Papers by Keyword: Drilling

Abstract: Exit burrs are formed on the end of hole and have some undesirable characters leading to assembly quality problem. Deburring is one of the practical procedures used to solve this problem. Nevertheless, this step is a time consuming and causes high operation cost. This work studied the experimental investigations in drilling forging brass using a special tungsten carbide drilling tools. The exit burr height and workpiece diameter were measured at various spindle speeds and feed rates based on 2^k plus center point experimental design and investigated by analysis of variance (ANOVA). The results of ANOVA indicated that spindle speed and feed rate on exit burr height and workpiece diameter were statistically significant at the level of significance of 0.05.

Abstract: Drilling and lateral cutting are two cutting modes used by roadheaders in rock cutting. Accurate estimation of the depth of cut (DOC) of the cutterhead of a roadheader is critical for improving the performance and reliabilityofthe roadheader. Some models have been developed for calculating the DOC of a cutterhead in lateral cutting mode. However, an effective method for computing the DOC of a cutterhead in drilling mode is yet to be developed. As thecharacteristicsof the drilling process are significantly different from those of the lateral cutting process, the models developed for calculating the DOC in lateral cutting mode are not suitable for estimating the DOC ofacutterhead indrilling mode. In this study, a quantitative analysis of the DOC in drilling mode is developed via an investigation ofrock breakout patterns. The results show that in anydrilling case, the DOC of the picks on the cylindrical and conical parts of a cutterhead cannot be calculated by using the advance distance per revolution of the cutterhead. The DOC of a pick is affected by the difference between the cutting radii of the pick and its adjacent picks. It is also affected by the interaction between cutting lines. While the distance between two cutting lines in lateral cutting mode is fixed, the distance betweentwo cutting lines inthe drilling mode can vary. The outcome of the studycan help optimisation of cutterhead design and operation.

Abstract: In terms of machinability are titanium alloys classified in the group of difficult to cut materials. The main factors determining this status are limited tool life, high generated cutting forces (torque) and temperature in cutting zone caused by low thermal conductivity as well as chemical reactivity with cutting tool. Solid carbide drills still remain as preferred choice in hole making process when machining Ti6Al4V alloy. Besides cutting conditions, tool and cutting edge geometry significantly affect the value of torque. Reduction of process energy requirements can be achieved by appropriate optimization of these parameters. Mathematical model describing influence of cutting speed, feed rate, clearance angle and cutting edge radius on investigated variable with high reliability coefficient (R²=96.72%) was found. Drilling experiments were designed and carried out using Taguchi orthogonal array L₁₆.

Abstract: The method of imparting ultrasonic vibration to the cutting tool is known to improve the shape accuracy and finished surface roughness. However, a uniform evaluation of this function in drilling has not been achieved, and the cutting process cannot be checked from the outside. The aim of this study is to investigate the cutting characteristics in deep hole drilling when an ultrasonic vibrator on the table of a machining center provides vibration with a frequency of 20 kHz to the work piece. The ultrasonic vibrations in this system reach the maximum amplitude in the center of the work material. We evaluated the change in finished surface roughness between the section where drilling starts to the point of maximum amplitude with ultrasonic vibration. The main cutting conditions are as follows: cutting speed (V) 12.6 (mm/min); feed rate (s) 30, 60 (mm/rev); depth of cut (t) = 32 (mm); work material, tool steel; cutting tool material, HSS; point angle (σ) 118 (°); and drill diameter (φ) 4 (mm). Lubricant powder was also added to clarify the cutting effect, and compared the condition in which there was no ultrasonic vibration. The results showed that surface roughness at the point of maximum amplitude was better than that with no vibration.

Abstract: The drilling of carbon fiber reinforced plastics (CFRP) involves many problems such as an extremely short tool life or CFRP delamination occurring at the exit surface of drill. In an effort to solve these problems, this experiment observed the form of the drill’s tool edge. Then, an investigated the form of the tool edge with regard to low-cost, high-precision, and high-efficiency machining processes. The thrust direction of the cutting force is decreased as the CFRP delamination at the exit surface of drill is decreased. It is considered suppressing the delamination on the exit surface of drill by reducing the thrust force during drilling. In this experiment, the CFRP materials had a thickness of 4 mm. This experiment used sintered carbide, straight shank drill tooling with a diameter of 6 mm. Ten different types of straight shank drills with different point angles and coating treatment were tested. Additionally, this experiment an evaluated the cutting force, the cutting temperature, and the CFRP delamination at the exit surface of drill through the drilling and processing of 100 holes. Moreover, this experiment an evaluated the effects of chamfering of honing the tool edge with regard to the drilling and machinability of CFRP. This experiment used CFRP material with a thickness of 8 mm and four types of sintered carbide drills. As a result, the CFRP delamination distance of the exit surface of drill became smaller at point angles 130° and 140°. No differences in the cutting force or the cutting temperature were observed due to the different point angles. The results of the evaluation indicated that for the case without honing, the thrust force becomes 1/3 less than that for the case with honing of the drill tool. Additionally, in the case of without honing, CFRP delamination was suppressed at the exit surface of drill.

Abstract: This study investigated the cutting characteristics of electrodeposited diamond core drill when used to drill a CFRP under wet condition. The effects of different tool shapes, grain sizes and feed rates were examined. A normal core drill, an eccentric with slits core drill (E.S.), and an eccentric with slits and chamfers core drill (E.S.C.) were used. The normal core drill had the shape of a hollow cylinder. The E.S. core drill had the inner cylinder shifted from the center of this tool and slits in the bottom of this tool. The E.S.C. core drill had chamfers on the periphery of this tool. The normal core drill caused severe workpiece core jamming even at 1st hole drilling, and its electro-deposited area was covered entirely by adhered chips. In the case of the E.S. core drill and E.S.C. core drill, the workpiece core did not jam and the thrust force was smaller than that of the normal core drill. The effect of chamfers was little. The E.S.C. core drill with #200 caused smaller surface roughness than that with #100. However, the thrust force was two times larger, and the delamination was observed at the exit point of the hole. In the lower feed rate per revolution the better surface roughness and the lower thrust force were obtained irrespective of the tool shape while the cutting speed showed little effect.

Abstract: This study described the effect of mechanical properties on the roundness of a drilled hole in the drilling of low-rigidity workpieces. A thin-thickness part workpiece model involving a beam plate structure fixed on both ends was used in the study. The effects of feed, workpiece length, distance from the fixed end to the drilling point, and mechanical properties of the workpiece on the roundness of the hole were investigated. The thrust force increased with feed and the roundness became worse with feed. The hole was enlarged in the longitudinal direction of the workpiece at the upper section of the hole. An increase in the workpiece length decreased the rigidity of the workpiece and deteriorated the roundness of the hole. The roundness error was extremely small when the drilling point was near the fixed end. Carbon steel, aluminum alloy, stainless steel, and titanium alloy were used as workpiece materials. The thrust force in the drilling of titanium alloy and stainless steel was considerably larger than that of the carbon steel and aluminum alloy. The roundness of the hole was worse in the drilling of titanium alloy and stainless steel than that in the drilling of carbon steel and aluminum alloy. Plastic deformation occurred in the workpieces made of titanium alloy and stainless steel, which is probably because the workpiece was yielded by the large thrust force. The value of the ratio of the thrust force in drilling to the Young’s modulus of the workpiece was used in evaluating the deflection of the workpiece and the roundness error of the hole in drilling.

Abstract: Drilling experiments of titanium alloy Ti6Al4V were conducted. Taking the speed and feed as the process variables, a set of experimental cutting forces are obtained and compared. From the experimental results it is concluded that within the experimental extent the thrust force and torque of drilling process rises with the feed rate. The lower spindle speed resulted in the greater amount of thrust. Feed rates have greater influence on the thrust force than the spindle speed. The combination of greater feed rate and lower spindle speed results in the maximum amount of thrust. However, combination of greater feed rate and spindle speed resulted in maximum amount of torque.

Abstract: Drilling is the most used machining process in the assemble of Glass/epoxy composites. Material removing leads to damage and delamination in the drilling process. The present paper deals the effect of drill wt.% of multi walled carbon nanotubes (MWCNTs) on the drilling of glass/epoxy composites in term of torque and push-out delamination. Glass/epoxy composites manufactured by using pre-preg method. The filled rates were considered as 0.5, 1 and 2 wt.%. MWCNTs. Also, the unfilled composite samples were used for comparison. Various cutting speeds (40, 50 and 60 m/min) and feed rates (0.075, 0.1 and 0,125 mm/rev) for coated drills were used. The experimental result showed that the machinability properties of glass/epoxy composites samples can be improved with filling MWCNTs. Higher cutting speed and feed rate increase delamination. Push-out more severe than that of peel-up delamination.

Abstract: Natural fiber composites are presently replacing the synthetic fiber in many fields. The present research work study is an attempt to manufacture and test the sisal/banana fiber reinforced polymer composites. Composite have been manufactured using banana and sisal fiber along with epoxy resin as reinforcement. With these composites drilling has been carried out to study the factors and combination of factors that influence the delamination of drilled unidirectional sisal-banana fiber reinforced composites. Drilling experiments were performed based on the L9-Taguchi method. Delamination factor evaluated for the selected parameters spindle speed, feed and diameter of the drill tool with the help of signal to noise ratio, ANOVA analysis and to obtain the conditions for minimum delamination.