The Effect of 3D Printing Process Parameters on the Mechanical Properties of PLA Parts

Taking the PLA molded by FDM as the research object, the influence of various process parameters on mechanical properties is investigated through comparative experiments, which provides reference and help for the promotion and application of FDM molding technology. During the molding process, the PLA material undergoes the process of melting to solidification, thus the performance of the molded part is worse than the original due to thermal shrinkage and other reasons. To improve the quality and mechanical properties of the molded parts, the experiment is designed using an orthogonal test method in parallel with nine different sets of process parameters (layer thickness, build direction, filling speed, and infill density, etc.). Ultimately, the mechanical properties of PLA are tested and the results are analyzed respectively to determine the main factors affecting the mechanical properties and their optimal level combination. Among them, fill rate is the crucial factor in compressive property, while build direction has a significant effect on surface roughness, tensile property and bending property.

Process Influences in the Combined Compacting and Back-Injection Process to Produce Back-Injected Self-Reinforced Composites (SRCs) – Analysis via Multiple Regression Modelling

A new process to produce back-injected self-reinforced composites (SRCs) is presented. In contrast to other investigations on back-injection of SRCs, a process is presented which allows compacting and back injection of SRCs in one step where the SRCs are partly consolidated only via melt pressure inside the cavity. The mechanical properties of SRCs depend to a large extent on the process parameters of temperature and pressure during manufacture. These parameters are not yet known for back-injected areas. Sensors inside of the cavity measure the influences on the temperature and pressure conditions in the cavity. Initial studies on adhesion were carried out and analysed. For this purpose, shear tests of the back-injected component were carried out and a maximum shear strength of 5.81 MPa was determined for the materials used here. The investigations also show a dependence on the Distance from the Gate (DG) and the Mass temperature (TM). First microscopic examinations show good bonding between the SRC and the injection molded part, with no voids or air pockets in the boundary layer. It can also be seen that successful consolidation takes place in the area of the back injection.

Investigation of Deformation Analysis of Glass Fiber Reinforced Polymer Injection Molded Component

Warpage is one of the most crucial problems in injection molded products. Factors affecting warpage include Material, Part geometry, gate location, Fiber content & orientation, temperature, etc. Since many factors cause shrinkage and warpage, it is very difficult to distinguish the predominant factor. In the present study, we have focused on contribution of fiber content on warpage of injection molded part. Basic requirement of the part is flatness at sealing area within given tolerance. The required flatness should be within a given tolerance for effective functioning of the component. Flow simulation software has been used to assess the effect of fiber content on warpage and in turn flatness of the component.

Application of Selective Induction Heating for Improvement of Mechanical Properties of Elastic Hinges

Injection molding is a polymer processing technology used for manufacturing parts with elastic hinges. Elastic hinges are widely used in FMCG (Fast Moving Consumer Goods) packaging (e.g., bottle closures of shampoos, sauces) and in the electrical engineering industry. Elastic hinge is a thin film that connect two regions of the injection molded part, where significant shear rates are present, which can lead to the degradation of polymers and the decrease in mechanical properties. Selective induction heating is the method that improves the flow of the polymer melt through thin regions by the local increase in mold temperature. In this study, selective induction heating was used to improve mechanical properties of elastic hinges by the reduction of material degradation due to high shear rates. To verify the change of shear rates, selective induction heating simulation and injection molding simulations were performed. The linear relation between mold temperature and maximum shear rate in the cross-section was identified and the mechanical tests showed significant differences in hinge stiffness, tensile strength and elongation at break.

Study about the technique of determining residual stress of loading measuring method

Nondestructive test method for residual stress in a structural member is always an important research subject, as a new technique for measuring residual stress loading measuring method needs to consummate for the convenience of engineering. The paper proves that nondestructive test loading measuring method is effective and accurate when compared with the result from hole-drilling method. Taking the measurement of residual stress of injection-molded part in automotive lamp as example, the residual stresses in the surface of injection-molded parts of automotive lamp measured by the two methods are very close based on the two measuring results. It shows that loading measuring method, a new method is used to measure the residual stress, has enough accuracy and credibility when it is used to measure the residual stress of complicated injection-molded part. It provides a basis for popularization and application of loading measuring method in engineering. The paper discusses the basic principles of loading measuring method and detailed procedure of the measurement of residual stress by loading measuring method; it gives out some advices to reduce the test errors.

A Cost-Effective Method for Rapid Manufacturing a Precision Mold With Microstructures Using Hybrid Manufacturing Technologies

Injection molding is a cost-effective to manufacture molded products by injection molding machine. A precision part with microstructures can be fabricated effectively through a precision mold. In this study, a cost-effective method for rapid manufacturing a precision component and a precision injection mold with microstructures by integrating additive manufacturing, rapid tooling, and computer numerical control milling. It was found that of the dimensional accuracy of a precision component in the length, width, and height can be controlled at approximately 30 µm. Injection molding was performed using an injection mold with microstructures with a microstructure of 950 µm and the dimensional accuracy of a molded part in the length, width, and microstructure can be controlled at approximately 60 µm, 50 µm, and 10 µm, respectively. The remarkable findings of this study can be used for the fabrication of molds or dies efficiently and economically for trial production in the mold industry since the quality of the precision component and the precision mold can meet the standards of the general industry.

Defect Minimization of an Injection Molded Plastic Component Using Conformal Cooling Channels

The cooling process is an essential aspect while designing for uniform heat transfer between the mold and the molded part. Improper design and placement of cooling channels result in non-uniform cooling and thus results in differential shrinkage and warpage on the final product. The installation of the channels yet plays a crucial role in the cooling of the part. Conforming channels that are placed at an optimum distance from the part to enhance the cooling process. In this paper, the performance parameters of straight drilled channels are compared with the conformal cooling channels for an electric alarm box. The analysis indicates that the conformal cooling method improved and enhanced the cooling process and reduced the defects like warpage and differential shrinkage by 25.5% and 28.0% respectively.

Optimization of SLS forming parameters in the dimensional accuracy of formed parts

In selective laser sintering powder forming, the performance and dimensional accuracy of the formed part are affected by the process parameters. Different materials have different process parameters, and there is still no reference standard for PA materials. To solve this problem, in response to this problem, PA2200 material was selected, and the influence of scanning interval and scanning speed on the dimensional accuracy of the formed part was analyzed. Through theoretical analysis and experiments, the optimal process parameters were obtained. The best combination of parameters is a scanning speed of 4000mm/s, a scanning interval of 0.5mm, and the size of the molded part has a X-axis deviation -0.35%, a Y-axis deviation -0.4%, and a Z-axis deviation -0.25%.

The use of numerical analysis of the injection process to select the material for the injection molding

The article presents the methodology of using the results of computer simulation of the injection process to assess the suitability of the material for the injection molding. Computer simulation of the basic phenomena occurring during the filling phase, packing, and cooling phase of the injection molding provides a number of different results, containing typical information both on the suggested technological parameters of the process and on the dimensional accuracy of the molded part, but also allows obtaining data on the production efficiency and energy demand of the processing machine. On the basis of this information, it is possible to assess the suitability of the polymer materials used in the simulation, intended for the production of products from a specific industry, taking into account various criteria, mainly of an economic or qualitative nature.

Microstructure and Tribological Properties of TPU/Fluoropolymer Composites

A network of poly(tetrafluoroethylene) (PTFE) microfibers in a thermoplastic polyurethane (TPU) was prepared by melt mixing the TPU with solid PTFE particles. The effect of rotor speed on the fiber dimensions was investigated. Higher shear stress was found to be the critical parameter for producing thinner PTFE fibers, rather than the shear rate imposed by the mixer. Shear stress transfer from the melt to the PTFE crystal results in solid phase plastic deformation, and the efficiency of the deformation depends on the shear stress in the matrix. All of the PTFE fiber/TPU composites show lower coefficients of friction compared with the neat TPU. The magnitude of the coefficient of friction was found to correlate with the interfacial area between PTFE and TPU generated by the microfiber network. However, for macroscale PTFE agglomerates, the reduction in the coefficient of friction is mostly affected by the uneven distribution of PTFE in the bulk and on the molded part surface.