Scratch Tests on Granite Using Micro-Laser Assisted Machining Technique

2015 ◽  
Author(s):  
Hossein Mohammadi ◽  
John A. Patten
Keyword(s):  
Laser Heating ◽  
Laser Power ◽  
Single Point ◽  
Brittle Materials ◽  
Past Research ◽  
Depth Of Cut ◽  
Shear Stresses ◽  
Granite Sample ◽  
Laser Assisted Machining ◽  
Scratch Tests

In this study, micro-laser assisted machining (μ-LAM) technique is used to perform scratch test on a granite sample. Rocks are generally considered as brittle materials with poor machinability and severe fracture can be resulted when trying to cut them due to their low fracture toughness. Due to increasing demand for these materials in industry with many applications, finding a fast and cost effective process with higher product quality seems essential. In past research in our research group, it has been demonstrated that machining of brittle materials such as semiconductors and ceramics in ductile regime is possible due to the high pressure phase transformation (HPPT) occurring in the material caused by the high compressive and shear stresses induced by a single point diamond tool tip. Scratch tests were performed on the granite sample and to further augment the process, traditional cutting is coupled with the laser to soften the material and get the higher depth of cut. In this research, results of scratch tests done on granite, with and without laser heating have been compared. The effect of laser heating was studied by verifying the depths of cuts for scratch tests with varying the laser power during the process. Microscopic images and three-dimensional profiles of cuts taken by using a white light interferometer were investigated. Results show that using laser can increase depth of cut and with 15 W laser power it is increased — for different regions of granite sample — from 25% to 95%.

Anisotropy Effect on Cutting Monocrystal Sapphire by Micro-Laser Assisted Machining Technique

2016 ◽  
Author(s):  
Hossein Mohammadi ◽  
John A. Patten
Keyword(s):  
Laser Heating ◽  
Removal Rate ◽  
Single Point ◽  
Brittle Materials ◽  
Single Crystal Silicon ◽  
Shear Stresses ◽  
Crystal Silicon ◽  
Anisotropy Effect ◽  
Fracture Damage ◽  
Scratch Tests

Machining of hard and brittle materials such as ceramics and semiconductors has been a challenge for many years. They have many applications in optics, MEMS and electronic industries due to their many desirable properties, such as being light weight, strong, and hard. Achieving good surface finish, avoiding surface and subsurface damage and at the same time achieving a high material removal rate are extremely challenging for these materials. Materials such as single crystal silicon and sapphire have a crystal orientation or anisotropy effect which makes their machining even more difficult. Because of this characteristic, their behavior is directional and they have different fracture toughness for each direction. In past works in our research group, it has been demonstrated that machining of brittle materials in ductile regime is possible due to the high pressure phase transformation (HPPT) occurring in the material caused by the high compressive and shear stresses induced by a single point diamond tool tip. In the current study scratch tests were performed on the monocrystal sapphire in four different perpendicular directions and to further augment the process, traditional cutting is coupled with a laser to heat and soften the material to either enhance the ductility, resulting in a deeper cut, or reducing brittleness leading to decreased fracture damage. Results of scratch tests, with and without laser heating, for different cutting loads have been compared. The effect of laser heating was studied by analyzing the image of cuts and verifying the depth of cuts which were made using varying laser power during the process. Microscopic images and three-dimensional profiles of the cuts taken by using a white light interferometer were investigated.

Single Point Diamond Turning of Silicon by Using Micro-Laser Assisted Machining Technique

2014 ◽  
Author(s):  
Hossein Mohammadi ◽  
H. Bogac Poyraz ◽  
Deepak Ravindra ◽  
John A. Patten
Keyword(s):  
Fiber Laser ◽  
Cutting Tool ◽  
Single Point ◽  
Diamond Turning ◽  
Depth Of Cut ◽  
Beam Diameter ◽  
Diamond Cutting ◽  
Laser Assisted Machining ◽  
Diamond Cutting Tool ◽  
Si Wafer

In this study, single point diamond turning (SPDT) is coupled with the micro-laser assisted machining (μ-LAM) technique. The μ-LAM system is used to preferentially heat and thermally soften the work piece material in contact with a diamond cutting tool. In μ-LAM the laser and cutting tool are integrated into a single package, i.e. the laser energy is delivered by a single mode fiber laser to and through a diamond cutting tool. This hybrid method can potentially increase the critical depth of cut (DoC), i.e., a larger ductile-to-brittle transition (DBT) depth, in ductile regime machining, resulting in a higher material removal rate (MRR). An IR continuous wave (CW) fiber laser, wavelength of 1064nm and max power of 100W with a beam diameter of 10μm, is used in this investigation. In the current study SPDT tests were employed on single crystal silicon (Si) wafer which is very brittle and hard to machine by conventional methods. Different outputs such as surface roughness and depth of cut for different set of experiments were analyzed. Results show that an unpolished surface of a Si wafer can be machined in one pass to get a very good surface finish. The Ra was brought down from 1.2μm to 275nm only in one pass which is a very promising result for machining the Si wafer.

Force Analysis, Mechanical Energy and Laser Heating Evaluation of Scratch Tests on Silicon Carbide (4H-SiC) in Micro-Laser Assisted Machining (µ-LAM) Process

2009 ◽  
Author(s):  
Amir R. Shayan ◽  
Huseyin Bogac Poyraz ◽  
Deepak Ravindra ◽  
Muralidhar Ghantasala ◽  
John A. Patten
Keyword(s):  
Laser Beam ◽  
Cutting Forces ◽  
Laser Heating ◽  
Cutting Tool ◽  
Work Piece ◽  
Force Analysis ◽  
Diamond Cutting ◽  
Laser Assisted Machining ◽  
Scratch Tests ◽  
Diamond Cutting Tool

The purpose of applying a laser beam in the micro-laser assisted machining (μ-LAM) process is to preferentially heat and thermally soften the surface layer of the work piece material (4H-SiC) at the interface with a diamond cutting tool. In the μ-LAM process the laser beam (1480 nm and 400 mW) is delivered to the work piece material through a transparent diamond cutting tool. Thus the cutting tool and the laser system are integrated and coupled; in contrast with other LAM processes where the cutting tool and laser are separate and distinct systems. Scratches were made on a 4H-SiC substrate using the μ-LAM process. The characteristics of the scratches, such as depth and width, are principally a function of the cutting tool geometry, applied forces, cutting speed, and laser heating. White light interferometer microscopy and Atomic Force Microscopy (AFM) techniques were used to measure the geometry (depth and width) of the scratches. Force analysis was carried out to evaluate the laser heating effect on the cutting forces and the measured depth of cut. The force analysis included an evaluation of the mechanical work, specific energy, and understanding the effect of laser heating on the cutting process. The scratch tests performed on 4H-SiC with the laser heating showed that there is a greater than 50% reduction in relative calculated hardness values of work piece material, resulting in a significant reduction in cutting forces.

An Experimental Study on Single Point Diamond Turning of an Unpolished Silicon Wafer via Micro-Laser Assisted Machining

2014 ◽  
Vol 1017 ◽  
pp. 175-180 ◽  
Author(s):  
Hossein Mohammadi ◽  
H. Bogac Poyraz ◽  
Deepak Ravindra ◽  
John A. Patten
Keyword(s):  
Single Point ◽  
High Hardness ◽  
Industrial Applications ◽  
Diamond Turning ◽  
Shear Stresses ◽  
Workpiece Material ◽  
Crystal Silicon ◽  
Laser Assisted Machining ◽  
Diamond Cutting Tool ◽  
Si Wafer

Single Pointe Diamond Turning (SPDT) of silicon can be an extremely abrasive process due to the hardness of this material. In this research SPDT is coupled with the micro-laser assisted machining (μ-LAM) technique to machine an unpolished single crystal silicon (Si) wafer. Si is increasingly being used for industrial applications as it is hard, strong, inert, light weight and has great optical and electrical properties. Manufacturing this material without causing surface and subsurface damage is extremely challenging due to its high hardness, brittle characteristics and poor machinability. However, ductile regime machining of Si is possible due to the high pressure phase transformation (HPPT) occurring in the material caused by the high compressive and shear stresses induced by the single point diamond tool tip. The μ-LAM system is used to preferentially heat and thermally soften the workpiece material in contact with a diamond cutting tool. Different outputs such as surface roughness (Ra, Rz) and depth of cuts (DoC) for different set of experiments with and without laser were analyzed. Results show that an unpolished surface of a Si wafer can be machined in two passes to get a very good surface finish.

Micro-Laser Assisted Feasibility Test on Soda-Lime-Glass

2013 ◽  
Author(s):  
Deepak Ravindra ◽  
Surya Chaitanya Ponthapalli ◽  
John Patten
Keyword(s):  
Laser Heating ◽  
Single Point ◽  
Soda Lime ◽  
Optical Quality ◽  
Soda Lime Glass ◽  
Workpiece Material ◽  
The Subject ◽  
Traditional Manufacturing ◽  
Feasibility Test ◽  
Scratch Tests

Soda lime glassis the most prevalent type of glass, used for glass containers and windowpanes. It is difficult to machine in traditional manufacturing processes due to its extreme hardness and brittleness. Good optical quality surfaces can be achieved by removing the material in a ductile manner. The strength, hardness and fracture toughness of the workpiece material are the governing factors that control the extent of brittleness. The main goal of the subject research is todetermine the effect of laser heating (using the μ-LAM process) on the material removal of sodalime glass using a single point diamond tool. The results show that the micro-laser assisted scratch tests were successful in demonstrating the enhanced laser heating and thermal softening in glass resulting in greater depths of cuts when compared to similar applied loads for cuts with no laser.

Laser-Assisted Machining of Reaction Sintered Mullite Ceramics

2001 ◽  
Author(s):  
Patrick A. Rebro ◽  
Yung C. Shin ◽  
Frank P. Incropera
Keyword(s):  
Cutting Force ◽  
Laser Heating ◽  
Laser Power ◽  
Material Removal ◽  
Operating Conditions ◽  
Laser Assisted Machining ◽  
Feed Force ◽  
Grinding Tool ◽  
Continuous Chip ◽  
Mullite Ceramics

Abstract The present study focuses on the evaluation of the laser-assisted machining (LAM) of pressureless sintered mullite ceramics. Due to mullite’s low thermal diffusivity and tensile strength, a new method for applying laser power is devised to eliminate cracking and fracture of the workpiece during laser heating. The LAM process is characterized by means of cutting force and surface temperature measurements for a variety of operating conditions. Estimated material removal temperatures and the ratio of the feed force to the main cutting force are used to determine material removal mechanisms and regimes for brittle fracture and semi-continuous and continuous chip formation. Surface roughness and subsurface damage are compared for typical parts produced by LAM and grinding. Tool wear characteristics are investigated for variations in laser power, and hence material removal temperature, during LAM of mullite with carbide tools.

Low Speed Motion Control Experiments on a Single Point Diamond Turning Machine Using CMAC Learning Control Algorithm

1997 ◽  
Vol 119 (4) ◽  
pp. 775-781 ◽  
Author(s):  
G. Larsen ◽  
S. Cetinkunt
Keyword(s):  
Machine Tool ◽  
Control Algorithm ◽  
Single Point ◽  
Brittle Materials ◽  
Diamond Turning ◽  
Servo Control ◽  
Depth Of Cut ◽  
Positioning Accuracy ◽  
Tool Positioning ◽  
Highly Nonlinear

Diamond turning of brittle materials such as glass, ceramic, germanium, and zinc sulfide has been of considerable research interest in recent years due to applications in optics and precision engineering systems. When diamond turning brittle materials, material removal should be kept within the ductile regime to avoid subsurface damage (Evans, 1991; Nakasuji et al., 1990). It is generally accepted that ductile regime machining of brittle materials can be accomplished using extremely low depth of cut and feed rates. Furthermore, the tool positioning accuracy of the machine must be in the nanometer range to obtain optical quality machined parts with surface finish and profile accuracy on the order of 10 nm and 100 nm respectively (Nakasuji et al, 1990, Ueda et al., 1991). Nanometric level positioning accuracy of the machine tool axes is difficult particularly at low feed rates due to friction and backlash. Friction at extremely low feed rates is highly nonlinear due to the transition from stiction to Coulomb friction, and as such is very difficult to model. Standard proportional-integral-derivative (PID) type controllers are unable to deal with this large and erratic friction within the requirements of ultra precision machining. In order to compensate the effects of friction in the machine tool axes, a learning controller based on the Cerebellar Model Articulation Controller (CMAC) neural network is studied for servo-control. The learning controller was implemented using “C” language on a DSP based controller for a single point diamond turning machine. The CMAC servo control algorithm improved the positioning accuracy of the single point diamond turning machine by a factor of 10 compared to the standard PID algorithm run on the same machine and control system hardware.

Simulation and Experimental Study on Temperature Fields for Laser Assisted Machining of Silicon Nitride

2009 ◽  
Vol 419-420 ◽  
pp. 521-524
Author(s):  
Xue Feng Wu ◽  
Hong Zhi Zhang ◽  
Yang Wang ◽  
Chao Xie
Keyword(s):  
Silicon Nitride ◽  
Laser Heating ◽  
Laser Power ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Transfer Model ◽  
Beam Diameter ◽  
Power Laser ◽  
Laser Assisted Machining ◽  
Translational Speed

Laser assisted machining (LAM) is an effective method machining difficult-to-machine materials such as ceramics which uses a high power laser to focally heat a workpiece prior to material removal with a traditional cutting tool. A laser assisted machining experiment system was set up and a transient, three-dimensional heat transfer model was developed for LAM of silicon nitride using Finite Element Method to understand the thermal process of laser heating. The model was based on temperature-dependent thermophysical properties and the heat generated was neglected due to cutting which is assumed to be small compared to the heat generated by laser heating. The experiments were carried out to investigate the effects of operating parameters, such as laser power, laser translational speed, rotational speed, laser beam diameter and preheating time on temperature distribution. An infrared radiation thermometer was used to measure the surface temperature histories and the experimental results were in good agreement with predictions. The laser power and laser translational speed have the greatest influence on the temperature.

Experimental Investigation of Effect of the Laser-Assisted Finish Turning of Ti-6Al-4V Alloy on Machinability Indicators

2017 ◽  
Vol 261 ◽  
pp. 135-142 ◽  
Author(s):  
Witold F. Habrat
Keyword(s):  
Titanium Alloy ◽  
Cutting Force ◽  
Laser Power ◽  
Laser Scanning ◽  
Experimental Studies ◽  
Cutting Speed ◽  
Depth Of Cut ◽  
Finish Turning ◽  
Laser Assisted Machining ◽  
Melted Zone

In this paper, the experimental studies of the finish turning of Ti-6Al-4V titanium alloy with the laser-assisted machining were described. For the tests, a cemented carbide tool was used. The influence of the laser heating on the microstructure of Ti-6Al-4V titanium alloy for kinematics corresponding with the turning process was determined. For a laser scanning rate of 80 m/min and laser power 1200W, the maximum depth of the melted zone was about 50 μm. The beneficial effect of laser assisted machining on components of the cutting force was established. For a cutting speed of 80 m/min, feed rate 0.1 mm/rev, depth of cut 0.25 mm and laser power 1200 W, over 60% reduction of the tangential components of cutting force was observed. The chip-breaking effect for the conventional and the laser-assisted processes was determined. Roughness parameters of the surface after the conventional and laser-assisted turning are compared.

Influence of Ultrasonic Assistance on Material Removal Mechanism of Hard and Brittle Materials Based on Single-Point Scratch

2011 ◽  
Vol 487 ◽  
pp. 413-418 ◽  
Author(s):  
Feng Jiao ◽  
Bo Zhao
Keyword(s):  
Material Removal ◽  
Single Point ◽  
Brittle Materials ◽  
Shielding Effect ◽  
Depth Of Cut ◽  
Cutting Depth ◽  
Critical Cutting Depth ◽  
Material Hardness ◽  
Ultrasonic Assisted ◽  
Hard And Brittle Materials

In order to deeply study the influence of ultrasonic assistance on material removal characteristics of hard and brittle materials, a series of ultrasonic assisted single-point scratch experiments have been carried out in this paper. Experimental results show that the assisted ultrasonic vibration is benefit to increase the critical cutting depth and enlarge the ductile regime of material removal. The main reason can be explained as the influences of blank cutting phenomenon, the decrease of the normal cutting force under the same depth of cut, the decrease of the material hardness under ultrasonic excitation and the shielding effect of lateral crack.

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