Drilling Technology

Fundamentals and Recent Advances

J. Paulo Davim

• Publisher: De Gruyter Oldenbourg
• Year: 2018
• eBook ISBN: 9783110478716
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

This book aims to provide recent information on advances in drilling technology. The use of advanced machines, appropriate strategies and special drilling tools can signifi cantly reduce the machining time required for drilling operations, and consequently the production costs, and improve the quality of the holes produced. For these reasons an improvement of the drilling technology is very important for the modern manufacturing industries. This book can be used as a research book for fi nal undergraduate engineering course or at postgraduate level. It can also serve as a useful reference for academics, researchers, mechanical, industrial, production, manufacturing and materials engineers, professionals in drilling technology and related matters.

Viktor P. Astakhov and Swapnil Patel

1 Efficient drilling of high-silicon aluminum alloys

Abstract: This chapter presents the most important features of high-penetration rate (HPR) drilling of high-silicon aluminum alloys (HSAA). It explains a necessity of implementation of HPR tools and well-designed machining operations that has become possible due to development of a number of new tool materials and coatings, new cutting inserts and tool designs, new tool holders, powerful precision machines, part fixtures, advanced controllers and so on. As the penetration rate is the product of the tool’s (workpiece) rotational speed and cutting feed, the major constraints of these two parameters are considered and a number of practical recommendation for increasing the penetration rate are made as the first level of the analysis. At the second level of the analysis, the correlations between the chemical composition and physical properties of HSAA and drilling tool/process parameters are explained. As HSAA are die casting alloys, the casting defect and their influence on tool performance are analyzed. It is pointed out that polycrystalline diamond (PCD) is a material of choice for HPR drilling tools for HSAA. The common problems with the existing PCD drilling tool are analyzed and the basic design of a cross-PCD drill is suggested.

1.1 Introduction

In the context of a global competition, manufacturing companies are compelled to improve their productivities through the optimizations of their production operations including machining. Aluminum die casting alloys are lightweight, offer good corrosion resistance, ease of casting, good mechanical properties and dimensional stability. They are widely used as foundry alloys for a variety of different applications. For example, engine blocks and pistons for air compressors employed in the automotive industry are cast from Al–Si-based alloys. Casting alloys are distinguished from wrought alloys that contain 95% or more aluminum and are not used for castings but are used for applications such as can stock, gutters, siding, airplane skins and so on. In the automotive industry, transmission and engine components are made of high-silicon aluminum alloys (hereafter, HSAA), which have a high strength-to-weight ratio. Aluminum is cast at a temperature of 650°C (1200°F). It is alloyed with silicon (9%) and copper (3.5%) to form the Aluminum Association 380 alloy (UNS A03800). Silicon increases the melt fluidity and reduces machinability. Copper increases hardness and reduces ductility. By greatly reducing the amount of copper (less than 0.6%), the chemical resistance is improved by making AA 360 (UNS A03600) well suited for use in marine environments and in automotive transmissions (valve bodies, case and torque converter housings). HSAA with more than 13% Si are used in automotive transmissions (pump cover) and engines (for cylinder castings).

1.2 Short analysis of the known studies

There have been various literatures for tool performance in metal-matrix composites (MMCs) and all literature show agreement with difficulty in machining MMCs – tool-like hardness of reinforcement particles in MMCs results in excessive tool wear and poor surface properties of the workpiece [1]. An oblique cutting force model constructed by Dabade et al. [2] showed 40% to 60% of the reinforced particles contribute to the abrasion at chip-tool interface. El-Gallab et at. [3] studied tool performance of PCD, TiN-coated carbide tools and Al2O3/TiC tools and concluded that PCD tools show superior wear resistance over other tool materials. Furthermore, PCD tool wear can be minimized by increasing feed and cutting speed (as high as 0.45 mm/rev and 894 m/min were tested). Umer et al. [1] developed a finite element model to study tool performance for machining Al-based MMCs and showed that tool stresses increase with increase in feed and cutting tool temperature increase with increase in cutting speed. El-Gallab et al. [3] recommend 25 μm grain size. PCD was used by Muthukrishnan et al. [4] (Grade 1500) to machine A356/SiC/10p and results confirmed that higher cutting speeds result in relatively easier removal of the hard SiC particles. However, at higher speed, tool wear was much higher due to abrasive properties of SiC. Caroline et al. [5] conducted a tool wear study for machining A380 reinforced with 20 vol.% SiC with PCD and chemical vapor deposition (CVD)-coated carbide; higher wear was observed on CVD insert compared to PCD insert. PCD insert outlasted three times the CVD insert. Tool wear is believed to be caused by a combination of the abrasive wear and the adhesive wear mechanisms [6] that explains faster rate of flank wear on the CVD insert than PCD insert. Caroline et al. [5] also concludes that aluminum film adhered to diamond tool surface, very often plugs some tool material with it as the layer gets scratched by SiC, which was also implied by El-Gallab et al. [3]. In author’s opinion, however, tool wear is not of prime concern in HPR drilling (e.g., 12 mm drill diameter, 24,000 rpm and feed not less than 0.3 mm/rev) in modern manufacturing plant setting. The prime concerns are the quality of drilled holes (taken as the criterion of tool life) and tool reliability assured by the proper selection of most suitable drill geometry, tool material and precise manufacturing of the drill as per the tool drawing. Unbiased tool manufacturer’s evaluation is necessary to achieve best precision in manufacturing quality of the HPR drills.

For carbide turning inserts, formation of built-up edge (BUE) at lower speeds defines the tool wear, and thermal softening defines tool wear at higher speeds and feeds concluded by Seeman et al. [6]. Majority of researchers agree on the actual surface roughness achieved by cutting tool being better than theoretical surface roughness [7]. There have been various studies conducted to learn tool performance, tool wear and workpiece surface integrity while machining MMCs. However, none or very few studies show actual production-based scenario. Die cast MMCs are not just difficult to machine because of abrasive-reinforced particles [8] but also due to presence of various inclusions, porosity and impurities. In addition, condition of machining surface also plays very important role in tool wear. For example, drilling of cored holes where die casting supplier has 1.8 mm positional tolerance on core location requires very different approach than a blind hole where presence of porosity is very common. In our experience, studying tool wear in an assumed homogeneous mixture is faraway to resolve actual production issues. Innovative tool designs and root cause analysis techniques are must to keep the production cost low and quality at the best.

1.3 Urgent need for high-efficiency drilling and constraints

1.3.1 The rising need for innovation

Drilling of HSAA always presented a great challenge even in the recent past with relatively low cutting speeds and carbide cutting tools due to their unique properties, such as combination of a soft easy-to-adhere Al matrix and highly abrasive particles including silicon and sludge. This challenge, however, was never properly addressed due to two reasons:

1. The machining time in a cycle time of manufacturing part was so insignificant that the reduction of machining time did not affect the machining efficiency. This is because manual part loading–unloading, part and tool setting on the machine, part gaging in the machine and so on took most of this time. As a result, a reduction of the machining time due to the use of advanced (and thus more expensive) cutting tools and optimization of machining processes was not requested and, therefore, discouraged as manufacturing professionals did not see any benefits of such activities.
2. In the not-too-distant past, the components of a machining system were far from perfection, and thus it was not possible to utilize the advantages of advanced drilling tools. Tool specialists were frustrated with old machines having insufficient power and no rigid spindles, part fixtures that clamped parts differently every time, part materials with inconsistent essential properties, tool holders that could not hold tools without excessive run outs assuring their proper position and starting bushing plates that had been used for years without replacement; low concentration often contaminated metal working fluids (hereafter MWFs) also known as coolants that were more damaging than beneficial to the cutting tool, manual sharpening and presetting of cutting tools and limited range of cutting speeds and feeds. Under these conditions, the most advanced (and thus expensive) drilling tools, therefore, performed practically the same (or even worse) as basic tools made in local tool shops. As a result, any further development in tool improvement was discouraged as leading tool manufacturers did not see any return on investment in such developments.

This has been rapidly changing since the beginning of the twenty-first century as global competition forced many manufacturing companies; first of all car manufacturers, to increase efficiency and quality of machining operations. To address these issue...

Table of contents

• Cover
• Title Page
• Copyright
• Contents
• Preface
• About the Editor
• List of contributing authors
• 1 Efficient drilling of high-silicon aluminum alloys
• 2 Deep hole gun drilling of nickel-based superalloys
• 3 A new model pertaining to highspeed drilling of titanium alloy (Ti-6Al-4V)
• 4 Drilling of composite materials: methods and tools
• 5 Challenges of machining natural fiber-reinforced composites: A review
• 6 Analysis and optimization of hole quality parameters in cenosphere-multiwall carbon nanotube hybrid composites drilling using artificial neural network and gravitational search technique
• Index