Burr Size Research Articles

Numerical and experimental investigation on grinding-induced exit burr formation

Exit burrs are easily generated on workpiece edges. In grinding process, particularly, exit burrs could deteriorate the highly required precision and even affect the functionality of components. Therefore, to understand the burr formation mechanism and control it in grinding process is of great significance. To this end, this paper investigates the features and mechanism of exit burr formation, as well as the influence of grinding conditions including grinding speed, grinding depth, wheel granularity, and grinding pass sequences on the exit burr formation of 12CrMoV stainless steel using the Al2O3 grinding wheels. A 3D finite element (FE) model of single-grit scratching process was developed for explaining the exit burr formation procedures. The effects of different grinding conditions on the exit burr sizes were analyzed, and the characteristics of the exit burr sizes and hardness were observed via experiments. It was found that the whole procedure of exit burr formation during grinding could be divided into six stages: steady-state grinding, pre-initiation, appearance of the fourth deformation zone, formation of plastic deformation band, burr development, and finish of burr formation. The burr sizes were strongly determined by the wheel granularity and grinding depth, rather than the grinding speed. For the same required grinding depths, using whether single pass or multiple passes of the grit has a very small impact on the exit burr sizes. The hardness of the burr root part is relatively stronger than that of the burr rollover part, while the burr hardness would increase when decreasing the grinding depth.

Analysis of the Influence of Blanking Clearance on the Wear of the Punch, the Change of the Burr Size and the Geometry of the Hook Blanked in the Hardened Steel Sheet.

In this thesis, the results of an experimental analysis of blanking angled hooks with a punch of a sloping face in a thin steel sheet with a hardness of 55 HRC are presented. The blanking punch was made of K340 cold-work tool steel. Tests were carried out for three values of clearance, 5%, 10%, and 15% of sheet thickness. The results of the analysis of the influence of the number of cuts made by the punch on the growth of the burr at the sheet edge were presented. Moreover, the influences of the clearance on the initial values of burr (bh), deflection (Hb), and the bending radius (Rb) of the hook have been shown. The influence of the friction path on the intensity of degradation of working surfaces and the blanking edges of the punch was also demonstrated. The obtained results allow the selection of the proper clearance and new tool materials for blanking blades working in particularly difficult tribological conditions.

Association between debulking area of rotational atherectomy and platform revolution speed-Frequency domain optical coherence tomography analysis.

In this study, we sought to investigate the association between revolution speed of rotational atherectomy (RA) and debulking area assessed by frequency domain-optical coherence tomography (FD-OCT). The number of patients with severe calcified coronary artery disease requiring treatment with calcium ablation, such as RA, is increasing. However, there is little evidence available regarding the association between debulking area and revolution speed during RA. We retrospectively investigated 30 consecutive severely calcified coronary lesions in 29 patients who underwent RA under FD-OCT guidance. The association between preset revolution speed of RA and burr size-corrected debulking area of the calcified lesion was evaluated using a multivariable regression model with nonlinear restricted-cubic-spline, which can help assess nonlinear associations between variables. The median age of study participants was 73 years (quartile 65-78); 82.8% were male. The median burr size was 1.5 mm (1.5-1.75); median total duration of ablation was 120 s (100-180). FD-OCT revealed that the post-procedural minimum lumen area increased significantly from 1.64 mm2 (1.40-2.09) to 2.45 mm2 (2.11-2.98) (p < .001). In addition, the burr size-corrected debulking area increased significantly as the preset revolution speed decreased (p = .018), especially when the revolution speed was less than 150,000 rpm. This result implies that additional lumen gain will be obtained by decreasing rpm when the burr speed is set at <150,000 rpm. FD-OCT demonstrated that RA with lower revolution speed, below 150,000 rpm, has the potential to achieve greater calcium debulking effect in patients with severe calcified coronary lesions.

Long-term cardiovascular prognosis after rotational atherectomy in hemodialysis patients: Data from the J2T multicenter registry

BackgroundHemodialysis (HD) patients have heavy calcium deposits in their stenotic coronary arteries and worse post-percutaneous coronary intervention (PCI) prognoses than those who do not undergo HD. Rotational atherectomy (RA) facilitates PCI success in severely calcified lesions. We aimed to identify clinical and procedural characteristics that predict HD patients' long-term prognoses after PCI that included RA in the drug-eluting stent (DES) era. MethodsThis study included 302 patients who underwent regular HD from J2T Multicenter Registry database of 1090 consecutive patients who underwent RA to treat de novo calcified lesions at three university hospitals between 2004 and 2015. The primary endpoint was cardiovascular (CV) death. ResultsDuring the 5-year observation period, 59 CV deaths (19.5%) occurred. The CV death group and non-CV death group had comparable profiles except significantly lower left ventricular ejection fraction, higher brain natriuretic peptide (BNP), lower rate of RA burr upsizing, and lower rate of final thrombolysis in myocardial infarction (TIMI) 3 flow achievement in the CV death group. Cox regression analysis revealed that increasing ablation burr size (hazard ratio [HR]: 0.33; 95% confidence interval [CI]: 0.13–0.81), final TIMI 3 flow (HR: 0.07; 95% CI: 0.02–0.28), lower BNP level, and optimal medication were independently associated with better CV mortality in HD patients. ConclusionIn the DES era, oral medications at the time of PCI and stepwise calcium ablation were associated with improved long-term CV mortality in HD patients who are scheduled to undergo RA to treat severely calcified coronary artery stenoses, as therapeutic strategies.

Safety and Long-Term Efficacy of Drug-Coated Balloon Angioplasty following Rotational Atherectomy for Severely Calcified Coronary Lesions Compared with New Generation Drug-Eluting Stents.

Objectives This study sought to assess the safety and long-term efficacy of drug-coated balloons (DCB) following aggressive intracoronary image-guided rotational atherectomy (iRA) for severe coronary artery calcification (CAC), and to compare this strategy with new generation drug-eluting stents (nDES) following iRA. Background Ischemic events following the treatment of CAC is still relatively high. Thus, more innovative strategies are required. Methods We evaluated 123 consecutive patients (166 lesions) with de novo CAC undergoing an iRA (burr size; 0.7 of the mean reference diameter by intracoronary imaging) followed by DCB (DCB-iRA; 54 patients, 68 lesions) or nDES (nDES-iRA; 69 patients, 98 lesions). Follow-up angiography was obtained at > 6 months. Results The target vessels (right coronary and circumflex), bifurcation (67.6% versus 47.9%), reference diameter (2.28mm versus 2.49mm), and lesion length (11.89mm versus 18.78mm) were significantly different between the two groups. The median follow-up was 732 days. TLR and TVR in DCB-iRA and nDES-iRA at 3 years were similar: 15.6% versus 16.3% (P=0.99) and 15.6% versus 23.3% (P=0.38). In 41 well-matched lesion pairs after propensity score analysis, the cumulative incidence of TLR and TVR in DCB-iRA and nDES-iRA at 3 years was 12.9% versus 16.3% (P=0.70) and 12.9% versus 26.1% (P=0.17), respectively. On QCA analysis, although the acute gain was smaller in DCB-iRA (0.85 mm versus 1.53 mm, P<0.001), the minimum lumen diameter at follow-up was similar (1.69 mm versus 1.87 mm, P=0.29). The late lumen loss was lower (0.09 mm versus 0.52 mm, P=0.009) in DCB-iRA. Conclusions DCB-iRA is feasible for CAC.

Investigation on chip formation and surface integrity in micro end milling of maraging steel

3J33B maraging steel is a high-strength steel which is used for fabricating precision elastic components. In this paper, experiments were carried out to investigate chip formation, surface roughness, and top burr formation in micro end milling of 3J33B from an energy perspective. Chip formation and surface roughness in the centerline position of the slots were analyzed based on the average specific cutting energy. Surface roughness and burr size of the two sides of the slots were compared to the variation of the instantaneous specific cutting energy in a half cutting revolution. It was found that the chips became more fragmentized with an increase in the specific cutting energy due to the plowing effect. The formation of the down-milling side required more specific energy than that of the up-milling side. It was proven that the increment of the specific energy on the down-milling side was related to the better surface finish and greater size of top burrs. At last, some suggestions on parameter selection for surface improvement were proposed according to the research results.

Study of Surface Roughness and Burr Formation After Milling of Carbon Fiber/Titanium Stacks

This work aims to study the influence of cutting parameters (cutting speed, feed rate, cutting depth and tool cutting edge angle) regarding surface roughness and burr formation during the milling of a mixed structure comprised of titanium and carbon fiber (stack). The parameters were varied from maximum to minimum, just as the tool cutting edge angle of the insert, through a full factorial design with 32 trials. The analyses were performed by measuring the surface roughness and burr size along with metallographic analyses through optic microscopy and scanning electron microscopy. The results showed that the surface roughness was higher for carbon fiber and burr size was higher for titanium. There were a number of tests with delamination of the carbon fiber, and the best cutting parameters to minimize surface roughness and burr formation were tool cutting edge angle of 45º, a feed rate of 0.028 mm/tooth, cutting depth equal to 0.26 mm and cutting speed equal to 150 m/min.

An experimental investigation on the formation of burrs in micro milling of Zr-based amorphous bulk metallic glass

Fabrication of precision micro components demands part quality having burr free edges and acceptable surface finish to comply with its requirements of proper functionality. Machining conditions influence process performances in different ways. The present study examines the effect of cutting parameters like cutting speed, feed per tooth (feed rate) and axial depth of cut on the formation of top burrs and surface finish produced in micro-channels made through full immersion micro end milling process carried out on a workpiece made of amorphous bulk metallic glass (BMG). The process modelling is done based on response surface methodology and parametric analysis is performed to examine the influence of the process parameters on the process responses, namely the burr size formed in up-milling and down-milling sides and the surface roughness of the bottom surface of the micro-channels. The study also undertakes multiple response optimisation analysis that determines the optimal values of the cutting parameters that yield lower burr sizes and lower surface roughness.

An experimental investigation on the formation of burrs in micro milling of Zr-based amorphous bulk metallic glass

Fabrication of precision micro components demands part quality having burr free edges and acceptable surface finish to comply with its requirements of proper functionality. Machining conditions influence process performances in different ways. The present study examines the effect of cutting parameters like cutting speed, feed per tooth (feed rate) and axial depth of cut on the formation of top burrs and surface finish produced in micro-channels made through full immersion micro end milling process carried out on a workpiece made of amorphous bulk metallic glass (BMG). The process modelling is done based on response surface methodology and parametric analysis is performed to examine the influence of the process parameters on the process responses, namely the burr size formed in up-milling and down-milling sides and the surface roughness of the bottom surface of the micro-channels. The study also undertakes multiple response optimisation analysis that determines the optimal values of the cutting parameters that yield lower burr sizes and lower surface roughness.

Optimization of Turning Parameters to Minimize Burr by Using Taguchi Design Method

Reducing burr formation in machining operations is of vital importance as they can decrease the functionality of components and can cause injuries. Nowadays, additional processes for deburring are often necessary. To avoid deburring, the modification of turning processes is a promising approach. Here, different parameters have a significant influence on burr formation. This paper presents the influence of cutting parameters like cutting speed, feed rate, depth of cut on the burr size of 5A06, 6061 and 6063 aluminum alloy during turning on CNC lathe. A plan of experiments based on Taguchi method has been used to acquire the data. An orthogonal array, signal to noise (S/N) ratio and analysis of variance (ANOVA) are employed to investigate machining characteristics using fine turning tool within the domain of experiments considered. Experimental runs were chosen following L9 orthogonal array of Taguchi. Analysis of variance was undertaken to find out the influence of process parameters on the response noted. Predicted values are finally checked for accuracy through a confirmation test. Confirmation tests have been carried out to predict the optimal setting of process parameters to validated the proposed method and obtained the values 0.024 mm, 0.006 mm, and 0.009 mm for burr height of 5A06, 6061 and 6063 aluminum alloy respectively. In this paper, methods for burr minimization in various cutting processes are presented. Burr reduction strategies for turning of different materials are presented.

Improved analytical prediction of burr formation in micro end milling

In the fields of aerospace, bio-medicine and other optical devices, micro end milling is widely used to fabricate miniature parts and features which require a high quality of machining. Generally, the accurate prediction of burr formation is one significant factor to improve the quality of machined parts and performance of micro components and features. This paper investigates the burr formation mechanism in micro end milling by considering the minimum chip thickness, as well as the size effect of cutting edge radius. The improved analytical model is developed to predict the size (height and width) of Poisson burr and exit burr. The proposed model is validated by the micro end milling experiments with different cutting parameters, where the error percentage of comparison results is limited to 16.8%. Furthermore, the effects of spindle speed, feed per tooth and axial depth of cut on the burr size are analyzed based on the prediction model and experimental results. The proposed analytical method offers a basis for the control and minimization of burr formation as well as cutting parameters optimization.

Rotational atherectomy in CTO lesions: too risky? Outcome of rotational atherectomy in CTO lesions compared to non-CTO lesions.

The aim of this study was to determine the feasibility of rotational atherectomy (RA) in chronic total occlusion (CTO) PCI and compare the success and complication rates of RA in CTO lesions versus non-occluded lesions. Data on RA in CTO are rare and it is unknown how procedural success and risk of RA in CTO lesions compare to RA in non-CTO lesions. RA was performed in 392 out of 17,919 PCI procedures (2.2% of the PCI cohort) and classified as RA CTO (n=75) and RA non-CTO (n=317). Procedural success and MACCE in both groups were assessed by two investigators. All RA procedures were analysed for dissections prior to RA, which were defined according to the NHLBI classification. Baseline characteristics were not significantly different in the two groups but, in RA CTO, lesion type was more complex (p<0.001), stented segments were longer (35.0±22.7 vs. 46.0±24.8 mm, p<0.001) and mean burr size was smaller (1.61±0.17 vs. 1.49±0.18 mm, p<0.001). Procedural success and complications were not different (RA non-CTO 96.2% and RA CTO 94.7%, RA non-CTO 2.5% and RA CTO 4.0%, respectively). RA performed in dissection planes had a 100% procedure success rate in CTO and a 92% success rate in non-CTO. RA in CTO is as safe and as effective as RA in non-CTO. The presence of dissections prior to RA in CTO lesions as well as in non-CTO lesions does not seem to have a negative impact on outcome.

Modeling and drilling parameters optimization on burr height using harmony search algorithm in low-frequency vibration-assisted drilling

Increasing demands call for the burr-free workpiece in precision manufacturing. Low-frequency vibration-assisted drilling (LFVAD) has been applied to improve the fabrication process. Prediction and minimization of burr size are one of the major research topics in precision machining. In this paper, an LFVAD parameters optimization model was proposed including harmony search (HS) algorithm and a modified LFVAD burr height analytical model. The burr height model of LFVAD was developed using existing analytical burr height model for conventional drilling (CD) and vibration-assisted drilling (VAD). The developed burr height models were then employed with HS algorithm, which is a new meta-heuristic optimization method based on the imitation of music improvisation process, to determine the optimal machining parameters for a given twist drill that results in minimum exit burr height. Experimental results show that the burr height of the optimized LFVAD decreased by 52.75% compared with the CD, and decreased by 17.59% compared with the un-optimized LFVAD. The simulation and experimental results demonstrate that under suitable LFVAD parameters, the burr height could be reduced.

Advantages of Transradial Rotational Atherectomy versus Transfemoral Approach in Elderly Patients with Hard-Handling Calcified Coronary Lesions - A Single Center Experience.

Balloons cannot pass through severely calcified coronary lesion (SCCL), and sometimes they cannot be opened at a high pressure even if they can pass through the lesion. There are limited data on rotational atherectomy (RA) via transradial access (TRA) in this setting. The aim of this study was to evaluate in-hospital and 1-year outcomes in elderly patients with SCCL who underwent RA via TRA. Eighty-six consecutive elderly patients with de novo SCCL who underwent RA were enrolled and divided into TRA (n = 45) and transfemoral access (TFA, n = 41) groups in this retrospective analysis from 2008 to 2013. Baseline characteristics and in-hospital and 1-year endpoints were compared between both groups. Compared to TFA, 6Fr guide catheters were used significantly more in the radial approach (p < 0.001). In the TRA group, the rate of burr size (1.25 mm) was higher and the mean burr size was smaller (p = 0.021) than that in the TFA group. Vascular access site complications, bed rest time and hospital stay were significantly lower in the TRA group compared with the TFA group (p = 0.029, < 0.001, < 0.001, respectively). However, there was no significant difference in major adverse cardiac events during hospitalization and after 1 year follow-up between both groups (p = 0.338, 1.000, respectively). TRA is a useful alternative to TFA in elderly patient with SCCL. The advantages of TRA over TFA include reduced time of bed rest and hospital stay and vascular complications at the puncture site.

Investigation of Influence of Drill Geometry and Thrust Force During Drilling of Aluminium 2014 Alloy on Burr Formation Through Design of Experiments and Nueral Network

Abstract Drilling is a hole making process on machine components at the time of assembly work, which were identify everywhere. In precise applications quality and accuracy play wide role. Now a day’s industries are suffered by cost incurred during deburring, especially in precise assemblies such as aerospace/aircraft body structures, marine works and automobile industries. Burrs produced during drilling causes dimensional errors, jamming of parts and misalignment. Therefore, deburring operation after drilling is often required. Now, reducing burr size is a burning topic. In this study experiments are conducted by choosing various input parameters selected from previous researchers. Effect of alteration of drill geometry on thrust force and burr size of drilled hole investigated as per taguchi design of experiments and found optimum combination of most significant input parameters from ANOVA to get optimum reduction in burr size by design expert software. Drill thrust influences more on burr size, clearance angle of drill bit causes variation in thrust, burr height observed in this study. Compare these output results with neural network software @easy NN plus. Finally, concluded that increasing the number of nodes increases the computational cost and decreases the error in nueral network. Good agreement was shown between the predictive model results and the experimental responses.

Experimental investigation on burr formation in vibration-assisted micro-milling of Ti-6Al-4V

Titanium alloys have been widely used in aerospace, marine and medical industries, due to their high strength, good corrosion resistance and excellent heat resistance. High tool wear rate and low machining accuracy limits conventional micro-milling to meet increasing stringent demand. In this paper, a prototype of two-directional vibration stage and its control system are developed for non-resonant mode vibration-assisted micro-milling system. A series of slot milling experiments are carried out to investigate the effects of vibration parameters on burr generation. The results show that vibration-assisted micro-milling is an effective way to reduce burr size when choosing appropriate vibration parameters and directions.

Optimization of machining parameters during Drilling by Taguchi based Design of Experiments and Validation by Neural Network

Drilling is a hole making process on machine components at the time of assembly work, which are identify everywhere. In precise applications, quality and accuracy play a wide role. Nowadays’ industries suffer due to the cost incurred during deburring, especially in precise assemblies such as aerospace/aircraft body structures, marine works and automobile industries. Burrs produced during drilling causes dimensional errors, jamming of parts and misalignment. Therefore, deburring operation after drilling is often required. Now, reducing burr size is a serious topic. In this study experiments are conducted by choosing various input parameters selected from previous researchers. The effect of alteration of drill geometry on thrust force and burr size of drilled hole was investigated by the Taguchi design of experiments and found an optimum combination of the most significant input parameters from ANOVA to get optimum reduction in terms of burr size by design expert software. Drill thrust influences more on burr size. The clearance angle of the drill bit causes variation in thrust. The burr height is observed in this study. These output results are compared with the neural network software @easy NN plus. Finally, it is concluded that by increasing the number of nodes the computational cost increases and the error in nueral network decreases. Good agreement was shown between the predictive model results and the experimental responses.

How many names for a beloved genus? – Coalescent-based species delimitation in Xanthium L. (Ambrosiinae, Asteraceae)

The species category is the fundamental unit in biology. In the last decades, several studies have been carried out, using sequence information and phylogenies to resolve issues in taxonomically problematic groups. The multispecies coalescent theory, and the species-delimitation methods developed in the last years based on that, offer powerful and objective tools to determine species boundaries using sequence data.The genus Xanthium is a morphologically variable complex with several local forms, nowadays become cosmopolitan due to human-mediated dispersal. Past taxonomic treatments of the genus were based essentially on the burr morphology. They varied considerably in number of recognized species, depending on the importance that the different authors gave to burr traits such as burr size, pubescence, number and length of spines in the burrs, and the degree to which those are hooked.We used sequence information from two plastid regions (the intergenic spacer regions psbA-trnH and trnQ-rps16) and two nuclear ones (ITS1-5.8 S-ITS2 rDNA, and the single-copy nuclear marker D35). Two of the most advanced coalescent-based species delimitation methods (BP&P and STACEY) were applied, in order to objectively determine species boundaries in Xanthium.Results from the species-delimitation methods strongly support scenarios with a reduced number of species. Prior on the effective population size parameter (θ) had a strong influence on BP&P results. Analyses with large and small θ prior supported species delimitation scenarios with four and five species, respectively. STACEY recognized five cluster in the dataset, all supported by high posterior probability values. Five species are identified in Xanthium, in a great extent corresponding to the infrageneric classification given for the genus in past taxonomic revisions.

Study on micro helical milling of small holes with flat end mills

Helical milling as an eco-friendly hole-making process has various advantages comparing to conventional drilling process and has been widely studied. But micro helical milling for small holes was not investigated. This paper focuses on preliminary studies on micro helical milling of small holes with flat micro end mills. The cutting phenomena of the radial and axial cutting edges are considered and discussed separately. Based on the size effect existing in microcutting processes, the minimum undeformed chip thicknesses (hmin) for both radial and axial cutting edges are identified for work material copper C26000 by finite element method and micro helical milling experiments. Since burrs are noticed during experimental studies, burrs at the hole entrance are analyzed elementarily and it shows that the burr size has a relation with the critical conditions in micro helical milling. The study turns out that the ratio of hmin to cutting edge radius in micro helical milling is from 0.6 to 0.68 and is larger than that of conventional microcutting processes for various materials, which is usually in the range from 0.14 to 0.43. It is a good sign for micro helical milling of small holes with higher productivities since the ratio of hmin to tool cutting edge radius is larger than that of conventional microcutting processes.

Modeling of burr thickness in micro-end milling of Ti6Al4V

Mechanical micro-machining of Ti6Al4V is finding great demand because of its wide range of application in various fields such as communication, optics and biomedical devices. Increasing demands on functioning and performance requires components to be free from burrs after the machining process. Presence of burrs on micro-mechanical parts or features significantly affects quality and proper assembly of the parts. Also in micro-machining, the size of burr is comparable to that of micro-features. Since the formation of burr is inevitable in any machining process, generally the deburring operation is performed to remove burrs. Burr thickness is one of the important parameters which describe the time and method necessary for the deburring operation. Burrs on micro-parts are generally characterized using scanning electron microscope, which is a time-consuming, costly and non-value-added activity. However, a proper mathematical model will help predict burr thickness easily. In this article, a mathematical model to predict burr thickness during micro-end milling of Ti6Al4V is presented. The proposed model was developed based on the principle of continuity of work at the transition from chip formation to burr formation. Ti6Al4V titanium alloy is one of the materials which generates segmented (saw-tooth) chips at low cutting speeds. Hence, initially an appropriate material constitutive model was selected based on better prediction of burr thickness. Then, to reduce the prediction error, machining temperature was evaluated for all experimental conditions and included in the model. From the initial study, it was found that Hyperbolic TANgent material model gives a better prediction compared to Johnson–Cook material model. Later, after including machining temperature into the model it was observed that the prediction error was reduced. The proposed model was validated with the experimental results.