41 Figure 4.7 Feed force variation in double tool turning of gray cast iron (0.08 mm/rev, 1 mm depth of cut and 2 mm distance between two cutting tools). 51 Figure 4.12 Flow chart of the cutting force evaluation subroutine 52 Figure 4.13 Thermogram of the mild steel workpiece during cutting (75 m/min cutting speed, 0.08 mm/rev, depth of cut 0.5 mm and the distance between the cut 10 mm tools).
List of Tables
Nomenclature
Introduction
- Parallel Turning Process
- Cutting Forces
- Cutting Temperature
- Cutting Tool Vibration
- Tool Wear
- Surface Roughness and Dimensional Deviation
- Objectives and Organisation of the Thesis
Tool thermocouple measures the average temperature of the contact area between the cutting tool and the work material. The condition of the cutting tool can be identified by the amplitude of the vibration signal.
Review of Literature
- Introduction
- Multi-tool Machining
- Cutting Force, Temperature and Tool Wear in Machining
- Cutting Force
- Cutting Temperature and Heat Generation
- Tool Wear and Tool Life
- Surface Roughness
- Dimensional Deviation
- Chip Morphology
- Cutting Tool Vibration
- Research Gaps
- Scope and Objectives of the Present Work
- Experimental investigation on cutting forces and temperature during double tool turning process
- Investigations on diametral error, tool wear and chip morphology during double tool turning process
- Experimental investigation on the effect of machining parameters on surface roughness generated during double tool turning process
It was concluded from the experiment that a warm s ot exists in the chi tem erature distribution. its hot s ot is located near the tool chi inter ace at a distance o µm from tool tip and the temperature is 825 C. The chip temperature increases with increase in cutting speed and it is very dominant in the runs o m/s. It was found that shear banding appears to be the predominant mechanism of chip segmentation up to a preheating temperature of 260 C. The fracture along the shear plane increases at 350 C. Preheating affects the shear band thickness to a considerable extent and it decreases with the increase in temperature.
Details of Experiments
- Introduction
- Development of Cutting Tool Fixture
- Experimental Setup
- Measurement of Cutting Forces and Cutting Temperature
- Measurement of Cutting Tool Vibration
- Measurement of Diametral Error of Workpiece and Cutting Tool Wear
- Surface Roughness Measurement
- Conclusion
The rear cutting tool has the same feed as the front cutting tool as they are mounted on the same carriage. The cutting depth of the rear cutting tool can be varied using an independent cross slide. The test set-up has been developed to measure cutting forces, cutting temperature, cutting tool vibration and workpiece diametral error.
Two dynamometers were used to simultaneously measure the cutting forces of the front and rear cutting tools. The dynamometer of the rear cutting tool is connected to an integrated four-channel charge amplifier (brand: Kistler, model: 5070), as shown in Figure 3.4 (c). The effect of cutting conditions on the cutting forces, cutting temperatures and vibrations of the cutting tool are discussed in Chapter 4.
Cutting Forces, Cutting Temperature and Cutting Tool Vibration in Double Tool Turning Process
Introduction
Experimental Procedure
- Experimental Setup
- Workpiece and Cutting Tool Material
- Cutting Conditions
Since the rear cutting tool is held in an inverted position, the direction of cutting force of the rear cutting tool is opposite to that of the front cutting tool. An accelerometer was used to measure the acceleration along the cutting direction for both the front cutting tool and the rear cutting tool. In the present work, an overhang distance of 30 mm is maintained for both the front and rear cutting tools.
The fundamental frequency of the front and rear cutting tool is obtained by excitation test and its value was found to be 337 Hz and 417 Hz respectively. Time-domain vibration signal from the front cutting tool during turning of gray cast iron (75 m/min cutting speed, 0.08 mm/rev feed, 1 mm depth of cut, 2 mm tool separation distance and 58 mm workpiece diameter). Frequency domain vibration signal from face cutting tool during turning of gray cast iron (75 m/min cutting speed, 0.08 mm/rev feed, 1 mm depth of cut, 2 mm tool separation distance and 58 mm workpiece diameter).
Results and Discussion
- Effect of Distance Between Cutting Tools on Cutting and Feed Forces
- Effect of Distance Between the Front and Rear Cutting Tools on the Cutting Temperature Tools on the Cutting Temperature
On the other hand, there is considerable variation of cutting forces with the cutting speed. So, in this condition, the cutting forces are also lower, although more than 185 m/min cutting speed. The reason for keeping a smaller distance between the cutting tools was to take some advantage of the preheating effect of front cutting tools to reduce the forces of rear cutting tools.
Reduction of cutting forces and feed was achieved for a cutting speed of 75 m/min. For the main cutting force at a cutting speed of 75 m/min, the values of b are 0.86 and 0.95 for the front and rear tools, respectively. In double tool turning, the effect of cutting speed and depth of cut on the cutting and feed forces are similar to the conventional turning process.
Estimation of Cutting Forces and Cutting Temperature in Single Tool Turning with a Simplified Model in Single Tool Turning with a Simplified Model
As a first approximation, the cutting temperature and strain rate are assumed to be constant during the process, but the strain varies from 0 to a maximum value. Cutting time can be considered the order of chip thickness divided by cutting speed. The cutting temperature in the primary shear zone is estimated as follows (Ghosh and Mallik, 2010).
The power during the plastic deformation process that occurs in the primary deformation zone is calculated as. whereFcandFf are the main cutting force and the friction force respectively, V is the cutting speed and increase the cutting ratio given by. 4.12). The flowchart of the main program for obtaining the cutting force by minimizing the shear angle using interval bisection method. At a separation distance of 50 mm, the vibrations are increased, which increased the main cutting force on both cutting tools.
The Influence of Machining Parameters on Cutting Tool Vibration in Double Tool Turning Process Tool Vibration in Double Tool Turning Process
From the figures it can be observed that, with the increase in cutting speed 75 to 185 m/min, cutting tool vibration decreases. Pre-cutting tool vibration amplitude in cutting direction (0.08 mm/revolution feed and 1 mm cutting depth). Rear cutting tool vibration amplitude in cutting direction (0.08 mm/revolution feed and 1 mm cutting depth).
As the distance between the front and rear cutting tool increases, the vibration of the cutting tool decreases. Thus, the present experimental research reveals the influence of cutting speed on the tool vibration of front and back cutting tools. Increasing the cutting speed reduces tool vibration for both the front and rear tools.
Conclusion
As the distance between the front and rear cutting tool increases, the cutting tool moves towards the chuck, and therefore the rigidity of the workpiece during machining is improved. Improved rigidity of the workpiece contributes to the reduction of the vibration of the cutting tool. The front cutting tool is held in a tool holder. In addition, the rear tool holder base plate is made of cast iron, which also helps to improve damping performance. Due to the superior damping properties of the material and the rigidity of the rear tool holder, it is found that the vibration of the rear cutting tool is far less than that of the front cutting tool.
The vibration of the front cutting tool is higher than that of the rear cutting tool for the selected cutting conditions. The cutting tool vibration of the front and rear cutting tool decreased with increasing cutting speed. Furthermore, the vibration of the front cutting tool was higher than that of the rear cutting tool for the selected cutting conditions while double turning the gray cast iron tools.
Diametral Error, Cutting Tool Wear and Chip Morphology in Double Tool Turning Process
- Introduction
- Experimental Procedure
- Results and Discussion
- The Effect of Depth of Cut
- Physical Explanation for the Improvement of the Accuracy through the Double Tool Turning through the Double Tool Turning
- Temperature during Double Tool Turning
- Cutting Tool Wear
- Chip Morphology
- Conclusion
During rotation, the cutting forces of the front part as well as of the rear cutting tool are measured. When the second (rear) cutting tool was engaged, the rear cutting tool limited the deflection of the workpiece due to the front cutting tool. Thus, it can be said that the greater depth of cut of the front cutting tool leads to greater diametral error.
The diameter error was proportional to the cutting force of the front cutting tool when the machining was carried out without the rear cutting tool. It was observed that flank wear on the rear cutting tool was less due to the heat generated by the front cutting tool and reduced coefficient of friction. The chips produced due to the rear cutting tool experienced higher temperature compared to the front cutting tool.
The Influence of Machining Parameters on Surface Roughness in Double Tool Turning Process
- Introduction
- Experimental Procedure
- Results and Discussion
- Effect of Cutting Speed on Surface Roughness
- Effect of Feed on Surface Roughness
- Effect of Depth of Cut and Tool Separation Distance on Surface Roughness
- Comparison of Surface Roughness Between Double Tool Turning Process and Conventional Turning Process Turning Process and Conventional Turning Process
- Cost Comparison of Single and Double Tool Turning Process Process
- Conclusion
It can be seen that the average surface roughness increased as the depth of cut increased. Variation of surface roughness with depth of cut for AISI 1050 steel (cutting speed 125 m/min and tool separation distance 2 mm). Variation of surface roughness with depth of cut for gray cast iron (125 m/min cutting speed and 2 mm tool separation distance).
For the same cutting conditions for gray cast iron, the average surface roughness value is 2.4 µm. Average surface roughness of twin tool turning and conventional turning process for gray cast iron. The average surface roughness increased with the increase in depth of cut for AISI 1050 steel for all the selected cutting conditions.
Conclusions and Scope for Future Work
Conclusions
- Effect of Cutting Parameters on Cutting Forces, Cutting Temperature and Cutting Tool Vibration
- Influence of Cutting Parameters on Diametral Error, Tool Wear and Chip Morphology Wear and Chip Morphology
- Effect of Cutting Parameters on Surface Roughness in Double Tool Turning Process Tool Turning Process
The influence of cutting speed on cutting tool vibration was evaluated during double tool turning of gray cast iron workpiece. It was observed that the cutting tool vibration of both the front cutting tool and rear cutting decreased with the increase in the cutting speed. The rear cutting tool vibration was found to be less than the front cutting tool vibration for the selected cutting conditions.
In the double tool turning process, the back cutting tool provided additional support for the workpiece and also removed the work material. The rear cutting tool was found to have less flank wear compared to the front cutting tool for the cutting conditions considered. During dual tool rotation there was a noticeable difference between the chips created by the front cutting tool and the back cutting tools.
Scope for Future Work
The distance between the cutting tools had no effect on the average surface roughness of either gray cast iron or AISI 1050 steelwork materials for all cutting conditions examined. Compared to the single tool turning process, the dual tool turning process produced a superior surface finish on the machined gray cast iron and AISI 1050 steel work surfaces. Lower average surface roughness for AISI 1050 steel and gray cast iron work materials was obtained in double tool turning compared to single tool turning.
Double tool turning leads to lower machining costs compared to conventional turning processes and is therefore economical.
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Publications from the Present Thesis
