Rapid mold temperature control in injection molding by using steam heating

The rapid heating cycle has the advantage of improving product quality in injection molding. In this study, steam heating was combined with cool water on the same mold design to achieve dynamic mold surface temperature to establish control. By applying the steam system on a TV housing mold, the advantage of using steam heating for injection molding was then evaluated and compared with water heating by experiment and simulation. The effect of steam on the quality of the part was also studied. Results showed that as steam was used, the heating time of the simple mold plate can be reduced from 18 s to 8 s with the heating rate of 9 °C/s, and the cooling time is reduced over water heating. When the target temperature is changed from 70 °C to 110 °C, the heating time of the TV housing mold plate varies from 7 s to 19 s. For the product quality, steam heating showed an improvement in both the gloss and hardness of the TV housing.     

Mold temperature control using high-frequency proximity effect induced heating

A rapid heating in an injection molding cycle has the advantage of improving product quality without significant increase in cycle time. In this study, high-frequency proximity effect induced heating (HFPEIH) was developed and combined with water cooling to achieve dynamic mold surface temperature control. By applying the HFPEIH system on a pair of mold plates separated with a small gap, the relevant influence of HFPEIH design was evaluated under various parameters including different mold plate material, inductor designs, and inductor channel depths beneath mold surface as well as mold separations. Simulation was also conducted and verified with experiments. Results show that all the heating rates range within 2 °C/s to 4 °C/s for the mold plate size of 100 mm by 100 mm. For the inductor design with three channels of circular cross section, the heating rate is fastest whereas one inductor design of rectangular shape exhibits the best the uniformity of temperature distribution. When the channel depth is reduced from 12 mm to 4 mm, the heating rate is increased significantly. The heating rate is also sensitive to mold plate surface area. When stainless steel N700 was used as the plate materials in a smaller plate of 60 mm by 60 mm, the heating rate can reach 7.6 °C/s using one channel inductor design. The mold separation exhibits that it is less sensitive to the heating rate within 1 mm to 5 mm range and when it is greater than 5 mm, the heating rate starts to decrease slightly. All the simulated results show good coincidence with experimental measurements.     

Feasibility evaluation of gas-assisted heating for mold surface temperature control during injection molding process

Dynamic mold surface temperature control has the advantage of improving molded part qualities without significant increases in cycle time. In this study, a gas-assisted heating system combined with water cooling and different mold designs to achieve dynamic mold surface temperature control was established. The feasibility of using gas-assisted heating for mold surface temperature control during the injection molding process was then evaluated from experimental results. The effect of mold design as well as heating conditions including hot gas temperature, gas flow capacity, and heating time on the heating efficiency and the distribution uniformity of mold surface temperature were also studied. Results showed that as hot gas temperature and gas flow capacity increased, as well as increasing heating times from 2 s to 4 s, mold surface temperature increased significantly. Fan shaped gas channel design exhibits better mold surface temperature distribution uniformity than tube shaped gas channel design. During gas-assisted heating/cooling, it takes 2 s to increase mold surface temperature from 60 °C to 120 °C and 34 s for mold surface to return to 60 °C. In addition, under specified heating conditions and using the best composite mold designs, the heating rate can reach up to 30 °C/s, a rate well-suited to industrial applications.     

Gas-assisted mold temperature control for improving the quality of injection molded parts with fiber additives

A rapid heating cycle has the advantage of improving product quality in injection molding. In this study, gas-assisted mold temperature control (GMTC) was combined with cool water to achieve dynamic mold surface temperature control. By applying the GMTC system on the mold of a rectangular plate, the advantages of using GMTC for injection molding were evaluated and compared with the traditional injection molding process using different gas gap sizes and gas flow capacities. The effect of GMTC on the quality of the part was also studied. Results showed that when GMTC was used, the heating rate can reach 28 °C/s. For an initial mold temperature of 60 °C, and an air gap size of 8 mm, after 6 s heating, the mold surface temperature can reach 147.8 °C, 167.2 °C, and 229 °C with gas flow capacities of 100, 200, and 300 l/min, respectively. When the gas gap size is changed from 4 mm to 8 mm, the uniformity of temperature distribution shows a clear improvement. When GMTC was used for injection molding of parts with fiber additives, the part surface was clearly improved.     

感应加热电源在注塑机料筒加热上的应用研究

介绍感应加热电源在注塑机料筒加热上的应用,设计一种半桥式串联谐振电路拓扑结构的电磁感应加热电源,通过在一个内直径40mm、外直径100mm的注塑机料筒上实验,得出谐振电容和谐振电感参数的变化与电源输出功率之间的关系。设计1台样机,实验结果表明该电源工作稳定可靠,对进一步研究具有一定的参考价值。     

管道防腐涂装的感应加热

为了解决管道防腐涂装生产中的加热问题,给出了多种尺寸系列工件的感应加热设计方案。通过实验和现场运行考验,证明了设计的可行性和良好效果。同时给出了主要试验数据结果。其经济效益和社会效益显著,现已在全国各地推广应用。     

铜棒料非均匀感应加热设备

本文介绍铜棒料非均匀感应加热设备的组成及结构特点。为实现等温压延、挤压,需要坯料可控非均匀加热,以保证轧辊、模具的尺寸、寿命等。并用铜棒料进行了均匀和非均匀加热试验,确定加热功率、时间、温度等参数,以及作业制度。该设备可在控制台上设定上述参数后自动工作。     

Passive mold temperature control by a hybrid filming-microcellular injection molding processing

Microcellular injection molding (also known as Mucell process) with supercritical fluid (SCF) content is capable of producing parts with excellent dimensional stability while using less material, lower injection pressure, and achieving a shorter cycle time. However, most of microcellular processing studies were done on interior morphology, microstructure of the microcellular products, researches and reports on the splay-like appearance, or even a rougher swirl surface which is the restriction for the application of the microcellular injection molding are insufficient. This study investigates the influence of mold temperature on the surface roughness of Polyethylene terephthalate (PET)/Polycarbonate (PC) parts molded by hybrid filming–microcellular injection processing. The PET film is considered as a passive mold temperature controller because of its lower heat transfer coefficient (0.16 J/kg °C) compared with mold base steel of 31.5 J/kg °C. Temperature field changes of mold base caused by different film thickness (0.125 mm, 0.188 mm) were analyzed. The surface roughness of microcellular parts with/without film was measured by a 3D laser microscope. It was found that surface toughness decreases while film thickness increases with minimum surface roughness 1.8 μm. Compared with conventional mold temperature (60 °C), the hybrid molded parts with 0.125 mm film lowered surface roughness from 26 μm to 5.6 μm, to 1.8 μm of 0.188 mm film. And the hybrid processing also improved the uniformity of foamed parts surface quality by eliminating swirl and even surface roughness.     

Augmented control strategies for radiant floor heating systems

A dynamic model of a radiant floor heating (RFH) system useful for control analysis is developed. The overall model consists of a boiler, distribution system, an embedded tube floor slab and building enclosure. The overall model is described by non‐linear differential equations which were solved using finite numerical methods. Two control strategies for improving the temperature regulation in RFH systems are proposed. These are: a multistage on–off control and an augmented constant gain control (ACGC). Simulation results show that the multistage control maintains zone air temperature close to the setpoint better than the existing on–off control scheme does. Likewise, ACGC gives good zone temperature control compared to the classical proportional control. The ACGC is shown to be robust to changes in weather conditions and internal heat gains. The advantage of the control strategies proposed is that they eliminate the use of outdoor temperature sensors required in some existing control schemes. Being simple and robust, the proposed control schemes are good candidate controls for RFH systems. Copyright © 2002 John Wiley & Sons, Ltd.     

基于模糊神经网络的感应加热电源温度控制

通过对原有感应加热电源温度控制方法的分析,提出了一种适合于非线性系统基于模糊神经网络的温度控制方法,并介绍了该系统的组成及实现方法。     

单片机在感应淬火设备上的应用

介绍了感应淬火温度控制的原理，设计出以8031单片机为核心的温度控制的硬件、软件。应用表明：热分析仪抗干扰能力强，温度控制效果好，能够用于现场生产控制。     

模糊理论结合PID控制方法在集中供热系统中的应用

集中供热系统是一个具有大惯性、纯滞后特点的复杂非线性系统,为了提高系统稳定性,实现合理用热,将模糊自适应控制和常规PID控制两种控制方法结合并使用模糊工具箱进行了系统仿真实验。实际结果表明,同常规的PID控制方法相比,模糊自适应PID控制方法有效提高了集中供热系统的鲁棒性、稳定性和自适应的能力。在集中供热的复杂系统中,能更好的满足用户的热需求     

Temperature control of bench-scaled batch reactor equipped with a monofluid heating/cooling system

An advanced control concept, Predictive Functional Control （PFC）, is applied for temperature control of a bench-scaled batch reactor equipped with monofluid heating/cooling system. First principles process models are developed. Based on achieved models, significant process variables, which are difficult or impossible to measure online, are estimated from easily measured variables, and cascade PFC control strategy has been projected and implemented in Matlab RI 4. The dynamics of individual subunits is explicitly taken into consideration by internal model in the control algorithms, and model uncertainty, various process disturbances are compensated by modifi- cation of internal model. The experimental results present an excellent capability of tracking the set point, and the success of PFC technique as a process control paradigm is illustratively demonstrated.     

A Trajectory Planning Approach for the Regulation of the Induction Motor

An output feedback passivity based controller is suitably combined with an off-line trajectory planning for the equilibrium to equilibrium regulation of the nonlinear induction motor. As obtained from computer simulations, the proposed dynamic feedback controller naturally sustains the presence of un-modelled constant load torque perturbations and it is robust with respect to discontinuous variations of the rotor resistance parameter.     

Effect of decoration film on mold surface temperature during in-mold decoration injection molding process

In-mold decoration (IMD) during injection molding is a relatively new injection molding technique and has been employed for plastic products to improve surface quality and achieving colorful surface design, etc. During IMD processing, the film is preformed as the shape of mold cavity and attached to one side of the mold wall (usually cavity surface), then molten polymer is filled into the cavity. Heat transfer toward the mold cavity side during molding IMD part is significantly retarded because the film is much less thermal conductive than metal mold. To investigate the effect of film on temperature field, polycarbonate (PC) was injection molded under various conditions including coolant temperature, melt temperature, film material and film thickness. Simulations were also conducted to evaluate the melt–film interface temperature and its influence from film initial temperature and film thermal properties. For PC film, it was found that the heat transfer retardation results in the mold temperature drop in cavity surface and the maximum temperature drop as compared to that of conventional injection molding without film may be as high as 17.7 °C. For PET film, this maximum mold temperature drop is about 13 °C. As PC film thickness increases, the retardation-induced mold temperature difference also increases. The initial film temperature (30 °C and 95 °C) may affect the melt–film interface temperature at the contact instant of melt and film by about 12 °C to 17 °C. When thermal conductivity of film increases from 0.1 W/(m–k) to 0.2 W/(m–k), melt–film interface temperature may vary by 22.9 °C. The simulated mold temperature field showed reasonable agreement with experimental results.     

Multiperiod heating storage control for distributed electric heating considering wind curtailment accommodation

Electric heating is perceived as an effective way to tackle heavy wind curtailment and severe smog in northern China, wherein distributed electric heating (DEH) accounts for a significant proportion. However, more research is required with regard to its thermal characteristic. This paper presents the multiperiod heating storage control for a DEH load to reduce wind curtailment. To cope with intermittent wind power, a novel multi-objective and layered optimization method is proposed by decomposing the integrated electricity and heating optimization problem into the electricity optimization subproblem and the heating optimization subproblem. Additionally, the influence of solar radiation on the thermal characteristic of the DEH load is considered in the building thermal process model when creating the day-ahead schedule of the DEH load control, and this is also regarded as the basis for grouping DEH users. Last, the simulation and economic feasibility analysis based on the data measured by the DEH system of Jilin Province, China, are carried out. The results show that this proposal can reduce the electricity cost for DEH users by 25%, and the critical feasible price for curtailed wind power is varying between 86.1 and 115.3 yuan/MWh according to different subsidy methods.     

低温辐射加热炉

本文阐述了低温辐射加热的基本原理和低温辐射传热及加热温度均匀的技术,以此为基础设计出新型干燥炉——低温辐射加热炉。该炉用同一个热源进行辐射与热风复合加热,它既适用于簿的、形状简单的工件加热,又适用于厚的、形状复杂的超大工件的加热。     

Effect of cavity surface coating on mold temperature variation and the quality of injection molded parts

Suiting for high gloss surface of injection molded parts free of painting is a great concern from both environment and cost effective considerations. As a result, variable mold temperature controls to achieve the mentioned goal have been paid great attentions. In this study, TiN and Teflon of various thicknesses were coated on the cavity surface of a tensile bar mold designed with double gate. During the injection molding process, melt–mold interface temperature was analyzed and simulated. In a regular injection molding of ABS resin using P20 as the mold material, the initial melt temperature may drop from 240 °C to about 65 °C after 0.01 s of contact with the cavity surface when the coolant temperature is 60 °C. For a TiN surface coating of 4 µm, the interface contact temperature was raised to 73.6 °C. For a Teflon coating of 22 µm, the contact surface temperature is as high as 100 °C initially (about 25 °C higher) and remains above 80 °C for about 0.4 s. Teflon coating on the cavity surface eliminates the weld-line marks, improves part surface smoothness and results in better tensile strength for weld line than TiN coating. Moreover, the cooling time was almost not affected. When surface coating is combined with infrared heating, not only the tensile strengths of the weld line were further enhanced but also the heating rate at mold surface is enhanced.     

加热炉节能燃烧技术

提高燃料热值和空气温度可以提高加热炉炉温，并减少燃烧消耗。在低热值燃料中添加高热值燃料和回收烟气余热预热空气，是加热炉的两项重要的节能燃烧技术。有必要研究最佳燃料混合比和合理选择空气预热器。