Investigation into deep hole drilling of austenitic steel with advanced tool solutions

Deep hole drilling processes for high-alloyed materials are characterised by worn guide pads and chatter vibrations. In order to increase feed rates, process stability and bore quality in STS deep hole drilling, various investigations were carried out with adjustments to the tool. First, a new process chain for the production of tribologically optimised guide pads and their effects on the guide pad shape is described in detail. The results of these studies show that the shape change in the area of the axial run-in chamfer through a micro finishing process leads to a better bore hole quality. Furthermore, the influence of guide pad coating and cooling lubricant on the deep hole drilling process was investigated. In addition, the machining of the austenitic steel AISI 304 is analysed by using a conventional steel boring bar and an innovative carbon fibre reinforced plastic (CFRP)-boring bar. While the conventional drill tube oscillates with different eigenfrequencies, the CFRP-boring bar damps chatter vibrations of the drill head and stabilises the process. Even at higher feed rates up to f = 0.3 mm, it is possible to machine austenitic, difficult-to-cut-materials with significantly reduced vibrations.

Investigating the Cutting Force Monitoring System in the Boring Process

Due to the closed environment during deep hole boring, it is impossible to observe the working state of the boring bar. Studies show that monitoring the cutting force is the most direct and effective way to reflect the processing status. In this regard, a cutting force monitoring system is designed in the present study for the boring process. The main idea of the designed monitoring system is the piezoelectric effect of the strain gauge. When the tool tip is subjected to the cutting force, the sensor deforms and the strain sensor generates a voltage signal. Accordingly, the cutting force can be obtained by establishing the correlation between the voltage and the applied cutting force. The force of the boring bar and the output of the sensor were analyzed, and an experimental platform for monitoring the boring force was built. This method is applied in a case study and the obtained results demonstrate that the developed cutting force monitoring system has good compatibility, high precision and good dynamic characteristics. It is found that that the measurement error of the designed system in the boring process is less than 9.18%, which meets the accuracy requirements of measurements in the dynamic cutting force under machining conditions.

3D MODELING, SIMULATION AND ANALYSIS OF ANTI-VIBRATION BORING BAR

This study presents the capabilities of the engineering dynamic analysis according to the Finite Elements Method (FEM), demonstrated on a 3D virtual prototype of a part "Anti-vibration boring bar" for lathe. The analysis is performed with help of CAE system Ansys. The modal frequencies are determined which are necessary for optimizing the constructive parameters of the product during the design stage.

HIGH RIGIDITY AND VIBRATION ENDURANCE BAR FOR DEEP HOLES

Different constructions of bars are analyzed in the article, all of which are based on the idea of creating prestressed state in material. Improved construction of bar is proposed for equable spreading of elasticity zone along axis of boring bar.

THE EFFECT OF FEED RATE AND CUTTING SPEED TO SURFACE ROUGHNESS DURING HOLE BORING OF ALUMINUM WITH ANTI-VIBRATION BORING BAR

this study is focusing on the experimental investigation of the effects of cutting parameters on surface roughness during hole boring of 8062 aluminums with anti-vibration boring bar on lathe. Several experiments were conducted with different cutting conditions. Based on the results and using “Minitab 19” software, a mathematic model was made to predict the surface quality in connection with different cutting conditions. Finally, an experiment analysis was carried out to verify the analytical results.

Dynamic analysis and vibration control of two-degree-of-freedom boring bar with fractional-order model of magnetorheological fluid

The dynamic analysis and vibration control of a kind of damping boring bar system with magnetorheological fluid absorber are studied. A two-degree-of-freedom dynamic model of boring bar with magnetorheological fluid dynamic vibration absorber is established, in which the magnetorheological fluid damper adopts the fractional-order Bingham model. The forced vibration of the system is studied, and the approximate analytical solution is obtained by the averaging method. By comparing the analytical solution with the numerical solution, the accuracy of the analytical solution is proved by their high degree of fit. And the parameters of boring bar system are optimized by using the analytical solution. To reduce the amplitude of the system, a semi-active control strategy of modified relative velocity method is used to suppress the resonance response of the boring bar. Under the semi-active relative velocity control, the approximate analytical solution of the system is also obtained by means of averaging method. The stability of the system under semi-active control is analyzed by using the Lyapunov method. Compared with passive control, the semi-active relative velocity control has a very great effect on the vibration amplitude suppression. The results can provide a reference for the study of dynamics and vibration control of the systems with magnetorheological fluid control.

Investigation Into Deep Hole Drilling of Austenitic Steel With Optimised Tool Solutions

Deep hole drilling processes for high-alloyed materials are characterised by worn guide pads and chatter vibrations. In order to increase feed rates, process stability and bore quality in STS deep hole drilling, various investigations were carried out with adjustments to the tool. First, a new process chain for the production of tribologically optimized guide pads and their effects on the guide pad shape is described in detail. The results of theses studies show that the shape change in the area of the axial run-in chamfer through a micro finishing process leads to a better bore hole quality. Furthermore, the influence of guide pad coating and cooling lubricant on the deep hole drilling process was investigated. In addition, the machining of the austenitic steel AISI 304 is analyzed by using a conventional steel boring bar and an innovative CFRP-boring bar. While the conventional drill tube oscillates with different eigenfrequencies, the CFRP-boring bar damps chatter vibrations of the drill head and stabilizes the process. Even at higher feed rates up to f = 0.3 mm, it is possible to machine austenitic, difficult-to-cut-materials with significantly reduced vibrations.