IDENTIFICATION OF CHARACTER AND INTENSITY OF WEAR OF PVD COATED TWIST DRILLS IN DRILLING OF C 45 MATERIAL

This article is aimed to investigation of four different PVD coatings of STATON company in order to determine a wear behavior on twist drills when drilling C45 material. A pearlite-ferrite structure of C45 material is common material for automotive industry and highly abrasive to cutting tools. Our comparative study is focused on flank wear of the cutting wedge of observed drills deposited at STATON. The article shows differences in chemical composition and their effects on wear behavior at the corner of the drill and along the cutting edge. We also demonstrate that chemical composition has significant influence on the temperature of a build-up edge during cutting.

Piezoelectric driven mandibular ridge split technique with immediate implant placement: A case report

Narrow dentoalveolar ridges pose a major challenge for the successful placement of endosseous implants. This case report focuses on a Piezoelectric driven mandibular Ridge Split technique without vertical osteotomy for an immediate implant placement in a narrow alveolar ridge measuring 3.0mm. Following anaesthesia, a mucoperiosteal flap was elevated after giving a mid-crestal incision distal to 35 along the entire edentulous ridge. Then, with the help of a micro-saw and horizontal spreaders, an osteotomy site of required diameter was achieved. Finally twist drills were used and implants were placed in the expanded site. Clinically, healing was uneventful with no step defect in the expanded buccal bone and the final occlusion obtained was satisfactory. The Piezo-electric driven Ridge Split technique promises to be a minimally invasive option for horizontal augmentation of narrow alveolar ridges- predictability within a short interval of time and with minimal risk of fracture.

Drilling of a Bidirectional Jute Fibre and Cork-Reinforced Polymer Biosandwich Structure: ANN and RSM approaches for Modelling and Optimization

The present study examined the effects of drilling parameters such as spindle speed (N), feed rate (f), diameter of the tools (d) and drill geometry such as twist drills (HSS-TiN) and brad & spur drills (BSD) used on delamination damage in a biosandwich structure consisting of an epoxy matrix reinforced with bidirectional jute fibres and cork (JFCE). Response surface methodology (RSM) and artificial neural networks (ANNs) were exploited to evaluate the influence and interaction of the cutting parameters on the delamination factor (Fd) at the output during drilling. In addition, several optimization methods, such as desirability-based RSM, the genetic algorithm (GA) and the fmincon function, were applied to validate the optimal combination of cutting parameters (f, N and d) in the structures studied in biosandwiches during this research. According to the experimental results, severe damage was indeed observed with the BSD tool (Fd = 1.684) compared to the HSS-TiN tool (Fd = 1.555) for the same cutting conditions. To obtain the minimum Fd, the optimum conditions obtained by GA were respectively 1397.54 rev/min, 51.162 mm/min and 5.981 mm for HSS-TiN for f, N and d.

Robotic thermocoagulative hemispherotomy: concept, feasibility, outcomes, and safety of a new “bloodless” technique

OBJECTIVE The authors present a new “bloodless” technique for minimally invasive robotic thermocoagulative hemispherotomy (ROTCH). Such a method is being described in the literature for the first time. METHODS A robotic system was used to plan five sets of different trajectories: anterior disconnection, middle disconnection, posterior disconnection, corpus callosotomy, and temporal stem and amygdalar disconnection. A special technique, called the “X” technique, allowed planar disconnection. Registration was performed with surface landmarks (n = 5) and bone fiducials (n = 1). Coregistration with O-arm images was performed one or two times to confirm the trajectories (once for middle disconnection, and once for disconnection of the temporal stem and amygdala or body of the corpus callosum). Impedance measured before ablation allowed for minor adjustments. Radiofrequency ablation was performed at 75°C–80°C for 60 seconds. Surgical procedures were performed with multiple twist drills. After removal of the electrode, glue was used to prevent CSF leak, and a single stitch was applied. Follow-up CT and MRI were immediately performed. RESULTS The pathologies included Rasmussen's encephalitis (n = 2), hemispheric cortical dysplasia (n = 2), posttraumatic encephalomalacia (n = 1), and perinatal insult (n = 1). The mean ± SD (range) age was 6.7 ± 3.6 years (5 months to 10.2 years), and the right side was affected in 4 patients. The mean ± SD seizure frequency was 7.4 ± 5.6 seizures per day (1 patient had epilepsia partialis continua). The mean ± SD number of trajectories was 15.3 ± 2.5, and the mean ± SD number of lesions was 108 ± 25.8. The mean ± SD maximum numbers of trajectories and lesions required for middle disconnection were 7.1 ± 1.7 and 57.5 ± 18.4, respectively. All but 1 patient had class 1 outcomes according to the International League Against Epilepsy Outcome Scale at a mean ± SD (range) follow-up of 13.5 ± 1.6 (12–16) months; the remaining patient had a class 2 outcome. The estimated blood loss was < 5 ml for all patients. Complications included repeat surgery (after 2 weeks) for a “skip” area (n = 1) and a small temporal hematoma (n = 1), which resolved. CONCLUSIONS ROTCH seems to be a safe, feasible, and bloodless procedure, with a very low morbidity rate and promising outcomes.

Model of Dependence Between the Parameters of Surface Roughness and the Parameters of Form and Location During the Machining by Drills with the use of Artificial Neural Networks

This paper presents a model of dependence between the parameters of surface roughness and the parameters of cylindricity and eccentricity in drilling operation for the enhancing steel EN 42CrMo4, hardness 28 HRC, with twist drills DIN 338 made of high-speed steel EN HS6-5-2, with normal blade. The quality of machining, besides the accuracy of measures, completely determined with the values of the parameters of the surface roughness and the parameters of form and location, hence this paper is oriented to the creating models between parameters of the quality of a machined surface and parameters of deviations from form and position. By the developing models based on artificial neural networks and using experimental results, it is possible to analyse the quality of machining on the basis of parameters of a surface roughness.

Geometric Optimization of Drills Used to Repair Holes in Magnesium Aeronautical Components

Magnesium alloys are used in the aeronautical sector due to their excellent strength/weight ratios, motivated by the reduction of weight that their use entails. In this sector, drilling is one of the most common operations, if not the most, due to the large number of holes that are used in joining processes, mainly by riveting. The appearance of cracks is a risk to the structural safety of the components, such that it is necessary to regularly check them for maintenance and/or repair tasks. The present study tries to determine the optimization of the characteristics of the twist drills, which are re-sharpened successively to restore the cutting edge after use, as well as the operating parameters in machining. For this purpose, a full factorial experimental design was established, analyzing through the analysis of the variance (ANOVA) the response variables. Surface integrity was considered to carry out a global vision of the quality obtained, covering as response variables the surface roughness, the size of the burrs and the modification of the hardness produced, in addition to a topological characterization by optical means of machined surfaces. The main conclusion is that it is possible that the geometric optimization of the tools and the operating parameters considered in this study in drilling processes allow them to be performed, while maintaining quality and environmental requirements, and at the same time, maximize the productivity of operations.