Effect Of Drill Geometry Research Articles

Surface quality optimization of CFRP plates drilled with standard and step drill bits using TAGUCHI, TOPSIS and AHP method

Purpose Drilling of carbon fiber reinforced plastic (CFRP) composite plates with high surface quality are of great importance for assembly operations. The article aims to optimize the drill geometry and cutting parameters to improve the surface quality of CFRP composite material. In this study, CFRP plates were drilled with uncoated carbide drill bits with standard and step geometry. Thus, the effects of standard and step drill bits on surface quality have been examined comparatively. In addition, optimum output parameters were determined by Taguchi, ANOVA and multiple decision-making methods. Design/methodology/approach Drill bit point angles were selected as 90°, 110° and 130°. In cutting parameters, three different cutting speeds (25, 50 and 75 m/min) and three different feeds (0.1, 0.15 and 0.2 mm/rev) were determined. L18 orthogonal sequence was used with Taguchi experimental design. Three important output parameters affecting the surface quality are determined as thrust force, surface roughness and delamination factor. For each output parameter, the effects of drill geometry and cutting parameters were evaluated. Input parameters affecting output parameters were analyzed using the ANOVA method. Output parameters were estimated by creating regression equations. Weights were determined using the analytic hierarchy process (AHP) method, and multiple output parameters were optimized using technique for order preference by Similarity to An ideal solution (TOPSIS). Findings It has been determined from the experimental results that step drills generate smaller thrust forces than standard drills. However, it has been determined that it creates greater surface roughness and delamination factor. From the Taguchi analysis, the optimum input parameters for Fz step tool geometry, 90° point angle, 75 m/min cutting speed and 0.1 mm/rev feed. For Fd, are standard tool geometry, 90° point angle, 25 m/min cutting speed and 0.1 mm/rev feed and for Ra, are standard tool geometry, 130° point angle, 25 m/min cutting speed and 0.1 mm/rev feed. ANOVA analysis determined that the most important parameter on Fd is the tip angle, with 56.33%. The most important parameter on Ra and Fz was found to be 40.53% and 77.06% tool geometry, respectively. As a result of the optimization with multiple criteria decision-making methods, the test order that gave the best surface quality was found as 4–1-9–5-8–17-2–13-6–16-18–15-11–10-3–12-14. The results of the test number 4, which gives the best surface quality, namely, the thrust force is 91.86 N, the surface roughness is 0.75 µm and the delamination factor is 1.043. As a result of experiment number 14, which gave the worst surface quality, the thrust force was 149.88 N, the surface roughness was 3.03 µm and the delamination factor was 1.163. Practical implications Surface quality is an essential parameter in the drilling of CFRP plates. Cutting tool geometry comes first among the parameters affecting this. Therefore, different cutting tool geometries are preferred. A comparison of these cutting tools is discussed in detail. On the other hand, thrust force, delamination factor and surface roughness, which are the output parameters that determine the surface quality, have been optimized using the TOPSIS and AHP method. In this way, this situation, which seems complicated, is presented in a plain and understandable form. Originality/value In the experiments, cutting tools with different geometries are included. Comparatively, its effects on surface quality were examined. The hole damage mechanism affecting the surface quality is discussed in detail. The results were optimized by evaluating Taguchi, ANOVA, TOPSIS and AHP methods together.

Investigation on the Effect of Drill Geometry and Pilot Holes on Thrust Force and Burr Height When Drilling an Aluminium/PE Sandwich Material.

Composite materials are widely employed in the naval, aerospace and transportation industries owing to the combination of being lightweight and having a high modulus of elasticity, strength and stiffness. Drilling is an operation generally used in composite materials to assemble the final product. Damages such as the burr at the drill entrance and exit, geometric deviations and delamination are typically found in composites subjected to drilling. Drills with special geometries and pilot holes are alternatives used to improve hole quality as well as to increase tool life. The present study is focused on the drilling of a sandwich composite material (two external aluminum plates bound to a polyethylene core). In order to minimize thrust force and burr height, the influence of drill geometry, the pilot hole and the cutting parameters was assessed. Thrust force and burr height values were collected and used to perform an analysis of variance. The results indicated that the tool and the cutting speed were the parameters with more weight on the thrust force and for burr height they were the tool and the interaction between tool and feed. The results indicated that drilling with a pilot hole of Ø4 mm exhibited the best performance with regard to thrust force but facilitated plastic deformation, thus leading to the elevation of burr height, while the lowest burr height was obtained using the Brad and Spur drill geometry.

Effect of Drill Point Angle on Surface Integrity when Drilling Titanium Alloy

Surface integrity of machined component is of major importance for the reliability and safety requirements during in service especially for the aerospace applications. This paper presents an investigation on the effect of drill geometry on the surface integrity of drilled hole of Ti-6AL-4V during drilling operation. Drilling experiments were conducted under the MQL using a special vegetable oil known as Jatropha oil. Experimental results revealed that drill point angle and coolant-lubricant conditions significantly influence the surface integrity which include surface roughness, micorhardness and microstructure defects. The surface roughness decreased with greater drill point angle. The subsurface deformation layer thickness was approximately 9 - 15 μm from the top of the machined surface. Microhardness profiles of the last hole indicated that the subsurface deformation extend up to a 150 to 200 μm until it reaches to the average hardness.

Drilling of Glass Fiber/Vinyl Ester Composites with Fillers

The design requirements in various engineering applications have necessitated the development of novel materials. The Glass Fiber (GF)/vinyl ester composites are one such class of materials finding widespread application owing to their superior mechanical and chemical properties. The addition of fillers has further increased their application spectrum. Although these materials can be produced to a near-net shape, but still drilling of holes is necessary to ascertain the assembly of complex products. With an increase in demand, it becomes imperative to develop high quality cost effective technology for their manufacturing. The present research initiative is an attempt to experimentally investigate the drilling characteristics of GF/vinyl ester composites. The effect of drill geometry, the cutting speed and the feed rate has been found on the drilling forces and the surface roughness of the drilled hole wall. The relative significance of the various parameters has been found using ANOVA. The results of the experimental investigation bring out certain important facts in context of the drilling behavior of GF/vinyl ester composites filled with fillers.

An experimental and statistical study on the effect of drill geometries on force and hole quality in drilling of glass fibre reinforced plastic

Aircraft manufacturing involves drilling of large number of holes, in which the joint can be critically affected by the quality of the hole. Effect of drill geometry on drilling of glass/epoxy laminates using twist, Zhirov and Multifaceted Drills (MFD), has been studied. The thrust force and hole quality were compared for each drill geometry. Zhirov drill cuts the hole with less force and best surface finish. MFD produces less delamination when compared with the other geometries. ANOVA was used to study the effect of drill geometries, spindle speed, and feed rate on thrust force, surface finish and delamination factor.

Analysis of dynamic characteristics of micro-drills

Micro-drills were modeled as long twisted beams. Models for the critical speeds and the critical buckling loads were developed based on the finite element method of analysis. The effects of transverse shear, rotary inertia and gyroscopic moments were included in this analysis. The models have the capability of analyzing a wide variety of geometrical cross-sections. A computer program was developed for the calculation of the variations of the critical speeds and of the buckling loads. The effects of drill geometry, boundary condition, rotational speed, and cross-sectional area on the buckling loads and the critical speeds were analyzed.