Analytical prediction of stability limit in turning operations

Unstable cutting due to chatter vibrations is one of the most important problems during metal cutting operations. Chatter can be a limitation for productivity and surface quality in turning operations, especially when long and slender tools and parts are involved. In this study, an analytical stability method for turning process is presented. The model takes the cutting geometry into consideration, and proposes a new solution procedure for the dynamic chip thickness at the insert nose. The analytically calculated absolute stable depth of cuts are compared with the chatter test results, and a good agreement is observed

Experimental analysis and modeling of orthogonal cutting using material and friction models

In this study, a process model for orthogonal cutting processes is proposed. The model involves the primary and secondary deformation zones. The primary shear zone is modeled by a Johnson-Cook constitutive relationship and a shear plane having constant thickness. The secondary deformation zone is modeled semi-analytically, where the coefficient of friction is calibrated experimentally. The cutting forces predicted using the calibrated sliding friction coefficients are in good agreement with the measurements. The experimental investigation of sliding friction coefficients also show promising results for the proposed model, which is still under development

Analytical stability models for turning and boring operations

In this paper an analytical model for stability limit predictions in turning and boring operations is proposed. The multi-dimensional model includes the 3D geometry of the processes. In addition a model for the chip thickness at the insert nose radius is also proposed to observe the effect of the insert nose radius on the chatter stability limit. Chatter experiments are conducted for both turning and boring in order to compare with analytical results and good agreement is observed

Analytical modeling of chatter stability in turning and boring operations: a multi-dimensional approach

In this study, an analytical model for the stability of turning and boring processes is proposed. The proposed model is a step ahead from the previous studies as it includes the dynamics of the system in a multidimensional form, uses the true process geometry and models the insert nose radius in a precise manner. Simulations are conducted in order to compare the results with the traditional oriented transfer function stability model, and to show the effects of the insert nose radius on the stability limit. It is shown that very high errors in stability limit predictions can be caused when the true process geometry is not considered in the calculations. The proposed stability model predictions are compared with experimental results and an acceptable agreement is observed

Modeling dynamics and stability of 5-axis milling processes

5-axis milling is an important machining process for several industries such as aero-space, automotive and die/mold. It is mainly used in machining of sculptured surfaces where surface quality is of extreme importance. Being one of the most important prob-lems in machining, chatter vibrations must be avoided in manufacturing of these com-ponents as they result in high cutting forces, poor surface finish and unacceptable part quality. Chatter free cutting conditions for required quality with higher productivity can be determined by using stability models. Up to now, dynamic milling and stability models have been developed for 3-axis milling operations; however the stability of 5-axis proc-esses has never been modeled. In this paper, a stability model for 5-axis milling opera-tions is proposed. The model can consider the 3D dynamics of the 5-axis milling proc-ess including effects of all important process parameters including lead and tilt angles. Due to the complex geometry and mechanics of the process, the resulting analytical equations are solved numerically in order to generate the stability diagrams

Tornalama işlemlerinde süreç kararlılığının analitik olarak modellenmesi

Unstable cutting due to chatter vibrations is one of the most important problems during metal cutting operations. In this study an analytical method which takes the cutting geometry and nose radius into consideration is proposed. The analytically calculated absolute stable depth of cuts are compared with the chatter test results and good agreement is observed

Increasing productivity in high speed milling of airframe components using chatter stability diagrams

In this study, the application of chatter stability diagrams in industrial operations is presented with representative cases. Challenges arising due to the practical aspects of production systems are discussed in detail. Effects of tool, tool holder, spindle and CNC machine on chatter stability diagrams are presented. The implementation of the stability diagrams under such challenges is presented through real application examples showing significant reduction in machining times

Modeling of temperature distribution in orthogonal cutting with dual-zone contact at rake face

In this study, an analytical model is developed in order to calculate the temperature distribution in orthogonal cutting with dual-zone contact at the rake face. The study focuses on heat generation at the primary shear zone and at the rake face. The material behavior at the primary shear zone is represented by Johnson-Cook constitutive equation whereas the contact at the rake face is modeled by sticking and sliding friction zones. This new temperature distribution model allows obtaining the maximum temperature at the rake face and helps determining two dimensional temperature distribution in the chip. The simulation results obtained from the developed model are also compared with experimental results where good agreement is observed

Analytical and experimental investigation of rake contact and friction behavior in metal cutting

In this study, the friction behavior in metal cutting operations is analyzed using a thermomechanical cutting process model that represents the contact on the rake face by sticking and sliding regions. The relationship between the sliding and the overall, i.e. apparent, friction coefficients are analyzed quantitatively, and verified experimentally. The sliding friction coefficient is identified for different workpiece-tool couples using cutting and non-cutting tests. In addition, the effect of the total, sticking and sliding contact lengths on the cutting mechanics is investigated. The effects of cutting conditions on the friction coefficients and contact lengths are analyzed. It is shown that the total contact length on the rake face is 3-5 times the feed rate. It is observed that the length of the sliding contact strongly depends on the cutting speed. For high cutting speeds the contact is mainly sliding whereas the sticking zone can be up to 30% of the total contact at low speeds. From the model predictions and measurements it can be concluded that the sticking contact length is less than 15% for most practical operations. Furthermore, it is also demonstrated that the true representation of the friction behavior in metal cutting operations should involve both sticking and sliding regions on the rake face for accurate predictions. Although the main findings of this study have been observed before, the main contribution of the current work is the quantitative analysis using an analytical model. Therefore, the results presented in this study can help to understand and model the friction in metal cutting

Analytical modeling of cutting process mechanics and dynamics for simulation of industrial machining operations

Machining has been one of the most widely used manufacturing methods since the industrial revolution. Although the technological developments enabled machine tools to be stronger, work faster and produce more precise parts, the process parameters are still selected based on the experience. Selection of the acceptable or optimum parameters can only be possible by conducting extensive amount of experiments or by the help of the process models. The main aim of this thesis is to develop analytical models in order to represent the true mechanical and dynamical behavior of metals during cutting operations. Analytical models for the orthogonal and oblique cutting processes are proposed. These models are used as a base in order to simulate commonly used industrial operations such as turning and 5 axis milling. Moreover, an initial approach is proposed in order to model cutting behavior when the cutting tool has a hone radius. The proposed models are step ahead from the previous ones as they represent the rake face contact and friction in a more accurate manner, and have the ability to calibrate the material model parameters and friction by few tests. The dynamic behavior during cutting is also a very important aspect. For this, a stability model which includes multi-dimensional nature of the cutting process is proposed. All the proposed models are verified by experiments and overall good agreement is observed. These models can be applied to industrial machining operations yielding shorter machining times, better surface quality, longer tool life, stable operations and less manufacturing costs