Burr Size Research Articles

Machining-Induced Burr Suppression in Edge Trimming of Carbon Fibre-Reinforced Polymer (CFRP) Composites by Tool Tilting

Several challenges arise during edge trimming of carbon fibre-reinforced polymer (CFRP) composites, such as the formation of machining-induced burrs and delamination. In a recent development, appropriate-quality geometric features in CFRPs can be machined using special cutting tools and optimised machining parameters. However, these suitable technologies quickly become inappropriate due to the accelerated tool wear. Therefore, the main aim of our research was to find a novel solution for maintaining the machined edge quality even if the tool condition changed significantly. We developed a novel mechanical edge-trimming technology inspired by wobble milling, i.e., the composite plate compression is governed by the proper tool tilting. The effectiveness of the novel technology was tested through mechanical machining experiments and compared with that of conventional edge-trimming technology. Furthermore, the influences of the tool tilting angle and the permanent chamfer size on the burr characteristics were also investigated. A one-fluted solid carbide end mill with a helix angle of 0° was applied for the experiments. The machined edges were examined trough stereomicroscopy and scanning electron microscopy. The images were evaluated through digital image processing. Our results show that multi-axis edge-trimming technology produces less extensive machining-induced burrs than conventional edge trimming by an average of 50%. Furthermore, we found that the tool tilting angle has a significant impact on burr size, while permanent chamfer does not influence it. These findings suggest that multi-axis edge trimming offers a strong alternative to conventional methods, especially when using end-of-life cutting tools, and highlight the importance of selecting the optimal tool tilting angle to minimize machining-induced burrs.

Does initial use of large versus small burr size in left main stem bifurcation impact clinical and procedural outcomes?

Abstract Background Coronary calcifications, detected in up to 25% of treated coronary lesions nowadays, has a well-known association with complications during PCI, particularly for left main stem (LMS) interventions. Current guidelines recommend coronary artery bypass grafting for patients with LMS disease, particularly with high SYNTAX score ≥ 33. However, in those with increased surgical risk, PCI can be used particularly with use of rota-ablation (RA). RA is a well-established treatment for heavily calcified disease particularly in non LMS sites. However, data on the safety and efficacy of use of RA in LMS bifurcation management is limited. Current guidelines recommend using a small burr size at the start, with upsizing burrs if required. Whether upfront use of large burr size ≥ 1.75 versus smaller burr size in this context in is safe or effective is unknown. Methods This was a retrospective, single centre, study. Included patients undergoing RA to LMS bifurcation disease. Standard procedures for RA were applied to each case, following current national and international intraprocedural standards. The main study outcomes were overall mortality at 1 year, and a comparison of mortality at 1 and 4 years between groups and repeat target lesion revascularization at 4 years. Results To our knowledge, this is the largest series of LMS rota-ablation cases, with the longest available follow up. Between June 2009 and October 2021, we included 243 patients with a mean age of 74.7±9 years. Males formed 80% of the cases. 51.4% of patients were treated with a large bur size ≥ 1.75mm, with more males being treated with large burr size. Most treated lesions were true bifurcations (85.6%). Treated lesions were complex (Syntax score = 35.3 ± 10.6). Radial access was used in almost two thirds of patients, with size 7F sheath being the most used. Intravascular ultrasound was more commonly used with large burr size (p = 0.017). Upfront 2-stent techniques, predominantly culotte, was employed more often with large burr size. Provisional technique was used more often in the small burr size group. The burr size to vessel size was 0.4 in small burr group versus 0.48 in large burr size using stent size as a surrogate for vessel size. Post dilatation balloons were larger as well as stent size in the large burr group. The overall 1-year mortality for the group was 12.7% similar to international literature. Importantly, procedural complications were not different between groups, and similarly mortality at 1 and 4 years, p = 0.082 and p = 0.384 respectively. There was no difference between groups in terms of repeat vessel revascularization at 4 years p=0.487. Conclusions Upfront use of large burr size ≥ 1.75 is feasible and safe to treat LMS bifurcation disease with no increase in procedural complications or mortality and target lesion revascularization on long term follow up. It is notable that in-hospital mortality for this cohort was low at 1.6% in comparison to previous studies.1 and 4 year mortality KM curves

Current application and results of the combined use of intravascular lithotripsy and rotational atherectomy for the treatment of calcified coronary lesions

Abstract Background Intravascular lithotripsy (IVL) and rotational atherectomy (RA) might be used simultaneously (Rotatripsy) to treat calcified lesions during percutaneous coronary intervention (PCI), though data on the effectiveness and sequence of their use is limited. Purpose To identify indicators for the use of Rotatripsy and to assess its safety and success rates, both acutely as at one-year follow-up. Methods Patients undergoing PCI with IVL and RA across six centers in two European countries from May 2019 to December 2023 were included. Demographic, clinical, procedural and follow-up data were collected. Angiographic and intracoronary imaging (ICI) data were analyzed centrally. Efficacy endpoints included device success (delivery of the RA-burr and IVL-balloon across the target lesion and administration of therapy without related complications), technical success (TIMI 3 flow and residual stenosis <30% by quantitative coronary analysis) and procedural success (composite of technical success with absence of in-hospital major adverse cardiovascular events (MACE: cardiac death, myocardial infarction or target vessel revascularization). Safety endpoints comprised rotatripsy-related complications and MACE at one-year follow-up. Results A total of 114 patients (75±9 years, 78% male) underwent rotatripsy for 120 lesions. Patients presented with an ACS in 58(51%) cases and chronic coronary syndrome in 56(49%). The left anterior descending artery(n=66, 55%) was the most frequently treated target vessel, with diverse lesions being addressed, including bifurcations(30%), ostial(18%), CTO(7%) and in-stent(12%) lesions. The mean burr size was 1.5±0.2mm with a maximum rotational speed of 171±15k rpm and burr/vessel ratio of 0.46±0.2. IVL involved an average of 68±25 pulses and a balloon size of 3.5±0.5mm. The predominant used sequence of rotatripsy was RA followed by IVL(n=106, 88%). Among these cases, IVL was electively combined with RA in 68(57%) lesions, and used for balloon underexpansion(n=37, 31%) and stent crossing failure after RA(n=1, 1%). Additionally, IVL served as bail-out strategy after RA and stenting in 10(8%) and preceded RA in 4(3%) lesions, particularly when balloon/stent delivery failed after IVL. After rotatripsy, stents were implanted in 116(97%) lesions and drug-eluting balloon used in 3(3%). ICI was utilized in 69(58%) target lesions. Device, technical and procedural success were 97%, 94% and 93%, respectively. Therapy-related complications occurred in 4 patients(4%), and included two(2%) coronary perforations, one(1%) dissection and one(1%) burr entrapment. At one-year follow-up (present in 77(67%)), MACE was observed in 7(6%). Conclusions Rotatripsy demonstrated efficacy across diverse clinical and anatomical settings, with the majority of procedures electively employing RA before IVL. High success rates and low complication rates were observed, with few patients experiencing MACE at one-year follow-up.

Practices and outcomes of rotational atherectomy in China: The Rota China registry.

Rotational atherectomy (RA) remains an integral tool for the treatment of severe coronary calcified lesions despite emergence of newer techniques. We aimed to evaluate the contemporary clinical practices and outcomes of RA in China. The Rota China Registry (NCT03806621) was an investigator-initiated, prospective, multicenter registry based on China Rota Elite Group. Consecutive patients treated with RA were recruited. A pre-designed, standardized protocol was recommended for the RA procedure. The primary safety endpoint was major adverse cardiovascular events (MACE: composite of cardiac death, myocardial infarction, or ischemia-driven target lesion revascularization) at 30 days. The primary efficacy endpoint was procedural success. Between July 2018 and December 2020, 980 patients were enrolled at 19 sites in China. Mean patient age was 68.4 years, and 61.4% were men. Radial access was used in 79.1% patients, and 32.7% procedures were guided by intravascular imaging. A total of 22.6% procedures used more than 1 burr, and the maximal burr size was ≥1.75 mm in 24.4% cases, with burr upsizing in 19.3% cases, achieving a final burr-to-artery ratio of 0.52. Procedural success was achieved in 91.1% of patients, and the rate of 30-day and 1-year MACE was 4.9% and 8.2%, respectively. Multivariable analysis identified the total lesion length (HR 1.014, 95% CI: 1.002-1.027; p = 0.021) as predictor of 30-day MACE, and renal insufficiency (HR 1.916, 95% CI: 1.073-3.420; p = 0.028) as predictor of 1-year MACE. In this contemporary prospective registry in China, the use of RA was effective in achieving high procedural success rate with good short- and long-term outcomes in patients with severely calcified lesions.

Experimental and statistical damage analysis in milling of S2‐glass fiber/epoxy and basalt fiber/epoxy composites

AbstractS2‐glass fiber reinforced plastics (S2‐GFRP) and basalt fiber reinforced plastics (BFRP) have emerged as crucial materials due to their exceptional mechanical properties, and milling of composite materials plays an important role in achieving desired properties. However, they have proven challenges due to relative inhomogeneity compared with metals, resulting unpredictability in quality of milling operations. The objective of this work is to investigate the effect of cutting parameters, tool geometry and tool surface materials on the surface quality of composites using burrs as a metric. S2‐GFRP and BFRP composites were produced by the vacuum infusion method. Helical and straight flute end mills were manufactured from high‐speed steel (HSS) and carbide rounds, and half of them were coated with titanium nitride using reactive magnetron sputtering technique. Taguchi L18 orthogonal array is used to determine the effect of tool material, tool angle, coating, cutting direction, spindle speed, and feed rate on the machining quality of S2‐GFRPs and BFRPs with respect to burr formations. Milling experiments were conducted under dry conditions and then the burrs were imaged to calculate the total area and length. Statistical analysis was also performed to optimize the machining parameters and tool type for ensuring the structural integrity and performance of the final composite parts. The results showed that the selection of tool material has the most significant impact on the burr area and length of the machined surface. The novel image analysis allows to analyze the extent of the burr size with a desirable operation speed for industrial applications.Highlights Aerospace grade S2‐Glass (S2‐GFRP) and basalt fiber reinforced plastics (BFRP) were manufactured. Carbide and HSS end mills were fabricated and coated with titanium nitride protective layer. FRPs were machined at various process parameters designed by Taguchi method. Distinctive image processing was firstly used to compute milling induced Burr area and length. Statistical analysis was performed to quantify the contribution of parameters and optimize milling.

Laser and mechanical micro-drilling for aerospace applications

Traditional laser percussion drilling encounters challenges related to poor geometry and thermal defects. At the same time, mechanical micro-drilling while generating high-quality holes, faces issues such as premature drill breakage and difficulty drilling at acute angles. This review paper introduces a novel approach to micro-drilling Inconel 718 alloy sheets at acute angles by combining sequential laser and mechanical drilling. The study showcases the feasibility and fundamental characteristics of this innovative technique. Results indicate that the sequential laser-mechanical micro-drilling approach mitigates the drawbacks associated with laser-drilled holes, leading to reduced burr size, decreased machining time, and increased tool life when compared to conventional mechanical drilling methods. This advancement holds promise for enhancing precision and efficiency in aerospace applications, paving the way for improved manufacturing processes in the aerospace industry.

Research on production of microgroove arrays on TiAl intermetallic alloy by micro milling

TiAl intermetallic alloy is a superior lightweight material with excellent performance, and its micro features or components have promising applications in manufacturing fields. In this work, an investigation of micro milling of microgroove arrays on TiAl alloy was studied. The effects of cutting parameters including the feed per tooth (fz) and depth of cut ( ap) on the milling force, surface morphology, surface roughness and burr size of the micro-slots were investigated. The wear types and mechanisms of the micro end mills were also studied. The results showed that the optimal cutting parameters were fz = 3.5 μm/z and ap = 4 μm, which provided the best surface roughness Sa of 152 nm, top-burr heights on up- and down-milling sides of 19 and 19.5 μm respectively. Using the optimized cutting parameters, microgrooves with a width of 500 μm, aspect ratio of 5 and array period of 10 were fabricated successfully. Surface topography, dimensional accuracy and perpendicularity of the microgroove arrays were characterized. Results demonstrated that an increase in the microgroove number, microgroove edge chipping as well as burrs of the entrance and exit increased gradually. The dimensional error between the obtained width and the designed width of the microgroove was less than 2%, and the slope of the sidewalls reached more than 89°. The wear mechanisms of the micro end mills were abrasive wear and adhesive wear, and wear types were coating delamination, cutting edge chipping, and tool nose breakage.

Risk of hearing loss in non-operated ear due to mastoid drilling

Background: The study purpose is to evaluate the effect of drill-generated high intensity noise on hearing sensitivity in contralateral ear. Methods: Sixty patients who underwent mastoidectomy were studied to see the effect of mastoid drilling on hearing sensitivity in normal ear using pure tone audiometry (PTA) and distortion product otoacoustic emission (OAE) values recorded preoperatively and postoperatively. Results: For PTA, there is no significant hearing loss for 0.25 kHz and 0.50 kHz for all PODs. For 1 kHz, 2 kHz and average PTA there is significant temporary hearing loss from POD 1 to POD 7 which normalizes around POD 30. However, there is significant temporary threshold shift for 4 kHz and 8 kHz from POD 1 to POD 5 and the hearing sensitivity improves to preoperative levels at POD 7. For OAE, 1 kHz, 4 kHz and average OAE there is significant temporary hearing loss from POD 1 to POD 7 which normalizes around POD 30. However, there is significant temporary threshold shift for 2 kHz and 6 kHz from POD 1 to POD 5 and hearing sensitivity improves to preoperative levels at POD 7. There is a significant correlation between drilling duration and PTA averages and OAE averages. Conclusions: Sensorineural hearing loss is more prevalent following modified radical and radical mastoidectomy as compared to canal wall up mastoidectomy. The factors influencing postoperative contralateral ear sensorineural hearing loss are type and size of burr and the duration of burr use.

Effect of the chip thickness and the exit angle on the burr formation and break-out of the workpiece edge in the case of milling

The milling processes often cause defects on the workpiece edge, such burr and break-out which significantly affects the part quality. The burr formation can be controlled during the process with the adjustment of appropriate parameters. The planar exit angle (EA) and the exit order have a promising effect on burr formation. However, the accurate calculation of the EA is difficult, moreover, the uncut chip thickness at the exit point also depends on the EA value. The former researches dealt only with the EA but the dependent uncut chip thickness was neglected. The aim of the current research is to investigate the burr formation at the face milling of AlSIMg7. During the research, the effect of the EA and uncut chip thickness is examined as a new approach, independently of each other. During the experiments, the size of the burr and the edge break-out is measured by an image processing-based method. The results showed that the uncut chip thickness at the exit point has a considerable effect on burr formation. Based on the experimental results, it can be stated, that the distribution of burr size and edge break-out is not normal. The behaviour of burr is quite complex and can only be described with statistical methods. The distribution of the examined defects can be approximated by the combination of two or three probability density functions.

In-hospital Outcomes of Rotational Atherectomy in ST-Elevation Myocardial Infarction: Results From the Multicentre ROTA-STEMI Network

BackgroundAlthough the use of rotational atherectomy (RA) is off-label in the setting of ST-elevation myocardial infarction (STEMI), it can be the only option in severely calcified culprit lesions to achieve procedural success. We sought to investigate the safety and feasibility of RA during primary percutaneous coronary intervention (PPCI). MethodsThis was a retrospective observational study of patients who underwent RA during PPCI from 12 European centres. The main outcomes were procedural success (defined as successful stent implantation with final thrombolysis in myocardial infarction [TIMI] flow 3 and residual stenosis < 30%) and in-hospital mortality. A comparison of patients presenting with and without shock was performed. ResultsIn 104 patients with RA during STEMI, the mean age was 72.8 ± 9.1 years, and 35% presented with cardiogenic shock. Bailout RA was performed in 76.9% of cases. Mean burr size was 1.42 ± 0.21 mm. Procedural success was achieved in 86.5% of cases, with no difference between shocked and nonshocked patients (94.4% vs 82.4%; P = 0.13). In-hospital stent thrombosis occurred in 0.96%, perforation in 1.9% and burr entrapment in 2.9% of cases. In spite of equally high procedural success, in-hospital mortality was higher in shocked (50%) compared with nonshocked patients (1.5%; P < 0.0001). ConclusionsPatients presenting with STEMI requiring RA, represent a high-risk population, frequently presenting with cardiogenic shock. In this analysis of selected patients, RA was performed as a bailout strategy in the majority, and, as such, RA seems to be feasible with a high procedural success rate. In the absence of cardiogenic shock, RA-facilitated PCI seems to be associated with low in-hospital mortality.

Experimental and statistical investigation into surface characteristics in micro milling of bottom pouring/gravity stir cast Al6061 alloy

Micro milling offers the best way to create micro channels; however, the burr formation and surface roughness of the micro channel are difficult to control. Micro channel fabrication and their characterization of stir cast Al6061 are rarely investigated. In the present study, Al6061 alloy was processed by the bottom pouring stir casting method. The micro channels were fabricated on a base and stir cast Al6061 alloys using TiSIN-coated micro end mill tools. The influence of micromachining parameters such as spindle speed, feed rate, and depth of cut on burr formation, cutting force, burr size, and surface roughness was investigated. A comparison was made between the findings obtained from the micro milling of the base and stir cast Al6061 alloys. The surface morphology of fabricated micro channels was analysed and correlated with the roughness profile to understand the channel profile and burr formation. The top burr formation mechanism in stir cast Al6061 alloy was investigated in detail. Low feed rate, low depth of cut, and high spindle speed produced the micro channel with fewer burrs, low surface roughness, and low cutting forces. At the optimum parameter, stir cast Al6061 alloy showed an approximate 420%, 16%, and 300% increase in Fy, Fz, and Ra, respectively, as compared to the base Al6061 alloy. Adhesion wear, built-up edge, and microchipping were found to be the main tool wear mechanisms in micro machining of stir cast alloy. This study directs the choice of cutting parameters for the stir cast micro milling process.

Burr formation mechanism and morphological transformation in grinding of nickel-based superalloy honeycomb cores under ice freezing and MQL conditions

Nickel-based superalloy honeycomb core (NBSHC) is extensively used in aerospace field due to the light weight, high specific strength and high temperature resistance. The burrs of NBSHC are extremely prone to be formed during machining and the insufficient welding strength or false welding between NBSHC and skin is generated because of the large or unreasonable burr morphology, resulting in premature failure of the parts. In this work, a novel method of ice freezing combining with minimum quantity lubrication (MQL) was proposed to grind NBSHC to improve the burr morphology and size. The burr formation mechanisms of NBSHC under ice freezing and MQL conditions were revealed by single abrasive particle grinding cell wall and verified by grinding experiments. The grinding force, burr morphology transformation mechanisms and size were investigated in-detail by experiments combining with FEM results. The results indicated that MQL and ice freezing decreased the plastic flow property of material by reducing the temperature and friction of NBSHC, thereby promoting the transformation of burr size from large into micro, and the burr shape from long strip into block. Decreasing grinding depth can also improve the burr morphology by decreasing the volume of plastic flow material. The improving effects of full of ice freezing were better than MQL for NBSHC grinding. The machining efficiency under full of ice combining with MQL was 3 times of that under quasi-dry grinding. These findings are significant for improving the machining quality and exploring the burr morphology transformation of NBSHC.

Grinding performance and acoustic emissions of structured CVD diamond micro-grinding tools

Micro-fabrication plays an increasingly important role in aerospace, biomedicine and other fields. CVD diamond has great application prospects in the preparation of micro-grinding tools due to its good wear resistance. In this work, the structured CVD diamond micro-grinding tool is proven to have better machining accuracy and wear resistance through the surface roughness and burr size after machining. According to the measured force signal results, the structured CVD diamond micro-grinding tool can reduce the axial force by 20% and the radial force by 10%. The reduction of the axial-to-radial force ratio proves that the structured CVD diamond micro-grinding tool has higher cutting efficiency. The relationship between acoustic emission signal characteristic value and surface roughness is determined by time domain analysis of acoustic emission. Through wavelet transform and machine learning, the wear degree of the common and structured CVD diamond micro-grinding tool is analyzed and predicted, and the accuracy rate is more than 99%.

Machining Temperature, Surface Integrity and Burr Size Investigation during Coolant-Free Hole Milling in Ti6Al4V Titanium Alloy

Modern Aircraft structures use titanium alloys where the processing of holes becomes essential to assemble aerospace parts. Considering the limitations of drilling, the study evaluates the helical milling for hole processing in Ti6Al4V. The experimental evaluation was conducted by considering burr size, surface roughness, machining temperature, and microhardness under coolant-free conditions. The axial feed and cutting speed were varied at three levels, and nine experiments were conducted. The results exhibit a lower machining temperature during helical milling than during drilling. In addition, the helical milling helped to lower the surface roughness and size of the exit burrs. However, helical-milled holes showed higher subsurface microhardness than conventionally drilled holes. The process variables were influential on machining temperature magnitude. The highest recorded temperature of 234.7 °C was observed at 60 m/min of cutting speed and 0.6 mm/rev feed. However, the temperature rise did not affect the microhardness. Strain hardening associated with mechanical deformation was the primary mechanism driving the increase in microhardness. Helical-milled holes exhibited an excellent surface finish at lower axial feeds, while chatter due to tool deformation at higher feeds (0.6 mm/rev) diminished the surface finish. The surface roughness increased by 98% when the cutting speed increased to 60 m/min from 20 m/min, while a moderate increment of 28% was observed when the axial feed increased to 0.6 mm/rev from 0.2 mm/rev. Furthermore, the formation of relatively smaller burrs was noted due to significantly lower thrust load and temperature produced during helical milling.

Secondary rotational atherectomy is associated with reduced occurrence of prolonged ST-segment elevation following ablation.

Elevation of the ST segment after percutaneous coronary intervention (PCI) using rotational atherectomy (RA) for severely calcified lesions often persists after disappearance of the slow-flow phenomenon on angiography. We investigated clinical factors relevant to prolonged ST-segment elevation following RA among 152 patients with stable angina undergoing elective PCI. PCI procedures were divided into two strategies, RA without (primary RA strategy) or with (secondary RA strategy) balloon dilatation before RA. Incidence of prolonged ST-segment elevation after disappearance of slow-flow phenomenon was higher in the 56 patients with primary RA strategy (13%) than in the 96 patients with secondary RA strategy (3%, p = 0.039). Univariate logistic regression analysis showed levels of low-density lipoprotein cholesterol (LDL-C) (odds ratio [OR] 0.95, 95% confidence interval [CI] 0.93-0.99; p = 0.013), levels of triglycerides (OR 0.97, 95%CI 0.94-0.99; p = 0.040), and secondary RA strategy (OR 0.23, 95% CI 0.05-0.85; p = 0.028) were inversely associated with occurrence of prolonged ST-segment elevation following ablation. However, hemodialysis, diabetes mellitus, left-ventricular ejection fraction, lesion length ≥ 20mm, and burr size did not show significant associations. Multivariate logistic regression analysis modeling revealed that secondary RA strategy was significantly associated with the occurrence of prolonged ST-segment elevation (Model 1: OR 0.24, 95% CI 0.05-0.95, p = 0.042; Model 2: OR 0.17, 95% CI 0.03-0.68, p = 0.018; Model 3: OR 0.21, 95% CI 0.03-0.87, p = 0.041) even after adjusting for levels of LDL-C and triglycerides. Secondary RA strategy may be useful to reduce the occurrence of prolonged ST-segment elevation following RA.

Machine vision based burr length measurement in abrasive waterjet trepanning

The demand for realizing products through near-net shape manufacturing routes, which eliminates the need for secondary finishing operations, is increasing in high-value industries. Making holes is one of the very frequent operations in realizing these products in various industries. On the other hand, burr formation is an issue in machining ductile material. Burr removal requires a secondary operation that increases manufacturing costs. In this context, abrasive waterjet (AWJ) machining suits better as the AWJs can realize near-net shape parts from ductile materials. Although the burr formation by the AWJs is considerably minimal relative to their conventional counterparts, the available cutting energy influence the burr shape and size. In this work, initially, the effect of waterjet pressure, effective standoff distance (SoDeff), and material thickness on the burr length and shape in AWJ trepanning were studied. A machine vision approach was used to measure the burr length and validated with the measurements from the confocal microscope. The result shows that the machine vision system captured the length of the burr with an error percentage of 11.05 % at the waterjet pressure of 300 MPa and 12.55 % at 350 MPa. Following this, the micrographs were taken to analyze the effect of material thickness on the burr and the material removal mechanism in the vicinity of the burr. Finally, a sacrificial layer-based solution is proposed and demonstrated to avoid even the minimal burr formed in AWJ trepanning.

Influence of tool wear on chip-like burr formation during micro-milling, and image processing based measurement of inwardly-deflected burrs

During micro-milling, the regular top-burrs usually bend in a direction laterally opposite to the milled feature. This top-burr morphology changes as the cutting edge condition progressively deteriorates with inherent tool wear. An edge-chipped tool tends to produce unusual top-burr that resembles an incompletely separated chip. Such chip-like burr also has a tendency to flow inside the micro-milled feature. This article, for the first time, explores the integral roles of worn-out tool geometry, micro-milling mechanics and process parameters on chip-like burr formation on Ti–6Al–4V during machining using 0.5 mm diameter TiAlN-coated WC-6Co tools under minimum quantity lubrication. Round-edges of the coated micro-mill progressively pass through break-in wear, steady abrasive wear, adhesive wear, coating delamination, and edge-chipping. A comprehensive analysis is presented here to explore the mechanism of chip-like burr formation considering the changes in tool geometry and corresponding variations in chip-tool-work tribological contact, cutting forces, stress distribution, burr root thickness, burr nano-hardness and surface roughness. Further, an algorithm for digital image processing is developed for efficient and reliable measurement of the burr size and corresponding inwardly-bent fraction. Subsequently, the roles of process parameters are assessed to explore the scopes of controlling the inward bending of the chip-like burrs.

Comparison of rotational and orbital atherectomy: A systematic review of efficacy and safety in patients who underwent percutaneous coronary intervention

Background: To assess the clinical results of CAD patients who underwent orbital atherectomy (OA) and rotational atherectomy (RA). Methods: PICO criteria for publication in the last 5 years and preferred reporting elements for systematic reviews and meta-analyses (PRISMA) were used to systematically choose publications. Boolean operators were used to search for keywords. The effectiveness of each chosen article was evaluated using the STROBE checklist. Results: Five articles of non-randomized observational analysis were selected, which involved 72.982 patients whom underwent RA, while 6.431 others underwent OA which is a new atherectomy method that was approved for use in coronary arteries in 2003. Although some studies still showed varying results due to different data collection tools, overall data showed there was no difference between the two techniques in terms of contrast volume, outcomes of coronary artery dissection, periprocedural myocardial infarction (MI), arterial perforation caused by device, cardiac tamponade, in-hospital mortality, slow flow/no reflow, 30-day of mortality, target vessel revascularization (TVR), MI and major adverse cardiovascular events (MACE). The burr size and rotational speed for RA may lead to complication rates. Conclusion: Except for a shorter fluoroscopy time with OA, there are no discernible differences between OA and RA in patients with calcified CAD undergoing PCI.

Study on the evolution and suppression strategy of the interlayer gap in the drilling of CFRP/Al stacked materials

In aircraft assembly operations, interlayer gap formation during drilling through stacked materials positively affects interlayer burr size. Removing these burrs needs disassembly, deburring, and reassembly, and these processes are time-consuming, expensive, and non-value-added. This study visualizes the real-time variation of the interlayer gap to understand its evolution process and proposes a method of designing feed motion for reducing the interlayer gap. First, a real-time measurement method of the interlayer gap and deflection using a 2D laser displacement sensor is proposed, and the evolution of the interlayer gap in the drilling of stacked materials is described. Besides, a simplified analytical model of the stacks is built to explain the development of interlayer gaps during stack drilling. Then, a variable feed method based on the discrete sine curve is proposed to suppress the interlayer gap. Finally, the drilling experiments of the constant feed and the discretized sine curve feed are performed to compare the change of interlayer gap, and the results showed that the maximum interlayer gap (excluding the effect of chips), the maximum interlayer gap (not excluding the effect of chips), the final interlayer gap and the average interlayer gap was reduced by 25.2 %, 45.1 %, 72.7 % and 35.9 %, respectively. In addition, a small interlayer gap corresponds to a small flexural deformation, which helps reduce the material's stress. The bending deformation of the Al layer is reduced by 54 %, and its maximum stress value can be reduced by 22 %.

Study on the Mechanism of Burr Formation by Simulation and Experiment in Ultrasonic Vibration-Assisted Micromilling

Due to the strong plasticity of Inconel 718 and the significant size effect of micromachining, a large number of burrs will be produced in traditional processing. The addition of ultrasonic vibration during machining can reduce the burr problem. The mechanism of burr generation in traditional micromilling (TMM) and ultrasonic vibration-assisted micromilling (UVAMM) was analyzed by simulation, and verified by corresponding experiments. It is found that applying high-frequency ultrasonic vibration in the milling feed direction can reduce cutting temperature and cutting force, improve chip breaking ability, and reduce burr formation. When the cutting thickness will reach the minimum cutting thickness hmin, the chip will start to form. When A/ƒz > 1/2, the tracks of the two tool heads start to cut, and the chips are not continuous. Some of the best burr suppression effects were achieved under conditions of low cutting speed (Vc), feed per tooth (ƒz), and large amplitude (A). When A is 6 μm, the size and quantity of burr is the smallest. When ƒz reaches 6 μm, large continuous burrs appear at the top of the groove. The experimental results further confirm the accuracy of the simulation results and provide parameter reference.