Teething Research Articles

Experimental study on deep hole drilling of GH4169 alloy

GH4169 alloy material has good corrosion resistance, radiation resistance and other excellent properties, and has been widely used in aerospace and other manufacturing fields. At the same time, due to its severe machining hardening phenomenon and high cutting force during machining, it is also one of the typical difficult-to-machine materials, and the deep hole drilling of GH4169 alloy has been rarely studied. In this paper, the deep hole drilling test of GH4169 is studied, and BTA system is adopted in the test, the wear and failure modes of the cutting tool, and the change of chip morphology were analyzed. Results showed that the middle cutter tooth wear focused on central blade, the wear of the center tooth occurs mainly at the tip of the cutter tooth, the wear of edge tooth mainly occurs at the arc of the tool tip where the main cutting edge is connected with the secondary cutting edge: the chips produced by the central cutter tooth are mostly short and small c-shaped chips, the chip produced by the middle tooth is not easy to break the chip, most of which are elongated spiral chip, the cuttings produced by the edge tooth are not easy to discharge, and most of them are hard spiral coils.

In Vitro Analysis of Quality of Dental Adhesive Bond Systems Applied in Various Conditions

Introduction: There are several methods of reducing a microleakage, and one of them is choosing appropriate adhesive material. The aim of the work was the in vitro analysis of 4 bonds: 3M ESPE “Single bond”, Dentsply “Prime and Bond Active”, Coltene “One Coat 7 Universal”, and Kuraray “Clearfil Universal Bond Quick”. Material and methods: 136 healthy molar teeth were collected and randomly split into 4 groups and Vth Class cavities were prepared. Chosen adhesives were used in four groups of teeth with the same composite. Teeth were the thermocycled, sealed, covered with lacquer, and submerged in 1% methylene blue solution for 24 h. After the thermocycling, the vertices of each tooth were sealed using dental wax. Each tooth was then fully covered with lacquer. All teeth were then submerged into 1% methylene blue solution for 24 h in room temperature. In the next step they were transversely cut through a center of restoration. The Olympus BX43 microscope was used to photograph each cut tooth. With the usage of Olympus stream software, measurement of the dye’s leakage was performed. Results. The statistical analysis proved that the most effective material when applied to ideally prepared cavity surface was Dentsply “Prime and Bond Active”. The second material was 3M ESPE “Single Bond”, third—Coltene “One Coat 7 Universal” and fourth—Kuraray “Clearfil Universal Bond Quick”. The most effective material applied to a too-dry surface was Dentsply “Prime and Bond Active”, second—3M ESPE “Single Bond”, third—Coltene “One Coat 7 Universal” and fourth—Kuraray “Clearfil Universal Bond Quick”. When it comes to too damp surfaces the best results were obtained with Dentsply “Prime and Bond Active” then Coltene “One Coat 7 Universal”, 3M ESPE “Single Bond” and Kuraray “Clearfil Universal Bond Quick”. Conclusion: The level of cavity dampness influences the quality of adhesives. Better results are obtained with over-dried surfaces than over-damp, which is connected with the dilution of the material.

Analyse of dynamic operation mode for drilling machine equipped with drill for pits digging

The working part of drilling machine is the drill. It is the one that performs soil dislocation, crushing, evacuation and depositing around the pit. Drilling machines with a drill operate according to dry rotating drilling method, where dislocation and evacuation of drilled soil are performed by the drill. To perform this, the drill is subject in the same time to rotation and vertical push-down. Milling cutter type equipment for pits digging was 3D generated in Mechanical Desktop. Cutter model was introduced in Algor medium and automatically digitized by this. After digitization, the user introduces in Algor the supporting set and loading set for all situations. The user has only available the possibility to refine the digitization within the entire model and not only in areas of interest (as it is mostly wanted). Two real situations were considered and analysed wherein the work equipment during digging process can be found: front stress on the cutter teeth performing material cutting and front stress on cutter teeth and body that go inside material and perform centring. In both situations, supporting has tried to follow real situations wherein work equipment components subject to analysis can be found. In both loading situations, it is noticed that the operating part is not at risk to crush under stress. It is also noticed that displacements of the knots belonging to analysed structures do not have greater values in either situations.

An effective thread milling force prediction model considering instantaneous cutting thickness based on the cylindrical thread milling simplified to side milling process

An effective thread milling force prediction model considering instantaneous cutting thickness is presented based on the cylindrical thread milling simplified to the side milling process. Firstly, based on the thread milling process simplified to side milling, an effective calculation model of instantaneous cutting thickness and a milling force model of single-layer cutter teeth are established considering the specific geometric profile of the cutting edge, chip groove angle, and tooth profile angle of the threaded milling cutter. Then, according to the time-domain difference of each layer of cutter teeth, a simplified thread milling force prediction model corresponding to the number of layers can be obtained. Finally, comparing the predicted values of the proposed model with the experimental results of cylindrical thread milling forces, the results show that the average prediction accuracy of Fx, Fy, and Fz are 90.75%, 83.56%, and 78.79%, respectively. The established simplified cylindrical thread milling force prediction model is accurate and reliable.

Influence of Electro-Erosive Modification Modes for Worn Working Surface of Dental Cutters on Restoration of its Cutting Ability

An experimental assessment has been made of the influence of electro-erosive modification modes for worn working surface of an cutter on the restoration of its cutting ability. The paper provides basic information on dental cutters. The provisions of the experimental research methodology are described, including a description of a device for modifying the worn surface of a dental cutter and a device for determining its cutting ability. Experimental data are presented and analyzed that reflect an effect on restoration of a cutting ability of a worn surface of a dental cutter, voltage of a storage capacitor and number of holes applied to it during its modification. Rational modes of modifying a worn-out surface of a dental mill that provide the greatest recovery of its cutting ability have been determined in the paper. It has been shown that with increasing voltage, the energy of the electric discharge acting on the treated surface increases, which leads to the formation of a single hole of a larger size on it, including metal flows along its edge that extend beyond the initial contour of the worn cutter teeth. These metal flows on the modified surface of the cutter play the role of peculiar cutting and deforming elements. It has been revealed that in the process of modifying the worn surface of the cutter, it is necessary to ensure that there is no overlap of the holes formed on it, i.e. the distance between the centers of adjacent holes should be greater than or equal to the size of metal deposits at their edges. In this case, the metal flows retain their original shape and have the highest height at these pulse parameters, which ensures a higher cutting ability of the modified cutter surface than when the holes are overlapped.

Dynamic milling force model for a milling cutter under vibration

Dynamic milling force under milling vibration is an important indicator for evaluating the milling stability of a milling cutter. The existing modeling methods for milling force ignore the milling vibration for the instantaneous milling behavior of a milling cutter and its teeth, the instantaneous cutter-workpiece engagement, and the milling force. The dynamic characteristics of the milling force need to be revealed. According to the influence characteristics of milling vibration on instantaneous cutter-workpiece engagement, a method for calculating the instantaneous milling attitude angle and the milling motion trajectory of a milling cutter and its cutter teeth was proposed that revealed the changing characteristics of the instantaneous milling behavior of the cutter teeth. The differential element method was used to characterize the distribution state of the milling force of a cutter tooth. The method for calculating the cutting layer thickness of the milling differential element and the instantaneous cutting boundary of the milling edge was put forward, and the instantaneous milling force model of the milling edge was established. By constructing an instantaneous milling force system for multi-tooth milling, a method for calculating the position vector relation variable and the force vector relation variable of the instantaneous milling force of adjacent cutter teeth was proposed, thus revealing the dynamic characteristics of the instantaneous milling force relationship of the adjacent cutter teeth. The dynamic characteristics and the response characteristics of the milling force were tested. The results showed that the calculated results of the dynamic milling force change characteristics of the milling cutter were quite similar to the experimental results. The influence mechanisms of milling vibration, cutter structure parameters, and milling parameters on the dynamic milling force of a milling cutter can be identified with the use of the above models and methods.

Modeling and experimental validation on temperature diffusion mechanism in high-speed bone milling

• High-speed bone milling heat is mainly caused by the friction effect between the bone chip and the cutter tooth. • Cutting edge temperature is determined by the equivalent static plane heat source. • The bone material temperature distribution is obtained according to the constant temperature moving heat source. • The thermal damage factors could be calculated based on the temperature diffusion mechanism model in bone milling. In orthopedic surgery, thermal damage of bone affects the accuracy of the prosthesis fixation and delays the postoperative recovery time. In order to avoid thermal damage in high-speed bone machining, it is necessary to establish an effective relationship among machining parameters, tool parameters, and temperature distribution of bone materials. Based on the characteristics of bone material and high-speed processing, this study proposes a novel temperature diffusion mechanism model (TDMM) in high-speed bone milling. According to the model, heat during high-speed bone milling is mainly generated by the friction effect between the bone chip and the cutter tooth. Then the cutting edge temperature of the milling cutter is determined by the equivalent static heat source, and cutting edge is regarded as a moving heat source with constant temperature. Under the action of the moving heat source, the bone material temperature distribution was determined. Moreover, the degree of thermal damage of bone materials under different machining and tool parameters was evaluated. Next, a high-speed bone milling experiment platform was established, in order to obtain accurate cutting edge temperature and bone material temperature. According to a large number of experimental measurements, the theoretical prediction temperature values of the cutting edge and bone materials were found to be within the reasonable error range of experimental measurements. The proposed model was proved to reasonably predict the temperature of the cutting edge and bone materials in high-speed bone milling. Experimental results indicate that the processing methods, tool diameter, cooling method, and cutting layer have a noteworthy impact on bone material distribution in bone milling. Spray cooling method can reduce the bone material temperature significantly. And the bone material temperature outside the cutting layer can be greatly lower than that in the cutting layer. This study also indicates that according to the TDMM, it is convenient for surgeons to select the appropriate machining parameters, and for engineers to optimize tool design.

An efficient full-discretization method for milling stability prediction

To address the vibration phenomenon in the milling process, this study proposed an implicit Adams method (IAM) to predict the stability of the milling process. The dynamic equation of milling process with regenerative chatter can be expressed as a delay linear differential equation. The cutter tooth cycle can be divided into the forced and free vibration stages. The forced vibration stage is discretized and IAM is used to construct state transition matrix. The stability of the system is determined based on Floquet theory and the stability lobe diagrams are obtained. Matlab simulation and experiment results show that IAM is an effective method to predict the stability of milling. First, compared with the typical discretization methods, the IAM method indicates a faster convergence rate. Next, in one- and two-degree freedom dynamic model, the stability lobe diagrams show that the prediction accuracy and computation efficiency of IAM are better than that of the first-order semi-discretization method (1st-SDM), second-order full discretization method (2nd-FDM), and the Simpson method (SIM). Finally, acceleration signals collected from cutting experiments are analyzed by mathematical statistics, time-domain method, and frequency-domain method. It is concluded that the simulation results are consistent with the experimental analysis results which verifies the effectiveness of IAM.

Temperature calculation of the tool and chip in slicing process with equal-rake angle arc-tooth slice tool

As a new gear processing technology, gear slicing technology has the characteristics of high efficiency, high precision and environmental protection. In this paper, the slicing process with equal-rake angle arc-tooth slice tool (ERA-ATST) is taken as the research object. Considering the particularity of the slicing process, a theoretical calculation method of tool and chip temperature is proposed. By analyzing the characteristics of the slicing process with ERA-ATST, a cutter tooth of the ERA-ATST is divided into several sections along the cutting edge, which are called micro-section tooth. For each of the micro-section tooth, the slicing process is simplified and equivalent to oblique cutting process. Comprehensively considering the influence of cutting speed, chip force and tool-chip contacting characteristics in slicing process, a temperature calculation model is established based on the generation mechanism of slicing heat. The tool and chip temperature is derived by averaging the results of several micro-section teeth. With the established model, an inner arc-spur gear slicing with the ERA-ATST is used as an example to calculate the temperature on the chip and rake face. The gear slicing test is carried out on the slicing machine tool. The measured chip temperature and rake face temperature are compared with the corresponding calculation results to verify the temperature calculation model. The proposed temperature calculation method provides a theoretical basis for the analysis and control of slicing heat in the gear slicing process.

Water Hummer Technology for Soil Destruction on Dredgers

The present investigation aims to propose a solution of the problem which is connected with slurry processing during the dredger’s operation under difficult conditions. On dredgers, depending on the degree of air dryness or low ambient temperatures very often arises technical problem that creates difficulties for the crew. It is connected with the fact that soil surface layer is very dense. It is very difficult to dredge the soil during extraction under water surface or unloading from the hold of a vessel at low ambient temperatures. The top layer of the very soil is characterized by a high degree of compaction and can be destroyed in two ways only. The first way is to use very powerful mechanical equipment (percussion mechanisms, vibration equipment, etc.). This method is associated with high energy spending and its use on a vessel is technically difficult. The second way is to use the soil cutting process with the use of mechanical cutters. Dredger’s operation with the use of milling equipment is always characterized by the fact that during soil mechanical treatment there is always occurs breakage of the cutter teeth or rapid wear of the cutting surfaces. A similar problem occurs when sandy or clay soil is extracted under water, which is compacted by its properties. In investigation a non-trivial solution was used to solve the problem of destruction of the compacted soil layer during the operation of the dredger. It was proposed to use the hydrodynamic method based on water hammer as the main mechanism for the destruction of compacted soil. As a result of the interaction of the compacted soil layer and high pressurized directed water jets, good performance of the dredger can be achieved. The two-dimensional mechanism of destruction of the compacted soil layer can be described by the condition of dynamic equilibrium of the three main flows - the jet, which flows from the conical nozzle and two flows along the soil surface. For these streams, a reactive force evaluation has been performed. Destructive jets can be generated by standard marine pumps in combination with the use of water hammer. Based on the results of the experiments, it was found that the qualitative destruction of the surface layer of compacted soil occurs using two or three phases of hydraulic water hummer.

Pre-packaged Insolvency in India: Lessons from USA and UK

Pre-packaged bankruptcy, commonly referred to as “Pre-packs” finds its roots in United States and United Kingdom; but is yet to be formally integrated in the Indian bankruptcy regime. While the latest Insolvency and Bankruptcy Code, 2016 has been helpful in improving the stressed asset statistics, the statute is still undergoing teething troubles and has scope for bringing in many improvements such as introducing Pre-packs. In this backdrop, this term paper discusses the basic features of Indian insolvency structure and how Pre-packs will fare in the market given the current regulatory regime. The paper analyses the corporate insolvency resolution process in India, highlights specific challenges to introduction of Pre-packs and presents a holistic overview of the benefits as well as disadvantages that Pre-packs would bring along with them.

Cutting force prediction based on study of cutter-workpiece engagement in flexible ball-end milling of panel molds

In this paper, the flexible cutting force forms the basis for investigating the stability of the process involved in milling hardened steel mold with a curved surface. The cutter-workpiece engagement, which changes along the curved tool path, is inevitably affected by cutter deflection. An analysis of cutter-workpiece engagement therefore plays a critical role in predicting the flexible cutting force. First, the influence of the curved surface milling force on ball-end cutter deflection is analyzed, and the effect of tool load on the deflection of the cutting edge at different discrete positions is evaluated. A model of the uncut thickness of the milling surface is then constructed, based on the three-dimensional trochoidal trajectory of the milling process. The rules relating to the cutting process of the uncut thickness with the cutting edge at different discrete positions are analyzed. A milling force prediction model relating to the milling of the curved surface is constructed that considers cutter deflection as a part of the cutter-workpiece engagement. Finally, a hardened steel mold milling experiment is carried out. This confirms that the amplitude and trend predicted by the milling force model and the experimental results are consistent. The results validate the capacity of the proposed method to accurately predict the cutting force for different cutter teeth with tool deflection. Application of the method shows that the milling forces are relatively stable when the lead angle is between 6° and 12° or − 6° and − 12°. When the lead angle exceeds 12° or is less than − 12°, both the milling forces and cutter deflection increase rapidly.

Artificial intelligence: In modern dentistry

Artificial intelligence (AI) is the ability of a digital computer or computer-controlled robot to perform tasks commonly associated with intelligent beings. There is marked increase in evolution of AI from the last decade, which has been showing tremendous improvement and dentistry is no exception. AI has its importance in dentistry, especially in oral medicine and radiology, which includes patient diagnosis, storage of patient data, and the assessment of genetic information which will provide improved healthcare for patients. Regardless of many improvements and advances, AI is still in its teething stage, but its potential is boundless. This article reviews on how this technology is tremendously utilized for easy and early diagnosis, proper treatment of lesions of oral cavity, advanced breakthroughs in image recognition techniques, screening of suspicious premalignant, and malignant changes of oral cavity with satisfying outcome. A thorough knowledge regarding the adaptation of technology will not only help in better and precise patient care but also reducing the work burden of the clinician.

“Am I audible? Are my slides visible?” – Do we need to flatten the webinar curve?

“Am I audible? Are my slides visible?” – Do we need to flatten the webinar curve?

Определение рациональных режимов торцево- го фрезерования на основе снижения ударно-вибрационных воздействий

The purpose of the article is to develop a method for determining the optimal machining modes of milling machines by estimating the vibration level and initial contact of a cutter tooth and a workpiece. The work is based on the use of experimental data obtained by measuring vibration characteristics, which serve the basis for determining the optimal milling modes of the end mill with a hexagonal plate. The experiment results in the development of a methodology for determining optimal milling modes (based on the obtained experimental data of the vibration level), and identification of the relationship between the initial contact line of the cutter tooth and the workpiece by means of a 3D model. The methodology of determining the optimal milling modes is developed on the basis of the experimental data of the vibration level. Based on the results of the conducted studies, the recommendations are given on setting the optimal processing modes for a cutter with a hexagonal plate taking into account the comparison of the obtained RMS values of the vibration velocity and General technical standards of permissible values of the overall vibration level. The relationship is revealed between the line of initial contact of the cutter tooth and the workpiece by means of a 3D model and the level of vibration.

A precision generating hobbing method for face gear with assembly spherical hob

In order to improve the processing precision and shorten the hob manufacturing cycle of the face gear, a precision generating hobbing method for face gear with the assembly spherical hob is proposed. Firstly, the evolution of the cylindrical gear to spherical hob basic worm is analyzed, then the spherical hob basic worm is designed, thus the basic worm and spiral angle equation of spherical hob are obtained. Secondly, based on the design method of the existing hob, the development method of the assembly spherical hob is analyzed, the cutter tooth and the cutter substrate of the assembly hob are designed, and the whole assembly is finished. Thirdly, based on the need of face gear hobbing, a numerical control machine for gear hobbing is developed, and the equation of the face gear is obtained. Fourth, for reducing the face gear processing errors induced by equivalent installation errors, the error analysis model is established and the impacts of each error on the gear tooth surface are analyzed. Finally, the assembly spherical hob is manufactured and the gear hobbing test is completed. According to the measurement results, the processing parameters of face gear hobbing are modified, and the deviation of tooth surface is significantly reduced.

Algorithms for modelling the load of teeth from pinion cutter tool used at worms machining

The turning of worms with tools of pinion cutter type means to generate helical surfaces by rolling. In this case, the process of detaching the chip by tool successive teeth is characterized by uneven variation of chip total area, calculated as sum of the areas corresponding to the chips simultaneously detached by all tool teeth in contact at a time with the machined part. As consequence, the cutting forces that load the tool cutting edges are also uneven which negatively impacts the machining process: uneven wear of tool teeth and uneven elastic deformation of technological system with bad effects onto the precision of generated worm flanks. This paper proposes the analytical modelling for both area and shape of the chips detached, during the machining process, by the successive teeth of the pinion cutter that generates a cylindrical worm. The tool tooth involute flanks and the arc from tooth head are modelled, thus delimiting the region formed by the successive active teeth of the tool. The model of the chip detached during the rolling between tool and part centrodes is determined and, on this base, the area of the chip detached for an increment of tool rotation is found. Starting from proposed model, a graphical application in CATIA environment was developed in order to calculate the cumulated area of chips simultaneously detached by tool teeth, which is further needed in order to reduce the cutting force unevenness.

Vibration analysis of milling process with helix-angle cutter based on Euler method

The chatter vibration is the major limiting factor in increasing the metal removal rates of the machine tools. In this paper, a program for dynamic analysis of thin-walled milling process with helical milling cutter is developed, based on Euler iteration. The program can take into account the characteristics of thin-walled workpiece, the contact separation between workpiece and cutter, the helical angle of cutter teeth and other actual cutting process characteristics. Based on the stability lobe diagram obtained by semi-discrete method, the stability simulation in different cutting parameters around the stable island was carried out. The unstable form of the cutting process was determined by spectrum analysis and Poincare mapping method. The results show that the method is in good agreement with the results of stability Lobe diagram and can capture the stability island in small radial cutting process. This method can well grasp the cutting force and vibration evolution process in cutting process, and provide an effective means for stability analysis of cutting process.

Parametric design and surface topography analysis of turbine blade processing by turn-milling based on CAM

The design and manufacturing level of the blade largely affects the performance of the aero engine. In this paper, the blade is taken as the research object, focusing on its design and processing. On the one hand, based on the mathematical method of fifth-order polynomial, a GUI module for parameterized design of different blade profiles is established. On the other hand, in CAM environment, the procedure division of turn-milling the blade, the generation of tool path, the optimization of NC program and the simulation of machining process are completed. On this basis, the experiment of machining the part by turn-milling is finished. In addition, in order to study the quality of the machined surface, a mathematical model for predicting the surface topography of turn-milling blade is established based on the surface unfolding and meshing of the workpiece. Then, the effects of the number of cutter teeth, tool rotation speed, feed rate, and the cutter radius on surface topography are analyzed qualitatively. Besides, the maximum surface residual height is used as an index to quantitatively compare the influence of different parameters on surface topography. Finally, the simulation reliability is verified by comparing with the experimental surface.

The process control for improving the durability of the cutting edge of the teeth of the cutter at their recovery

The features of the technology of laser deposition of wear-resistant powders on the cutting edge of the cutter tooth with control of the positioning of the focus of laser radiation are considered. The stabilization of the parameters of the laser technological complex and the positioning of the focus of the laser radiation makes it possible to increase the efficiency of the technological process of restoring the instrument, with its specified quality indicators.