or seeking engineering assistance for your application, you can talk to our customer service center about your sourcing requirements.
