Teething Research Articles

Cutting force calculation for gear slicing with energy method

A calculation method for cutting force in gear slicing is proposed based on energy method. In view of the particularity of gear slicing, the cutting edge on a cutter tooth is divided into three sections: cut-in edge, top edge, and cut-out edge. Then, the concept of micro-section edge is proposed for the three curved edges. The cutting force on micro-section edge is calculated according to oblique cutting theory. The vector sum of cutting forces on micro-section edges make up the cutting force on one section of the cutting edge. Then, the cutting force on single cutter tooth is obtained by the vector sum of cutting forces on the three sections of the cutting edge. For the calculation of whole cutting force acting upon the cutter, the number of cutter teeth participating in cutting is determined based on coincidence degree. As a result, the whole cutting force is obtained by the vector sum of cutting forces on the cutter teeth participating in cutting. The feasibility of this cutting force calculation method is proved by a calculation example and the effectiveness of this method is verified by finite element simulation.

Design Method for Screw Forming Cutter Based on Tooth Profile Composed of Discrete Points

The forming method has been widely used for manufacturing screw rotors with helical profile. This paper takes the manufacturing of screws for screw pumps as an example and uses the cubic spline interpolation method to obtain the tooth profile of the screw forming cutter according to the tooth profile at any end section of screws composed of discrete points and based on the principle of gearing mesh. Furthermore, this paper studies the space enveloping and geometric characteristics between the screw and cutter during the manufacturing process, combines the shape of the contact line, which is generated due to the cooperative motion of the machine tool, screw, and cutter, with spatial location parameters, and thus innovatively proposes a design method for the screw forming cutter based on discrete points, namely, the form-position geometric method (FPGM). It can be seen after comparing the proposed method with the principle of gear meshing that the cutter-workpiece enveloping solution model, simplified by the FPGM, can overcome the key technical difficulty, i.e., it is difficult to accurately calculate the cusp of the tooth curve; meanwhile, the proposed method can improve the precision of the cutter tooth profile design. Finally, the feasibility and superiority of FPGM are verified by experiments.

Determination of the Cutting Moments at Teeth Tip in the Case of the Milling Cutter with Multiple Teeth

This paper presents experimental results for milling process using a six components dynamometer for complete mechanical actions measurement. The aim is the cutting moments determination and their evaluation on the milling cutter with multiple teeth during the cutting process. To know the cutting moments to the teeth of the tool, the instantaneous position of the teeth during milling process is determined. To achieve this purpose a calculation algorithm was developed to obtain the milling cutter teeth position respectively the moments at the tips of the teeth.

Six-Axis Linkage Strategy and Its Models for Non-Circular Helical Gears Based on Diagonal Hobbing

Among cutter teeth of the hob when hobbing non-circular helical gears, there are some issues such as uneven load and wear. To solve those problems, a simultaneous six-axis hobbing model had been developed based on diagonal hobbing. Four probable working conditions were provided. Linkage models corresponding to the four conditions were verified by virtual hobbing, in which the profile accuracies were compared and analyzed. The four working conditions were analyzed including linear (or angular) velocities and linear (or angular) accelerations. Consequently, two implementation strategies including repeating axial shift and reciprocating axial shift were offered. The linkage models and their strategies have been verified by hobbing testing. Experimental results show that diagonal hobbing is superior to non-diagonal hobbing in that the hob life of the former is 3.68 longer than that of the latter, and the micro-topography in the teeth surface of the former is more stable during transmission.

‘Moderate universalism’ in China and the Nordic countries: reviewing the major challenges in unemployment protection

Rapid welfare expansion is taking place in China across a range of policy fields. In the Nordic countries, intra-Nordic diversity and significant policy changes are not difficult to identify despite the notion of universal Nordic welfare regimes. This article will bridge these very different worlds of welfare in an effort to classify the Chinese unemployment-protection system with a comparative framework aimed at furthering the emerging Sino-Nordic research dialogue. This research dialogue has gained relevance in recent years with the new official Chinese goal of building a more universal welfare system. Welfare research that includes China from a comparative perspective is still extremely rare. Despite the lofty Chinese goals, many Chinese policy challenges still loom large. These are the rural-urban divide exacerbated by the Chinese household registration system, coverage of unemployment insurance and social assistance, inadequate and declining benefit levels, and, finally, funding issues. As this article will also substantiate, Denmark and Finland are something approaching best cases for illustrating intra-Nordic diversity. As regards the Chinese challenges, it is explained how they can to some extent be understood as the teething troubles of a developmental welfare state, since the Nordic counterparts have faced similar issues during their eras of welfare expansion.

‘Moderate universalism’ in China and the Nordic countries: Reviewing the major challenges in unemployment protection

Rapid welfare expansion is taking place in China across a range of policy fields. In the Nordic countries, intra-Nordic diversity and significant policy changes are not difficult to identify despite the notion of universal Nordic welfare regimes. This article will bridge these very different worlds of welfare in an effort to classify the Chinese unemployment-protection system with a comparative framework aimed at furthering the emerging Sino-Nordic research dialogue. This research dialogue has gained relevance in recent years with the new official Chinese goal of building a more universal welfare system. Welfare research that includes China from a comparative perspective is still extremely rare. Despite the lofty Chinese goals, many Chinese policy challenges still loom large. These are the rural-urban divide exacerbated by the Chinese household registration system, coverage of unemployment insurance and social assistance, inadequate and declining benefit levels, and, finally, funding issues. As this article will also substantiate, Denmark and Finland are something approaching best cases for illustrating intra-Nordic diversity. As regards the Chinese challenges, it is explained how they can to some extent be understood as the teething troubles of a developmental welfare state, since the Nordic counterparts have faced similar issues during their eras of welfare expansion.

Reconstruction of Milling Force Coefficients in Asymmetrical Teeth Milling Thin-walled Part

Concentrated on the distortion problem of milling force coefficient calculation caused by the different cutter tooth radii in thin-walled parts milling,actual milling force coefficient is constructed,and is predicted through kernel partial least square regression method when milling parameters change. To construct actual milling force coefficient,theoretical milling force coefficient is deduced for two-teeth spiral milling cutter,nominal milling force is defined based on the milling process with cutter of different tooth radii,and cutter tooth radius error is deduced. Prediction model of actual milling force coefficient about milling parameters and their compositional variables,is established in high dimension space through kernel partial least square regression method based on the prominent nonlinear analysis and prediction ability of nuclear analysis; kernel parameters of Gaussian kernel function and the number of kernel principal components,whose impact on prediction model is analyzed,are set in certain value range in kernel partial least square regression method. At last,milling force coefficients are analyzed respectively when cutter tooth radius error is considered or not,and kernel partial least square regression prediction method and partial least square regression prediction method are compared; according to above data,the proposed construction and prediction methods of milling force coefficient have high calculation accuracy and prediction ability.

Mathematical modeling of power spent in face milling taking into consideration tool wear

In this paper, a mathematical model has been developed for the main drive power expended in face milling taking into consideration the wear of teeth on the back surface of the tool. The model considers the conditions of cutting, the size of the flank wear of the cutter tooth on the back surface, the properties of the material, and the geometric parameters of the tool. The paper has established the adequacy of the mathematical model of the main drive power expended in face milling. By monitoring the power of the main drive of modern CNC machines, it is possible to control the conditions of face milling in the process of change in the size of the flank wear of the cutter tooth on the back surface.

Geometrical model and tooth analysis of undulating face gear

A new gear set consisting of a planar noncircular gear and a specific face gear called undulating face gear is presented, which are able to transmit varying angular velocity. Based on the kinematics of planar noncircular pinion and rack, the formation mechanism of pitch curves of the undulating face gear is given, with the continuous transmission condition of the gear set discussed. Tooth surfaces of the undulating face gear are enveloped by the teeth of a shaper cutter when its pitch circle rolls on the pitch curve of the undulating face gear without sliding. According to the spatial meshing theory, the mathematical model of the face gear tooth surface is built. The phenomenon of tooth undercutting and tip-cutting of the face gear is investigated through three-dimensional machine design software to obtain its minimum inner radius and maximum outer radius. Furthermore, a computer program is developed to calculate the data of the face gear tooth surface and a motion simulation of the gear set without undercutting and tip-cutting is made, which is able to illustrate validity and correctness of the design theory.

Dynamic Analysis for High-speed Cutters of Five-axis CNC Milling Machine

Cutter vibration characteristics of five-axis milling machine in high-speed milling process were studied. Finite Element Modal Analysis for high-speed cutters with different parameters is conducted using finite element software.The impact of tooth number, extended length, diameter and material of milling cutter on the mode shapes and natural frequencies of milling cutter is researched in detail. Harmonic response curves of High-speed cutter under different frequency are calculated. Based on the response curve, the resonance frequency range of high-speed cutter is obtained in order to achieve high-precision milling and longer life of the tool. Analysis shows that: mode shapes of milling cutter are divided into strong vibration mode shapes and weak vibration mode shapes and its natural frequency become smaller with the increase of the cutter teeth number. Natural frequency of milling cutter decreases with the increase of extended length of milling cutter. The number of strong vibration mode is smaller with the increase of milling cutter diameter so that the milling cutter with large diameter can play a role of anti-vibration. Natural frequency of the high-speed steel cutter is lower than that of the diamond and carbide cutter. This research provides theoretical basis for the design of high speed milling cutter and reducing milling chatter.

The estimation of cutting force coefficients in milling of thin-walled parts using cutter with different tooth radii

The precise estimation of the cutting force coefficients in milling is very important, which has great impact on the precise calculation of the milling forces and the stability lobes of the system. On the basis of the imprecise estimation of cutting force coefficients in milling of thin-walled part using cutter with different tooth radii, the calculation process of actual cutting force coefficients is proposed in this article. First, based on the different amplitudes of milling forces caused by the long and short teeth of cutter, the nominal milling forces and nominal cutting force coefficients are constructed, and the radii error of the long and short teeth of cutter is calculated. Then, actual cutting force coefficients are derived based on radii error of cutter teeth. Finally, an experiment is performed to verify the validity of the calculation process of actual cutting force coefficients proposed in this article, and the results show that the actual cutting force coefficients obtained by consideration of radii error are more effective than theoretical cutting force coefficients obtained without consideration of radii error in the calculation of milling forces.

Bioinspired Crown-Cutter—The Impact of Tooth Quantity and Bevel Type on Tissue Deformation, Penetration Forces, and Tooth Collapsibility

Current keyhole biopsy devices are rather ungainly, inaccurate, and limited in application. A keyhole biopsy harvester was designed to facilitate peripheral cancerous tissue detection and resection at high speed and accuracy. The harvester's cutting tool, the crown-cutter, was bioinspired by the sea urchin's chewing organ—Aristotle's lantern. This paper focuses on the optimization of the crown-cutter with regard to the impact of different tooth quantity and bevel type on tissue deformation, penetration forces, and tooth collapsibility. Two sets of crown-cutter designs were manufactured and tested in push-in experiments using gelatin—the first set having no bevel and differing tooth quantity (4, 6, 8, 10 teeth) and the second set of constant tooth quantity and differing bevel type (no, inner, outer, and inner and outer bevel). The gelatin surface deformation and the penetration forces were evaluated utilizing a high speed camera and a universal testing machine, respectively. The experimental results on the crown-cutters of different tooth quantity (no bevel) showed a steady increase in the tissue deformation with the increasing amount of teeth. Unlike the bevel type, the different tooth quantity revealed significant differences with regard to the tissue deformation in between 4 versus 6-teeth and 10 versus 6-teeth cutters. As for the penetration forces, the significant difference was found only between 10 and 6-teeth cutters. In conclusion, reducing the cutter's tooth quantity resulted in lower tissue deformation, whereas differing the bevel type was found to have a negligible influence. Ultimately, a high ratio of outward to inward tooth collapsibility and a relatively low inner moment of inertia proved the 6-teeth cutter to be the most optimal.

Simultaneous prediction of surface topography and surface location error in milling

The machined surface topography, surface roughness and surface location error are very important evaluation indexes for machining quality, which directly affect the performance characteristics of the machined workpiece. In this paper, a new model of the arbitrary point of the cutter edge with respect to the arbitrary frame of the machining feature point is built. The proposed model incorporates the surface location error into the relative motion of the cutter with respect to the workpiece using the harmonic balance methods. Further, a nonlinear programming problem is proposed to obtain the scallop value of an arbitrary point on the nominal machined surface. Since the obtained scallop value of each point can be used for constructing the topography of the machined surface as well as calculating the surface roughness, the proposed model can simultaneously predict the surface topography, surface roughness and surface location error. Simulations and experiments indicate that feed per tooth, runout and number of cutter teeth are vital factors influencing the topology of the machined surface. The surface location error of the cutter due to the number of cutter teeth is an essential factor that influences the parallelism or perpendicularity of the machining feature. The effectiveness and feasibility of the proposed method is verified by a machining example.

Transplanting The Team Helps To Minimize The Startup Pains in Living Donor Liver Transplantation.Early Outcomes From a New Center in Western India.

Background:Living donor liver transplantation(LDLT)is the only optiont for patients with Decompensated cirrhosis or acute liver failure(ALF) in large parts of the world. Established Centers in Asia and India havegradually improved their outcomes having gone through their early teething troubles. However, the accessibility of patients needing transplants is limited by the waiting periods as well as geographic distance necessitating newer centers to come up. The luxury of the learning curve is not available to a new center. Theway out is to possibly get together transplant surgeons with LDLT experience and develop a program aroundthem. Methods: A new program was initiated by a center in Western India using a core group of surgeons withextensive experience in LDLTs. The team had experience of working together with clearly defined roles andresponsibilities. The other components of a successful LDLT program; imaging, anesthesiology, critical care,operating room services and hepatology were organized from the existing staff around this core. The protocols of the surgical team were uniformly applied with local modifications to minimize the learning curve. Result: It took less than 3 months from appointing the surgical team and performing thefirst LDLT. The center performed 30 Liver transplants within 9 month of its start. Like any program In India,the cadaveric donation rates were poorl; 2 deceased donor transplants were done - both from extendedcriteria donors. The median age of recipients was 55(9mths to 65 yrs; M/F=21/9). Out of 28 LDLTsthere were 2 left lobe grafts and 1 left lateral segment graft. The indications for transplantation were ALF in 3patient, HC C with cirrhosis in 2 and cirrhosis with decompensation in 24 patients. 30 day patient and graftsurvival was 84%.The median age of the living donors(n=28) was 43.5 years(20 to 58 years; M/F =9 / 21). There was no donor mortality. One donor required re-exploration for bleeding from divided hilar plate and 1 donor had bile leaks managed by ERC P and percutaneous drainage. Conclusion: A cohesive team built around transplant surgeons trained in performing LDLTs in local condition can minimize the learning curve in a new Living donor liver transplant center.

Subdivision of chatter-free regions and optimal cutting parameters based on vibration frequencies for peripheral milling process

Considering the self-excited and forced vibrations in peripheral milling processes, a novel optimization method of cutting parameters is presented. The optimization method proposed, which is based on the vibration frequency analysis during milling processes, can achieve the most stable cutting process in relative stable region (or conditional stable region). First, relationships between vibration frequencies and phase angle of tooth of cutter in milling processes are investigated. Four kinds of spindle speeds associated with several bifurcations and vibrations are defined. Second, chatter-free regions are subdivided according to these spindle speeds. It is shown that in the so-called subregion C, cutting parameters can be simultaneously optimized for higher material removal rate (MRR) and higher surface accuracy. Third, optimal control theory is employed to determine the optimal cutting parameters, which can achieve the most stable cutting process in relative stable region. Optimizations of spindle speeds and depth of cut are conducted by using the stability charts and performance contours diagrams. The results show that the optimal cutting parameters can also be obtained in the so-called subregion C. Finally, the numerical results are verified and analyzed through milling experiments.

An Overlooked Peer? Role of the Managing Editor in Nursing Journals

An Overlooked Peer? Role of the Managing Editor in Nursing Journals

Worm Shaving Cutter Tooth Stress and Deformation Analysis

This paper discusses a new type of worm gear shaver shaving cutter tooth contact point during deformation force, and the establishment of the shaving force model, through the instantaneous cutting force to analyze the force deformation cutter shaving cutter tooth and precision of impact. And making use of a simplified model for variable cross-section cantilever, analyzing of tooth stiffness at any cross section, find the maximum amount of deformation of worm gear shaving cutters do theoretical foundation structure optimization.

Study of Curve Planning Algorithm for Partition-Type Rotary Burrs

For traditional rotary burrs, cutter teeth converge at the vertex, which means small chip space and poor cutting condition. In order to increase the chip space and to improve the cutting condition, a new type of rotary burrs with partition blade teeth, which took the feasibility of the actual process into consideration, was proposed. The curve planning algorithm planned the blade curves on the tooth bottom contour surface, and adjusted the tooth bottom contour model by some parameters, such as the small central angle and the position of oblique planes, to control the contour and blade shape for rotary burrs effectively. Experimental results demonstrate the effectiveness of the proposed algorithm.

Design and Static Analysis of an Addendum Modified Helical Gear Tooth

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. We have several types of gears among which spur gears are used as pinion and gear between parallel shafts.. When the involute portion of the tooth mates with the non-involute portion of the other tooth an undercut is formed. Due to this the mating gear will try to scoop out metal from the interfering portion. In order to avoid undercutting and interference, addendum modification of the gear tooth is carried out. This paper describes about the modeling meshing and the analysis techniques. Effort has been taken to develop the tooth profile involute as well as the fillet region by calculating the co-ordinates using C-language. The output file of the C-program is converted to modeling software PRO/E for 3-D modeling with the help of a coupler software DXF file converter. Those PRO/E models are imported to an analysis software ANSYS for the proposed stress analysis.

The Research of Impact Ball End Mills Geometric Parameters on Processing Stable Region

In this paper, modal analysis of ball end mills is modeled by finite element to work out natural frequency and chatter model in tooling system and to calculate the limit curve of stability in single degree freedom system. The effect of cutter flute length and cutter tooth number on maching stability area is also discussed. The results of research show that steady critical cutting depth of milling system declines while the cutter flute length increases, but the trend is not linear, which shows increase partly. An engineering optimization design is made on milling cutter geometrical parameters based on this conclusion.