Hole Drilling Process Research Articles

Fixtureless assembly of sheet metal parts for the aircraft industry

A method is presented for fixtureless assembly of simple sheet metal parts (i.e. consisting of flat patterns and simple bends) used in the aircraft industry. Current industry practice relies on manually intensive procedures and rigid fixtures for part assembly. The present method relies on carefully toleranced alignment holes that are computer numerical control (CNC) machined into the parts at fastener locations. Parts are temporarily fastened at these alignment holes for their proper alignment together into the assembly, and then permanently fastened at all rivet and bolt locations. A simple procedure is used to characterize empirically the CNC hole drilling process in sheet metal for this method. A simple experiment, involving the assembly of four parts with rivets, successfully demonstrates the potential of fixtureless assembly.

Parametric study to improve laser hole drilling process

In the laser drilling process, the quality of the drilled holes is the main task. A method of studying the influence on the quality of the main process variables needs to be developed, which seeks to improve the quality and explains the drilling mechanism. In the present study, the effect of the laser parameters and the material properties on the hole quality when drilling is examined. A statistical approach, referred to as factorial design, is employed to test the significance level of the factors that affect the hole quality. Three materials, stainless steel, nickel and titanium, are considered. The experimental study yields tables of significance of each factor on the aspects that determine the quality of the holes. The hole geometry is evaluated by assigning marks for each geometric feature, the marking scheme being conducted relevant to the importance of the hole feature.

A process capability index sensitive to skewness

A new process capability indexCs , is proposed which extends the most useful index to date, the Pearn-Kotz-Johnson Cpmk , by not only taking into account that the process mean may not lie midway between the specification limits and incorporating a penalty when the mean deviates from its target, but also incorporating a penalty for skewness. The new index is specifically designed to help control skewness-prone manufacturing processes typified by a hole-drilling process. (The distribution of hole diameters produced by an in-control drilling process is usually near-normal but truncated on the left, at the drill diameter, and slightly skewed to the right. The characteristic behavior of a worsening hole-drilling process is a simultaneous increase in mean, variance and skewness, with little change in the lower percentiles of the distribution.) An estimator is proposed and its bias and variance is studued bt simulation. The simulation studies show taht the new estimator compares favourably with even when skewness is not present. Hence the use of is advocated for monitoring near-normal processes where loss of capability typically leads to asymmetry.

Influence of Defocus Length on Hole Features in Laser Drilling of Ceramics

Defocusing a laser beam is one of the most important factors to control the feature of drilling holes in ceramic materials. This suggests that laser beam energy is delivered and focused on the bottom of the drilling hole by multi-reflection from the internal wall surface of the hole. The deep hole drilling process of silicon nitride ceramics was simulated by the newly developed analysis model. The ray tracing method for a laser power intensity distribution analysis and difference method for thermal analysis was combined. The drilling hole is processed mainly by energy reflected from the internal wall surface of the hole. In this process laser beam intensity becomes higher in the center of the hole since the laser beam is focused by the wall-reflecting effect. The defocusing position from the material surface has direct effects upon the drilling process, which depends on reflection angle of a laser beam at the internal wall surface of the hole. The reflection angle controls the wall-focusing effect and determines the hole shape.

Laser pulse optimization for practical laser drilling

Laser drilling is a common commercially developed technique for material processing. From the application viewpoint, it is the end product for a laser system, for instance a drilled hole, that matters. Laser pulse profile is the most important parameter controlling the laser hole drilling process. An efficient and practical method is therefore needed to develop a relationship between the pulse parameters and the depth of hole produced in a known material. In the present study, dimensionless groups are developed to optimize laser pulse parameters to give information on workpiece materials. Consequently, an optimal laser pulse for drilling an aluminum workpiece is predicted.

The minimum cost economic analysis of multicutting and deformation region tools

Abstract The existing economic analyses of metal cutting processes enable the machining conditions to be identified which correspond to such things as minimum cost or maximum production rate. The work presented in this paperextends a previously published analysis for the deep hole drilling process where wear occurs at both cutting edge and pads. The minimum cost analysis showed that the interaction between the cutting edge and burnishing pads wear resulted in a cost-feed-speed surface exhibiting a number of marked steps, an effect not present in conventional single point analyses. This extension of the analysis involves investigation into the effects of the strategy adopted for the final regrinding of the drill where cost penalties may be incurred under certain circumstances. Also included in the analysis is the effect of using disposable drills.