Cut Thickness Research Articles

Modeling of the effects of phase shift on cutting performance in elliptical vibration cutting

In the elliptical vibration cutting process, the elliptical locus is considered to be a vital factor that affects cutting performance. Besides the cutting speed and vibration amplitudes, the phase shift (i.e., the phase difference between the two-directional output harmonic vibrations forming the elliptical locus) is an intrinsic parameter that determines the shape and inclination of the elliptical locus with respect to the cutting direction. In this paper, a numerical recursive search method is proposed to investigate the effect of phase shift in elliptical vibration cutting. It has been shown that the critical speed ratio for considerably improving the cutting performance has a sinusoidal correlation with the phase shift. For elliptical loci with arbitrary shapes, the developed model theoretically predicts the maximal influential thickness of cut, surface roughness, and the tool-workpiece contact ratio as a function of phase shifts. Experiments were conducted to validate the developed model through the evaluation of the machined surface profile, roughness, and dynamic cutting force. The obtained results offer a method to determine the proper machining variables in cutting hard and brittle materials during the elliptical vibration cutting process with an arbitrary locus.

Dry machining of aluminum for proper selection of cutting tool: tool performance and tool wear

Machining of aluminum and its alloy is very difficult due to the adhesion and diffusion of aluminum, thus the formation of built-up edge (BUE) on the surface. The BUE, which affects the surface integrity and tool life significantly, affects the service and performance of the workpiece. The minimization of BUE was carried out by selection of proper cutting speed, feed, depth of cut, and cutting tool material. This paper presents machining of rolled aluminum at cutting speeds of 336, 426, and 540 m/min, the feeds of 0.045, 0.06, and 0.09 mm/rev, and a constant depth of cut of 0.2 mm in dry condition. Five cutting tools WC SPUN grade, WC SPGN grade, WC + PVD (physical vapor deposition) TiN coating, WC + Ti (C, N) + Al2O3 PVD multilayer coatings, and PCD (polycrystalline diamond) were utilized for the experiments. The surface roughness produced, total flank wear, and cut chip thicknesses were measured. The characterization of the tool was carried out by a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) pattern. The chip underface was analyzed for the study of chip deformation produced after machining. The results indicated that the PCD tool provides better results in terms of roughness, tool wear, and smoother chip underface. It provides promising results in all aspects.

Analysis of the learning curve for pre‐cut corneal specimens in preparation for lamellar transplantation: a prospective, single‐centre, consecutive case series prepared at the Lions New South Wales Eye Bank

This study is the first paper to establish a learning curve by a single technician. Preparation of pre-cut corneal endothelial grafts commenced at Lions New South Wales Eye Bank in December 2014. The primary objective of this study was to review the safety and reliability of the preparation method during the first year of production. This is a hospital-based, prospective case series. There were 234 consecutive donor corneal lenticules. Donor lenticules were prepared by a single operator using a linear cutting microkeratome. Immediately prior to cutting, central corneal thickness values were recorded. Measurements of the corneal bed were taken immediately following lenticule preparation. Outcomes were separated by blade sizes, and intended thickness was compared to actual thickness for each setting. Early specimens were compared to later ones to assess for a learning curve within the technique. The main parameter measured is the mean difference from intended lamellar cut thickness. The mean final cut thickness was 122.36 ± 20.35 μm, and the mean difference from intended cut was 30.17 ± 37.45 μm. No significant difference was found between results achieved with early specimens versus those achieved with later specimens (P = 0.425). Thin, reproducible endothelial grafts can routinely be produced by trained technicians at their respective eye banks without significant concerns for an extended learning curve. This service can reduce perioperative surgical complexity, required surgical paraphernalia and theatre times. The consistent preparation of single-pass, ultrathin pre-cut corneas may have additional advantages for surgeons seeking to introduce lamellar techniques.

Mechanically aligned total knee arthroplasty carries a risk of bony gap changes and flexion-extension axis displacement.

The flexion-extension axis (FEA) of the femur is substantially changed after mechanically aligned total knee arthroplasty (TKA) due to a discrepancy in bone cut thickness between the posterior and distal femoral regions. This study assessed the bony gap changes and FEA displacement caused by this problem in osteoarthritis patients. The study enrolled 60 knees from 60 patients for whom primary TKA was planned due to medial knee osteoarthritis. All patients underwent computed tomography, and 3-dimensional (3D) bone models were reconstructed on 3D-planning software. Bone cuts of the distal femur and proximal tibia were simulated to be perpendicular to each mechanical axis. Bony gap change was computed as the difference in bone cut thickness between medial and lateral compartments. Each femoral condyle was assessed for potential FEA displacement, as the difference in bone cut thickness between posterior and distal femoral regions. The mean magnitude of bony gap discrepancy necessary for mediolateral balancing was 1.6 ± 3.3mm (range -7 to 8.2mm) at 0° extension and -0.2 ± 2.6mm (range -6.4 to 4.3mm) at 90° flexion. At least 2mm of bony gap discrepancy at 0° extension and 90° flexion was found in 40 patients (67%) and 26 patients (43%), respectively. In terms of femoral bone cut, posterior bone cut thickness was significantly larger than distal bone cut thickness in the medial compartment (p < 0.001). Bony gap discrepancy between distal and posterior regions of the femoral condyle was ≥2mm in 28 patients (47%). This study focused on two flaws of mechanically aligned TKA in OA patients. Substantial numbers of patients inevitably required >2mm of medial collateral ligament release at 0° extension and showed a bone cut discrepancy between distal and posterior regions, carrying a risk of FEA displacement and subsequent unnatural knee motions during knee extension and flexion. Level of evidence IV.

A study on process design of plate cold forging for machinability improvement of piston under drive brake

Reduction of energy in manufacturing industries is a current issue to keep the earth green. This energy saving yields the cost reduction in automotive industries. Many automotive part companies try to improve their manufacturing process to save the manufacturing energy. Specially, many attempts on changing the hot forging process into the cold forging process of plate forging have been tackled in the piston under drive brake used in an automotive transmission module. The turning process after hot forging changed to turning after plate cold forging for the energy and cost reduction. But two extrusion shapes in an outermost diameter of part let fall tool life by interrupted cut in turning. Therefore, it needs thickness reduction of two extrusion areas in the outermost diameter. This study suggests an effective way to reduce the thickness of interrupted cut in forging stage.

Dynamics of Stock Removal in Profile Milling Process by Shaped Tool

The article describes the mechanism of the stock removal during the milling of cylindrical and shaping cutters, the cutting of the latter is outlined around. It is shown that during the processing with concaved shaping cutter the contact angle of the cutter with the workpiece changes in the height of the tool because of curved cutting teeth. The current contact angle increases from the end to the transverse mirror plane of the cutter, causing the shift in end of operation time of elementary cutting blades, considered in small neighbourhood of diametral plane of tool. It is found that for the convex surface to be treated a minimum value of the current contact angle is typical for the surface of each cutter and the maximum value - for the transverse diametral plane of the cutter. The results obtained reveal the dynamics of the stock removal in the profile milling of shaping cutter and are necessary for high-quality project of efficient processes for profile milling of mechanical engineering products, wood working and other industries. When the counter circuit of profile milling with the cutter tool the contacting of the tool with a workpiece starts at zero point of cut layer thickness and ends its maximum value at the end of a single cut which causes an increase in the cutting force.

Efficacy of a novel iPod-based navigation system compared to traditional navigation system in total knee arthroplasty

Background: This prospective study aimed to verify the efficacy of a novel, hand-held, iPod-based navigation system in comparison to traditional navigation system for total knee arthroplasty (TKA).Methods: Limb alignment, tibial and distal femoral bone cut thickness and plane were recorded intraoperatively using both iPod-based and traditional navigation system in 36 knees undergoing primary TKAs.Results: Intraoperatively, the iPod-based navigation system showed good to excellent correlation and reliability for tibial and distal femoral bone cut thickness, plane of the femoral cut and limb alignment when compared to the traditional navigation system.Conclusions: Despite its quick registration feature, the iPod-based system has an efficacy similar to traditional navigation system and is a positive step towards making navigation systems for TKA more compact, user-friendly, time and cost-effective.

Patellar Cut and Composite Thickness: The Influence on Postoperative Motion and Complications in Total Knee Arthroplasty

BackgroundLittle data exist on the influence of patellar thickness on postoperative motion or complications after total knee arthroplasty (TKA). This study addresses the following questions: Is postoperative motion influenced by change in composite patellar thickness? Is change in patellar thickness associated with more complications? And do more complications occur in the knees with a patellar bone remnant (<12 mm) and a native patellar thickness <18 mm? MethodsIn total, 3655 TKAs were performed by 3 surgeons over a 28-year interval. All knees had caliper measurement of patellar thickness before the patellar cut, after implantation of the component and postoperative motion recorded in the database 1 or 2 years after TKA. ResultsPatellar composite thickness was the same (1034 knees), thicker (1617 knees), and thinner (1004 knees). A significant but weak relationship was identified between the change in patellar thickness and motion (P < .01, ρ = −0.046); an increase in “composite patellar thickness” of 10 mm would result in a 3° loss of knee motion. Significant differences were identified between change in thickness and manipulations (P < .05), ruptures (P = .01), and patellar clunk/crepitus (P < .01). Examining knees with bone remnant thicknesses (<12 mm/≥12 mm), there was no difference in fractures (P = .26). No extensor ruptures occurred in knees with remnant thickness <12 mm. Comparing knees with native bone thickness (≤18 mm/>18 mm), significant differences were found in fractures (P < .01) and patellar radiolucencies (P = .01). ConclusionAs this data does not demonstrate a strong tendency toward losing motion when the patellar thickness is increased, the authors recommend avoiding compromise of the patellar bone stock and tendon insertion. When native patellar bone is thin (<18 mm), we recommend maintaining 12 mm of patellar bone stock and accept the increase in composite thickness.

Reproducibility of single-pass donor DSAEK tissue preparation with the MORIA single-use microkeratome

To assess the reproducibility of single-pass cutting for preparation of ultra-thin (≤120μm) donor cornea grafts in Descemet stripping automated endothelial keratoplasty (DSAEK). All consecutive patients of DSAEK performed using the MORIA One Use microkeratome (MORIA, Antony, France) in between June 2014 and August 2015. Patient and donor central corneal thickness (CTT), microkeratome head, remaining stromal bed thickness (RSBT), number of cut and graft thickness at 1 month and 6 months postoperatively were recorded in this single-center prospective study. The mean preoperative donor graft CCT was 569.0±45.1μm and the mean donor endothelial graft CCT immediately after the cut was 116.5±28.7μm. At 1 month postoperatively, the mean CCT was 102.8±35.9μm. At 6 months, the mean CCT was 89.4±26.2μm. In all eyes, the mean CCT decreased from the post-cut (116.5±28.7μm) to the last visit (89.4±26.2μm) (P<0.01) due to in vivo deturgesence of the graft. We obtained 77.5% ultra-thin DSAEK immediately after the cut, 77.5% at 1 month and 89.8% after 6 months. Single-pass technique with the MORIA One Use microkeratome offers safe and reproducible DSAEK tissue preparation and allows achieving ultra-thin DSAEK in 89.8% of cases.

Analysis of the chip-splitting performance of a dedicated cutting tool in dry orbital drilling process

Orbital drilling technology, as an alternative of conventional drilling, is considered a promising option of hole-making work in the aircraft industry. However, in orbital drilling, unreasonable chips with irregular geometry and large size can cause the rapid increase of cutting force and cutting heat accumulation and eventually lead to serious tool wear and poor hole wall quality. To solve the problem, this paper designs a dedicated cutting tool with a chip-splitting structure to be used in the orbital drilling of TC4 titanium alloy under dry cutting condition. Based on the analysis of orbital drilling kinematics, the dedicated cutting tool, having front cutting edges with straight cutting segments and helical peripheral cutting edges, is first proposed. Furthermore, the width of cut, uncut chip thickness and length of cut are calculated considering the different characteristics of cutting condition for each tooth in a chip formation period. Particularly, the geometries of the undeformed chips are simulated and the relationships between the geometries and machining parameters are studied. Experimental study on the chip-splitting performance of the dedicated cutting tool in orbital drilling of TC4 titanium alloy is also conducted. The results show that with the dedicated cutting tool, the chip can be removed smoothly, which leads to higher machining quality and lower tool wear.

Study on predictive model of cutting force and geometry parameters for oblique elliptical vibration cutting

Elliptical vibration cutting (EVC), as one of the promising methods for ultra-precision machining, has aroused many scholars' attention. However, few studies focused on the basic mechanism of oblique EVC. In the present study, an analytical force model of oblique EVC has been developed, which only use the material properties, tool geometry and the physical laws of deformation. The transient thickness of cut and transient shear angle are considered in the proposed model. Based on the analysis of oblique EVC mechanism, the geometric parameters of oblique ultrasonic vibration assisted turning (UVAT) are predicted by this model, which are in good agreement with the experimental results available in the literature. The transient cutting force components of orthogonal EVC are also predicted, results of which are in accord with the experimental results. Thus this model is available to predict the geometry parameters and cutting force of the orthogonal EVC accurately. In addition, the proposed model can also be applied to predict geometric parameters and cutting force components of oblique EVC.

Specific energy based evaluation of machining efficiency

Rubbing and ploughing increase the tool tip energy demand in machining. An efficient set of cutting conditions would direct the energy into material shearing and hence selecting the efficient set is a value adding activity. In this work, a side milling tests were conducted on a milling machine tool to investigate the specific ploughing energy on AISI 1045 steel alloy, titanium 6Al–4V alloy and aluminium AW6082-T6 alloy materials. The relationship between the cutter swept angle and the specific ploughing energy is explored. An optimised model for width of cut and undeformed chip thickness at which ploughing effect would be minimal is proposed. The proposed methodology can be used to evaluate machining efficiency based on maximum specific shear energy and also to derive the specific ploughing energy for minimum tip energy demand.

Numerical Simulation of Chip Ploughing Volume and Forces in 5-axis CNC Micro-milling Using Flat-end Mills

It is a challenging task to avoid ploughing effects in micro-milling. When one tooth of the cutting tool crosses the minimum chip thickness boundary, the tool would enter into the ploughing zone with no chip formation. Therefore, it is significant to predict the ploughing volume and forces in micro-milling. In this work, the ploughing mechanism for micro-milling is proposed by considering the minimum chip thickness effects. A 3D chip geometry is developed to calculate chip thickness, ploughing volume and ploughing forces in micro 5-axis flat-end milling with a flat-end mill. The local parallel sliced tool based method is then applied to get cutter-workpiece engagement domain where the cutting flutes entry and exit the workpiece, minimum chip thickness and depth of cut are required to predict ploughing forces. Local parallel sliced method divides the cutting tool into several slices that are perpendicular to the tool axis along the local coordinate system. On each layer, the removal chip area is dividing into ploughing zone and shearing zone by the minimum chip thickness. Ploughing zone is the area as chip thickness is less than the minimum chip thickness. In the shearing zone, chip thickness is larger than the minimum chip thickness. The total chip ploughing volume is obtained by adding all ploughing area along axial direction.

The Utmost Thickness of the Cut Sheet for the Qualitative Oxygen-assisted Laser Cutting of Low-carbon Steel

The peculiarity of the laser cutting is its high speed combined with the high quality of the cut surface. The issues, how the cutting speed and cut roughness change with the sheet thickness, and what is the utmost thickness at which the quality is acceptable, are of practical importance. Theoretical models of the laser cutting developed today do not permit answering these questions. In the present work, the task is solved experimentally for the oxygen-assisted laser cutting of low-carbon steel. Under study was the dependence of the cut surface roughness on the cutting speed within the wide range of cut sheet thicknesses. The experiments were carried out with the CO2 laser. The empirical dependencies of the optimal cutting speed (at which the cut surface roughness is minimal) on the sheet thickness are found. It is demonstrated that there is the utmost thickness of 40...50 mm, and above it the qualitative cutting is impossible. The obtained results are compared to the similar ones obtained for the fiber laser.

Experimental Analysis of the Feasibility of Shaving Process Applied for High-Strength Steel Sheets

In recent years, the engineered materials were developed to improve their mechanical properties. A high-strength steel sheet is one of them, developed to serve the requirement of reducing weight of vehicles. Therefore, as a new material, many researches have been carried out to examine the use of sheet metal forming process applied for high-strength steel sheet. However, the feasibility of shaving process applied for it has not been investigated yet. In the present study, this feasibility was revealed by using experiments on two types of high-strength steel sheets: SAPH 440 and SPFH 590Y (JIS). The relationship between shaved surface feature and shearing clearance of high-strength steel sheets corresponded well with those of their conventional metal sheets. However, due to the high ultimate strength of these materials, it was revealed in this present study that there were not any suitable conditions of shaving process that could be applied to achieve the requirements of smooth cut surface overall material thickness.

Sensitivity of magnetic resonance imaging based on the detection of 19F NMR signals

The evaluation of the sensitivity of magnetic resonance tomography with a magnetic field of 7 T based on the detection of 19 F NMR signals was performed with the use of the solutions of trifluoroacetic acid, 1,1,1,3,3,3-hexafluoroisopropanol and sym -nonafluoroneopentanol, whose 19 F NMR spectra consist of single line signals. The scanning of a 12×12 cm zone with a resolution of 1.2 mm and a cut thickness of 4 mm for 10 min gave reliable images if the local concentration of 19 F atoms in the test zone exceeded 0.3–0.6%.

MATHEMATICAL MODEL FOR CHIP GEOMETRY CALCULATION IN FIVE-AXIS MILLING

This paper presents the method to calculate the geometries of instantaneous chip in five-axis milling. The inclination angle changes in between two consecutive CC-points were taken into account in the calculation. In the first stage, the engagement angle, the axial depth of cut and cut width were determined through the mapping technique. The engagement point of the Work piece Coordinate System (WCS) was mapped to a Tool Coordinate System (TCS). In the second stage, the engagement angle and depth of cut, which were defined in the first stage were then used as a primary input to obtain the cut thickness and cut width. Two simulation tests have been presented to verify the ability of the proposed model to predict the cut geometry. The first tests revealed that the inclination angle makes the size of the cut thickness and cut width fluctuate. The cut width increased when the tool inclination angle increased. For the cut thickness, its magnitude was influenced by two effects, the orientation effect and the tooth path effect. The final result was a compromise between these two effects. In the second simulation test, the proposed model was successfully implemented to support the feedrate scheduling method.

An atomistic simulation investigation on chip related phenomena in nanometric cutting of single crystal silicon at elevated temperatures

Nanometric cutting of single crystal silicon on different crystal orientations and at a wide range of temperatures (300–1500K) was studied through molecular dynamics (MD) simulations using two sorts of interatomic potentials, an analytical bond order potential (ABOP) and a modified version of Tersoff potential, so as to explore the cutting chip characteristics and chip formation mechanisms. Smaller released thermal energy and larger values of chip ratio (ratio of the uncut chip thickness to the cut chip thickness) as well as shear plane angle were obtained when cutting was performed at higher temperatures or on the (111) crystal plane, implying an enhancement in machinability of silicon. Nonetheless, the subsurface deformation depth was observed to become deeper under the aforementioned conditions. Further analysis revealed a higher number of atoms in the chip when cutting was implemented on the (110) crystal plane, attributable to the lower position of the stagnation region which triggered less ploughing action of the tool on the silicon substrate. Regardless of temperature of the substrate the minimum chip velocity angle was found while cutting the (111) crystal plane of silicon substrate whereas the maximum chip velocity angle appeared on the (110) surface. A discrepancy between the two potential functions in predicting the chip velocity angle was observed at high temperature of 1500K, resulting from the overestimated phase instability and entirely molten temperatures of silicon by the ABOP function. Another key observation was that the resultant force exerted by the rake face of the tool on the chip was found to decrease by 24% when cutting the (111) surface at 1173K compared to that at room temperature. Besides, smaller resultant force, friction coefficient at the tool/chip interface and chip temperature was witnessed on the (111) crystal plane, as opposed to the other orientations.

Preserving the PCL during the tibial cut in total knee arthroplasty

Previous studies have shown that the PCL insertion may be damaged during the tibial cut performed in total knee arthroplasty. We investigated the maximum thickness of a tibial cut that preserves the PCL insertion and to what extent the posterior slope of the tibial cut and that of the patient's tibial plateaus affect the outcome. MR images of 83 knees were analysed. The maximum thickness of a tibial cut that preserves the PCL using a posterior slope of 0°, 3°, 5° and parallel to the patient's slope of the tibial plateau, was evaluated. Correlations between the results and the degrees of the posterior slope of the patient's tibial plateaus were also investigated. The maximum thickness of a tibial cut that preserves the entire PCL insertion was, on average, 5.5, 4.7, 4.2 and 3.1mm when a posterior slope of 0°, 3°, 5° and parallel to the patients' tibial plateaus was used, respectively. When the 25th percentile was considered, the maximum thickness of a tibial cut that preserved the PCL was 4 and 3mm with a tibial cut of 0° and 5° of posterior slope, respectively. The maximum thickness of a tibial cut that preserved the PCL was significantly greater in patients with a sagittal slope of the tibial plateaus more than 8° than in those with a sagittal slope less than 8°. In cruciate retaining implants, the PCL insertion may be spared in the majority of patients by performing a tibial cut of 4mm, or even less when a posterior slope of 3°-5° is used. The clinical relevance of our study is that the execution of a conservative tibial cut, followed by a second tibial resection to achieve the thickness required for the tibial component to be implanted, may be an alternative technique to spare the PCL in CR TKA. II.

Analysis and modeling of force in orthogonal elliptical vibration cutting

This paper aims to reveal the material removal mechanisms of the elliptical vibration cutting (EVC) and present the predicted model of orthogonal cutting force. Further study of mechanism will be helpful to explain the phenomena that EVC can reduce the cutting force, lower cutting temperature, and improve the surface integrity. In each overlapping EVC cycle, almost all the parameters are time-varying, of which two important factors are focused: (i) transient thickness of cut and (ii) transient shear angle. The analysis model simplified the complex process of the EVC as conventional cutting (CC) which considering two transient variables. This paper presents a non-equidistant shear zone model to predict the shear angle, tool–chip friction angle, and shear stress in CC under the same conditions of the EVC. Then, the transient thickness of cut and transient shear angle are investigated. Thus, an analytical model of the force in EVC is proposed. The model is available to predict the cutting force of the EVC accurately without any experimental parameters in CC. In addition, experimental results available in the literature are conducted for comparison, which are in well agreement with the analysis model.