Chip Breaking Research Articles

Study on machinability of three-step drill in drilling Ti6Al4V

As the research progresses, titanium alloy materials have more applications in aerospace and other fields. However, problems such as chip winding and serious tool wear are easy to occur in the machining process. In this research, the three-step drill has changed the main cutting-edge structure, which is more conducive to chip breakage. Firstly, the drilling force of the three-step drill bit is analyzed, and the alternating stress that makes the chip thickness change is obtained by the cutting-edge structure of the three-step drill bit. The simulation and experiment are verified by each other, and the feasibility of three-step drilling to improve the processing quality is obtained. The results show that the improved drill has good chip breaking performance, low thrust force, and better machining performance compared with the twist drill. In addition, the improved drill can obtain a more complete inner wall of the hole and reasonably improve the surface quality. Through experiments, it is found that changing cutting parameters such as feed rate has different effects on chip thickness, thrust and tool wear. It was found that the drilling force was reduced by drilling Ti6Al4V material with the three-step drill. Moreover, the three-step drill can produce smaller chip thicknesses and make the chip more prone to breakage when compared with the twist drill. The high wear of three-step drill bits can also be better weakened by coating materials.

In-situ study of microstructures and sulphides and machinability of Bi-bearing free-cutting steels

ABSTRACT This study investigates the in-situ evolution of the morphology of heated microstructures and sulfides, and to detect the machinability of Bi-bearing high S, low C free-cutting steels. The results show that Bi particles soften, melt, and vaporize during heating process. Its temperature varies slower than that of steel, and causes extensive local expansion of austenite grains. Heat absorbed by small sulfides leads to their volume expansion and formation of larger sulfides by fusion, whereas heat absorbed by large sulfides causes enlargement in dependent spherical or ellipsoidal shapes. During the heating process, at temperatures between 1500°C and 1550°C, the nominal coarsening speed of the tail wave is higher than that of the triple junction, but their movement speeds are similar. The addition of Bi particles to steel enhances its machinability. The cutting heat melts Bi particles to form liquid Bi films, resulting in rapid chip breaking during cutting.

Sweetpotato chip texture and fat content: Effects of enzymatic modification of cell wall polymers.

Impacts of cell wall polymers on sweetpotato chip texture and fat content were investigated through enzymatic modification. Covington sweetpotato slices were treated with cellulase, hemicellulase, pectinase, pectin methyl esterase, protease, the enzyme blend Viscozyme, or no enzymes (control) at 40-45°C for 0.5-2 h. Treated slices were blanched, dried, and fried in triplicate per experimental condition. Breaking forces of 20 chips per frying replicate were measured followed by chip fat, moisture, sugar, alcohol insoluble solids, glass transition temperature, and color analyses. Untreated slices from each batch (daily check) were fried and analyzed to account for starting material variability. Viscozyme and protease-treated chips had the greatest reduction in breaking force from untreated chips (-30.9% and -23.7%, respectively), while pectin methyl esterase-treated chips had the lowest reduction in breaking force (-9.0%). Chips treated with Viscozyme for 2 h were 6.7-6.3 percentiles lower in fat than the control. Principal component analysis elucidated that chip breaking force was associated with unfried slice puncture force, alcohol insoluble solids, and chip color, and chip fat content was inversely associated with maltose content and glass transition temperature. Breaking down multiple cell wall polysaccharides or structural proteins weakened chip textures, while strengthening the pectic fraction resulted in harder chips. Chip fat reduction also occurred when multiple cell wall polysaccharides were broken down. Therefore, cell wall polymers impact sweetpotato chip texture and fat contents, and their attributes should be considered when selecting cultivars and processes for sweetpotato chips. PRACTICAL APPLICATION: Sweetpotato chips are an increasingly popular snack, but there is little understanding how cell wall polymers impact chip textures and fat contents. Raw sweetpotato slices were enzymatically treated to selectively modify cell wall polymers before frying. Chip breaking forces were lowered by protease or Viscozyme (cell wall enzyme blend) treatments, while breaking forces were increased with pectin methyl esterase. In addition, chip fat contents were reduced by the Viscozyme treatment. Since cell wall modifications could impact chip texture and fat content, cell wall polymer attributes should be considered in selection and processing of sweetpotatoes for chip manufacturing.

A new dynamic boring force calculation method using the analytical model of time-varying toolpath and chip fracture

The accurate prediction of dynamic cutting force has great significance for the quality control of the boring process for deep-cavity thin-walled parts. However, most of the classic and improved cutting force models commonly neglect the mechanism analysis of dynamic cutting force, resulting in the dynamic prediction of cutting force being almost impossible. To resolve this problem, a novel analytical dynamic cutting force prediction model for the boring process was proposed to consider the time-varying toolpath and chip fracture in the machining process. The generation mechanism of dynamic cutting force was analyzed by cutting theory and mathematical formula. The theory of maximum shear stress and the law of conservation of energy were applied to derive the dynamic cutting force for an entire rotation cutting cycle. Then, the proposed dynamic cutting force model was validated using a designed boring experiment and a classical cutting force model. The compared results showed that the dynamic cutting force model based on the proposed method had good agreement with the experimental data. Meanwhile, the advantage of accurate prediction was also further demonstrated by comparing the classic cutting force model. This paper presents an analytical dynamic cutting force prediction model for the boring process considering the toolpath and chip breakage. The underlying mechanism of the dynamic change of the cutting force was studied, and data supporting the improved quality of boring deep-cavity thin-walled parts was provided.

Novel use of ultrasonic-assisted turning in conjunction with cryogenic and lubrication techniques to analyze the machinability of Inconel 718

Industries have been pursuing a competent machining system that meets the necessity of sustainability without deteriorating tool wear or final part quality of components made from difficult-to-cut material ‘Inconel 718’. In this regard, a novel study, applying ultrasonic vibration along with lubrication (MQL) and cooling (LCO2) is proposed to enhance the machinability of Inconel 718. The purpose of this work is to examine the machinability of Inconel 718 in conventional and ultrasonic-assisted turning (UAT) under dry, wet, MQL, and LCO2. The experiments are performed on an in-house developed UAT setup, keeping all the machining parameters constant. The LCO2 considerably reduces edge chipping, nose wear, adhesion, and abrasion wear in both the processes. Quantitatively, the conventional turning under LCO2 reduces the flank wear by 32–60 %, power consumption by 4–41 %, and power consumption by 5–31 % compared to dry, wet, and MQL strategies. Similarly, the UAT under LCO2 reduces the flank wear by 32–53 %, power consumption by 11–40 % and power consumption by 5–31 % compared to dry, wet, and MQL strategies. The UAT reduces the surface roughness and power consumption compared to conventional turning when used under MQL and LCO2. The LCO2 in conjunction with ultrasonic vibration significantly reduces specific cutting energy and tool wear without compromising the surface quality. Moreover, the combination also helps in enhancing the chip breakability and reducing the strain localization. Ultimately, the UAT, along with LCO2 promotes sustainability in the machining of Inconel 718.

Experimental Research on Chip Morphology of Ti-5553 Cutting under High-Pressure Cooling

Because Ti-5553 is a kind of difficult-to-machining material, this study uses high-pressure cooling to assist machining and compares it with dry cutting to observe the change of chip morphology in the cutting process. Firstly, a comparative analysis of the chip's macroscopic morphology is carried out, and then the microscopic morphology difference of the chip and its influence on the macroscopic morphology are explored. Furthermore, it provides an intuitive basis for evaluating the cutting performance of Ti-5553 under high-pressure cooling. Experimental research shows that the chips generated under high-pressure cooling are more conducive to chip breaking.

Nonlinear characteristic and chip breaking mechanism for an axial low-frequency self-excited vibration drilling robot

Drilling is one of the essential material removal methods in the aerospace field. This study proposes a flexible variable-stiffness axial low-frequency self-excited vibration drilling scheme for automatic manufacturing platforms. Firstly, an elastic zone active conversion mechanism of the drilling actuator is established, which could realize robot stiffness control in different directions and the directional tool vibration excitation. Then, the nonlinear characteristic of self-excited vibration excitation and vibration waveform is analyzed under various inherent characteristics and drilling parameters. An interface separation chip breaking condition of dual-frequency self-excited vibration drilling is proposed based on the dynamic equivalent undamped state. Finally, the self-excited vibration drilling state, tool trajectory, chip breaking performance, chip morphology, and action mechanism of parameters coupling characteristics are investigated based on experiment and simulation results. This drilling system could produce stable self-excited vibration and smooth chip breaking without a vibration excitation device.

Comparative Study of the Drilling Operation in Duplex Stainless Steels with Drills of Two and Three Cutting Edges

The three cutting edge drills are not the most common drills, nevertheless, are characterized by superior stability, excellent precision and finishing, due to the intersection of three cutting edges at one point. In general, stainless steels are considered as difficult to machine materials due to their tendency to work harden, their toughness and relatively low conductivity, leading to poor surface finish, poor chip breaking and built-up-edge formation. In the case of duplex stainless grades, the high strength, and the very good corrosion resistance, only compared with austenitic steels, make these materials as an alternative to the austenitic stainless steels, with superior mechanical properties. In this study, the performance of the drills with two and three cutting edges were evaluated in the drilling of duplex stainless steels, when low-pressure external cooling or high-pressure internal cooling were applied. Whether used drills of two or three cutting edges, the most important factor to increase the number of holes made, is the use of high-pressure internal cooling, in detriment of external low-pressure external cooling. The drills of three cutting edges have better results in roughness and dimensional tolerance of the holes. However, these drills proved to be more fragile and more sensitive to the cutting parameters. The use of three cutting edges drills is recommended for situations where hole quality is more important, while two cutting edges drills is recommended for situations where productivity is the main objective.

Investigation of the cutting fluid’s flow and its thermomechanical effect on the cutting zone based on fluid–structure interaction (FSI) simulation

Cutting fluids are an important part of today’s metal cutting processes, especially when machining aerospace alloys. They offer the possibility to extend tool life and improve cutting performance. However, the equipment and handling of cutting fluids also raises manufacturing costs. To reduce the negative impact of the high cost of cutting fluids, cooling systems and strategies are constantly being optimized. In most existing works, the influences of different cooling strategies on the relevant process state variables, such as tool wear, cutting forces, chip breakage, etc., are empirically investigated. Due to the limitations of experimental methods, analysis and modeling of the working mechanism has so far only been carried out at a relatively abstract level. For a better understanding of the mechanism of cutting fluids, a thermal coupled two-dimensional simulation approach for the orthogonal cutting process was developed in this work. This approach is based on the Coupled Eulerian Lagrangian (CEL) method and provides a detailed investigation of the cutting fluid’s impact on chip formation and tool temperature. For model validation, cutting tests were conducted on a broaching machine. The simulation resolved the fluid behavior in the cutting area and showed the distribution of convective cooling on the tool surface. This work demonstrates the potential of CEL-based cutting fluid simulation, but also pointed out the shortcomings of this method.

Ratio Study of High-Pressure Lubrication and Cutting Parameters Effects on Machining Operations and Its Effect Towards Sustainable Machining: A Review

Machining is the art of developing sustainable mechanical components by transforming solid raw materials into the finished product. Because for any Nation to achieve sustainable development, the Nation must have quality manufacturing industries. This paper summarizes existing articles on the effects of high-pressure lubrication conditions on chip formation and temperature distribution. Also, surface roughness, tool wear, and vibrations in machining operations when considering the current trend. Furthermore, the study of nano-lubricant and their application in reducing friction and temperature were also reviewed. The study also examined other lubrication conditions, cutting parameters with the high-pressure machining operations to draw a definite conclusion. The review confirms that applying a high-pressure lubrication system is very efficient. However, it has some challenges. Cooling technology is not built into the system, discovered during this review. Therefore, the study will recommend a developed machine that can function in multiple faces. Industrial 4.0 additive manufacturing techniques can build the cryogenic system—making the lubricant delivery machine a sustainable technology in machining operation. A high-pressure-cryogenic-MQL lubrication process is needed for sustainable machining operations of various alloys and metal composite materials for automobile, aerospace, and structural applications. The sustainable lubrication system will also help eradicate high-temperature occurrence in the machining region with a sustainable way of removing the chips without experiencing chip breakage at the cutting region.

Machining characteristics investigations of duplex stainless steel by considering dual effect of chip breaker and cooling conditions

Duplex stainless steels (DSSs) use in many applications because of their superior properties like high corrosion, good strength, and low cost. On the other hand, machinability of DSSs is very low due to its superior ductility. This study investigates optimization of cutting parameters, cutting environments (dry and cold air), and chip breaker forms by Taguchi–Grey relational analysis in turning of 2205 grade DSS. The turning tests were conducted using Taguchi’s L16 mixed design by measuring and evaluating the cutting force components and surface roughness criteria (Ra and Rz). When turning of DSS2205 material in medium cutting condition, it is suitable to use low feed rate and high cutting speed for reducing of cutting force and surface roughness. In addition, it was shown that the chip breaker form is as important as the cooling medium in terms of minimizing Built-Up-Edge (BUE), which negatively affects the machinability outputs. Grey relational grade (GRG) indicated that the optimum results for all cutting conditions were the cutting speed of 160 m/min, the feed rate of 0.15 mm/rev, GM chip breaker, and cold air cutting environment. Experimental and ANOVA results indicated that the feed rate is the most important parameter on turning of DSS2205, followed by chip breaker, and cutting environment.

Evaluation of chip breaking in combined laser-turning process

Control of chip formation is one of the most critical challenges in turning processes. This paper deals with a novel combined turning process in which a high-power fiber laser is integrated into a Swiss type turning machine in order to rapidly ablate spiral grooves on the workpiece circumference. The workpiece was axially turned after ablating the defined spiral grooves by the laser. A stainless steel (DIN1.4571; X6CrNiMoTi17-12-2) and a carbon steel (DIN1.7139; 16MnCrS5) were chosen as the workpiece materials to compare the effects of the combined laser turning on the process performance. Different types of chips are formed under different cutting conditions. The experimental results indicate that by utilizing the developed technique, not only could the chips be practically shortened, but the cutting forces and surface roughness considerably decrease.

Effect of EDMed rake face grooves on the chip breaking capability of twist drills during deep hole drilling of Al 6061 aluminum alloy

ABSTRACT Deep hole drilling of ductile materials like Al6061 with conventional twist drills is challenging due to premature tool failure caused by chip clogging. Chip breakers, in the form of grooves of varying angles (0°, 5° & 10°) and depth (0.4 & 0.5 mm), created using EDM on the rake face, are proposed to overcome chip clogging. Tool wear, hole roughness, and diameter deviation were measured and analyzed along with chip morphology study for the six grooved tools and compared with plain drill. The grooved tools were successful in breaking the chips which allows for easy evacuation without any clogging. Grooved drills produced desired spiral chips compared to string chips produced by plain drill thus resulting in lesser tool wear rate. While the grooved tools showed stable but slightly higher roughness values, the conventional tools exhibited a linear increasing trend as the drilling progressed. The machined hole surfaces had defects such as feed marks, pitting, grooves, and burnished surfaces. The grooved tools produced comparatively more diameter deviation probably because the well broken chips entered into the drill land/hole surface space. From the results it is clear that groove angle and depth have significant effect on the drill machinability characteristics.

Drilling study on CFRP/Ti-6Al-4V stacks using chip breaker grooved drill

ABSTRACT Carbon fiber reinforced plastic/Ti-6Al-4V stacks are most commonly utilized in aircraft structures as they have a higher strength-to-weight ratio. Usually, these materials are stacked together and riveted by drilling holes. The holes produced during the operation require more precision and high quality. In general, the chips produced during the drilling of Ti-6Al-4V alloy stacked underneath the surface of CFRP material increase the damage and thrust force during drilling CFRP/Ti stacks. In this experimental investigation, a chip breaker in the form of a groove was machined on the rack face of the drill tool. Sixteen drilling experimental runs were conducted on CFRP/Ti-6Al-4V stacks along with standard and grooved tungsten carbide drills. Two input parameters such as cutting speed and feed with four levels were considered during drilling under a dry machining environment. The response attributes measured were thrust force, chip formation and delamination. Based on the study, a decrease in cutting force with an increase in the chip breakability was found at maximum speeds. Furthermore, a significant decrement was noticed in the delamination and formation of burrs with the grooved drill tool compared to the standard tool.

Effect of cutting parameters on chips and burrs formation with traditional micromilling and ultrasonic vibration assisted micromilling

In the traditional micromilling (TMM) of Inconel718 alloy, due to the influence of material plasticity and size effect, relatively large burr will be produced. In order to hinder the burr forming in micromilling, ultrasonic vibration in feed direction is applied to the workpiece to complete vibration cutting. Combined with trajectory simulation and cutting experiment, the burr formation mechanism of TMM and ultrasonic vibration assisted micromilling (UVAMM) was studied. The results show that when the ratio of amplitude (A) to feed per tooth (ƒz) is greater than 0.5, continuous cutting changes to intermittent cutting in the vibration cutting process. The fractured area with dimples on the burr increases with the increase of amplitude. Compared with TMM, UVAMM improves chip breaking ability, facilitates the propagation of burr crack, and effectively inhibits the formation of burr. When the chip breaking condition is reached, the burr shape is usually tearing or flocculent. Under the conditions of low speed (n), large ƒz, and large A, the burr suppression is more obvious.

Study on Chip Breakability Index During Longitudinal Turning of Cast and DMLS Additively Manufactured AlSi10Mg Aluminum Alloy

Study on Chip Breakability Index During Longitudinal Turning of Cast and DMLS Additively Manufactured AlSi10Mg Aluminum Alloy

Turning characteristics of titanium alloy Ti-6Al-4V with high-pressure cutting fluid

This study investigates the effect of high-pressure cutting fluid on the turning characteristics of Ti-6Al-4V alloy. A noncoated carbide tool was used to measure the cutting temperature using a tool-work thermocouple technique, and the cutting characteristics were evaluated with respect to the cutting temperature, chip breakability, and tool wear. Furthermore, the viability of TiAlN/AlCr2O3-coated tool was examined. The coolant jet when placed towards the cutting zone on the rake face is effective in reducing the cutting temperature because of the reduction in the chip-tool contact length. Based on this result, tools with a textured rake face were examined.

Experimental investigations on the ultrasonic vibration-assisted hard turning of AISI 52100 steel using coated carbide tool

Ultrasonic vibration-assisted turning (UVAT) is a hybrid and eco-friendly machining technique. The UVAT is performed by superimposing high frequency and low amplitude sound waves on the cutting tool in conventional turning. In the present work, a comparative evaluation of the machining performance is presented during conventional turning (CT) and ultrasonically vibration-assisted turning (UVAT) of AISI 52100 hardened steel (62 HRC). Hard turning experiments were performed using a PVD coated TiAlSiN carbide tool considering the effect of process parameters such as cutting speed, feed, and depth of cut. The performance is measured in terms of cutting force and surface roughness. This study observed a better surface finish during of around 8.29% in UVAT when compared to conventional turning. Better surface finish achieved under UVAT could be attributed to better chip breaking and disentanglement of the chip around the tool during UVAT against long curly chips produced that further entangled on the tool while CT. These entangled long curly chips affected the surface finish. On the other hand, no significant difference is observed in cutting force while hard turning under CT and UVAT. This is mostly due to the fact that, although UVAT has less cutting force at slower cutting speeds, but it behaves very identically with CT when cutting speed approaches tangential velocity. This study finds further scope for machinability studies considering the effect of vibrations superimposed on a tool in feed, tangential, and radial directions.

Cutting Depth Dictates the Transition from Continuous to Segmented Chip Formation.

The process of material cutting emerges from a series of nonlinear phenomena including frictional contact, plastic deformation, and fracture. While cutting dominated by shear deformation is of interest to achieve a smooth material removal and a high-quality surface finish, the fracture-induced chip breaking is of equal importance to prevent the formation of long chips. Here we show that discrepant observations and predictions of these two distinct cutting mechanisms can be reconciled into a unified framework. A simple analytical model is developed to predict the mechanism of chip formation in a homogeneous medium as a function of work piece intrinsic material properties, tool geometry, and the process parameters. The model reveals the existence of a critical depth of cut, below which the chip formation is gradually progressed by plastic deformation in the shear plane, and above which chips break off by abrupt crack propagation. The models' prediction is validated by systematic insitu orthogonal cutting experiments and literature data for a wide range of materials over multiple length scales.

Design, development and test of a novel broach for long polypropylene tubes

Polymers are frequently used for a variety of applications in industry. One relevant field is plastic tubing. As plastic tubes are manufactured from thermoplastic material through hot-extrusion their dimensional accuracy is only moderate. Wherever high accuracy on tube diameters and roundness are required, the conventional production techniques reach their limits and more complex technologies are needed. Known approaches from metal machining are deep hole drilling and internal broaching. However, machining processes with chip removal on polymeric materials are not so common. Therefore, the authors studied cutting operations of polypropylene experimentally. Based on their findings they designed and built an internal broach for the machining of polypropylene tubes. Finally, the authors tested their developed broaching tool in a relevant industrial environment. The tool not only fulfills the dimensional machining requirements but also solves the present chip evacuation problem in a unique way. It enables free cutting through the whole operation and creates continuous straight chips with no need for chip breakers. Consequently, the timely cleaning step, required in traditional broaching, can be eliminated, which reduces the lead time significantly. Furthermore, the set of materials allows dry broaching. Coolant is not necessary. This leads to less waste, a cleaner production line, and avoids damage through aggressive liquids. Lastly, their design ensures that no loss of dimension occurs when resharpening the tool.