The purpose and significance of plastic end cap injection mold design

Introduction to Plastic Cover Injection Mold Design Introduction Purpose: To design a plastic mold that can produce the given plastic parts, has a reasonable structure, and can ensure the accuracy and surface quality of the product. Ability to skillfully use PRO/E, AUTOCAD, and other three-dimensional CAD and CAM drawing software. Significance: As plastic products are widely used in various industries such as machinery, electronics, transportation, national defense, construction, and agriculture, the demand for plastic molds is increasing day by day, and the importance of plastic molds in the national economy is also becoming increasingly prominent. As a high value-added and technology-intensive product, the technical level of mold has become one of the important indicators of a country's manufacturing level. The main design significance of this topic is to master the general idea of ??injection mold design, know how to analyze and consider problems, be able to independently design a complete set of molds, and apply it to actual production. Since the 1980s, under the support and guidance of national industrial policies and a series of supporting national economic policies, my country's mold industry has developed rapidly, with an average annual growth rate of 13. In 1999, the output value of my country's mold industry was 24.5 billion. By 2000 my country's total mold output value is expected to be 26-27 billion yuan in 2018, of which plastic molds account for about 30%. In the future mold market, the proportion of plastic molds in the total mold volume will gradually increase.

After more than half a century, my country's plastic mold industry has developed greatly from its inception to the present, and the level of molds has been greatly improved. In terms of large molds, it has been able to produce 48-inch large-screen color TV plastic shell injection molds, a complete set of plastic molds for 6.5kg large-capacity washing machines, and plastic molds for car bumpers and overall dashboards; in terms of precision plastic molds, it has been able to produce camera plastic parts molds, Multi-cavity small module gear molds and plastic sealing molds. For example, the multi-cavity VCD and DVD gear molds manufactured by Tianjin Jinrong Tianhe Mechanical and Electrical Co., Ltd. and Yantai Polaris I.K Mold Co., Ltd. produce such gear plastic parts with dimensional accuracy, coaxiality, runout and other requirements that meet similar requirements abroad. The product level is high, and the latest gear design software is used to correct the tooth profile error caused by molding shrinkage and meet the standard involute tooth profile requirements. 1. Improve the design and manufacturing level and proportion of large, precise, complex and long-life molds. This is due to the increasing size, complexity and high precision requirements of plastic molded products, as well as the development of multiple cavities in one mold due to high productivity requirements. 2. Comprehensively promote the application of CAD/CAM/CAE technology in plastic mold design and manufacturing. CAD/CAM technology has developed into a relatively mature and innovative technology. In recent years, the prices of hardware and software for mold CAD/CAM technology have been reduced to a level generally acceptable to small and medium-sized enterprises, creating good conditions for its further popularization. ; The network-based CAD/CAM/CAE integrated system structure is beginning to take shape, which will solve the problem that traditional hybrid CAD/CAM systems cannot meet the requirements for division of labor and collaboration in the actual production process; the intelligence of CAD/CAM software will gradually increase; The 3D design of plastic parts and molds and the 3D analysis of the molding process will play an increasingly important role in my country's plastic mold industry.

3. Promote the application of hot runner technology, gas-assisted injection molding technology and high-pressure injection molding technology. Molds using hot runner technology can improve the productivity and quality of parts, and can significantly save raw materials and energy for plastic parts. Therefore, the widespread application of this technology is a major change in plastic molds. Formulating national standards for hot runner components and actively producing cheap and high-quality components are the keys to the development of hot runner molds. Gas-assisted injection molding can significantly reduce costs while ensuring product quality. It is currently being gradually promoted and used in the automotive and home appliance industries. Gas-assisted injection molding has more process parameters that need to be determined and controlled than the traditional ordinary injection process, and it is often used for complex large-scale products, making mold design and control more difficult. Therefore, it is necessary to develop gas-assisted molding flow analysis software. Seems very important. On the other hand, in order to ensure the accuracy of plastic parts, it is also very important to continue to research and develop high-pressure injection molding processes and molds, as well as injection compression molding processes and molds.

4. Develop new plastic molding processes and rapid and economical molds. To adapt to the production method of multiple varieties and small batches. 5. Improve the standardization level of plastic molds and the utilization rate of standard parts. The level of mold standard parts and the degree of mold standardization in my country are still low, and there is a big gap with foreign countries, which to a certain extent restricts the development of my country's mold industry. In order to improve mold quality and reduce mold manufacturing costs, the application of mold standard parts must be vigorously promoted. To this end, we must first formulate unified national standards and strictly produce according to the standards; secondly, we must gradually form large-scale production, improve the degree of commercialization, improve the quality of standard parts, and reduce costs; thirdly, we must further increase the variety of standard parts specifications. 6. The application of high-quality mold materials and advanced surface treatment technology is very necessary to improve the life and quality of the mold. 7. Research and apply high-speed measurement technology and reverse engineering of molds. Using a three-dimensional coordinate measuring instrument or three-dimensional coordinate scanner to achieve reverse engineering is one of the key technologies for plastic mold CAD/CAM. The research and application of diverse, adjustable, and inexpensive detection equipment is a necessary prerequisite for reverse engineering. Since the reform and opening up, with the rapid development of the national economy, the market demand for molds has continued to grow. In recent years, the mold industry has been developing rapidly at a growth rate of about 15%. All the ingredients of mold industry enterprises have also undergone tremendous changes. In addition to state-owned professional mold factories, collectives, joint ventures, sole proprietorships and private companies have also developed rapidly. Ningbo and Huangyan are the hometowns of molds in Zhejiang; some large group companies and rapidly rising township enterprises in Guangdong, such as Kelon, Midea, Konka and other groups have established their own mold manufacturing centers; Sino-foreign joint ventures and wholly foreign-owned mold companies now have Thousands.

In recent years, many mold companies have increased their investment in technological progress and regard technological progress as an important driving force for corporate development. Some domestic mold companies have popularized 2D CAD and have successively begun to use international software such as UG, Pro/E, I-DEAS, Euclid-IS, etc. Some manufacturers have also introduced Moldflow, C-Flow, DYNAFORM, Optris, MAGMASOFT, etc. CAE software, and successfully used in the design of stamping dies. The manufacturing technology of large-scale stamping dies represented by automobile panel molds has made great progress. Mold manufacturers such as Dongfeng Motor Corporation Mold Factory and FAW Mold Center have been able to produce some automobile panel molds. In addition, many research institutions and colleges and universities carry out research and development of mold technology. After years of efforts, significant progress has been made in mold CAD/CAE/CAM technology; significant contributions have been made in improving mold quality and shortening the mold design cycle. For example, the KMAS software for stamping molding analysis of automotive panels independently developed by Jilin University's Automotive Panel Molding Technology Institute, and the injection molds and automotive panel molds developed by the State Key Laboratory of Mold Technology of Huazhong University of Science and Technology conform to the progressive mold CAD/CAE/CAM software. , the cold stamping mold developed by the National Engineering Research Center for Mold CAD of Shanghai Jiao Tong University and the cold stamping mold and fine blanking mold CAD software developed by the Fine Blanking Research Center have many users in the domestic mold industry. Although China's mold industry has achieved remarkable development in the past ten years, there is still a large gap compared with industrialized countries in many aspects. For example, the proportion of precision processing equipment in mold processing equipment is relatively low; the popularity of CAD/CAE/CAM technology is not high; many advanced mold technologies are not widely used, etc., resulting in a considerable number of large, precise, complex and long-life molds. Molds are dependent on imports. In the future development of the mold industry, more attention should be paid to the strategic adjustment of its product structure, so that high-end molds with complex structures and high precision can develop faster. Our mold industry must closely follow the development of market demand. Without product demand and product upgrading, there would be no technological progress in the mold industry, and there would be no increase in scale and grade of mold products. For example, more than 90% of parts in automobile production rely on molds. In the Pearl River Delta and Yangtze River Delta, the output value of molds supporting the automobile industry has increased by about 40%. The level of mold technology determines the quality, efficiency and development capabilities of new products to a large extent.

It has become an important symbol to measure the level of a country's product manufacturing. It is necessary to actively promote the development of the mold industry in the central and western regions and strive to narrow the gap between developed and underdeveloped regions. Many regions in the central and western regions have realized the important role that the development of the mold industry plays in the manufacturing industry. For example, mold production has developed greatly in Shaanxi, Sichuan, and Hebei. Hebei Xinglin Body Manufacturing Group Co., Ltd., as a backbone enterprise in Botou, Hebei, has driven the development of a group of mold companies; Sichuan Yibin Push Mold Co., Ltd. has relied on its strong The capital investment will write a new chapter in the future. It is necessary to actively promote the innovation of the system of mold enterprises, especially state-owned enterprises, transform the operating mechanism, vigorously develop the mixed ownership economy, clarify property rights and improve the corporate governance structure. Fully explore the internal driving force for enterprise development. It is necessary to actively promote the separation of main and auxiliary manufacturing enterprises in the central and western regions with better industrial foundations, so that their mold workshops and branches can adopt a variety of effective implementation forms, transform mechanisms, and vigorously develop property rights in a short period of time. Modern professional mold enterprises that are clear, independent and self-operated, adapt to market operations and rapid response to mold production, cultivate "leading" enterprises that can represent the industry level, and drive the development of the regional industrial chain.

Chapter 1 Source of task and significance of design purpose 1.1 Source of design task Design title: Plastic cover material: PA Production batch: Mass production Technical requirements: ① No fillet R0.5 ② All dimensional tolerances are in accordance with SJ1372 -78 Level 4 Accuracy Figure 1-1 Product Parts Figure 1.2 Design Purpose and Significance This design topic is a common part plastic cover, but it has certain design significance for graduates doing graduation projects. It summarizes the design of box cover plastic parts requirements, content and direction. Through the design of this part mold, the designer's foundation for injection mold design is further strengthened, paving the way for designing more complex injection molds and gaining deeper experience. Chapter 2 Process Analysis of Parts 2.1 Process Analysis of Plastic Parts (1) Raw Material Analysis of Plastic Parts: Raw Material Analysis of Plastic Parts. The material of the plastic parts is nylon 6 (PA6), which is a thermoplastic. From the performance point of view, the plastic has excellent mechanical strength and stiffness, excellent toughness, self-lubrication, wear resistance and good chemical resistance. It also has the advantages of being non-toxic and easy to color. ①. Low melt viscosity, good fluidity, easy to produce overflow (overflow gap 0.02mm) ②. Plastic is easy to absorb moisture, needs to be preheated and dried before molding, and should be prevented from absorbing moisture again after drying. The moisture content during molding should not exceed 0.3 . Otherwise liquidity decreases. Products are prone to defects such as bubbles and silver wires. For parts with high precision requirements, humidity control is required after molding. After humidity control, the size of the product will swell. [1]③. The shrinkage rate of plastic is unstable (shrinkage rate is 1.5~2.5) [2]④. The cooling rate of plastic melt has a great influence on the crystallinity and product performance, so the mold should be correctly selected and controlled according to the wall thickness of the product If the temperature range (20 ~ 90 ℃) is too low, shrinkage and crystallization problems may occur. 2.2 Analysis of the structure, dimensional accuracy and surface quality of plastic parts 2.2.1 Structural analysis ① Structural analysis. Analysis from the parts diagram: The overall shape of the part is a box with a height of only 6mm. There are 30mm in the length direction. And there is a smaller outer core-pulling inside the lower inner wall. The core-pulling space is small, and the mold design and manufacturing are difficult. 2.2.2 Analysis of Dimensional Accuracy The important dimensions of this part, such as ?, ?, ?, etc., have a dimensional accuracy of MT2 level (GB/T14486-1993). The dimensional accuracy of secondary important dimensions such as ?, ? is MT3 (GB/T14486-1993). Based on the above analysis, the dimensional accuracy of this part is above average, which can be guaranteed for the dimensional processing of mold-related parts. Judging from the wall thickness of the plastic parts, the wall thickness is relatively uniform, which is beneficial to the molding of the plastic parts.

From the perspective of the wall thickness of the plastic parts, all wall thickness dimensions are 3mm, and the wall thickness is uniform, which is conducive to the molding of the plastic parts. 2.2.3 Surface quality analysis The surface of this part does not have any special surface quality requirements except that there are no defects or burrs, so it is relatively easy to achieve. In summary, it can be seen from the above analysis that when the process parameters are well controlled during injection molding, the molding requirements of the parts can be guaranteed.

2.3 Calculate the volume and mass of plastic parts Calculating the quality of plastic parts is to select an injection molding machine and determine the number of cavities in the mold. Calculate the volume of the plastic part: V=1955.68? (Process omitted) Calculate the mass of the plastic part: According to the design manual, the density of PA can be found to be ρ=1.12g/?, so the mass of the plastic part is: W=Vρ=1955.68×1.12× ?=2.19g Using a mold structure of 16 cavities in one mold, the injection molding machine model LY80 was initially selected considering its external dimensions. The injection volume of this injection molding machine is 116g, the injection volume pressure is 230mpa, and the clamping force is 800KN. The maximum mold opening stroke is 280mm, the maximum installation size is 350mm×350mm, the molding height is 150mm~350mm, and the ejection stroke is 100mm [3] Chapter 3 Determination of Plastic Molding Characteristics and Process Parameters Search relevant literature and refer to the actual application situation of the factory PA molding process parameters can be selected as follows (appropriate adjustments can be made according to the actual situation during mold trial) Injection molding temperature: including barrel temperature and nozzle temperature. Barrel temperature: Feeding area temperature? Choose 70℃ rear section temperature? Choose 240℃ middle section temperature? Choose 250℃ front section temperature? Choose 250℃ nozzle temperature. Choose 250℃. Melt temperature: 240~250℃. Barrel constant temperature: 220℃ Mold temperature: 60~100℃ Injection pressure: 100~160Mpa Injection time: 0.1s holding pressure: 50 of the injection pressure Holding time: 10s Back pressure: 2~8Mpa Accurate adjustment is required Cooling time: 30s

Injection speed: It is recommended to use a faster injection speed. Measuring stroke: 0.5~3.5D. Residual material amount: 4mm. Preheating rod: dry for 4 hours at 80℃. Recovery rate: 10% can be added. Shrinkage rate of recycled material: 0.7~2.0 Gate system: Point-type machine downtime: no need to clean with other materials, the molten material remains in the barrel for up to 20 minutes. Susceptible to thermal degradation. Note: The barrel is equipped with a standard screw, and the special geometric dimensions have higher plasticizing capacity. The above-mentioned straight-through nozzle can be used. [4] Chapter 4 Design of Gating System 4.1 Selection of Parting Surface The plastic part is a plastic cover with no special requirements on surface quality, but the outside is often in contact with human hands when screwed in. Therefore, it is best to form a naturally rounded corner on the upper end surface. In addition, the height of this part is 6mm and it is matched with another workpiece. Therefore, the coaxiality of the lower mating parts should be ensured, that is, they should be placed on the same side of the mold cavity. Therefore, it is more reasonable to choose the following parting surface. Figure 3-1 Parting surface 4.2 Molding position of plastic parts This plastic part uses one mold of 16 pieces during injection molding, which means 16 cavities are required. Considering the complexity of the mold structure of the pouring system and other factors, the following cavity arrangement is planned. : Figure 3-3 Cavity Arrangement The biggest advantage of using the cavity arrangement shown in the figure above is that the length and size of the runner from the end of the main channel to each cavity are correspondingly equal. Therefore, the stress on each runner is relatively balanced, making it easier to mold plastic parts. Comprehensive consideration of the arrangement of the mold cavity and the external dimensions of the plastic parts, the standard mold base type is initially selected as -250×315-T-?GB/T12556.1-19904.3 Design of the runner (1) Main channel design according to the design manual The relevant dimensions of the nozzle of the LY80 injection molding machine were found: the diameter of the front hole of the nozzle: ? = 4.8mm The spherical radius of the front end of the nozzle ? = 12.6mm According to the relationship between the main channel of the mold and the nozzle R = ? (1 ~ 2) mmD = ? (0.5 ~1)mm, take the spherical radius of the main channel R=13.5mm, take the diameter of the small end of the main channel d=Ф5mm, in order to facilitate the extraction of the aggregate from the main channel, the main channel is designed to be conical and its slope is?~?After conversion, we get The diameter of the large end of the main flow channel is D=Ф8.5mm. In order to allow the molten material to enter the shunt channel smoothly, an arc transition with a radius of r=5mm can be designed at the discharge end of the main flow channel.

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Plastic cover injection mold design

Plastic cover injection mold design

Introduction

Purpose: To design a mold that can produce the given plastic parts with reasonable structure and Plastic molds that can ensure the accuracy and surface quality of products.

Ability to skillfully use PRO/E, AUTOCAD, and other three-dimensional CAD and CAM drawing software.

Significance: As plastic products are widely used in various industries such as machinery, electronics, transportation, national defense, construction, and agriculture, the demand for plastic molds is increasing day by day, and the importance of plastic molds in the national economy is also increasing. protrude. As a high value-added and technology-intensive product, the technical level of mold has become one of the important indicators of a country's manufacturing level. The main design significance of this topic is to master the general idea of ??injection mold design, know how to analyze and consider problems, be able to independently design a complete set of molds, and apply it to actual production.