Ya Jun Zhang

Research of Precision Injection Control System Based on the on-Line Measurement of Polymer Melt Density

Based on the quality factors of the precision injection product, the control system structure of precision injection molding product and proposes the on-line measurement of melt density which controls the injection weight is analyzed in this thesis. The important of the on-line measurement of melt density is shown in this paper. Then, the approach of off-line and on-line measurement of melt density is introduced. At last, the control approach and the precision injection control principle of using the on-line measurement of melt density is discussed also.

Light Distribution Design on Different LED Lamp

LED has characters of small size, long life and low power consumption, and it is environmental friendly. These advantages make LED have a huge market in the lighting industry. LED with the light distribution design can meet the requirements of the application under different circumstances. With the acknowledgement of the principles of light distribution design, based on optical engineering software LightTools, we study the light distribution design of LED back light module for direct-down illumination and LED shadowless lamp. After the secondary optics light distribution design of the LED light, its transmittance and uniformity has been noticeably improved. We depict different types of micro-structure on the surface of 3mm thickness PMMA diffuser, test and analysis the optical properties of the diffuser under different microstructure.

Investigation on Transmittance and Uniformity of Light Diffuser Plate of Scattering Optical Transmission Polymer

In this paper, the relations between scattering intensity and the radius of scattering particles, the refractive and the wavelength have been studied based on the MATLAB software, and the relations between the concentration of the particles, the radius and the refractive and the optical properties of diffuser have also been simulated by the Light Tools software based on the Monte-Carlo Method. The results show that with the increasing of radius and the wavelength, the distribution of scattering light energy gets concentrated. With the increasing of the particles, the transmittance decreases, and the uniformity increases first and decreases later. With the increasing of radius, the transmittance decreases. With the increasing of the index of refractive, the transmittance increases first and decreases later.

Optimal Design of Micro Plastic Heat Radiator

A new type of plastic micro heat radiators is designed in this paper. The radiator is prospected to be used in electronic system, chemical engineering system, etc. It is made of modified Phenylene sulfide with high thermal conductivity. A series of numerical simulations are carried out to optimize the structure of the radiator. The structure of the radiator includes the thickness of the fin and the distance between fins. The results show that the performance of the micro plastic heat radiator is very close to that of the metal heat radiator with the same dimension.

Effect of Aspect Ratio of Micro Sphere Lens Arrays on the Optical Property of Diffuser

The effect of the aspect ratio of micro sphere lens arrays on the optical properties of diffuser including transmittance and haze have been simulated by the LightTools software, and the results show that with the increasing of the aspect ratio, the haze rises first and drops later while the transmittance decreases all the time. Later, the mold with uniform micro sphere lens arrays arranged in regular triangle has been fabricated successfully by the ball embossing method. Then, the micro sphere lens arrays diffuser with aspect ratio of 0.19, 0.23, 0.26 and 0.29 have been made using the hot embossing method in polypropylene (PP) substrate. Last, haze and transmittance of the micro sphere lens arrays PP diffuser made are verified both by experiment and simulation and the results of experiment and simulation are consistent well.

Effects of Wall Slip on Filling Flow for Polymer Melt in Micro Injection Molding

Effect of wall slip on melt filling flow behaviors in micro injection molding are investigated based on analysis of wall slip mechanism for polymer melt flowing at filling stage. By means of comparisons, slip coefficients in different microchannels are confirmed. With finite element method, the relationship between slip velocity and inlet flow rate or length-diameter ratio is analyzed. The results indicate that the wall slip happen for polymeric melt in microchannels, and slip coefficients are related with the size characteristics of microchannels. Moreover, wall slip velocity has the size effect and increase with the decrease of the section size of microchannels, which cause melt velocity distribution to smooth. At the same time, slip velocity is proportional to length-diameter ratio of microchannel, namely when wall shear stress is uniform, the slip velocity rises with increasing length-diameter ratio of microchannel.

Design and Simulation Analysis of a New Type of Micro Metal-Plastic Heat Radiator

With the development of micro-nanomachining technology (MNMT), micro heat radiator is getting attention. In this paper, the heat dissipation mechanism of light emitting diode (LED) ball lamp is introduced. And the LED heat radiator is simplified. On the basis of that, a new type of micro metal-plastic heat radiator of LED is put forward. And the LED heat radiator is simplified. A series of numerical simulations are carried out to compare the heat dissipation performance of micro heat radiator respectively made by metal, plastic, metal-plastic composite by the FloEFD software. Micro metal-plastic heat radiator structures, including fin spacing, fin thickness, fin height and substrate thickness, are carry out to be simulated.

An Investigation into the Influencing Factors for Polymer Melt at the Filling Stage in Micro Injection Molding

The flow behaviors for polymer melt at the filling stage in micro injection molding are different from those in conventional injection molding due to the miniaturization of plastic parts. This paper focuses on the study of the effects of three main influencing factors, including the microscale viscosity and wall slip, on melt filling flow in microscale neglected those in conventional injection molding process. The theoretical models and the interrelation of these factors in microscale channels were constructed by means of the model correction method. Then, the micro melt flow behaviors were investigated with comparisons of the available experimental data. The results indicate that the dimensions affect the shear rates and viscous dissipation, which in turn affects the apparent viscosity. Finally, the conclusion is that the melt flow behaviors in microchannels are different from those in macrochannels owing to these significant influencing factors.

The Method of Improving Precision of Micro Injection Molding Machine Temperature Control

the temperature control accuracy of polymer melt is the main factor affecting quality precision of final products. In this paper, we study the method of improving the precision of temperature control based on control system of micro injection molding machine. In order to avoid big overshoot in the traditional PID control, we use gradual approximation control method based on gradual approximation mathematical algorithm to realize fast and accurate temperature control of the micro injection molding machine. Experiment results show that effective combination of the traditional PID and gradual approximation method can realize accurate temperature control of micro injection molding machine, and precision of temperature control can be improved up to±0.5°C.

Research of Heat Transfer Performance on Tablet Microstructure Heat Exchanger Used for LED Lamps

With successful development of LED lamps, the dissipation of LED lamps has become the core problem. If the heat produced during the work cant be loss in time, the high temperature of the lamps will affect their service lives or even damage the LED permanently. In this paper, based on the principle of finite element method, using thermal simulation software, the effect of the geometric characteristics micro-structure of the heat exchanger combining polymer micro-scale fins and metal base on the heat transfer characteristics was simulated. The impact of the fin width, wing fin pitch, fin height and thickness of the substrate on the tablet microstructure heat transfer characteristics was analyzed. The results provide some technical reference for the design and application of the micro heat exchanger.