Hole-making Process Research Articles

Simple die pressing for making artificial holes in single-grain Gd1.5Ba2Cu3O7−y superconductors

The presence of artificial holes in single-grain REBa2Cu3O7−y (RE123, RE: rare-earth elements) bulk superconductors can facilitate oxygen diffusion into superconducting grains through the increased surface area. In addition to the enhancement of oxygen diffusion, the mechanical properties and thermal conductivity of bulk superconductors can be improved by filling holes with a metallic conductive phase. This study presents a new and simple hole-making process for single-grain RE123 bulk superconductors. Artificial holes 3 or 5 mm in diameter were made for Gd1.5Ba2Cu3O7−y (Gd1.5) powder compacts prior to the sintering/melt growth process using specially designed pressing dies. The die pressing neither induced cracking in powder compacts nor influenced thermal procedures for the Gd123 growth. Single-grain Gd1.5 bulk superconductors with holes were successfully fabricated by a top-seeded melt growth (TSMG) process using Gd1.5 powder compacts with holes. The die pressing was proven as a time-saving process in comparison with the conventional method which makes holes in sintered or melt-processed hard bodies by mechanical drilling. The detailed fabrication process of single-grain Gd1.5 bulk superconductor with holes, magnetic levitation forces, and magnetic flux density, estimated for the single-grain Gd123 bulk superconductors with holes, are reported.

Evaluation of the drilling-induced delamination of compound core-special drills using response surface methodology based on the Taguchi method

The hole-making process in composite parts today is required to be more accurate and efficient, which can affect the in-service life and decrease manufacturing cost. Thus understanding the key factors affecting their qualities is of vital importance to develop effective machining strategies. To this end, this study proposes a model with response surface methodology (RSM) based on the Taguchi method to evaluate the influence of drilling parameters on delamination by compound core-special drills. The model with RSM includes three steps: (1) design and experiments, (2) response surface modeling through regression, and (3) optimization. A series of experiments were conducted to test the proposed model. It was found that the key factors affecting drilling-induced delamination include: cutting velocity ratio, feed rate, inner drill type, and inner drill diameter. Therefore, some experimental implications can be proposed accordingly.

Microstructure, Morphology, and Nanomechanical Properties Near Fine Holes Produced by Electro-Discharge Machining

Fine holes in metal alloys are employed for many important technological purposes, including cooling and the precise atomization of liquids. For example, they play an important role in the metering and delivery of fuel to the combustion chambers in energy-efficient, low-emission diesel engines. Electro-discharge machining (EDM) is one process employed to produce such holes. Since the hole shape and bore morphology can affect fluid flow, and holes also represent structural discontinuities in the tips of the spray nozzles, it is important to understand the microstructures adjacent to these holes, the features of the hole walls, and the nanomechanical properties of the material that was in some manner altered by the EDM hole-making process. Several techniques were used to characterize the structure and properties of spray-holes in a commercial injector nozzle. These include scanning electron microscopy, cross sectioning and metallographic etching, bore surface roughness measurements by optical interferometry, scanning electron microscopy, and transmission electron microscopy of recast EDM layers extracted with the help of a focused ion beam.

Investigation on drilling-grinding of CFRP

It is difficult to machine polymer matrix composites reinforced by carbon fibre, and the holemaking process is the most necessary machining process for composite plate products. Conventional drills have a very short life in the drilling of this kind of composites and the quality of the hole is very poor. In this paper, the cemented or plated diamond core tools are tested to make holes in carbon fibre/epoxy composite plates. The effects of machining parameters, cooling and chip removal on the tool life, and the hole quality are investigated. The results indicate that the material removal mechanism of the two kinds of diamond tools is not like the cutting effect of the conventional drilling but similar to that of grinding. Satisfactory effects in making holes in the composites are obtained—quite acceptable machined hole quality, low costs, and long wear-resistant endurance.

Influence of Drill Geometry in Drilling Carbon Fiber Reinforced Plastics

Twist drill is widely used in hole-making process in industries, due their low production cost and ease of regrinding after wear. However, drilling of fiber reinforced plastics with twist drill often results in defects and damages, such as delamination, debonding, spalling and fiber pullout. The chisel edge of twist drill is the mainly influence for the thrust force and the hole quality in drilling carbon fiber reinforced plastic (CFRP) laminates. Pre-drilled pilot hole or reduce chisel edge can eliminate the threat for twist drill in drilling induced-delamination. Drilling-induced thrust force was selected as quality character factors to optimize the drilling parameters (drill type, feed rate and spindle speed) to get the smaller the better machining characteristics by Taguchi method. The results show that the feed rate and drill type are the most significant factor affecting the induced-thrust in drilling CFRP laminates.

Helical Feed Milling with MQL for Boring of Aluminum Alloy

MQL is applied to the helical feed milling hole-making process of aluminum alloy. It is difficult to drill on aluminum alloy without cutting fluid because the adhesion to the tool leads to a chip jam, the tool breakage or low accuracy. By employing the helical feed milling, cutting temperature will decrease, each chip length will become short and a chip jam in a hole will be avoided, because the intermittent cutting is realized. As a result of employing the helical feed milling with MQL, it was shown that the shape error is decreased, a burr formation is decreased, machining temperature becomes low and the cutting force becomes small comparing with drilling process. Shape error by helical feed milling with MQL is comparable with that with flood coolant. In this case, small mist particle counts under 5μm, which affects working environment, are almost constant if the spindle speed varies. Scattered mist particle counts are less when MQL is employed over 20000 min-1 spindle speed comparing with the flood coolant.

Some considerations on tool wear and workpiece surface quality of holes finished by reaming or milling in a nickel base superalloy

Higher-strength heat-resistant superalloys are continually being developed to meet the engineering requirements for increased efficiency of gas turbine engines. In addition, work on machinability assessment is needed to fill the gap between the material development and manufacturing capabilities before considering the implementation of such materials in production lines. The present paper presents selected results on optimization of cutting conditions for hole-making processes of a new aerospace nickel (RR1000)-based superalloy manufactured via a powder route. The mechanical properties and the chemistry of RR1000 alloy indicate lower machinability when compared with the current disc alloys (e.g. Inconel, Waspaloy, Udimet). The hole-making processes, involving a succession of roughing (drilling) and finishing (normal/special reaming or plunge milling) operations, were evaluated through a multicriteria procedure consisting of the following output measures: tool life, hole accuracy, surface roughness, workpiece surface integrity, and level of cutting torque. It was found that simultaneous fulfilment of multicriteria quality measures is more dependent on the selection of tooling/cutting edge preparation involved in the finishing step rather than the relatively narrow intervals of operating parameters. While drilling and normal reaming lead to surface overheating (white layers) and material dragging, the change of edge preparation (e.g. double-relief angle) on the special reamers or the use of alternative cutting strategies (e.g. plunge milling) can generate finished holes within the required surface integrity standards. An original relationship between a derived measure from output sensory signals (i.e. specific cutting energy per tooth per revolution) and workpiece surface integrity (i.e. depth of strained material) has been investigated to assist further the selection of the ‘best’ finish machining operation. Additionally, this approach opens the avenue towards online surface integrity inspection via ‘key sensory measures’.

Tool wear in friction drilling

This study investigates the tool wear in friction drilling, a nontraditional hole-making process. In friction drilling, a rotating conical tool uses the heat generated by friction to soften and penetrate a thin workpiece and create a bushing without generating chips. The wear of a conical tungsten carbide tool used for friction drilling a low carbon steel workpiece is studied. Tool wear characteristics are quantified by measuring its weight change, detecting changes in its shape with a coordinate measuring machine, and making observations of wear damage using scanning electron microscopy. Energy dispersive spectrometry is applied to analyze the change in chemical composition of the tool surface due to drilling. In addition, the thrust force and torque during drilling and the hole size are measured periodically to monitor the effects of tool wear. Results indicate that the carbide tool is durable, showing minimal tool wear after drilling 11,000 holes, but observations also indicate the progressively severe abrasive grooving on the tool tip.

Experimental and Numerical Analysis of the Friction Drilling Process

Friction drilling is a nontraditional hole-making process. A rotating conical tool is applied to penetrate a hole and create a bushing in a single step without generating chips. Friction drilling relies on the heat generated from the frictional force between the tool and sheet metal workpiece to soften, penetrate, and deform the work-material into a bushing shape. The mechanical and thermal aspects of friction drilling are studied in this research. Under the constant tool feed rate, the experimentally measured thrust force and torque were analyzed. An infrared camera is applied to measure the temperature of the tool and workpiece. Two models are developed for friction drilling. One is the thermal finite element model to predict the distance of tool travel before the workpiece reaches the 250°C threshold temperature that is detectable by an infrared camera. Another is a force model to predict the thrust force and torque in friction drilling based on the measured temperature, material properties, and estimated area of contact. The results of this study are used to identify research needs and build the foundation for future friction drilling process optimization.

Microstructural Alterations Associated With Friction Drilling of Steel, Aluminum, and Titanium

Friction drilling, also called thermal drilling, is a novel sheet metal hole-making process. The process involves forcing a rotating, pointed tool through a sheet metal workpiece. The frictional heating at the interface between the tool and workpiece enables the softening, deformation, and displacement of work-material and creates a bushing surrounding the hole without generating chip or waste material. The bushing can be threaded and provides the structural support for joining devices to the sheet metal. The research characterizes the microstructures and indentation hardness changes in the friction drilling of carbon steel, alloy steel, aluminum, and titanium. It is shown that materials with different compositions and thermal properties affect the selection of friction drilling process parameters, the surface morphology of the bore, and the development of a highly deformed layer adjacent to the bore surface.

Helical Feed Milling with MQL for Boring of Aluminum Alloy

MQL is applied to the helical feed milling hole-making process of aluminum alloy. lt is difficult to drill on aluminum alloy without cutting fluid because the adhesion to the tool leads to a chip jam, the tool breakage or low accuracy. By employing the helical feed milling, cutting temperature will decrease, each chip length will become short and a chip jam in a hole will be avoided, because the intermittent cutting is realized. As a result of employing the helical feed milling with MQL, it was shown that the shape error is decreased, a burr formation is decreased, machining temperature becomes low and the cutting force becomes small comparing with drilling process. Shape error by helical feed milling with MQL is comparable with that with flood coolant. In this case, small mist particle counts under 5μm, which affects working environment, are almost constant if the spindle speed varies. Scattered mist particle counts are less when MQL is employed over 20000 min-1 spindle speed comparing with the flood coolant.

COMPASS: Computer oriented materials, processes, and apparatus selection system

Abstract Today's competitive manufacturing environment requires a shortened product development time. Although great emphasis has been placed on concurrent engineering, it is still a challenge for engineers to bridge the gap between design and manufacturing. This paper proposes a new approach to an emerging concept, Meta Planning, which brings manufacturing issues upstream by generating timely and appropriate feedback to design engineers. While a product or feature is being designed, all feasible downstream manufacturing processes can be compared. A meta planner can be integrated into existing CAD/CAPP/CAM systems to automate high-level process planning such that heterogeneous processes can be organized into a coherent plan. COMPASS (Computer Oriented Materials, Processes, and Apparatus Selection System), developed as a meta planner, has the basic framework to provide essential information regarding production cost, cycle time, and product quality for all of the candidate processes. It is a tool that helps design engineers identify potential manufacturing problems in the earlier stages of product development. Three different hole-making process models are implemented in COMPASS to illustrate the mechanism that analyzes and compares different manufacturing processes. Close interaction between design parameters and manufacturing performance for selected processes is demonstrated through a detailed case study involving a single feature.

Modeling transverse motions of a drill bit for process understanding

A model for drill bit transverse motions is proposed that identifies process conditions affecting hole quality and helps in the interpretation of drilling signal patterns produced during the hole-making process. A two-dimensional model of a drill rotating in a hole with clearance is presented. The simulation results, drilling force signal patterns, and hole geometry were found to be in close agreement. Drill rotation speed, drill stiffness, structural damping, drill hole clearance, and amplitude modulation of the forces acting on the drill appear to have a significant effect on drill bit transverse motions and on hole quality.

Measurement While Drilling - A New Tool (includes associated papers 15328 and 15343 )

Definition Measurement while drilling (MWD) is the downhole measurement of important parameters and (in most cases) the simultaneous transmission of those measurements to the surface while drilling. Need for MWD In the past, hole-making and formation evaluation processes have been accomplished with different technologies, separated in time. Drilling (hole-making)is a complicated technological process with many uncertainties. Ignorance of what is taking place downhole during this process has caused it to be viewed more as an art than as a science. The most important parameters controlling this process are the physical properties of the formation (and the pore fluid)being drilled, which are largely unknown at the time of drilling. The big mistakes that involve the loss of well control (blowouts) are well known. The many "small" mistakes (kicks, lost circulation, stuck pipe, lost cones, twistoffs, etc.) are not so well known, but cost considerable time and money. The conventional (wireline) formation evaluation process, while very important to the geologist, the petrophysicist, and the reservoir engineer, is also very expensive in terms of rig time and trouble cost. History The first U.S. patents and technical papers on MWD appeared in the early 1930's. The first practical approach that resulted in technical success was J.J. Arps' mud pulse system that made its debut in the 1950's. In the late 1960's, Exxon and Texaco experimented with downhole recording while drilling. The lack of high-density electronics packaging, a suitable memory medium, and the ability to ruggedize the systems adequately made them unattractive for extensive use. As a result of the efforts of SNEA (Elf Aquitaine)and Raymond Engineering, and with the financial assistance of the U.S. DOE, Teleco introduced the first commercial MWD system in 1978. At the current time, many companies are investing in this technology, while eight offer commercial services. Data Rate Requirements When designing or selecting an MWD system for use, one must specify the types of downhole information desired and the measurement rates needed. Some information is needed on a "time(ly) basis" and other on a "footage basis." To convert from a time base to a depth base, the drilling rate must be known. A curve of average penetration rate as a function of depth that is typical of the Gulf of Mexico was used to prepare Fig. It provides a rough guide as to the suitability of various mud-pulse data rates for providing multiple-service MWD.

An Integrated CAD/Automated Process Planning System

Abstract In this paper, the integration of an automated process-planning system with an interactive computer graphics system is presented. (The current system is capable of planning hole-making processes.) This paper discusses the graphics system, the generative automated process planning system, their interface and the possibility of interfacing with a larger CAD/CAM system. An example of planning a precision machined part is also presented.

Some aspects of the design and classification of drill bits. Part 2: Hole-making processes and definitions

In general, developments in the design of rotary drill bits have proceeded in three main directions dictated largely by the properties of the materials that were being drilled and by the materials that were available for constructing the bits. Typical examples are firstly, screw point augers and centre bits for drilling relatively soft materials such as woods; secondly, spade bits and twist drill bits, which have more robust cutting edges, for drilling metals; thirdly, diamond bits, roller-cone and fish-tail bits for drilling relatively hard brittle materials such as rocks. New materials are being developed that cannot conveniently be classified under these headings, eg filled plastics, laminates, etc. Consequently production engineers are being called upon to drill such materials, often with drill bits that have not been specifically designed for the tasks they are being called upon to perform. As a consequence of specialization, drill bits and drilling techniques have been developed by engineers in different fields of engineering virtually unknown to each other. In attempting to adopt a completely fresh approach to drill bit design the author was led to consider the various ways in which holes are manufactured and the roles played by drill bits. A brief reference is made to the methods used by animals and plants. This could provide a useful field for research into new hole-making methods. The importance of considering the way in which a drill bit is to be used is emphasised, and some suggestions for definitions are given, in an attempt to clarify some of the confusing terminology found in some of the literature on drill bits. A classification system is described which originated from a collection of information on drill bits.

Some aspects of the design and classification of drill bits. Part 2: Hole-making processes and definitions

Some aspects of the design and classification of drill bits. Part 2: Hole-making processes and definitions