Precision Injection Molding Research Articles

Multi-Objective Optimization Design of Mold Platens on Large Precision Injection Molding Machines

Mold platens play an important role in the injection process of injection molding machines. In this paper, a method of integrating NCGA with FEA is proposed to solve MOP of mold platens on large precision injection molding machines. A Pareto optimum is obtained as the result of the MOP analysis, from which proper solutions can be selected according to diverse design needs. Analytical results indicate NCGA is effective in solving MOP of mold platens.

Process Development in Precision Injection Molding by Cooling Rate Control Part I Control of Shrinkage Characteristics in Cylindrical PPS Parts

The dimensional accuracy of a molded product is an important element that determines qualities of parts and the development for high accuracy work has been researched. The new process "Precision injection molding by the cooling rate control" has been proposed to decrease the mold shrinkage ratio and to improve the dimension accuracy of molded products in this study. This method improved the crystallization of a resin while keeping pressure and holding the mold temperature after injection at a given mold temperature (i. e. initial mold temperature). Afterwards, leave a part of the molded product that requires high accuracy in the mold and cool it locally and rapidly. In this report, the shrinkage characteristics and the crystallinity were investigated when cylindrical parts were molded with polyphenylene sulfide (PPS). The results showed that the mold shrinkage ratio at rapid cooling is smaller compared to the ratio at normal cooling, and the rapid cooling method showed the improvement in the circularity of molded products, however the lower crystallinity and the water-pressure strength reduction were not caused. Therefore, this molding method was effective to improve the accuracy of molded products without the reduction in physical properties of PPS. On the other hand, the effect of the rapid cooling was limited in the case where the initial mold temperature is higher than the glass transition temperature (Tg), that is, Tg seems to have influence on the shrinkage characteristics of the product. The clarification of the mechanism should be solved in the future.

Research on the Key Technology of Precision Injection Molding Equipment for Light Guide Plate

The light guide plate is an important element of the LCD backlight module which demands a certain degree of transparency and uniformity of gray. The defects such as black spots and yellow surface appeared when the light guide plate was processed by domestic equipments. The main problem was caused by the plasticization unit. The Influencing factors of performance for polycarbonate (PC) special screw were discussed in this paper. The conveyance capacity of melt in the metering zone of injection screws with different flight width and channel depth was analyzed by POLYFLOW software. In order to obtain high surface hardness, corrosion resistance and smoothness of PC special screw, surface coating processing was the key point for injection molding light guide plate. Moreover, the peel strength of PC with different coating processing metallic block was tested and measured. he experimental results of the analysis showed that the nickel-tungsten alloy plating and physical vapor deposition can significantly improve stripping properties, corrosion resistance and smoothness. The influencing factors of coating and PC materials’ stripping were analyzed. Through industrial testing, the defective rate of light guide plate had been greatly reduced with physical vapor deposition compared to the screw with hard chromium plating.

Preparation of Artificial Kidney Stones of Reproducible Size, Shape, and Mass by Precision Injection Molding

To prepare artificial kidney stones of defined shape, size, mass, and material composition via precision injection molding of Ultracal 30 cement slurries into an inexpensive biodegradable mold. A calcium alginate and silica-based mold was used to prepare casts of varying shapes in a reproducible manner. Ultracal 30 cement slurries mixed 1:1 with water were injected into these casts and allowed to harden. The artificial stones were recovered and their physical properties determined. Ex-vivo and in-vivo responses to holmium laser lithotripsy were examined. Spheres, half spheres, cylinders, cubes, tapered conical structures, and flat angulated structures were prepared with high precision without post-molding manipulations. Large spheres of average mass 0.661 g (+/- 0.037), small spheres of average mass 0.046 g (+/- 0.0026), and hexagons of average mass 0.752 g (+/- 0.0180) were found to have densities (1610-1687 kg/m(3)) within the expected range for Ultracal 30 cement stones. Ex-vivo holmium laser lithotripsy of small spheres in saline showed uniformly reproducible efficiencies of comminution. Implantation of a tapered conical stone into the ureter of a porcine model demonstrated stone comminution in vivo consistent with that seen in the ex-vivo models. We present an environmentally safe, technically simple procedure for the formation of artificial kidney stones of predetermined size and shape. The technique does not require the use of hazardous solvents or postprocedural processing of the stones. These stones are intended for use in standardized experiments of lithotripsy efficiency in which the shape of the stone as well as the mass can be predetermined and precisely controlled.

Multiple Quality Characteristics Optimization of Precision Injection Molding for LCD Light Guide Plates

A light guide plate is a key component that enables backlight modules to provide sufficient light source for liquid crystal displays (LCDs). Hence, this study aims to investigate the relationship between precision injection molding process parameters and light guide plate's quality characteristics. Taguchi method and grey relational analysis are applied to determine the optimal processing conditions for light guide plates and back-propagation neural network (BPNN) is used to establish a quality prediction system for molded light guide plates. First, the study determines the quality characteristics of light guide plates and uses Taguchi method to plan experiment. Nonetheless, since the Taguchi method is mostly used to optimize single quality characteristic, which often fail to represent process parameter optimization of the overall quality, this study takes advantage of grey relational analysis and integrates multiple qualities to determine the optimal process conditions for light guide plates. The Taguchi method is chosen to design the learning parameters for the BPNN, which is free from the drawbacks of the traditional trial-and-error method and speeds up network convergence to determine preferable combinations of learning parameters. As the experiments reveal, the prediction system established in this study is effective in accurate prediction of the qualities of light guide plates.

Characteristics of mould separation and its effects on qualities of thin wall injection moulded parts

Precision injection moulding of thin walled parts has become an important concern in the computer, communication, and consumer electronics plastics industry. Previous studies in precision injection moulding control focus on the injection screw and the associated operations. In the present study, the influence of relevant parameters including injection speed, melt temperature, mould temperature, filling-packing switchover, and packing pressure on the mould plate separation under different clamping pressure were investigated as part of precision moulding control. A two cavity tensile test specimen mould equipped with four linear variable displacement transducers across the parting surfaces of the mould was used. A computer based monitoring system was built to detect the mould separation signals. Mould separation can also be identified from part weight and thickness variation and exhibits relevant correspondence with them. It was found that owing to the high injection speed required for thin wall moulding, mould separation is not negligible. In all situations, mould separation decreases with increasing clamping pressure. As melttemperature andmouldtemperatureincrease,mouldseparationincreases, resulting in an increase in part weight and thickness. Similarly, when packing pressure and injection speed increase, mould separation also increases. Earlier switchover from filling to packing can decrease mould separation as well as part weight and thickness. Among all the parameters studied, packing pressure exhibits the greatest influence on mould separation and on the associated weight and thickness change. This influence also becomes larger when the moulded part becomes thinner, owing to the larger injection moulding pressure. PRC/1746

Disposable polymeric high-density nanovial arrays for matrix assisted laser desorption/ionization-time of flight-mass spectrometry: I. Microstructure development and manufacturing.

In order to meet the expected enormous demand for mass spectrometry (MS) throughput as a result of the current efforts to completely map the human proteome, this paper presents a new concept for low-cost high-throughput protein identification by matrix assisted laser desorption/ionization-time of flight-(MALDI-TOF)-MS peptide mapping using disposable polymeric high-density nanovial MALDI target plates. By means of microfabrication technology precision engineered nanovial arrays are fabricated in polymer substrates such as polymethylmethacrylate (PMMA) and polycarbonate (PC). The target plate fabrication processes investigated were precision micromilling, cold embossing and injection moulding (work in progress). Nanovial dimensions were 300, 400 or 500 microm. Typical array densities were 165 nanovials/cm2, which corresponds to 3,300 vials on a full Applied Biosystems MALDI target plate. Obtained MALDI data displayed equal mass resolution, accuracy, signal intensity for peptide standards as compared to high-density silicon nanovial arrays previously reported by our group [7], as well as conventional stainless steel or gold targets.

Feedstock and process for precision injection moulding system: K.Hens et al. (Thermat Precision Technology Inc, USA.)

Feedstock and process for precision injection moulding system: K.Hens et al. (Thermat Precision Technology Inc, USA.)

Precision Injection Molding Process Assisted by Infrared Radiation. 2nd Report. Prediction of Temperature Distribution within Polymer and Mold by Numerical Simulation.

In this study, a numerical simulation for analyzing the temperature and velocity distributions within the polymer melt was performed for an innovative injection molding process. The most important characteristic of this process is that infrared radiation energy is applied in order to control the temperature distributions within the molten polymer during the filling stage. The model used in the present study assumes that molten polymer flows at constant mean velocity between two parallel mold walls. One mold is made from metal and the other from material that is transparent to the radiation. The governing equations were solved by a finite-difference method using the control volume approach under realistic molding conditions, and the effects of radiation heating on the temperature profiles were investigated. The results clearly showed that the radiation heating prevented the usual temperature drop in the vicinity of the molded polymer surface, and decreased the shear rate within the flow passage. It was also shows that the efect on the process time (decrease in productivity). caused by this process, was much smaller than that caused by the conventional process which utilizes conduction heating.

A Robust Model to Realize an Adaptive Control System for Precision Injection Molded Parts

The competition in the manufacturing of precision injection molded parts has made the application of advanced manufacturing technology, such as, adaptive control a critical consideration for survival. This paper deals with the development of a robust model for precision injection molding process which is necessary to realize such a control. The robust model was developed in two steps. First, an optimal molding window was established using design of experiments technique to ensure minimum output variation due to uncontrollable noise factors. In the second stage, an empirical model representing the molding process within the optimal window was developed. The model was then tested for its predictive capabilities. It was found that the average error of the predictive model was 0.13%. A systematic method of determining the model is outlined. The use of this model to realize an on-line adaptive control system is discussed.

Less scrap in precision injection moulding

Less scrap in precision injection moulding