Analysis and correction of the machining errors of small plastic helical gears by ball-end milling

Many small-size precise plastic helical involutes gears are used in electrical appliances to transmit rotary movements con- tinuously and smoothly. Ball-end milling is an effective method for trial manufacture or small batch production of this type of gear, but the precision of the gear is usually low. In this research, the main sources of the errors of the gear, machining errors of the tooth profile and trace of the gear obtained were analyzed. The correction amounts for these errors are then determined by using a CNC gear tester. They are used to generate a new 3D-CAD model for gear machining with better nrecision.

Fabrication of micro gear wheels by micropowder injection molding

The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based thermoplastic binder. Microinjection molding was fulfilled at about 423 K under 100 MPa. The heating system was applied to the die to improve the fluidity of the feedstock and subsequently the cooling system was used to enhance the strength of the green compacts after injection by decreasing the temperature of the die. The gear wheels were realized successfully with their addendum circle diameter ranging from 800 to 200 um and with the center hole as small as 60 um.

IMPROVE THE KINETIC PERFORMANCE OF THE PUMP CONTROLLED CLAMPING UNIT IN PLASTIC INJECTION MOLDING MACHINE WITH ADAPTIVE CONTROL STRATEGY

The kinetic characteristics of the clamping unit of plastic injection molding machine that is controlled by close loop with newly developed double speed variable pump unit are investigated. Considering the wide variation of the cylinder equivalent mass caused by the transmission ratio of clamping unit and the severe instantaneous impact force acted on the cylinder during the mold closing and opening process, an adaptive control principle of parameter and structure is proposed to improve its kinetic performance. The adaptive correlation between the acceleration feedback gain and the variable mass is derived. The pressure differential feedback is introduced to improve the dynamic performance in the case of small inertia and heavy impact load. The adaptation of sum pressure to load is used to reduce the energy loss of the system. The research results are verified by the simulation and experiment, The investigation method and the conclusions are also suitable for the differential cylinder system controlled by the traditional servo pump unit.

CALCULATION OF CONTACT STRESS OF PLASTIC GEARS

A calculation method of contact problem of plastic gears based on three parameter model of viscoelasticity material is presented. In this calculation method, the influence of temperature upon the property of plastics is considered and an iteration process of temperature-elasticity module-friction coefficient is proposed. From the rolling contact problem of two viscoelastic cylinders with parallel axis, a set of normal-tangential contact coupled integral equations is obtained. Through numerical treatment and normal-tangential iteration, the normal contact stress,tangential stress and contact width of plastic gears are acquired.

Injection molding and debinding of micro gears fabricated by micro powder injection molding

Micro powder injection molding （μPIM） was investigated for possible mass production of micro-components at rela- tively low cost. However, scaling down to such a level produces challenges in injection molding and debinding. Micro gears were fabricated by μPIM from in-house feedstock. The effect of injection speed and injection pressure on the replication of the micro gear cavity was investigated. Solvent debinding and thermal debinding processes were discussed. The results show that micro gears can be successfully fabricated under the injection pressure of 70 MPa and the 60% injection speed. Either too low or too high injection speed can cause incomplete filling of micro gears. The same is the case with too low injection pressure. Too high injection pressure can bring cracks. Solvent debinding of micro gears was performed in a mixture of petroleum ether and ethanol. Subsequently, micro gears were successfully debound by a multistep heating schedule.

Novel Plastic Encapsulation Holding Method for Automobile Glass Using Injection Molding Process

Glass positioning and holding is difficult in the process of injection molding encapsulation of automobile glass. A suction cup or soft resin is always introduced in this process. However,these materials cannot hold glass tightly,thus resulting in the unsteady quality of toughened glass and encapsulated plastic. To solve this problem,a novel holding method called magnetic high-pressure holding with twin bags is proposed to address the features of toughened glass and the encapsulation injection process. Firstly,a pair of permanent magnets is introduced as energy source,followed by the magnetization of a couple of magnetic particle bags. Contact between the single bag and the glass surface will enable the couple of magnetic particle bags to hold glass tightly and to self-adapt the freeform of the glass. Secondly, an experimental system with mechanical and control systems is designed. This system is controlled by the opening and closing force of the mold,which turns the magnetic field on or off to hold or loosen the glass. The magnetic field distributions are measured at important positions of the permanent magnets and in the magnetized particles in the experiments to determine the holding performance. Finally, the process of determining the parameters of the magnet and its attenuation is analyzed, including the minimum friction force between the glass and the particle bag during injection molding,the magnetic energy product and the magnetized filed distributions,and the re-checking method for these parameters. The theoretical analysis and the experimental result show that this flexible holding system may produce sufficient holding force,which not only protects glass but self-adapts the glass freeform as well. The production practice meets the technical requirements of injection molding with a defect-free surface,with no scratches and cracks on the glass and no slight glass movements in the mold cavity.

Computer Aided Alloy Design of High Performance Prehardened Mold Steel for Plastic

prehardened mold steel for plastic, Thermo-Calc ＆ DICTRA software package, machinability, heat treatment technology, free cutting phase.

Development of a plastic injection molding training system using Petri nets and virtual reality

In this study, Virtual Reality (VR)-based plastic injection molding training system (VPIMTS), which can be modeled as an integrated system with a task planning module, an intelligent instruction module, a simulation module, and virtual envi-ronment (VE) module, was developed. Presented in this paper are an architecture of VPIMTS, a practical knowledge modelling approach for modelling the training scenarios of the system by using Petri nets formalism and key techniques (FEM, injection molding procedure modelling) which have been developed independently. The utilization of the Petri net model realized the environment where the trainee can behave freely, and also made it possible to equip the system with the function of showing the next action of the trainee whenever he wants. The overall system is a powerful approach for highly improving the trainee’s comprehension and injection molding study-efficiency by building digital, intelligent, knowledgeable, and visual aids.

Numerical Analysis of Plastic Gear Stiffness

This paper established practical 3-D gear models to study the stiffness influe ncing factors of a loaded gear by finite element method, such as friction parameters, material properties, an d gear structures. The research shows that, in elastic deformation, gear stiffness increases when sliding frict ion ability of contact pair decreases; meanwhile, the gear structure, especially asymmetric design in gear’ s shaft direction will also decrease gear stiffness.

Manufacture of μ-PIM gear mold by electroforming of Fe-Ni and Fe-Ni W alloys

The micro gear mold for powder injection molding was made by electroforming process of Fe-Ni and Fe-Ni-W alloys using UV-lithography process. Kinetics and activation energies in electroplating of both alloys were investigated to determine the best process conditions. Fe content within electrodeposited Fe-Ni alloys increased with the increase of rotating disk speed and the decrease of temperature and it is considered from the calculated activation energy of iron content that the rate determining step is controlled by mass transfer. Iron content in Fe-Ni electrodeposit varied from 58.33% to 70.45% by increasing current density from 2 to 6 A/drn2. Also, iron content in Fe-Ni-W electrodeposit increased from 59.32% to 70.15%, nickel content decreased from 27.86% to 17.07% and the content of tungsten was almost consistent in the range of 12.78%-12.82% although the current density increases from 1.5 to 5 A/dm^2. For the electroforming of micro gear mold, SU-8 mandrel with 550 μm in diameter and 400 μm in height was prepared by UV-lithography processing. Subsequently, Fe-36Ni and Fe-20Ni-13W alloys micro gear molds were electroformed successfully. Surface hardness values of the electroformed micro molds were measured to be HV490 and HV645, respectively.

Computer aided design of free-machinability prehardened mold steel for plastic

In order to improve the machinability but not to impair other properties of the prehardened mold steel for plastic, the composition was designed by application of Thermo-Calc software package to regulate the type of non-metallic inclusion formed in the steel. The regulated non-metallic inclusion type was also observed by SEM and EDX. Then the machinability assessment of the steel with designed composition under different conditions was studied by the measurement of tool wear amount and cutting force. The results show that the composition of free cutting elements adding to mold steel for plastic can be optimized to obtain proper type of non-metallic inclusion in the aid of Thermo-Calc, compared with the large volume fraction of soft inclusion which is needed for promoting ductile fracture at low cutting speeds, the proper type of inclusion at high cutting speeds is glassy oxide inclusion. All those can be obtained in the present work.

Warpage prediction of the injection-molded strip-like plastic parts

For most strip-like plastic injection molded parts, whose cross section size is much smaller than their length, the traditional Hele-Shaw model and three-dimensional model do not work well in the prediction of the warpage be- cause of their special shape. A new solution was suggested in this work. The strip-like plastic part was regarded as a little-curved beam macrnscopically, and was divided into a few one-dimensional elements. On the section of each elemental node location, two-dimensional thermal finite element analysis was made to obtain the non- uniform thermal stress caused by the time difference of the solidification of the plastic melt in the mold. The stress relaxation, or equivalently, strain creep was dealt with by using a special computing model. On the bases of in-mold elastic stress, the final bending moment to the beam was obtained and the warpage was predict- ed in good a^reement with practical cases.

Compensation modification of plastic gear tooth profile considering meshing deformation

The plastic gear is widely used in agricultural equipment,electronic products,aircraft,and other fields because of its light weight,corrosion resistance,and self-lubrication ability.However,it has a limited range of working conditions due to the low modulus and thermal deformation of the material,especially in high-speed and heavy-duty situations.A compensation modification method(CMM)is proposed in this paper to restrain the heat production of the plastic gear tooth surface by considering the meshing deformation,and the corresponding modification formulas are derived.Improving the position of the maximum contact pressure(CP)and the relative sliding velocity(RSV)of the tooth surface resulted in a 30%lower steady-state temperature rise of the modified plastic gear tooth surface than that of the unmodified plastic gear.Meanwhile,the temperature rise of plastic gear with CMM is reduced by 19%compared with the traditional modification of removal material.Then,the influences of modification index and the segment number of modification on the meshing characteristics of plastic gear with CMM are discussed,such as maximum CP and steadystate temperature rise,RSV,transmission error,meshing angle,and contact ratio.A smaller segment number and modification index are beneficial to reduce the temperature rise of plastic gear with CMM.Finally,an experiment is carried out to verify the theoretical analysis model.

Influence of niobium and yttrium on plastic deformation energy and plasticity of Ti-based amorphous alloys

Many amorphous alloys have been developed to date,but the low plasticity has limited their application.To achieve an amorphous alloy with high plasticity,a series of(Ti_(40)Zr_(25)Cu_(9)Ni_(8) Be_(18))_(100-x)TM_(x)(x=0,1,2,3,4 at.%,TM=Nb,Y)alloys were designed to study the influence of Nb and Y addition on the plasticity.The amorphous samples were prepared using the vacuum melting and copper mold casting process.The microstructures,glass forming ability and mechanical properties of the alloys were investigated by X-ray diffractometry(XRD),scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),depth-sensitive nanoindentation,and uniaxial compressive test.The plasticity of different bulk amorphous alloys was investigated by measuring the plastic deformation energy(PDE)during loading.The relationship between the PDE value and plasticity in bulk amorphous alloys was explored.Results show that Nb addition decreases the PDE value and promotes the generation of multiple shear bands,which significantly increases the fracture strength and plasticity,while the addition of Y element reduces the fracture strength and plastic strain of the alloy.

Microcellular Foaming of Plasticized Thin PC Sheet I.Effects of Processing Conditions

Novel microcellular foams using thin plasticized PC sheet were prepared by compression molding. The measurement results showed that T of plasticized PC was decreased and the molecular chain mobility was increased. Decrease in T and increase in chains mobility were contributed to the widen of foaming temperature window. Effects of processing conditions on cell size, cell density and relative density were also investigated. The experimental results show that the temperature, tributyl citrate and foaming agent content have more effects on the structures and morphology of the plasticized PC microcellular foam. Effects of experimental conditions on cell size distribution have also been discussed.

基于Creo-Plastic Advisor的注塑模具模流分析与模具设计

Creo作为美国参数技术公司(PTC)推出的设计软件,在机械CAD/CAE/CAM领域应用广泛,Creo针对塑料产品设计和注塑模具而开发的模流分析系统可对塑料产品进行填充分析。以遥控器前盖为例,详细介绍了应用Creo中的Plastic Advisor功能对塑件进行最佳浇口位置、塑料填充、冷却质量、缩痕分析的方法和过程。根据分析结果进行浇注系统设计和注塑参数优化,根据产品结构特点进行侧向分型滑块机构和模架设计,最终完成遥控器前盖模具的结构设计。研究表明,使用Creo的Plastic Advisor对塑件进行模流分析,方法易于掌握,分析结果可靠有效,能够帮助设计者提高模具设计效率,缩短设计周期,降低设计成本。

Filling Behavior of Wood Plastic Composites

WPC （wood plastic composites） are a young generation of composites with rapidly growing usage within the plastics industry. The advantages are the availability and low price of the wood particles, the possibility of partially substituting the polymer in the mixture and sustainable use of the earth＇s resources. The current WPC products on the market are to a large extent limited to extruded products. Nowadays, there is a great interest in the market for consumer products in more use of WPC as an alternative to pure thermoplastics in injection molding processes. This work presents the results of numerical simulation and experimental visualization of the mold filling process in injection molding of WPC. The 3D injection molding simulations were done with the commercial software package Autodesk~ Moldflow Insight 2016 （AMI）. The mold filling experiments were conducted with a box-shaped test part. In contrast to unfilled polymers, the WPC has reduced melt elasticity so that the fountain flow often does not develop. This results in irregular flow front shapes in the molded part, especially at high filler content.

Multi-scale analysis of void evolution in large-section plastic mold steel during multi-directional forging

The void evolution of large-section plastic mold steel during multi-directional forging(MDF)was investigated using multiscale analysis.To simulate the forging process of the plastic mold steel(SDP1 steel)and realize micro-void reconstruction in a representative volume element(RVE),MDF experiment and void-characteristic evaluation of the SDP1 steel were carried out.Traditional upsetting and stretching forging(TUSF)and MDF were simulated to comparatively analyze the evolution of temperature,effective stress,and effective strain.By embedding RVE with a micro-void and using boundary condition by point tracking into the forging process,the single-void evolution in TUSF and MDF was studied.The effect of void orientation on single-void evolution was also investigated.The multi-scale analysis revealed the following results.(1)Compared with TUSF,MDF achieved a higher efficiency in void closure.(2)The closing efficiency of the void increased with the increase in angle h(the angle between the Z and long axes of the void).(3)The closing efficiency increased with the increase in the orientation angle during the forging process.On the basis of the important role of the main stress in each forging step on the void closure,an integral formula of the main stress was proposed.When main compressive-stress integration reached-0.4,the closed state of the void could be accurately determined.

Pro/E Plastic Advisor在注射模设计中的应用

Plastic Advisor作为Pro/E中的CAE分析插件,能够较好地模拟塑料的注射成型过程,从而把CAD过程和CAE过程紧密结合,使设计人员在CAD阶段就能够对制件的成型工艺以及模具的结构设计有比较清晰的认识,从而减少设计时间,提高设计效率。通过ABS后盖注射模设计实例,介绍了Plastic Advisor在注射模设计中的应用。

Pro/E中Plastic Advisor分析软件在PP-R管件注射模设计中的应用

介绍了Pro/E中Plastic Advisor分析软件在注射模设计过程中的作用,以及采用PlasticAdvisor分析软件进行注塑模流道系统设计方案的评估优化的方法。在理论分析和计算的基础上,利用Plastic Advisor分析软件通过优化浇口位置和合理地配置工艺参数,将壁较厚的PP-R管件的熔接痕减到最小,为提高PP-R管件的模具质量提供可靠的技术保证。