Explore the vast range of titles available.

With the development of electronic products in the direction of miniaturization and lightweight, the specifications of thread gradually become minor, and the high-precision forming of micro threads has become an urgent problem to be solved. In this paper, the extrusion forming process of the micro internal thread was mainly studied on the nickel-plated aluminum alloy parts. The process route suitable for the internal thread forming on electroplated parts was designed, and the key parameters of thread bottom hole diameter and thread tapping speed were determined by experiment. Aiming at the typical problem of internal thread blocked by a broken tap, a thread repair method based on laser ablation was proposed and the laser processing parameters were optimized. Eventually, the manufacturing of M1 micro internal thread on nickel-plated aluminum alloy parts was successfully realized.

An implant’s thread design plays a key role in enhancing primary stability by optimising the distribution of loading forces and biomechanical structural interlocking. An increase in bone-to-implant contact (BIC) surface availability affects osseointegration timing and leads to different biomechanical behaviours. To assess their theoretical impacts on osseointegration functionality, this study aims to analyse and compare the surface areas of two different thread designs: progressive knife-edge and V-shaped metric ISO ones. Six implant models are virtually created, with progressive knife-edge threads, non-self-tapping ISO threads, and ISO threads with tapping areas, considering two arbitrary diameters (3.8 mm and 4.6 mm). For both diameters, the models also have identical lengths (9.5 mm) and external outlines. The total, superior half, and inferior half external surface areas are measured using a digital tool (SolidWorks 2023 SP 5.0, Dassault Systèmes, Waltham, MA, USA). Then, the percentage difference in external surface area (ΔESA) is calculated. A greater ΔESA is found in the knife-edge design compared to the ISO thread self-tapping implants for the 4.6 mm diameter (ΔESA = +9.9%). However, for the 3.8 mm diameter, the ΔESA is −1.5% in favour of the ISO self-tapping model. Considering the apical half of the models, the ΔESA is always greater in the knife-edge models, varying from +9.3% to +23.5%. Implants with progressive knife-edge threads offer a significantly larger external surface area than those with ISO threads for the 4.6 mm rather than the 3.8 mm diameter. Considering the apical halves of the implants, the tapping area negatively affects the ΔESA, as well as the ISO thread design. Future research is needed to investigate whether the inspected surface area differences correspond to significant primary and secondary stability variations.

Because the thread is easy to install, disassemble, and replace, and most of the threads have been standardized, the miniaturized internal thread structure is quite special, the size is extremely small, and the space position is limited, so that the current common measurement mechanism cannot achieve effective measurement. Based on the above reasons, this research aims to develop a portable miniaturized metric internal thread contact detector. The parameter values that can be detected by the detector respectively include the hole diameter value under the inner thread before tapping, the minor diameter value and the major diameter value of the internal thread after tapping. Then, use the quadratic element measuring instrument to measure three parameter values, namely the lower diameter value, the smaller diameter value of the internal thread, and the value of the major diameter of the internal thread. It is then verified with the theoretical value of the metric internal thread, which proves that the experimental parameter values designed in this study are consistent with the theoretical values. That is to say, the miniaturized metric internal thread detector can be applied to any miniaturized metric internal thread detection place, and can accurately detect the obtained parameter values, and can overcome the detection limitation given by the miniaturized internal thread in the space structure. Finally, the easy availability of the detector and the relatively low cost are its main development advantages.

The small blind internal thread (SBIT) plays a very important role to firmly fastening some functional components on the cover of 3C electronic products. The small internal thread was made in a blind hole using a fluteless forming tap (FFT) without producing chips. However, the four geometric parameters of the FFT (tool width ( W ), tooth root diameter ( D 2 ), front-end diameter ( D f ), and tooth angle ( θ )) will affect the thread filling rate ( f ) and minimum torque ( T ) in tapping process. This study reports the Box-Behnken design (BBD), combined with DEFORM-3D (finite element model) and MINITAB (regression analysis) software, to tap 7075-T6 aluminum alloy with small FFT to obtain reliable results of thread filling rate and minimum torque. The experimental results show that the BBD can accurately predict and simulate the thread filling rate of tapping 7075-T6 aluminum alloy. The modeling software and experimental design used in this research are very suitable for the optimal design of the FFT used in industrial production.

Lateral mass screw (LMS) is a more widely adopted method for posterior cervical spine fixation than the cervical pedicle screw (CPS). Despite its lower pullout strength, the insertions of LMS are more reproducible and have a lower risk. CPS insertion is a technically demanding procedure due to the small pedicle channel. Thus, CPS insertion has a high risk of pedicle wall perforation, resulting in neurovascular injury. For these reasons, surgeons may avoid CPS insertion despite its benefit of greater biomechanical strength. Therefore, an improvement in the CPS design is needed to avoid this catastrophic complication. To develop a new design of CPS, aiming to decrease pedicle wall perforation, while maintaining the biomechanical properties comparable to those of standard CPS. To reduce the risk of pedicle wall perforation, a novel CPS design should be configured in tapered shape, with a tapering screw pitch and thread diameter with a self-tapping thread. A bilayer bone finite element model representing the cortical and cancellous bone of the cervical spine pedicle was used for pullout strength test. According to our CT-based study of cervical pedicle anatomy in a normal population, the final CPS was created according to the parameters that yielded the best biomechanical strength according to finite element studies. The safety of CPS insertion, in terms of pedicle wall penetration, was assessed in 3D-printed cervical spine models of C3-C7. The pullout test was subsequently performed in a tri-layer sawbones foam model to compare the novel CPS, convention CPS, and lateral mass screw. The final screw design was a taper configuration with core diameter from 2.5 to 2.0 mm, thread diameter from 4.0 to 2.5 mm and pitch length from 1.0 to 1.25 mm. A total of 60 screws (30 conventional CPS screw and 30 Novel CPS screw) were tested in 6 3D cervical spine models. No case of pedicle wall perforation were found in the novel-design CPS group. In the conventional CPS group, 8 pedicle wall perforations were encountered, which was a statistically significant difference (p = 0.002). The novel CPS screw design and conventional CPS screw yielded pullout strengths of 449.7 N and 495.0 N, respectively, which showed no statistical difference. The LMS screw yielded a pullout strength of 168.3 N, showing statistically less strength compared with the 2 types of CPS screws. The proposed novel CPS could decrease pedicle wall perforation and enhance the safety of screw insertion. Its pullout strength is comparable to that of a 3.5-mm standard CPS and superior to that of a 3.5-mm lateral mass screw.

During internal threading, small alterations in cutting parameters, tool geometry, or process characteristics produce considerable effects on torque and temperature behavior. Understanding these effects is critical to the design and development of new taps. In this work, the torque behavior for a tap operation is evaluated as a function of the number of threads, tool manufacturer, and angle of the taper region of the tool. The chip–tool interface temperature was analyzed, considering the influence of cutting speed and number of threads. Experimental tests were carried out using M10x1.5 taps and cutting speeds of 10 m/min and 25 m/min. Taps with two different geometries were considered in this analysis. The results show a difference in the distribution of the torque along the threads of the conical part between the tools. The presence of adhered material increased the torque during the reverse stage. The torque during the reverse stage for a tap with a damaged tooth was approximately 50% of the torque during the cutting stage. The temperature showed an increase with the number of threads stabilizing between the fourth and fifth threads and increasing again in the sixth filled due to adhesion of workpiece material.

In this study, the finite element method (FEM) was used to determine the effect of the optimal angle of the thread and double thread application among self-tapping screw (STS) design information on the improvement of the withdrawal capacity of the connection. It was modeled by reflecting the design information of an Italian STS distributed in the domestic wooden building market, and the stress distribution of the connections was compared according to the change in the thread angle. A cross laminated timber (CLT) composed of five layers was modeled as a member. The STS modeling was centered on the threaded area, and two threaded angles were applied: 90° and 95°. Additionally, the stress changes were compared when double threads located in the middle of the thread pitch in the screw pitch were applied to improve the withdrawal capacity of the connection. The domestic STSs were manufactured using four materials and two shapes. The finite element analysis and strength performance tests of the STS types indicated that the material properties, angle of the screw thread, and shape of the screw thread affect the Korean CLT withdrawal capacity.

Extrusion tapping (ET) poses a technical difficulty when processing internal threads with large depth, small diameter, and high-precision blind hole . In addition, conventional ET (CET) of Ti-6Al-4V small internal blind-hole threads with large length-to-diameter ratio is challenging given its small elastic modulus, large deformation resistance and easy cracking in cold forming. To this end, a novel longitudinal–torsional ultrasonic vibration–extrusion tapping (LT-UVET) is proposed to address the technical problem of these threads. On the basis of ultrasonic longitudinal–torsional vibration characteristics, the motion trajectory equations of LT-UVET were deduced. The motion model of LT-UVET was established, and the intermittent extrusion law and force state between the tap extrusion edge and the processed material were explored and studied. Furthermore, tapping experiments were conducted to compare the differences in torque, thread quality, microhardness, and tap wear obtained by CET and LT-UVET. The influence of different tapping speeds on the thread was studied through singlefactor experiment. According to experimental findings, the maximum tapping torque was reduced by 9 %–26 % compared with CET. Moreover, the surface integrity and the profile of the thread were improved. The overall microhardness of threads increased by 3 %–17 %. The wear area of the tap lobes in LT-UVET is reduced by 65 % compared with that of CET. Therefore, the introduction of longitudinal–torsional ultrasonic vibration into the extrusion zone enhances the machinability of Ti-6Al-4V, which in turn improves the quality of extruded threads and increases the efficiency of thread machining.

Miniscrews are used in orthodontic treatment and can be applied immediately after implantation, making their initial stability crucial. However, clinical reports show that the success rate is not 100%, and many researchers have tried to identify the factors influencing success and optimize designs. A review of the literature reveals that studies on the same geometric parameter of miniscrews using different indicators and different brand samples have led to conflicting results. This study will use consistent miniscrew conditions to verify whether the design differences in the literature are reasonable. This study employs the Taguchi method and ANOVA for optimization analysis. The four control factors comprise thread pitch, thread depth, tip taper angle, and self-tapping notch. Using an L9(34) orthogonal array, the experimental models are reduced to nine. The primary stability indicators for the miniscrew include bending strength, pull-out strength, insertion torque, and self-tapping performance. The results of the single-objective experiments in this study align with the findings from the other literature. However, when analyzed collectively, they do not yield the same optimal solution. Under equal weighting, the combined multi-objective optimal solution is A2B2C1D1. This study exhibits minimal experimental error, ensuring high analytical reliability. The findings confirm that the optimal design does not converge across four single-objective analyses, as different stability indicators yield contradictory trends in design parameters. Given that these four indicators already demonstrate notable discrepancies, the influence of additional stability factors would be even more pronounced. Therefore, a multi-objective optimization approach is essential for the rational design of miniscrews.

The principal aim of this work is the development of a specific experimental device used to identify the intrinsic characteristics of a thread and to characterize the influence of the tapping process. Two turns of thread engagement were only considered. The geometry of the tapping thread was visually inspected on a cross section of thread. Two tests of the screw-nut assembly were carried out. The first one that was used for analyzing the internal shear of thread consists in applying an axial displacement on the screw mounted on a fixed nut. In the second test, a tightening torque was applied on a pressure screw assembly to investigate principally the interface shear behavior of thread. Experiments revealed that the internal shear results in three-step spread over five distinct phases. The interface shear was quantified by the identification of the friction coefficient which was determined from the load-tightening torque relationship. The evolution of the friction coefficient versus the number of cycles of clamping/unclamping was also established. Therefore, the tribological behavior of each specimen was highlighted through thread wear analysis. The results and discussions are presented by comparing the cut and form triangular ISO thread and by studying the effect of the initial tap hole diameter.