Edge Chipping Research Articles

An experimental study on tool wear behaviour in micro milling of nano Mg/Ti metal matrix composites

With the development of metal matrix composites (MMCs), the mechanical properties of MMCs with a small volume fraction of nano-sized particles were found to be even superior to that with a larger content of micron-sized particles. However, the improved mechanical properties of MMCs bring tremendous challenges such as premature tool failure in Ti machining process. This study exhibits an investigation on tool wear in micro milling of magnesium-based MMCs reinforced with 1.98 Vol.% of nano-sized titanium particles using 0.5-mm diameter two-flute tungsten carbide micro endmills. The tool wear was characterised both quantitatively and qualitatively by observing tool wear patterns and analysing the effect of cutting parameters on flank wear, reduction in tool diameter, cutting forces, surface roughness, and burr formation. A finite element model was established to understand matrix deformation and interaction between tool-particle and further explain the tool wear phenomena observed. Additionally, cutting performance using AlTiN coated and uncoated was also investigated. The results indicated that the main wear mechanisms were identified as flank wear and edge chipping due to abrasive wear and chip adhesion in uncoated micro endmills. These wear mechanisms were confirmed by chip formation process produced by finite element modelling (FEM). It was also observed that the largest tool wear occurred at the smallest feed per tooth (0.75 μm/tooth) and smallest wear occurred at the largest feed per tooth (3 μm/tooth). Also, the effect of BUE on tool wear and surface generation was studied.

Tool wear behaviors and corresponding machined surface topography during high-speed machining of Ti-6Al-4V with fine grain tools

Abstract Rapid tool wear of machining Ti-6Al-4V causes the surface deterioration and manufacturing cost increasing. This work studied tool wear behaviors and machined surface topography during high-speed machining of Ti-6Al-4V. Firstly, detailed wear of tool rake face and flank face were studied in wear topography and chemical elements. Tool rake face was related to the combined effects of adhesion-diffusion-abrasion wear, while predominant wear mechanism of flank face was adhesion-abrasion. The cutting edge chippings and deformation destroyed the structure and strength of cutting tools. Secondly, the effects of tool wear on the corresponding surface topography were evaluated in surface roughness and defects. The tool flank wear should be controlled in less than 0.2 mm from the viewpoint of getting better surface topography.

Ultrasonic assisted high rotational speed diamond machining of dental glass ceramics

Subsurface damage and edge chipping remain a persistent technical challenge for the abrasive machining of dental restorations made from glass ceramics, and they impede the fabrication of long-lasting dental restorations. This paper reports on an integration of ultrasonic assistance to dental high-speed rotary abrasive machining for improvement of the surface quality of glass ceramics. An ultrasonic assisted computer-controlled high-speed rotary cutting apparatus was designed and fabricated with functions of ultrasonic vibration, automatic cutting, and force measurement. A multi-phase feldspar glass ceramic with the highest brittleness among glass ceramics was selected for the study. Machining forces, surface roughnesses, and edge chipping damage were evaluated for a range of cutting conditions with and without ultrasonic vibrations. Our most significant finding is that ultrasonic assisted machining led to a clear and consistent reduction of edge chipping and thus subsurface damage. Ultrasonic machining also achieved significant reductions in normal and tangential forces, and surface roughness at higher removal rates (p < 0.05). Our results suggest that ultrasonic assisted dental machining may be a way to improve quality and lifetime of ceramic dental restorations, whose failures are rooted in chipping damage and surface flaws using current machining techniques.

Investigating tool wear mechanisms in machining of Ti-6Al-4V in flood coolant, dry and MQL conditions

The objective of this study is to identify and explain tool wear mechanisms that dominate during machining of titanium alloy Ti-6Al-4V in dry, flood coolant, and minimum quantity lubrication (MQL) conditions. A series of experiments were conducted using end milling of Ti-6Al-4V by varying feed rate and depth of cut, while the cutting speed was kept constant at comparatively higher cutting speed. Both uncoated and titanium aluminum nitride (TiAlN)-coated carbide tools were used for machining Ti-6Al-4V at the same settings of parameters. It was observed that abrasion was the most dominant tool wear mechanism for all dry, flood coolant and MQL machining conditions. Edge chipping and tool nose wear were the next dominating tool wear mechanisms in conventional flood coolant machining, which may be associated with the thermal fatigue caused by the periodic cooling of tool tip from the high temperature generated during machining. On the other hand, adhesion was the second most dominant tool wear mechanism in the dry machining. Both the edge chipping and adhesion of chips to the cutting tools were reduced significantly in MQL machining. The delamination of coating film was observed when TiAlN-coated carbide tools were used for machining Ti-6Al-4V. The delamination was more significant in wet and MQL machining compared to dry machining, indicating the effectiveness of coated tools in dry machining condition compared to wet and MQL machining conditions. Among three conditions, MQL provided the least occurrences of tool wear, indicating suitability of MQL in productive machining of titanium alloys.

A Chipping reduction approach in Rotary Ultrasonic Machining of Advance Ceramic

Machining of ceramic material is difficult to achieve with conventional machining methods. The rotary ultrasonic machine plays a crucial role in the machining of such harder materials. During machining of ceramics, the edge chipping is one of the crucial factors which affect the quality of the product. This factor must be at the lowest level of better quality and minimum wastage. This paper demonstrates the mechanism of fracture and effect of support length on edge chipping size during the experimental study of advance ceramic (Al2O3). The investigation results showed that edge quality can be improved by increasing the support length to the workpiece.

A Study on CVD Diamond Coated Cutting Tools Wear Performance using Vibration and Acoustic Emission Signals

Maximizing the use of cutting tool inserts and effectively utilizing them in the automated manufacturing process is critical to reducing machine down time and improving part quality. Early removal of tooling inserts can lead to less productivity and increased costs. Utilization of tooling inserts beyond its stipulated life time can cause dimensional inaccuracies and undesirable surface deterioration. Optimizing the cutting tool insert life will require an appropriate method for finding out remaining useful life of tooling inserts based on respective machining conditions. In this present work, acoustic signals and vibration signals were acquired during machining to monitor the tool failure. The change in signal variations in acoustic emission and vibration signals were correlated to the corresponding tool wear during machining. In this regard, machining experiments were performed on AA2124/25%/SiCp material using four different CVD Diamond coated tungsten carbide cutting tools (MCD-Microcrystalline diamond coating, NCD-Nano-crystalline diamond coating, BDD-Boron doped diamond coating, BMTN-Boron doped graded layer diamond coating) at an suitable cutting conditions. The results indicated that burst type AE signals observed in MCD and NCD coated tools correlated to chip entanglement, edge chipping, and the corresponding vibration analysis shows a similar increase in amplitude in the final cutting pass. However, there was no abnormality seen in BDD and BMTN coated tools signal variation which indicates least tool wear.

Drilling studies on Particle Board composite using HSS twist drill and spade drill

Composite materials are finding increased application in different engineering fields due to its favorable properties. In composites, wood based composites are natural composites in which particle board (PB) is extensively used in domestic and commercial purposes mainly in wood based furniture. Among different machining processes, drilling is the most generally used machining process in wood working industry for assembly operations. But during drilling, delamination at entry and exit sides of a hole, edge chipping, surface damage, etc are the major damages occur during drilling of PB composites.Therefore, study of effect of drilling parameters and cutting environment on machining of PB composite is an important area and it needs a detailed analysis. In this study, drilling of PB composite using HSS twist drill and spade drill of ∅ 10 mm is investigated. The objectives of the study are to measure and analyze the effect of process parameters on surface roughness and drilling time of PB for the two different drills. Process parameters considered are spindle speed (rpm), feed (mm/rev) and machining environment (Dry, Flood coolant and Kerosene).Drilling experiments were performed on 10 mm thickness board based on L9 orthogonal array using twit drill and spade drill with the total of 18 experiments and average surface roughness (Ra) of all drilled holes surface was measured. From the results obtained with twist drill, machining time is decreased from 11.81 to 2.03 seconds with an increase of speed (S) and feed (f) for kerosene. Similarly, machining time is decreased from 18.54 to 2.97 sec with increase of “S” and “f” for the same kerosene with spade drill. With increase of “S” and “f” using kerosene, the Ra is decreased from 15.593 to 9.711 µm for twist drill. In the same way, the Ra is decreased from 15.3 to 10.083 µm with increase of “S” and “f” using kerosene for spade drill.

Influence of Edge Condition of Cutting Tool on Cutting Force and Surface Roughness While Machining Aluminum-Fly Ash Composites

Metal Matrix Composites (MMCs) are adopted to fabricate machine parts and automobile parts owing to its properties, however the MMCs are required to be machined to obtain final component. While turning these MMCs, the cutting tools fail due to notch wear followed by built up edge and macro chipping which leads to increase of cutting force and surface roughness. Hence present research paper is aimed at study of the cutting force and surface roughness while turning Al6061 Fly ash composite using CGGN120304 style, edge rounded carbide inserts. The cutting speed selected was between 150m/min to 650m/min in steps of 125m/min, feed of 0.15 mm/revolution, 0.2 mm/revolution, 0.25 mm/revolution and constant radial depth of cut of 1.0 mm. Experimentation were carried out following ISO3685 standards. The experimental results revealed that while turning composites, Surface roughness, Cutting force and burr folding were found lower when K10 grade carbide insert used with lower edge rounding. Cutting edges was found intact with 80 micron and 100 micron edge rounding at all machining parameters.

Machinability Studies on Stainless steel by abrasive water jet -Review

Stainless Steels are alloy steels with high resistance to corrosion and heat, strength, durability, low maintenance, fabrication flexibility and high hardness. Many studies have demonstrated the advantages of using Stainless Steels in the field of automotive and other industrial applications. Stainless steels are generally more challenging to machine due to high alloying content. The major problems with conventional machining of Stainless Steels are high work hardening, poor chip breaking, usage of various tools with different tool geometry, application of huge coolant supply during machining. These problems results in increased production time and cost. While machining Stainless Steels it is important to ensure that there is no machine vibration or tool chatter and conventional tools are prone to edge chipping. Because of these problems other alternate techniques are considered for machining of Stainless Steel. Abrasive Water Jet Machining (AWJM) is an effective method for machining, cutting and drilling of stainless steels. AWJ machining is a non-conventional machining process where material is removed by erosion of high velocity abrasives entrained in water jet. This paper discusses the machining studies on Stainless Steels by Abrasive Water Jet.

Reducing Edge Chipping of Micro-holes with Electrophoresis-assisted Micro-ultrasonic Machining

This paper proposes the method of electrophoresis-assisted micro-ultrasonic machining (EPAMUSM) to reduce edge chipping when machining holes in hard and brittle materials. By utilizing the electrophoresis effect of ultra-micro abrasive particles in work solution and the effect of electrophoresis-assisted electrical field, the abrasive particles in the solution can be gathered around the micro-tool, thereby reducing the edge chipping caused by direct hammering between the tool and the workpiece. EPAMUSM helps to improve the utilization of the abrasive particles and significantly improves the material removal rate compared with micro-ultrasonic machining (MUSM). Both single-factor and orthogonal experiments were performed to verify the method. The results show that abrasive particles gathered around the tool with the assistance of the electrophoretic effect and electrical field, and that the utilization of abrasive particles was enhanced during MUSM, which weakened the direct hammering between the tool and the workpiece. With the best parameter values (a machining force of 0.1 N, an abrasive-particle diameter of 0.1 μm, an electrical field voltage of 5 V, and an ultrasonic power of 21 W), micro-holes of 100 μm in diameter could be generated well in monocrystalline silicon. Compared with conventional MUSM, there was less chipping around the hole edge and the quality and material removal rate were improved greatly.

Pomiar geometrii i ocena powierzchni narzędzi za pomocą mikroskopu różnicowania ogniskowego

Possibility of measuring the geometrical features of cutting tools and surface roughness by means of a focus-variation microscope is presented. This technology supports manufacturers in the development of new products and in the quality control of cutting edges and geometry. All measurements, regardless of the application site, are characterized by high resolution, repeatability and traceability. Furthermore, focus-variation microscopy allows measurement of surface irregularities and edge chipping, giving a wide range of possibilities for numerical analysis of edge quality. The technology also provides the stability of measurement results obtained even under production conditions.

A study on the edge chipping according to spindle speed and inclination angle of workpiece in laser-assisted milling of silicon nitride

Ceramics are difficult to machine due to their high hardness and brittleness. As an effective method for machining ceramics, laser-assisted machining (LAM) has been studied by many researchers. In particular, many studies of methods to improve the machinability of silicon nitride using LAM have been performed. However, there is little research on the effect of the inclination angle of the workpiece, because varying the angle increases the difficulty of controlling the laser preheating and tool path. This paper investigates the effect of preheating temperature, spindle speed and inclination angle of the workpiece on edge chipping of silicon nitride in an effort to obtain an enhanced surface finish using laser-assisted milling (LAMill). The machining conditions were determined by considering the parameters that can reduce edge chipping using related theory. Experimental results showed a reduction in edge chipping based on increases in preheating temperature, spindle speed and inclination angle of the workpiece. Also, by increasing the spindle speed and the inclination angle of the workpiece, surface roughness was decreased due to reduction in the cutting force. The energy efficiency of LAMill by comparing the specific cutting energy according to the machining conditions is analyzed.

Thermoelastic Dissipation in Micromachined Birdbath Shell Resonators

Many MEMS gyroscopes rely on micro mechanical resonators to measure angular rotation. Maximizing their quality factor ( $Q$ ) will help improve accuracy. There are several energy dissipation mechanisms that limit $Q$ . This paper studies the role of thermoelastic dissipation (TED) in micro birdbath shell resonators. Fully coupled thermo-mechanical equations of physical behavior are solved for these shells using a finite-element method. Furthermore, an analytical model is developed to predict TED. The effects of material properties, shell geometry, edge chipping around the shell rim, trimming approaches, thin-film coatings, and operating temperature on thermoelastic $Q$ ( $Q_{{TED}})$ are studied. It is found that the shell material properties and rim thickness have significant impact on $Q_{{TED}}$ . However, edge chipping and most of the shell geometrical parameters do not have large impact. Additionally, this paper shows that some trimming approaches, such as forming grooves along the rim, can improve $Q_{{TED}}$ . A study of the effect of metal coatings on the resonator on $Q$ shows that the coating thickness and material are important factors affecting $Q$ and $Q_{{TED}}$ . The results presented in this paper provide guidelines for the design of other similar high- $Q$ resonators. [2016–0027]

Cutting performance of tools made of different materials in the machining of 42CrMo4 high-strength steel: a comparative study

This research conducted a comparative study on the wear mechanisms and cutting performance of the YT15 cemented carbide tool, KY1615 ceramic tool, and Ti(C,N)-based cermet tools including T1500A, self-made TMWNC, and TMWC in the machining of 42CrMo4 high-strength steel. The results indicated that the cemented carbide tool presented severe notch wear and chipping accompanied by adhesive wear, as a result of the continuous impact from chips and workpiece burrs and the bigger friction force with the workpiece. The ceramic tool exhibited serious abrasive wear and adhesive wear with obvious crater wear on the rake face and furrow-like scratches on the flank face, due to the bigger cutting force, higher cutting temperature, and the lack of binder phase in the tool material. The wear mechanism of Ti(C,N)-based cermet tools was mainly abrasive wear with crater wear and flank wear in virtue of the smaller affinity with the workpiece material, smaller friction coefficient against steels, and better oxidation resistance. At the different cutting speeds, the comprehensive cutting performance of cermet tools was better than that of cemented carbide tools and ceramic tools, indicating the advantage of cermet tools in the machining of 42CrMo4 high-strength steel. Meanwhile, when the cutting speed was lower at 150 m/min, the comprehensive cutting performance of self-made cermet tools with better edge chipping resistance and notch wear resistance was better than that of the commercially available cermet tool.

Unified curve of the edge chipping resistance in connection with the rounding radius indenter

The results of a combined computational and experimental research into the fracture resistance of ceramic materials by specimen edge chipping are provided. The chipping was performed with conic diamond indenters that had spherical tip radii of 100, 200 and 400μm. The computational analysis was conducted on the basis of finite element modeling by means of ANSYS software. The parameters of the basic distances in an analysis of the stress, strain, and displacement fields in the chipping zone for the tests (upper and lower limit) have been established for the above-mentioned indenters in order to ensure the correct comparative assessment of the materials under research. Unified curves of edge chipping resistance of the ceramic materials have been obtained for the indenters with various spherical tip radii.

Wear characteristics of polycrystalline diamond tools in orthogonal cutting of CFRP/Ti stacks

CFRP/Ti stacks have become a viable alternative to conventional composite laminates and metal alloys in various aerospace applications because of their enhanced mechanical properties and improved structural functions. Machining these multilayer stacks with acceptable quality still remains a great challenge for the modern manufacturing sectors due to the ineffective management of the tool wear performance resulting from the varying properties of the stacked constituents. This paper describes, on a fundamental basis, the wear characteristics of polycrystalline diamond (PCD) tipped tools during the orthogonal cutting of CFRP/Ti stacks. Two cutting sequence strategies, i.e., cutting from CFRP to Ti and cutting from Ti to CFRP, were implemented throughout the cutting tests. The experimental results confirm the predominance of the cutting sequence strategy in affecting the CFRP/Ti chip separation and the machined surface quality. The chip adhesion is a most influential factor leading to the disparate influences of the two cutting sequence strategies on the CFRP/Ti cutting responses. The PCD tool suffers severe crater wear due to the Ti phase cutting, while it undergoes minor flank wear owing to its superior wear resistance against abrasive carbon fibers. The wear signatures on the tool-chip contact zone via the scanning electron microscope (SEM) observation reveal that the Ti phase cutting dominates the formation of the tool crater wear land. The edge chipping occurs mainly due to the sudden force variation in the CFRP/Ti interface machining and the inherent brittleness of the PCD material. The fiber orientation seems to have a great impact on the wear behavior of utilized PCD tools by altering the tool-chip contact length.

Fabrication and cutting performance of Ti(C,N)-based cermet tools used for machining of high-strength steels

Two kinds of Ti(C,N)-based cermet tools, namely TMWNC and TMWC, were fabricated for the machining of high-strength steels. This research investigated the cutting performances of both tools in terms of chip morphology, cutting force, cutting temperature, and tool wear and failure mechanisms. The results reveal that at the same cutting speed, the life of TMWC tool is longer than that of TMWNC tool with lower cutting force and higher cutting temperature than those of TMWNC tool. For TMWNC tool, at a lower cutting speed of 150m/min, the tool failure is caused by abrasive wear. And when the cutting speed increases further, the surface flaking and nose breakage occur due to the comprehensive effects of adhesive wear, abrasive wear and thermal-mechanical fatigue. While for TMWC tool, the tool wear is severe with chipping, as a result of adhesive wear and abrasive wear. The research has proven the application feasibility of TMWNC and TMWC tools in the machining of high-strength steels. The TMWNC tool with higher fracture toughness presents better edge chipping resistance, and the TMWC tool with higher hardness and hot hardness exhibits better resistance against breakage.

Edge chipping mechanism and failure time prediction on carbide cemented tool during drilling of CFRP/Ti stack

To investigate the edge chipping during drilling of the CFRP/Ti stack with carbide cemented tools, a drilling experiment was carried out and a tool failure model was proposed. Thrust force, drilling temperature, and tool wear were analyzed. A tool stressing model and a tool failure model of edge chipping were constructed respectively. On the basis of these, the prediction model on the edge chipping was established to forecast the failure time. Drilling temperature, Vickers hardness, and cutting speed were considered during the prediction model building. The results demonstrate that adhesive wear has a great influence on the edge chipping. The damage of adhesive wear for tool rake face leads to the load variation on rake face and the initial crack. Under the action of shear stress, the crack starts at rake face and then expands to the flank face, resulting in tool edge chipping. The affinity interaction (between titanium alloy with carbide cemented) and the thermal residual stress are two critical factors for tool edge chipping. Tear easily occurs inside the binding phase or at the boundary between hard phase and binder phase. As the drilling temperature increases, the hardness of the carbide cemented will gradually decrease. The prediction result of failure time is similar to the experimental result, and the effectiveness of the prediction model is verified.

Machinability of CAD-CAM materials

Statement of problemAlthough new materials are available for computer-aided design and computer-aided manufacturing (CAD-CAM) fabrication, limited information is available regarding their machinability. The depth of penetration of a milling tool into a material during a timed milling cycle may indicate its machinability. PurposeThe purpose of this in vitro study was to compare the tool penetration rate for 2 polymer-containing CAD-CAM materials (Lava Ultimate and Enamic) and 2 ceramic-based CAD-CAM materials (e.max CAD and Celtra Duo). Material and methodsThe materials were sectioned into 4-mm-thick specimens (n=5/material) and polished with 320-grit SiC paper. Each specimen was loaded into a custom milling apparatus. The apparatus pushed the specimens against a milling tool (E4D Tapered 2016000) rotating at 40 000 RPM with a constant force of 0.98 N. After a 6-minute timed milling cycle, the length of each milling cut was measured with image analysis software under a digital light microscope. Representative specimens and milling tools were examined with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy. ResultsThe penetration rate of Lava Ultimate (3.21 ±0.46 mm/min) and Enamic (2.53 ±0.57 mm/min) was significantly greater than that of e.max CAD (1.12 ±0.32 mm/min) or Celtra Duo (0.80 ±0.21 mm/min) materials. SEM observations showed little tool damage, regardless of material type. Residual material was found on the tools used with polymer-containing materials, and wear of the embedding medium was seen on the tools used with the ceramic-based materials. Edge chipping was noted on cuts made in the ceramic-based materials. ConclusionsLava Ultimate and Enamic have greater machinability and less edge chipping than e.max CAD and Celtra Duo.

Experimental investigations of ceramic machining using µ-grinding and µ-rotary ultrasonic machining processes: A comparative study

ABSTRACTComparative experimental investigations of µ-grinding and µ-rotary ultrasonic machining (µ-RUM) were made on borosilicate and Zerodur materials to know the efficacy of the processes for micro electro mechanical system (MEMS) application. The electroplated diamond tool of Ø 300 µm for drilling operation and Ø 300 µm to Ø 6 mm for milling operation has been tried in the computer numerical control (CNC) machine with an HSK63 ultrasonic actuator. A suitable interface has been developed to hold the micro tool with the ER11 taper in the existing ER20 collet ultrasonic tool holder. Cutting force, edge-chipping area, and taper in drilling operation; and surface finish, material removal mode, specific energy and un-deformed chip thickness in milling operation were evaluated for both processes under the same material removal rate conditions. The experimental results showed that µ-RUM could perform in a less spindle speed machine as compared to µ-grinding. It was inferred that the maximum and minimum amount of reduction in cutting force, edge chipping, and taper were found to be (49.3%, 10.8%), (87%, 40%), and (95.56%, 4.76%), respectively, in µ-RUM compared to µ-grinding for drilling operation. It was also concluded that surface finish and ductile mode of fracture were higher in µ-RUM compared to µ-grinding for the milling operations. These effects were more pronounced as tool size decreased.