模具温度对高光成型制品收缩影响试验

以自主开发的车载蓝牙外壳模具和温控辅助装置为试验基础,对模具温度对高光制品成型收缩影响规律、不同模温条件下其它参数对制品收缩影响规律、及保证相同品质条件下各参数随模温变化规律进行试验研究。结果表明,模具温度对制品收缩影响最主要特点是当模温提升至塑料热变形温度之后制品线收缩率明显减小;在相同模温条件下,压力和温度因素对制品收缩影响显著,而时间因素影响甚微;随着模温的逐步提升,在熔体温度、注射压力一定条件下,制品线收缩率呈小幅减小趋势,而对于保压压力、保压时间或冷却时间则呈"V"字型小幅波动变化。     

工艺参数对高光注射成型制品复制率的影响

以自主开发的车载高光蓝牙外壳模具和温控辅助装置为基础,研究了工艺因素对高光注射成型制品复制率的影响。结果表明,高光成型制品复制率随着模具温度的升高而准线性增大;模温设定条件下,保压压力对制件复制率的影响最大,其次是保压时间,冷却时间影响最小,熔体温度和注射压力的影响以塑料热变形温度为分界点,当模温低于该温度时注射压力的影响较大,反之则相反;随着模温逐步升高,熔体温度和注射压力对制品复制率影响小幅度增大,保压压力、保压时间和冷却时间的影响呈倒"V"型小幅度波动,且均在塑料热变形温度附近达极小值。     

注射工艺参数对PC/ABS材料制品收缩与翘曲的影响

将计算机模拟注射成型过程和实验优化设计相结合,提供了一套经济有效便捷的方法对各工艺参数进行定量的统计分析。选用L27(3^13)正交表设计实验,通过研究注射速率来判断流动引起的收缩;计算模具温度、熔体温度、保压压力与保压时间来确定热诱导的收缩;研究浇口尺寸来判断剪切热对PC／ABS塑料制品收缩的影响程度。以洗衣机上盖为例,以Taguchi实验方法为设计准则安排CAE分析,在制品关键部位采集收缩翘曲量,通过对因素与水平进行的方差分析和直观分析,最后得出熔体温度和保压压力对PC／ABS塑料制件的收缩翘曲影响最大。     

药用塑料瓶成型后收缩性能分析

本以精密注射吹塑成型机为研究设备,从注吹成型工艺条件、塑料品种,进料口形式,模具及瓶体结构设计等方面研究分析药用中小型塑料瓶成型后的收缩性能,总结出如何获得高精度尺寸的塑料容器。     

粉末注射成型工艺参数对产品性能的影响

粉末注射成型是一项新型近净成型技术,被用于生产较小尺寸及形状复杂的制品。相比较传统的加工技术,虽然粉末注射成型工艺经济技术优势明显,但是该技术面临的技术问题也十分突出。结合该工艺的特点,本文论述了包括混料、注射成型、脱脂、烧结4道工序中涉及的工艺参数对制品质量的影响。粉末注射成型工艺在陶瓷、金属材料方面得到了很好的应用。     

汽车塑料制品成型工艺

塑料是节能型材料,具有价格低、性能优异(密度低、吸音、隔热、防震、电绝缘性和耐化学药品性优良、可复合增韧增强、生产能耗低等)。在汽车上的用量越来越大,适应的零部件范围不断扩展。现在,全塑车已经     

模具温度对高光注射成型制品表面沉降的影响

以自主设计的车载高光蓝牙外壳为例,对模具温度对高光注射成型制品表面沉降影响规律,相同及不同模温条件下其他成型参数对制品表面沉降影响规律进行成型模拟研究。结果表明:高光成型制品沉降指数明显小于普通成型,且随模具温度的升高呈准线性减小趋势;模具温度设定情况下,保压压力对制品沉降指数影响最大,熔体温度、注射压力和保压时间影响效应相当,冷却时间几乎不具影响;随着模具温度的逐步升高,制品沉降指数随熔体温度的升高、注射压力增大呈减小趋势,随着其他参数的变化则呈波动变化趋势,且均在塑料热变形温度附近达极限值。     

RHCM成型高光制品的结构设计技术

根据快速冷热成型(RHCM)对制品结构设计的基本要求,结合普通制品结构设计一般原则,研究了高光注塑制品的主体结构及其筋、凸起、孔、圆角等类型结构的基本设计技术,得出了高光注塑制品结构设计需要同时满足壁厚均匀性与结构协调性两个主要准则,并以音箱前面壳和液晶显示器(LCD)电视机前壳为例进行了设计研究,为高光制品结构设计提供了理论上的指导。     

RTM成型工艺对复合材料制品性能的影响

RTM(树脂传递模塑的简称)成型工艺是一种将树脂注入闭合模具中浸润增强材料的复合材料成型工艺。工艺参数对复合材料制品性能有很大的影响。本文对注射压力、注射温度、真空辅助、注胶口和排气口的位置、纤维含量和结构等工艺参数对复合材料制品性能的影响进行了概述。     

Research on the reduction of sink mark and warpage of the molded part in rapid heat cycle molding process

Rapid heat cycle molding (RHCM) is a recently developed innovative injection molding technology to enhance the surface quality of the plastic parts without extending the molding cycle. Most of the common defects that occur in the plastic parts produced by conventional injection molding (CIM), such as flow mark, silver mark, jetting mark, weld mark, exposed fibers, short shot, etc., can be well solved by RHCM. However, RHCM is not a nostrum for all the defects in injection molding. Sink mark and warpage are two major defects occurring in RHCM. The purpose of this study is to investigate and further solve the sink mark and warpage of the molded parts in RHCM. To solve the problem of sink mark, a new “bench form” structure for the screw stud on the product coupling with a lifter structure for the injection mold was proposed. The external gas assisted packing was also proposed to reduce the sink mark in RHCM. To solve the problem of warpage, design of experiments via Taguchi methods were performed to systematically investigate the effect of processing parameters including melt temperature, injection time, packing pressure, packing time and also cooling time on the warpage. Injection molding simulations based on Moldflow were conducted to acquire the warpages of the plastic parts produced under different processing conditions. A signal to noise analysis was conducted to analyze the effect of the factors, and the optimal processing parameters were also found out. ANOVA was also conducted to quantitatively analyze the percentage contributions of the processing parameters on the warpage. The verification results show that part warpage can be reduced effectively based on the optimal design results.     

模具温度对快速热循环成型制品复原性的影响

为深入了解模具温度对快速热循环注塑成型制品复原性的影响,以自主开发的车用蓝牙高光模具和成型温控辅助装置为基础,研究了快速热循环注塑成型模具温度对制品复原性的影响,并分析了不同模具温度条件下其他参数对制品复原性的影响及相同品质条件下各参数随模具温度的变化规律.结果表明,当模具温度升至塑料热变形温度附近时,复制率明显提高;在相同模具温度条件下,压力和温度对制品复制率的影响较明显,时间对制品复制率的影响甚微;随着模具温度逐步升高,在熔体温度、注射压力不变条件下,制品复制率呈小幅升高趋势,对于保压压力、保压时间和冷却时间则呈"V"字型小幅波动变化.     

Effects of cavity surface temperature on reinforced plastic part surface appearance in rapid heat cycle moulding

The influences of the cavity surface temperature just before filling on surface appearance and texture of the moulded reinforced plastic parts in rapid heat cycle moulding (RHCM) are investigated. Two typical reinforced plastics including ABS/PMMA/nano-C_aCO₃ and 20% fibre reinforced polypropylene (FRPP) are tested in experiments. The roughness, gloss and morphology of the part surface are characterized with white light interferometer, gloss meter, and optical microscope, respectively. It is observed that the cavity surface temperature just before filling has a significant influence on part surface appearance. With the increase of the cavity surface temperature just before filling, aesthetic quality of the moulded part can be greatly improved. There is a critical value of the cavity surface temperature just before filling for each plastic. As the cavity surface temperature reaches the critical value, part surface appearance will reach the optimal level with low roughness and high gloss. The weld mark for ABS/PMMA/nano-C_aCO₃ has a V-shaped structure while that for FRPP has a hump-shaped structure. With the increase of the cavity surface temperature just before filling, the width of the V-shaped weld mark reduces gradually until it disappears completely while the height of the hump-shaped weld mark decreases firstly and then increases. The mechanisms for the improvement of surface appearance by increasing cavity surface temperature just before filling and the generation of the V-shaped and hump-shaped weld mark are disclosed.     

Heating/cooling channels design for an automotive interior part and its evaluation in rapid heat cycle molding

Rapid heat cycle molding (RHCM) is a recently developed innovative injection molding technology. Rapid heating and cooling of the injection mold is the most crucial technique in RHCM because it not only has a significant effect on part quality but also has direct influence on productivity and cost-efficiency. Accordingly, Heating and cooling system design plays a very important role in RHCM mold design. This study focuses on the heating/cooling system design for a three-dimensional complex-shaped automotive interior part. Heat transfer simulation based on finite element analysis (FEA) was conducted to evaluate the thermal response of the injection mold and thereby improve heating/cooling channels design. Baffles were introduced for heating/cooling channels to improve heating/cooling efficiency and uniformity of the mold. A series of thermal response experiments based on full factorial experimental design were conducted to verify the effectiveness of the improved heating/cooling channels design with baffles. A mathematical model was developed by regression analysis to predict the thermal response of the injection mold. The effects of the cavity surface temperature on weld mark and surface gloss of the part were investigated by experiments. The results show that the developed baffle-based heating/cooling channels can greatly improve thermal response efficiency and uniformity of the mold. The developed mathematical model supplies an efficient approach for precise predication of mold thermal response. As the cavity surface temperature raises to a high enough level, automotive interior parts with high gloss and non-weld mark surface can be obtained.     

气辅成型工艺参数对制品成型质量的影响趋势研究

对截面形状为s-3的加强筋进行工艺参数优化分析,讨论了气辅成型工艺参数对成型质量的影响程度,获得了一组较好的工艺参数组合.以此为参考标准,改变某一个工艺参数而保持其他工艺参数不变,对比研究4种不同截面形状加强筋在气辅成型条件下的成型情况,并考察了单个工艺参数对成型质量的影响趋势情况.     

Analysis of thermal cycling efficiency and optimal design of heating/cooling systems for rapid heat cycle injection molding process

Rapid heat cycle molding (RHCM) is a molding process that the mold cavity is rapidly heated to a high temperature before plastic melt injection, and then cooled quickly once the cavity is completely filled. Heating/cooling efficiency and temperature uniformity of the RHCM system are two key technical parameters to ensure a high productivity and high-quality products. In this study, a numerical model to analyze the heat transfer in heating and cooling phases of RHCM was built. The effect of heating/cooling medium, layout and structure of the heating/cooling channels, mold structure, etc., on heating/cooling efficiency and temperature uniformity was studied and discussed by analyzing the thermal responses of the molding system in RHCM process. Based on the simulation results, the optimization design of the RHCM mold with hot-fluid heating was performed. Then, a new RHCM mold structure with a floating mold cavity was proposed to improve the heating/cooling efficiency and temperature uniformity. The effectiveness of this new mold structure was also verified by numerical experiments. At last, a RHCM production line with steam heating and water cooling was constructed for a thin-wall plastic part. In testing production, the molding systems can be heated and cooled rapidly with a molding cycle time of about 72 s. The production results show that the aesthetics of the molded parts was greatly enhanced and the weld mark on the plastic part’s surface was completely eliminated.     

Optimization of plastic injection molding process parameters for manufacturing a brake booster valve body

The plastic injection molding (PIM) process parameters have been investigated for manufacturing a brake booster valve body. The optimal PIM process parameters is determined with the application of computer-aided engineering integrating with the Taguchi method to improve the compressive property of the valve body. The parameters considered for optimization are the following: number of gates, gate size, molding temperature, resin temperature, switch over by volume filled, switch over by injection pressure, and curing time. An orthogonal array of L₁₈ is created for the statistical design of experiments based on the Taguchi method. Then, Mold-Flow analyses are performed by using the designed process parameters based on the L₁₈ orthogonal array. The signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) are used to find the optimal PIM process parameters and to figure out the impact of the viscosity of resin, curing percentage, and compressive strength on a brake booster valve body. When compared with the average compression strength out of the 18 design experiments, the compression strength of the valve body produced using the optimal PIM process parameters showed a nearly 12% improvement.     

The effects of fibres on the plastic shrinkage cracking of high strength concrete

Plastic shrinkage cracking in concrete usually occurs during the first 5 hours after placing and therefore the mechanics of fibre reinforcement were studied during this period. Two types of polypropylene fibres were mixed at 0.1% by volume. The development of bond strengths and the stresses which the fibres could sustain across cracks were measured by uniaxial tensile tests during the first 5 hours after mixing. Fibre stresses up to 130 MPa at 5 hours were achieved which were equivalent to a composite post-crack strength of 65 kPa. Restrained ring tests were used to assess the amount of cracking which occurred during the first 24 hours in a different high strength mix and, although the results were very variable, the fibres were found to reduce the crack area by between 40% and 85% compared with plain concrete, depending on fibre type.     

复合材料螺旋桨RTM成型工艺研究

为开展复合材料螺旋桨成型工艺的研究,分析了不同成型工艺的特点,提出采用树脂传递模塑成型技术(RTM)制作螺旋桨模型,制订了模具制备方案、纤维剪裁和铺层实施方案以及RTM工艺流程,制作了螺旋桨模型,并提出了工艺改进方案,进而开展了螺旋桨模型的强度试验.强度试验结果显示:随着载荷的增加,各测点处的应变值均呈线性增长,当加载到8 k N时各测点应变均在弹性范围内,桨叶未发生破坏.研究表明:采用本文制定的模具制备方案,特别是针对桨叶纤维布剪裁、铺层的难题提出的适合复杂型线纤维布剪裁和铺层的实施方案,用于成型夹芯复合材料螺旋桨模型可以满足预期强度要求,验证了本文工艺的可行性.