Analytical derivation of thread profile in internal thread milling process

Thread milling is a new machining process as compared to thread tapping. As a thread making process in use for a long time, thread tapping did not have any alternative processes except the thread turning for limited cases until computer numerical control (CNC) technology had enabled the three axes synchronized motion. Therefore, investigations about the thread milling process are less as compared to other machining processes. In this work, the thread profile in the internal thread milling process was derived analytically. Experimental work was also performed to verify the performance of the analytical model. It was revealed that the thread profile produced by the cutting edge of the tool is not a straight line but a curve, and the average slope through the thread profile is less than the slope of the cutting edge of the tool. Besides, the effective thread profile enlarges along the vertical axis and constricts laterally as the ratio of thread mill diameter to thread diameter increases.

Additive Manufacturing of Thermoplastic M8 Fasteners Using Photopolymer Jetting Technology for Low-Strength Fastening Applications

This study investigates the spatial accuracy of additively manufactured M8 fasteners fabricated using photopolymer jetting technology. A number of M8 bolts and their mating M8 nuts are fabricated using Stratasys Object 260 Connex 3 polyjet printer with Vero cyan, Vero magenta, Vero white, and Vero grey thermoplastic resins. Vero series thermo-plastics were used as they offer durability, strength, and flexibility. The additively manufactured nuts and bolts are fabricated with the intention of introducing thermoplastic fasteners that could eventually substitute metal fasteners in certain low strength joining applications such as in fluidics, electronics, biomedical engineering, food packaging, and automobile industries. Manufacturing constraints and critical conditions for fabrication are presented. Vital printing and manufacturing constraints, dimensional stability analysis, and the subsequent dimensional changes for the fabricated fasteners are thoroughly illustrated. Dimensional stability of the printed structures was examined under an ultra-compact 3D laser sensor and the imaging results are also presented. The fabricated thread profile superimposed precisely with the CAD model’s ISO thread profile dimensions. The dimensional performance of the fabricated M8 fasteners was examined in every orientation and along each axis of the fasteners. The high-quality manufacturing of fasteners using photopolymer jetting reached the maximum precision requirements and fitted under IT 06 transition fit grade.

Arthroscopic Suture Anchor Design Finite Element Study

AIM: This in-vitro study investigated arthroscopic suture anchors’ main design parameters effect on surrounding bone. METHODS: Thirty-dimensional arthroscopic suture anchor designs’ models were created on engineering CAD software by changing thread profile, pitch, and anchor tip profile as design parameters. These models were imported into ANSYS Workbench for finite element analysis. Bone was simplified and modeled as two coaxial cylinders. Tensile vertical load of 300 N, and oblique at 45º to the vertical axis, were applied to each model as two loading conditions while the simplified bone base was fixed in place as a boundary condition. RESULTS: The finite element analyses on all models under both loading conditions showed stresses within physiological limits on bone. Trapezoidal teeth and inclined cut teeth designs showed the lowest values of stresses and deformations respectively on the bone under oblique loads, while curved tooth and square tooth designs showed the lowest values of stresses and deformations respectively on the bone under vertical loads. General ascending or descending trend was recorded by increasing pitch from 1.2 to 1.5 to 1.8 mm on the total deformation and maximum Von Mises stress on bone and anchor body. Tapered tip slightly increased bone and anchor stresses. CONCLUSION: Arthroscopic anchors thread profile has minor affect on cortical bone behavior. Trapezoidal teeth, square tooth, and inclined cut teeth profiles showed the lowest values of stresses and deformations on cortical bone. Increasing thread pitch of arthroscopic suture anchors increases or decreases stress on the bone, and anchor body according to thread profile edges. Anchor tip profile negligibly affects both deformations and stresses on bone and anchor body.

Numerical analysis and mechanic theoretical derivations for optimizing the V-thread profiles in dental implant system

Background The thread design of the dental implant is an important feature to be considered in the optimization of the dental implant structure. The present study aimed to investigate the effects of V-thread profile design dimensions, including depth, width, pitch, thread helix angle and triangle thread apex angle on the mechanical characteristics of the bone-implant interface. A total of 588 V-thread implant system models were constructed to investigate the effects of the dimension parameters on the stress distribution generated around the bone-implant interface under vertical occlusal force. Furthermore, the force transfer at the bone-implant interface was analyzed theoretically to analyze the force transmission mechanism at bone-implant for an optimized V-thread profile in the implants. Results The optimum thread pitch ranged from 1.0 mm to 1.2 mm, when the triangle thread depth and width was 0.1 mm. The theoretically derived results showed that, with the same implant diameter, when the thread depth was 0.1 mm and the thread pitch was 0.9 mm, the optimal thread width was found to be 0.1026 mm. This derived result was consistent with the simulation analysis results. Conclusions To design the optimal V-shape threads, the implant and thread dimensions, such as the implant diameter, thread pitch, thread width, thread helix angle and triangle thread apex angle should be comprehensively considered. The optimal designed thread in this study can dissipate the chewing load, as a result of the appropriate ratio of tensile force and shear force on bone-implant interface. The optimum designed thread profile can take full advantage of the carrying capacity of the tensile and shear of the bone, thereby bearing a high chewing load.

TECHNOLOGICAL PROVISION OF THE ACCURACY FOR THE THREAD FORM OF ROD PUMPS

Aspects of thread manufacturing used in downhole rod pumps are considered. Technological defects of distortion of lateral surfaces of a thread profile arising in the course of processing on CNC machines are described, and the factors which most influence formation of these defects are established. The influence of profile defects on the reliability of the threaded connection during the operation of rod pumps is analyzed, as well as the research on the dynamics and oscillations of machine systems is analyzed. With the performed analysis the mathematical model of real technological system in the course of machining process is created and investigated. The main technological factors that have the greatest influence on the occurrence of error in the shape of the thread surface are identified. With the help of software for analysis of dynamic systems, the necessarily calculations were performed and the behavior of the dynamic system in the process of forming the thread profile was considered. Based on the analysis of the obtained results, a system for managing the parameters of the technological process of threading and technological solutions formulated. The introduction of which had a positive impact on the stability of the machining process and reduce the frequency of the above defect.

The Effect of Threads Geometry on Insertion Torque (IT) and Periotest Implant Primary Stability: A High-Density Polyurethane Simulation for the Anterior Mandible

The implant geometry provides a key role in the osseointegration process and is able to improve the mechanical interaction and primary stability into the bone tissue. The aim of the present investigation was to compare different implant profiles to evaluate their influence on the primary stability on high-density polyurethane block. Methods: A total of 100 implants were used on 20 pcf polyurethane density in the present investigation, i.e., 20 implants for each of 5 groups (A, B, C, D, and E), characterized by different thread pitch and geometry. The insertion torque (IT), and Periotest mean values were recorded during the implant positioning. Results: Mean values for insertion torque values were higher for the group C and group E implant profiles when compared to all other groups (p < 0.01). No significant differences were detected between these two groups (p < 0.05). Lower IT (<20 Ncm2) were presented by groups A, B, and D (p < 0.05). All groups showed negative Periotest values. Group C implants showed the lowest level of Periotest values (p < 0.05). No significant Periotest differences were found between group B and group D and between group A and group E (p > 0.05). Conclusions: Implants with a wider and V-thread profile and a round apex showed a higher stability in a standardized polyurethane foam. Their use could be suggested in high-density bone in clinical practice.