Model Of Cutting Process Research Articles

A study of cutting process stability of a boring bar with active dynamic absorber

In this paper, the use of an active dynamic absorber to suppress machine tool chatter in a boring bar is studied. The vibrations of the system are reduced by moving an absorber mass using an active device such as an piezoelectric actuator, to generate an inertial force that counteracts the disturbance acting on the main system. An equivalent lumped mass model of a boring bar with active dynamic absorber is considered. A cutting process model that considers the dynamic variation of shear and friction angle, that causes self-excited chatter during the cutting process, is applied to the lumped mass model. The theory of regenerative chatter is also applied to the model. Stability boundaries have been calculated for maximum permissible width of cut as a function of cutting speed. A comparison of the boundaries for chatter-free cutting operation of a plain boring bar, a boring bar with passive tuned dynamic absorber and a boring bar with active dynamic absorber is provided in this paper. The comparison shows that a substantial increase in the maximum permissible width of cut for stable cutting operation, over a range of cutting speeds, is obtained for a boring bar equipped with an active dynamic absorber.

On-Line Tool Wear Estimation Using Force Measurement and a Nonlinear Observer

On-line tool wear monitoring in metal-cutting operations is essential for an on-line process optimization. In this paper, tool flank wear is estimated on-line by utilizing a nonlinear observer with the feedback of cutting force measurements. Based on a previously developed cutting process model for turning, a nonlinear observer is designed such that the estimated flank wear converges to the actual flank wear development in the presence of poor initial estimates. The stability analysis for the resulting observer error dynamic system is carried out using a physical limitation of the actual flank wear development and the Total Stability Theorem. The experimental results show that the proposed nonlinear observer estimates the flank wear quite well not only in the presence of poor initial estimates but also in the presence of unexpected fluctuations in the cutting force measurements. However, the method has drawbacks resulting from difficulties in obtaining accurate model parameters. An adaptive version of the presented nonlinear observer, periodically calibrated by off-line direct tool wear measurements using computer vision, is considered to be a promising strategy for industrial implementation.

Operation Planning Based on Cutting Process Models

This paper describes model based operation planning for pocket milling operations. The tool path and cutting conditions are determined based on the geometric model of workpieces and the physical models of the cutting process. The tool path is generated by using the Voronoi diagram of a cutting area. Cutting conditions to achieve the maximum metal removal rate are determined by evaluating the physical models of cutting torque, chatter vibration, and machining error. To maintain a favorable cutting state, the radial depth of cut is controlled by modifying the tool path distance at the circle path segment and by adding additional tool path segments at the corner. Examples are shown to demonstrate the effectiveness of the method.

Real-Time Model Reference Adaptive Control of 3-D Sculptured Surface Machining

The paper deals with a new method for the productive machining of molds and dies which have an artistic geometry characterized by sculptured surfaces. The method developed is referred to as a “Real Time Model Reference Adaptive Control” which autonomously adjusts the optimal feedrate such that the material removal should always be maximized with respect to the capability of a given tool and a given geometry of a workpiece by using a real time simulation of a software-based cutting process model. The practical feasibility of the proposed scheme has been verified through experiments performed on the prototyped system.