Un molde se compone de muchas partes.. La calidad de las piezas afecta directamente a la calidad del molde., y la calidad final de las piezas está garantizada por el acabado. Por lo tanto, es importante controlar el acabado. En la mayoría de las empresas nacionales de fabricación de moldes, los métodos utilizados en la etapa de acabado son generalmente de molienda, mecanizado eléctrico y tratamiento ajustador.
En este punto, es necesario controlar muchos parámetros técnicos como la deformación de la pieza, tensión interna, shape tolerance and dimensional accuracy. In the specific production practice, it is difficult to operate, but there are still many effective experience and methods worth learning from.
The processing of mold parts can be roughly divided into three types according to the appearance and shape of the parts: plate, special-shaped parts and shaft. The common process is roughly as follows: rough machining – tratamiento térmico (quenching and tempering) – fine grinding – electrical machining – fitter (tratamiento de superficies) – assembly processing.
1. Part heat treatment
In the heat treatment process of parts, while making the parts obtain the required hardness, it is also necessary to control the internal stress to ensure the dimensional stability of parts during processing. Different materials have different treatment methods.
With the development of the mold industry in recent years, the types of materials used have increased. In addition to Cr12, 40Cr, Cr12MoV and cemented carbide, new materials such as powder alloy steel V10 and asp23 can be used for some convex and concave dies with high working strength and severe stress, which have high thermal stability and good microstructure.
For parts made of Cr12MoV, quenching treatment is carried out after rough machining. Después de apagar, there is a large residual stress in the workpiece, which is easy to cause cracking during finishing or work. Después de apagar, the parts should be tempered while hot to eliminate the quenching stress.
The quenching temperature is controlled at 900-1020 ℃, then cooled to 200-220 ℃, discharged for air cooling, and then quickly returned to the furnace for tempering at 220 ℃. This method is called one-time hardening process, which can obtain high strength and wear resistance, and has a good effect on molds with wear as the main failure form.
For some workpieces with many corners and complex shapes encountered in production, tempering is not enough to eliminate quenching stress. Stress relief annealing or multiple aging treatments are required before finishing to fully release the stress.
For V10, aps23 and other powder alloy steel parts, because they can withstand high-temperature tempering, secondary hardening process can be adopted during quenching, quenching at 1050-1080 ℃, and then tempering at 490-520 ℃ for many times. High impact toughness and stability can be obtained, which is very suitable for molds with blade failure as the main failure form.
Powder alloy steel has high cost, but its performance is good. It is becoming a widely used trend.
2. Grinding of parts
There are three main types of machine tools used for grinding: surface grinder, internal and external grinder and tool grinder. During finishing grinding, the generation of grinding deformation and grinding cracks should be strictly controlled. Even very small cracks will be exposed in subsequent processing. Por lo tanto, the feed of fine grinding should be small and not large, the coolant should be sufficient, and the parts with dimensional tolerance less than 0.01mm should be grinded at constant temperature as much as possible.
According to the calculation, when the temperature difference of 300mm long steel parts is 3 ℃, the material has 10.8 μ M, 10.8=1.2 × three × 3 (1.2 deformation per 100mm μ M/ ℃), and the influence of this factor should be fully considered in each finishing process.
It is very important to select appropriate grinding wheels for fine grinding. In view of the high vanadium and high molybdenum status of die steel, Gd single crystal corundum grinding wheels are more suitable. When machining cemented carbide and materials with high quenching hardness, diamond grinding wheels with organic binder are preferred. The organic binder grinding wheels have good self grinding performance, and the roughness of the workpiece can reach ra=0.2 μ m. En años recientes, with the application of new materials, CBN grinding wheels, es decir. cubic boron nitride wheels, have shown very good machining results. The results of finishing machining on CNC forming grinding machines, coordinate grinding machines, CNC Internal and external grinding machines are better than other types of grinding wheels.
During grinding, the grinding wheel shall be trimmed in time to maintain the sharpness of the grinding wheel. When the grinding wheel is passivated, it will slide and squeeze on the surface of the workpiece, causing burns on the surface of the workpiece and reducing the strength.
Most of the plate parts are processed by surface grinding machine. En proceso de procesamiento, we often encounter a kind of long and thin sheet parts, which is difficult to process.
Because the workpiece deforms and clings to the surface of the worktable under the adsorption of magnetic force during machining. When the workpiece is taken down, the workpiece will be deformed again, and the thickness measurement is consistent, but the parallelism cannot meet the requirements. The solution can be magnetic isolation grinding. During grinding, the contour block is placed under the workpiece, and the four side blocks are used to resist. During machining, small feed and multi light knife are used. After one side is machined, the contour block can not be placed, Direct adsorption processing can improve the grinding effect and meet the requirements of parallelism.
Shaft parts have revolving surfaces, and internal and external cylindrical grinding machines and tool grinding machines are widely used for their processing. During the processing, the head frame and the center are equivalent to the bus. If there is a runout problem, the processed workpiece will also have this problem, which will affect the quality of the parts. Por lo tanto, the head frame and the center should be tested before processing.
During inner hole grinding, the coolant shall be poured to the grinding contact position to facilitate the smooth discharge of grinding. For machining thin-walled shaft parts, it is best to use the clamping process table, and the clamping force should not be too large, otherwise it is easy to produce “inner triangle” deformation on the circumference of the workpiece.
3. EDM control
Modern mold factories cannot lack EDM, which can process all kinds of abnormal and high hardness parts. It is divided into wire cutting and EDM.
The machining accuracy of slow wire cutting can reach ± 0.003mm, and the roughness Ra0.2 μ m。 At the beginning of processing, check the condition of the machine tool, check the deionization degree of water, water temperature, perpendicularity of wire, tension and other factors to ensure a good processing state.
Wire cutting is the removal of a whole piece of material, which destroys the original stress balance of the workpiece and easily causes stress concentration, especially at the corners. Por lo tanto, when R ＜ 0.2 (especially at sharp corners), suggestions for improvement shall be made to the design department.
The method to deal with stress concentration during machining can use the vector translation principle. Antes de terminar, leave an allowance of about 1mm, pre process the approximate shape, and then carry out heat treatment to release the machining stress before finishing, so as to ensure the thermal stability.
When machining punch, the cutting position and path of wire should be carefully considered. The best effect is achieved by drilling and threading. In high-precision wire cutting, the number of times of cutting is usually four, which can ensure the quality of parts.
When machining the female die with taper, the straight edge shall be roughened for the first time, the taper shall be machined for the second time, and then the straight edge shall be fine machined. De este modo, it is not necessary to carry out the vertical fine machining of section x, and only the straight edge of the cutting edge section shall be fine machined, which saves time and cost.
The first step of EDM is to make electrodes, which can be divided into coarse and fine electrodes. The shape of finish machining electrode shall be in good conformity, and it is best to use CNC machine tool for machining. In terms of electrode material selection, red copper electrode is mainly used for general steel processing.
Cu-W alloy electrode has good comprehensive performance. Especialmente, the consumption in the processing process is obviously smaller than that of red copper. With sufficient scouring liquid, it is very suitable for machining difficult materials and finishing machining of parts with complex cross-section shape.
When making electrodes, it is necessary to calculate the clearance and number of electrodes. When machining large areas or heavy electrodes, the workpiece and electrode shall be firmly clamped to ensure sufficient strength and prevent loosening. During deep step machining, attention shall be paid to the loss of electrodes and arc discharge caused by poor liquid discharge.
4. Surface treatment and assembly
The tool marks and grinding marks left on the part surface during machining are the places where the stress is concentrated and the source of crack propagation. Por lo tanto, after machining, it is necessary to strengthen the part surface and polish it by fitter to eliminate the hidden dangers of machining. Some edges, acute angles and orifices of the workpiece shall be blunt and R-shaped.
Generalmente, machined surfaces produce 6-10 μ The metamorphic hardening layer of about M is gray white in color. The hardening layer is brittle and has residual stress. Before use, the hardening layer shall be fully eliminated by surface polishing and polishing.
In the process of grinding and electrical machining, the workpiece will be magnetized to a certain extent, with weak magnetic force, and it is very easy to absorb some small things. Por lo tanto, before assembly, demagnetize the workpiece and clean the surface with ethyl acetate.
Durante el proceso de montaje, first refer to the assembly drawing, find out all the parts, then list the equipment sequence between the parts, and list all the precautions, and then start to assemble the mold. Generalmente, the guide post guide sleeve is installed first, then the mold base and the male and female mold are installed, and then the clearance at each place, especially the clearance between the male and female mold, is assembled and adjusted. After the assembly is completed, the mold inspection shall be carried out and the overall situation report shall be written.
For the problems found, the reverse thinking method can be adopted, es decir, from the post process to the front process, from finish machining to rough machining, check one by one until the crux is found and the problem is solved.
Practice has proved that good finishing process control can effectively reduce out of tolerance and scrap of parts, and effectively improve the first-time success rate and service life of the die.
Original link: https://www.xianjichina.com/news/details_276749.html
Source: xianji.com
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Acerca de Huizhou Dj Moulding Co., Limitado
Dj Mold es un Fabricante de moldes de China de moldes de plástico- molde de inyección, moldes de fundición a presión, moldeo por soplado de plástico, moldeo rotacional, médico moldeo por inyección de plástico, dos disparos moldeo por inyección de plástico, moldeado de inserción, sobremoldeo, moldeo por inyección de metal, micro moldeo por inyección, moldeo por inyección de polvo, moldeo por inyección de cerámica, moldeo por inyección de líquido, moldeo por inyección husky, molde del hogar, molde de fundición, morir herramienta de molde, moldes personalizados, moldes de porcelana, herramientas de creación rápida de prototipos, herramientas de creación de prototipos de plástico, herramientas de punzonadora, matriz y herramientas para piezas de teléfonos móviles / celulares, piezas de automóviles, aspiradoras, herramientas recargables, telefonos, fotocopiadoras, ordenadores, altavoces multimedia, y muchos otros productos electrónicos y electrodomésticos.. Y también un fabricante de productos de plástico., fabricante de moldes China- Partes plásticas, tanque de agua de plástico, bolas de plastico, contenedores de plástico, hebilla de plastico, ancla de plastico, percha de plastico, cuchara de plástico, accesorio de tubería de plástico, caída de plástico, vajilla de plastico, copas de plástico, botellas de plástico, bandeja de plástico, envase cosmético de plástico, Contendor de plastico, recipiente de plástico para alimentos, sillas de plastico, Tapas de plástico, cierre de tapa de plástico, tubos de plastico, tuberías de agua de plástico, perillas de plástico, tubo de plastico, cajas de plástico para uso general, rejillas de plástico, etc..
Contacto:
Persona: James Yuan
Empresa: Huizhou Dj Moulding Company Limited
Agregar: Pueblo LongGang,Ciudad de LongXi,Condado de BoLuo,Ciudad de HuiZhou,La provincia de Guangdong, porcelana
Tel: 86-752-6682869
Correo electrónico: [email protected]
Sitio: https://www.jasonmolding.com/custom-injection-molding/
