Polycrystalline Diamond Inserts Research Articles

Machinability Measurements in Milling and Recurrence Analysis of Thin-Walled Elements Made of Polymer Composites

The milling of polymer composites is a process that ensures dimensional and shape accuracy and appropriate surface quality. The shaping of thin-walled elements is a challenge owing to their deformation. This article presents the results of milling polymer composites made of glass and carbon fibers saturated with epoxy resin. The milling of each material was conducted using different tools (tools with polycrystalline diamond inserts, physically coated carbide inserts with titanium nitride and uncoated carbide inserts) to show differences in feed force and deformation after the machining of individual thin-walled samples. In addition, the study used recurrence analysis to determine the most appropriate quantifications sensitive to changes occurring in milling different materials with the use of different tools. The study showed that the highest forces occurred in milling thin-walled carbon-fiber-reinforced plastics using uncoated tools and the highest feeds per revolution and cutting speeds. The use of a high feed per revolution (0.8 mm/rev) in carbon-fiber-reinforced plastics machining by uncoated tools resulted in a maximum feed force of 1185 N. A cutting speed of 400 m/min resulted in a force of 754 N. The largest permanent deformation occurred in the milling of glass-fiber-reinforced composite samples with uncoated tools. The permanent deformation value of this material was 0.88 mm. Low feed per revolution (0.1 mm/rev) resulted in permanent deformations of less than 0.30 mm for both types of materials. A change in feed per revolution had the most significant effect on the deformations of thin-walled polymer composites. The analysis of forces and deformation made it possible to conclude that high feed per revolution were not recommended in composite milling. In addition to the analysis of machining thin-walled composites, the novelty of this study was also the use of recurrence methods. Recurrence methods were used to determine the most appropriate quantifications. Determinism, averaged diagonal length and entropy have been shown to be suitable quantifications for determining the type of machined material and the tools used.

Working towards the minimum surface damages and failure analysis of Joule heat effects in manufacturing diamond cutting tools

This study explores the fracture morphology for the minimum damages on the machined surface when wire electrical discharge machining (WEDM) polycrystalline diamond (PCD) cutting tool inserts. Usually, material removals from PCD blanks involve electro-thermal energies which produce mechanical forces and thermal effects; their interactions via parametric control then result in unexpected surface damages such as chipping-off, cracks, delamination, grain dislodgement, craters and graphitisation. As a result, the produced PCD inserts’ tool life is shortened. In this work, to minimise the surface damages with the least compromise on the productivity, the underlying mechanisms of material removal and the corresponding surface roughness were revisited, from the modified Joule heat models to the validation experiments. The root causes of the surface damages on the PCD inserts in association with the discharging energy were geometrically defined and analytically postulated; whilst the corrective actions were implemented via experiments with statistical examinations. The results suggested that the controlled discharge energy could effectively increase the material removal rate, while also reducing the minimum surface damages on the coupled crater area, crack areas and chipping-off volume. In the proposed prevention plans, some predictable results in groups involving multiple criteria optimisations were confirmed, with a good balance between the least surface damages and the material removal by practical production runs. The effects and causes of control parameters on the surface damages are presented in statistical plots and micrographs with quantitatively and qualitatively analysis. The underlying mechanisms are resolved and discussed in detail.

Machinability analysis and multi-response optimization using NGSA-II algorithm for particle reinforced aluminum based metal matrix composites

In this study the effects of reinforcement particle size and cutting parameters on machining performance variables like cutting force, maximum tool-chip interface temperature and surface roughness of the machined surface have been investigated while machining Aluminum based metal matrix composites (MMCs). MMC bars with silicon carbide reinforcement having 10 % volume fraction and particle sizes of 5 μm, 10 μm and 15 μm are machined with polycrystalline diamond (PCD) inserts. Experiments are performed using central composite design (CCD) having four parameters with three levels. Response surfaces for each performance variables are generated using polynomial models. Single variable and interaction effects have been investigated using principal component analysis and 3D response charts. Multi-response optimization has been performed to minimize surface roughness and maximum tool-chip interface temperature using non-dominated sorting genetic algorithm II (NSGA-II). In addition, constraints have been applied to the optimization search to filter design points with high cutting forces and low material removal rate. Most of the optimal solutions are found to be with moderate cutting speeds, low feed rate and low depth of cuts.

Turning of Aluminium Composites: Characteristics and Future Prospects

Aluminium matrix composites have widespread applications in different industrial areas including automobile and aerospace owing to their improved mechanical and tribological properties over conventional monolithic materials. As such, machining of these metal matrix composites is an important aspect to be studied in order to manufacture desired components with close tolerances. Presence of hard abrasive ceramic reinforcements in composites increases the chance of tool wear and hence, increased machining cost during conventional machining process. In order to improve machining characteristics of aluminium composites, machining is carried out using specialized carbide tools (both coated and uncoated), polycrystalline diamond inserts, CVD diamond coated inserts, etc. This paper presents a state-of-the-art review on turning of aluminium composites. Factors affecting machinability like content, size, and morphology of reinforcement along with matrix hardness are discussed. Effect of process variables such as cutting speed, feed rate, depth of cut, etc. on response variables such as tool wear, surface finish, cutting forces, cutting temperature, etc. has been highlighted. Moreover, failure mechanisms involved in turning process occurring due to debonding, plastic deformation, particle fracture, etc. are deliberated in this study. Various modelling and optimization studies in this area are discussed in detail as well. Furthermore, scope for future work in this area including sustainable machining is also elucidated.

Performance Comparison of PCD Insert and Uncoated Insert in Novel CNC Green Machining of SS316L Stainless Steel for Maximizing Material Removal Rate

Aim: This research is about comparing the performance of poly-crystalline diamond (PCD) insert and uncoated cemented carbide insert for improving the material removal rate (MRR) in CNC turning. Materials and Methods: The material investigated in this research was SS316L. PCD insert was set as the experimental group and uncoated insert was set as the control group. The cutting parameters employed in this process were cutting speed, feed rate and depth of cut. Totally 27 samples per group were machined by using the selected parameters. Results: The mean MRR value obtained for the PCD tool is 0.22593 g/s, whereas it is 0.07600 g/s for the uncoated tool. The significance value obtained among the experimental group and control group is 0.000 (p<0.05). Conclusion: Within the limits of this study, the outcome of the research shows that MRR is more when the specimen is machined by PCD insert than machined by uncoated insert.

Nanosecond-Fiber Laser Cutting and Finishing Process for Manufacturing Polycrystalline Diamond-Cutting Tool Blanks

This paper presents a nanosecond-fiber-laser-based method for manufacturing polycrystalline-diamond (PCD) tool blanks. The effects of variations in the process path and operating parameters on the cut-surface morphology and surface-quality of the processed PCD workpieces have been analyzed. The results obtained in this study reveal the reactive fusion cutting mechanism to yield a processing depth of 155.2 µm at 30-W average laser power, 200-ns pulse width, and 30-kHz pulse frequency. The successful cutting of a 1.2-mm-thick PCD workpiece via implementation of the horizontal-shifting and vertical layer–by-layer processing methods is reported. Compared to the wire-electrical-discharge machining (WEDM), the proposed approach yields superior cut-surface roughness (Ra = 0.378 µm). Moreover, the laser processing was performed on a single-axis curved stage, on which the workpiece placed at an inclination during laser cutting and finishing. Thus, a PCD insert with an orthogonally cut edge, flat and pit-free finishing surface, and excellent tool-surface roughness (Ra = 0.202 µm) was obtained, thereby verifying the feasibility of the proposed approach. Furthermore, it is evident that the nanosecond-fiber laser can be used to not only cut and finish PCD inserts but also produce PCD workpieces oriented at different rake and clearance angles.

New milling methodology for sealing planes in AlSi9Cu3(Fe) alloy machined with PCD tool

The use of self-moulding resins in industry makes it necessary to specify minimum values for the surface roughness parameters in order to avoid fluid leaks between the sealing planes. To meet this requirement, new tool classes, machining parameters, and methodologies are being used. Thus, this work applies a new methodology for plane milling, with the objective of increasing the tightness of the union with adhesive. The investigation was based on experimental planning techniques for the behaviour of the surface roughness in machining of AlSi9Cu3 alloy by frontal milling with refrigeration, carried out in a transmission union support, in high-speed cutting (HSC) machining centres. The evaluated parameters were the cutting speed (Vc) between 1250 m/min and 2250 m/min, and the feed per tooth (fz) between 0.050 mm/tooth and 0.100 mm/tooth. Two cutters with ten polycrystalline diamond (PCD) inserts were used to mill the sealing surface, with one of the cutters having eight cutting inserts and two scratching inserts. The cutoff considered was 2.5 mm and the statistical technique of design of experiment (DOE) was used to evaluate the experimental results. The optimum roughness values, achieved with the cutter with scratching inserts, were a Vc of 1250 m/min and fz of 0.05 mm/tooth.

Performance of surface textured PCD inserts with wettability chemical solutions for machining operation

Non-hazardous, toxic-free, allergic-free and less cost-orientated methods are expected by the industries and the industrial workers for the better working-environment. In this work, an effort is made to achieve this expectation by integrating the concept of surface texturing and lyophobic wettability for anti-friction and self-lubrication purpose. Turning experiments are conducted on Al 6061 T6 material using Non-Textured (NT) Poly-Crystalline Diamond (PCD) insert, Cross-Chevron Textured insert (CCT), dip and drop based lyophobic wettability solutions filled texture inserts (TDI and TDR) under dry conditions. Lyophobic wettability was formed using amino silane functionalisation on the insert surface. Cross-chevron textures are engineered on the insert's rake face using Nd: YAG laser texturing machine. The experimental results observed with the lesser main cutting force and thrust force for the dip based lyophobic wettability insert than the non-textured, cross-chevron textured and drop based lyophobic wettability inserts.

Precision Hard Turning of Ti6Al4V Using Polycrystalline Diamond Inserts: Surface Quality, Cutting Temperature and Productivity in Conventional and High-Speed Machining.

This article presents the results of an experimental investigation into the machinability of Ti6Al4V alloy during hard turning, including both conventional and high-speed machining, using polycrystalline diamond (PCD) inserts. A central composite design of experiment procedure was followed to examine the effects of variable process parameters; feed rate, cutting speed and depth of cut (each at five levels) and their interaction effects on surface roughness and cutting temperature as process responses. The results revealed that cutting temperature increased with increasing cutting speed and decreasing feed rate in both conventional and high-speed machining. It was found that high-speed machining showed an average increase in cutting temperature of 65% compared with conventional machining. Nevertheless, high-speed machining showed better performance in terms of lower surface roughness despite using higher feed rates compared to conventional machining. High-speed machining of Ti6Al4V showed an improvement in surface roughness of 11% compared with conventional machining, with a 207% increase in metal removal rate (MRR) which offered the opportunity to increase productivity. Finally, an inverse relationship was verified between generated cutting temperature and surface roughness. This was attributed mainly to the high cutting temperature generated, softening, and decreasing strength of the material in the vicinity of the cutting zone which in turn enabled smoother machining and reduced surface roughness.

Minimum Quantity Lubrication through the micro-hole textured PCD and PCBN inserts in the machining of the Ti–6Al–4V alloy

A novel cutting tool development with the micro-hole textures on the flank and rake face of the cutting inserts helps in the reduction of tribological properties. The machining of Ti–6Al–4V alloy leads to some challenges during machining namely higher cutting temperature, and rapid tool wear. In this research, a comparison study has been performed with the new cutting tool inserts with surface modification such as Polycrystalline Cubic Boron Nitride (PCBN) and Polycrystalline Diamond (PCD) inserts for high-speed machining of Ti–6Al–4V alloy. The influence of the micro-hole textured insert on the machining of the Ti–6Al–4V alloy was investigated with the Minimum Quantity Lubrication (MQL) method. Compared to modified PCBN inserts, modified PCD inserts showed better results in all the performance characteristics.

An Experimental and Numerical Approach to Study the Performance of Modified Perforated Cutting Tools on Machining of Ti–6Al–4V Alloy

In this research, the main aim is to reduce the unfavorable effects that occurred during machining of the Ti–6Al–4V alloy by perforating the rake face and the flank face of the cutting insert. The main novelty in this research is that machining of Ti–6Al–4V alloy with the micro-hole textured insert helps in the improvement of tribological properties and also reduces cutting temperature at chip–tool interface with proper lubricating effect. To validate the micro-hole textured tools, it is compared with conventionally available insert. The deformation of Ti–6Al–4V alloy with modified cutting inserts was simulated, considering tool as rigid body and workpiece as elasto-plastic material. DEFORM 3D software was used for the simulation of the machining process with the updated Lagrangian formulation. To predict the cutting temperature and chip morphology, the thermo-mechanical analysis was applied using Johnson–Cook material model for the machining process. The turning of the Ti–6Al–4V alloy was carried out with the modified polycrystalline diamond (PCD) cutting inserts (Design 1 and Design 2) and commercially available PCD insert (normal insert). Coconut oil was used as a micro-pool lubricant during the machining process under minimum quantity lubrication environment. In the present work, the turning performance characteristics such as cutting temperature, cutting vibration, tool wear, chip morphology and surface integrity were measured during machining of the Ti–6Al–4V alloy. The experimental results of cutting temperature and chip morphology were validated with the simulation results with better accuracy. The machining results of Design 2 cutting insert showed maximum reduction of 30%, 38%, 45% and 35% in cutting temperature, cutting vibration, tool wear and surface roughness, respectively, when compared with machining under normal insert and Design 1 cutting insert. It is also evident from the results that machining with Design 2 cutting insert significantly improved the process performance of the product quality at higher feed rates.

Tailored Chip Breaker Development for Polycrystalline Diamond Inserts: FEM-based Design and Validation

Chip evacuation is a critical issue in metal cutting, especially continuous chips that are generated during the machining of ductile materials. The improper evacuation of these kinds of chips can cause scratching of the machined surface of the workpiece and worsen the resultant surface quality. This scenario can be avoided by using a properly designed chip breaker. Despite their relevance, chip breakers are not in wide-spread use in polycrystalline diamond (PCD) cutting tools. This paper presents a systematic methodology to design chip breakers for PCD turning inserts through finite element modelling. The goal is to evacuate the formed chips from the cutting zone controllably and thus, maintain surface quality. Particularly, different scenarios of the chip formation process and chip curling/evacuation were simulated for different tool designs. Then, the chip breaker was produced by laser ablation. Finally, experimental validation tests were conducted to confirm the ability of this chip breaker to evacuate the chips effectively. The machining results revealed superior performance of the insert with chip breaker in terms of the ability to produce curly chips and high surface quality (Ra = 0.51–0.56 µm) when compared with the insert without chip breaker that produced continuous chips and higher surface roughness (Ra = 0.74–1.61 µm).

Machinability of Rolled Aluminum using Advanced Coated Cutting Tools and Its Characterization

Because of multiple properties like higher values of corrosion resistance, formability, weldability along with greater structural utility aluminum alloys are generally gaining more and more demand in industries and household. With this the requirement for searching of higher quality cutting tool to machine aluminum is also growing. Here different cutting tools like MTCVD+TiCN+Al2O3, MTCVD+TiCN+Al2O3+TiOCN, MTCVD+TiN+TiCN+Al2O3+TiN, PVD AlTiN, cemented carbide (k-10) insert brazed with Polycrystalline Diamond and Polycrystalline Diamond Inserts are being used to machine rolled aluminum in dry condition and then comparative analysis are made. The cutting is of orthogonal type and capstan lathe is used for the same. Under different conditions of cutting the surface roughness along with morphology of chip are analyzed. Under constant depth of cut (doc) along with variable velocities and feed, the turning operation is performed. With SEM and XRD the identification including characterization of cutting tool were also performed. The polycrystalline diamond tool is found to give optimum surface finish, thin type of chip along with mirror like finish during machining operation.

Tool wear characterization in high-speed milling of titanium metal matrix composites

Titanium metal matrix composites (Ti-MMCs) have been successfully incorporated into a vast number of products within various industrial sectors. Despite excellent mechanical and physical features, due to the presence of hard and abrasive ceramic particles in metal matrices of Ti-MMCs, various issues have been emerged regarding machining and machinability of Ti-MMCs. Among critical machinability attributes, tool/insert wear and surface quality, in principle average surface roughness, Ra, are the principal critical attributes. This study plans to present an experimental analysis of wear characterization of polycrystalline diamond (PCD) and carbide inserts during high-speed milling of Ti-MMCs. The main wear modes observed were adhesion, abrasion, and diffusion. Oxidation was also observed at under those cutting conditions with elevated temperature. Regardless of the insert used, edge chipping was also observed in milling tests under various levels of cutting. It was observed that cutting speed and depth of cut are the major cutting parameters affecting wear rate in carbide X500 and PCD inserts. Meanwhile, surface roughness Ra was not affected by the cutting parameters used when using PCD insert. Promising tool wear rates also were recorded under low levels of cutting speed and high levels of feed rate when using carbide insert X500.

Effect of lead on the machinability of brass alloys using polycrystalline diamond cutting tools

The international safety regulations are pushing the manufacturers of water systems and equipment to remove lead from material compositions due to the potential human hazard of lead absorption. The usage of green lead-free brass alloys is becoming mandatory in many important markets, demanding the manufacturers to quickly adapt their production techniques both casting and machining to this new reality. Regarding machining, lead has been used to facilitate the chip control, working as a natural chip breaker and reducing the tool wear. Therefore, the reduction of lead composition in brass alloys contributes to a machinability decrease of the materials leading to higher cutting forces, long chips and higher tool wear. This work focuses on the machinability characterization of three different brass alloys (leaded, medium-leaded and minimally leaded) by means of cylindrical external turning process with polycrystalline diamond inserts. A parametric study covering three different depths of cuts, three feed rates and four cutting speeds was conducted for three brass alloys with two repetitions. Cutting forces, chip morphology and surface roughness were analysed and compared between alloys. Complementary microstructural and mechanical characterization of the alloys were performed. Analysis of variance was performed to analyse the results. Cutting forces, power consumption, specific cutting pressure, roughness and chip morphology identification were used as comparison criteria among the tested materials. Results have demonstrated the decrease of machinability with the lead reduction, with higher cutting forces and longer chips. Polycrystalline diamond tools used in this work could be a good option to overcome the machinability challenges of the lead-free brass alloys.

Drilling of Hard Rock by Means of Polycrystalline Diamond Inserts

A specialized measurement unit is developed to determine the basic parameters in the drilling of hard rock by bits with polycrystalline diamond inserts. The unit permits the collection of information and its wireless transfer to a computer.

Лабораторные исследования износостойкости режущих элементов буровых долот, армированных алмазно-твердосплавными пластинами

Лабораторные исследования износостойкости режущих элементов буровых долот, армированных алмазно-твердосплавными пластинами

Feature extraction on an intelligent polycrystalline diamond insert clock testing method and prediction of product performance

Increasing applications of polycrystalline diamond inserts in rock drilling is visibly seen as the discovery of new oil wells and tunnelling projects for metro lines are on a continuous rise around the world. As a result, the market consumption of polycrystalline diamond inserts is increasing severely. However, the sudden increased requirement of polycrystalline diamond inserts has also triggered a global competition as new players are increasing each day. The prevailing situation offers a dynamic challenge to the manufacturers to successfully stay in the business, and hence, enhancing product quality has become an essential requirement. In other words, to stay competitive and to remain ahead of the pack, it is critical to build up innovative testing capabilities of the polycrystalline diamond insert so as to pre-empty the undesirable functional characteristics of the polycrystalline diamond insert as well as to proactively engage the production floor for ensuring high product quality. This manuscript unveils a developed intelligent polycrystalline diamond insert testing platform that would link the failure characteristics of the polycrystalline diamond insert to the fracture mechanics through the study of process digitisation of the tool–work interface. An experimental set-up was developed, which incorporates a dynamometer, acoustic emission and accelerometer, for the digitisation of data signals in a feature extraction engine. The feature extraction engine in turn is used to monitor the failure of polycrystalline diamond cutting inserts during machining. The raw data fed through the feature extraction engine were used to identify the progression of failure in terms of flank wear or tool life for the polycrystalline diamond cutting inserts. The system comprises three key elements, which are (a) sensing and conditioning, (b) information extraction and (c) performance and failure analysis. The results of this experiment build the feature extraction engine that tracks the progression of flank wear in the polycrystalline diamond cutting inserts with reasonable accuracy. Furthermore, the break-in testing of a randomly selected insert from the production floor was applied to the feature extraction engine platform to predict the produce performance. This method also alerts the in-process manufacturing stages and enabled to considerably reduce the production scrap of polycrystalline diamond inserts.

Oil well drill bit failure during pull out: Redesign to reduce its consequences

Abstract A drill bit with polycrystalline diamond (PDC) inserts lost one of its three blades when operating in an oil well, leading to a costly failure. Operating conditions and associated stresses were analyzed, bit core material in the failure and adjacent areas was analyzed and tested, and fracture surfaces identified. Base material is a Ni-Cu-Mn matrix with tungsten carbide precipitates. Fracture surfaces showed cleavage planes and loss of particles, indicating a brittle fracture. Microstructures and hardness were similar in all analyzed regions, and according to specifications. The symmetry and characteristics of the fracture surfaces allow defining that the loads that caused the failure were not applied during the drilling operation. The blade broke apart due to a downward force applied at its base. Finite elements numerical modeling allowed pinpointing a specific moment in the pulling operation, in which a 28 ton overpull force was recorded, as the immediate operational event that caused the failure. Operating procedures that reduce the likelihood and amplitude of impact loads, are difficult to implement; more promising is the alternative for a redesign of the drill bit. Commercial designs focus mostly on the efficiency of the cutting cycle; blade geometry can be also optimized to take into account the pull out conditions. The most efficient redesign for this specific drill bit model relies in a re-machining of the blade base, so that a large overpull load would crack a small sector, on which a PDC insert is located. In this gecko-tail type solution, only one insert would be lost, preserving the integrity of the rest of the drill-bit. Subsequent repair would involve standard thermal spray base metal techniques, including reconstitution and brazing of a new insert.

On the Development of a Chip Breaker in a Metal-Matrix Polycrystalline Diamond Insert: Finite Element Based Design With ns-Laser Ablation and Machining Verification

This paper reports the development of an original design of chip breaker in a metal-matrix polycrystalline diamond (MMPCD) insert brazed into a milling tool. The research entailed finite element (FE) design, laser simulation, laser fabrication, and machining tests. FE analysis was performed to evaluate the effectiveness of different designs of chip breaker, under specified conditions when milling aluminum alloy (Al A356). Then, the ablation performance of an MMPCD workpiece was characterized by ablating single trenches under different conditions. The profiles of the generated trenches were analyzed and fed into a simulation tool to examine the resultant thickness of ablated layers for different process conditions, and to predict the obtainable shape when ablating multilayers. Next, the geometry of the designated chip breaker was sliced into a number of layers to be ablated sequentially. Different ablation scenarios were experimentally investigated to identify the optimum processing conditions. The results showed that an ns laser utilized in a controllable manner successfully produced the necessary three-dimensional feature of an intricate chip breaker with high surface quality (Ra in the submicron range), tight dimensional accuracy (maximum dimensional error was less than 4%), and in an acceptable processing time (≈51 s). Finally, two different inserts brazed in milling tools, with and without the chip breaker, were tested in real milling trials. Superior performance of the insert with chip breaker was demonstrated by the curled chips formed and the significant reduction of obtained surface roughness compared to the surface produced by the insert without chip breaker.