Direct Fabrication of Microcantilever Structures with High Shape Accuracy Using Projection-Based Stereolithography.

Microcantilever structures such as microgears play an important role in precision mechanisms, where highly accurate cantilever characteristics guarantee the reliable function of these structures. Projection-based stereolithography (PSL) technology is widely used to fabricate sophisticated microstructures owing to its high precision and remarkable efficiency, and plenty of works have been done to improve the precision of structures with macroscale. However, the shape accuracy of microcantilever structures fabricated through PSL process is always neglected, which severely hinders its application in precision mechanisms. In this work, we investigated the influence of major factors on the shape accuracy of microcantilever structures in PSL process through orthogonal tests. Different resin materials were tested to investigate the influence of material properties. Printing experiments showed that for a given PSL system, microcantilever structures with confined size could be directly and accurately manufactured using a set of optimized processing parameters, which dramatically speed up the production process and effectively improved the reliability of microcantilevers. This work provides a comprehensive understanding of the capability of PSL to fabricate microcantilever structures and guides the manufacturing processes of micromechanisms with cantilever features, which effectually promotes the industrial application of PSL technology.

Educational simulator for mastoidectomy considering mechanical properties using 3D printing and its usability evaluation.

Complex temporal bone anatomy complicates operations; thus, surgeons must engage in practice to mitigate risks, improving patient safety and outcomes. However, existing training methods often involve prohibitive costs and ethical problems. Therefore, we developed an educational mastoidectomy simulator, considering mechanical properties using 3D printing. The mastoidectomy simulator was modeled on computed tomography images of a patient undergoing a mastoidectomy. Infill was modeled for each anatomical part to provide a realistic drilling sensation. Bone and other anatomies appear in assorted colors to enhance the simulator's educational utility. The mechanical properties of the simulator were evaluated by measuring the screw insertion torque for infill specimens and cadaveric temporal bones and investigating its usability with a five-point Likert-scale questionnaire completed by five otolaryngologists. The maximum insertion torque values of the sigmoid sinus, tegmen, and semicircular canal were 1.08 ± 0.62, 0.44 ± 0.42, and 1.54 ± 0.43 N mm, displaying similar-strength infill specimens of 40%, 30%, and 50%. Otolaryngologists evaluated the quality and usability at 4.25 ± 0.81 and 4.53 ± 0.62. The mastoidectomy simulator could provide realistic bone drilling feedback for educational mastoidectomy training while reinforcing skills and comprehension of anatomical structures.

Identification of the Production of Small Holes and Threads Using Progressive Technologies in Austenite Stainless Steel 1.4301.

This article focuses on the technologies used by a manufacturing company to produce threads in chrome-nickel steel 1.4301 at specific sheet thicknesses. To enhance production quality, two specific technologies were chosen for hole formation, considering the requirements of the company. Both conventional drilling and nonconventional laser cutting methods were evaluated as potential techniques for hole production. Conventional thread-cutting technology and progressive forming technology were employed to create metric internal threads. The aim of integrating these diverse technologies is to identify the optimal solution for a specific sheet thickness in order to prevent the occurrence of defective threads that could not fulfil the intended purpose. The evaluation of the threads and holes relies on the examination of surface characteristics, such as the quality of the surface, as well as the lack of any signs of damage, cracks, or burrs. Furthermore, residual stresses in the surface layer were monitored because these stresses have the potential to cause cracking. Additionally, extensive monitoring was performed to guarantee that the form and size of the manufactured threads were correct to ensure smooth assembly and optimal functionality.

Simulation Analysis and Process Evaluation of Cooling Hole Forming Precision in Mask Assisted Electrochemical Machining Based on GH4169.

Good heat dissipation performance of aero-engine an effectively improve the service performance and service life of aero-engine. Therefore, this paper studies the machining method of cooling holes of high-temperature existent material GH 4169 for aero-engine innovatively puts forward the mask electrochemical machining method of cooling holes and explores the entrance morphology and taper formation law of the hole structure of high-temperature resistant material GH 4169. The mathematical model of anode dissolution of cooling holes in ECM is established, and the influence of voltage and electrolyte flow rate on cooling holes in ECM is analyzed. Compared with the mask-less electrochemical machining, the inlet radius of cooling holes in mask electrochemical machining is reduced by about 16.0% and the taper is reduced by 52.8% under the same machining parameters, which indicates that the electrochemical machining efficiency of mask is higher and the machining accuracy is better. Experiments show that the diameter of the mask structure improves the accuracy of the inlet profile of the cooling hole in the ECM. The diameter of the mask increases from 2 mm to 2.8 mm, and the inlet radius of the cooling hole increased from 1.257 mm to 1.451 mm When the diameter of the mask is 2.2 mm, the taper of the cooling hole decreased by 53.4%. The improvement effect is best, and the thickness of the mask has little influence on the forming accuracy of the cooling hole.

Dimensional Analysis of Workpieces Machined Using Prototype Machine Tool Integrating 3D Scanning, Milling and Shaped Grinding.

In the literature, there are a small number of publications regarding the construction and application of machine tools that integrate several machining operations. Additionally, solutions that allow for such integration for complex operations, such as the machining of shape surfaces with complex contours, are relatively rare. The authors of this article carried out dimensional analysis of workpieces machined using a prototype Computerized Numerical Control (CNC) machine tool that integrates the possibilities of 3D scanning, milling operations in three axes, and grinding operations using abrasive discs. The general description of this machine tool with developed methodology and the most interesting results obtained during the experimental studies are given. For a comparative analysis of the influence of the machining method on the geometric accuracy of the test pieces, an Analysis of Variance (ANOVA) was carried out. The obtained results show that for four considered features (deviations of flatness, vertical parallelism, opening dimensions, and opening cylindricality), no statistically significant differences were detected. For the evaluation criteria, the probability level p exceeded the assumed confidence level α = 0.05 and ranged from p = 0.737167 to p = 0.076764. However, such differences were found for two others-a dimensional deviation between flat surfaces (p = 0.010467) and horizontal parallelism deviation (p = 0.0)-as well as for the quality of the machined surface defined by four surface texture parameters: Ra (p = 0.831797), Rt (p = 0.759636), Rq (p = 0.867222), and Rz (p = 0.651896). The information obtained by the ANOVA will be useful for the elimination the weaknesses of the prototype machine tool, further analysis of technological strategies, and to find possible benefits of integrating machining operations.

The Methods and Experiments of Shape Measurement for Off-Axis Conic Aspheric Surface.

The off-axis conic aspheric surface is widely used as a component in modern optical systems. It is critical for this kind of surface to obtain the real accuracy of the shape during optical processing. As is widely known, the null test is an effective method to measure the shape accuracy with high precision. Therefore, three shape measurement methods of null test including auto-collimation, single computer-generated hologram (CGH), and hybrid compensation are presented in detail in this research. Although the various methods have their own advantages and disadvantages, all methods need a special auxiliary component to accomplish the measurement. In the paper, an off-axis paraboloid (OAP) was chosen to be measured using the three methods along with auxiliary components of their own and it was shown that the experimental results involved in peak-to-valley (PV), root-mean-square (RMS), and shape distribution from three methods were consistent. As a result, the correctness and effectiveness of these three measurement methods were confirmed, which are very useful in engineering.