High Performance Machining

<div class="section abstract"> <div class="htmlview paragraph">Nondestructive tests are those tests which detect factors related to the serviceability or quality of a part or material without limiting its usefulness. Material defects such as surface cracks, laps, pits, internal inclusions, bursts, shrink, seam, hot tears, and composition analysis can be detected. Sometimes their dimensions and exact location can be determined. Such tests can usually be made rapidly. Processing results such as hardness, case depth, wall thickness, ductility, decarburization, cracks, apparent tensile strength, grain size, and lack of weld penetration or fusion may be detectable and measurable. Service results such as corrosion and fatigue cracking may be detected and measured by nondestructive test methods. In many cases, imperfections can be automatically detected so that parts or materials can be classified.</div> <div class="htmlview paragraph">The SAE Handbook describes the following nondestructive test methods:</div> <ol class="list nostyle"> <li class="list-item"> <div class="htmlview paragraph">SAE J359—Infrared</div></li> <li class="list-item"> <div class="htmlview paragraph">SAE J420—Magnetic Particle</div></li> <li class="list-item"> <div class="htmlview paragraph">SAE J425—Eddy Current</div></li> <li class="list-item"> <div class="htmlview paragraph">SAE J426—Liquid Penetrant</div></li> <li class="list-item"> <div class="htmlview paragraph">SAE J427—Penetrating Radiation</div></li> <li class="list-item"> <div class="htmlview paragraph">SAE J428—Ultrasonic</div></li> <li class="list-item"> <div class="htmlview paragraph">SAE J1242—Acoustic Emission</div></li> <li class="list-item"> <div class="htmlview paragraph">SAE J1267—Leakage Testing</div></li></ol> <div class="htmlview paragraph"><span class="xref">Table 1</span> summarizes the principal features of most of these tests. In addition to the tests described, other nondestructive tests exist which are less well established, but whose use is expanding. Among these are microwave tests, holography, and sonic tests. Microwaves are used to locate defects in nonmetallic substances and to determine some physical characteristics of those materials. Optical holography uses coherent light from a laser beam to detect strains and defects in materials by means of three-dimensional imaging and interferometry techniques. Acoustical holography uses ultrasonic waves to image discontinuities in the interior of solids. Recent refinements in sonic testing permit more objective determination of the physical properties of cast iron. Complete information concerning each nondestructive test can be obtained from books listed in the bibliographies of the aforementioned reports.</div> <div class="htmlview paragraph">Increasing consumer demand for product quality at reasonable cost has resulted in development of nondestructive tests which can be applied to materials and manufactured parts. Although a variety of complementary nondestructive methods is available, development time is generally required for application to specific materials or products. The effect of part contour, surface condition, heat treatment, composition variation, and other variables may limit the ability of certain tests to detect imperfections with desired accuracy.</div> <div class="htmlview paragraph">Nondestructive tests properly applied to basic material can add greater assurance of performance to design strengths, thereby affecting material and manufacturing economy. In addition, parts can be tested after each basic operation which is critical to service performance of the finished part. In-process nondestructive tests can also serve as basic components of feedback process control systems since all tests are based upon measurements which do not damage the material or part being inspected.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The Automotive industry widely uses cast iron due to its better mechanical performance and cost-effectiveness. However, repair welding or assembly of cast iron components remain highly challenging due to the material’s high carbon content, inherent brittleness, rapid thermal conductivity, and complex microstructural transformations. Multi-pass welding exacerbates these challenges by subjecting materials to repeated thermal cycling, accumulating residual stress, and inducing distortion – all of which potentially degrade the integrity of welded joints. A comprehensive understanding of welded joint behavior is essential to effectively mitigate these effects. Finite element analysis (FEA) serves as a powerful tool, enabling accurate prediction of thermal profiles, phase transformations, residual stress development, and resulting deformations. These valuable insights are critical for optimizing welding processes and enhancing overall joint quality.</div><div class="htmlview paragraph">This study investigates and validates the use of FEA-based simulation tools for multi-pass MIG welding of ductile cast iron plates, highlighting the effectiveness of virtual modeling in complex welding scenarios. A numerical simulation of 20 mm thick cast iron plates welded with Ni-Fe filler wire was conducted using SYSWELD software. The distortion, temperature distribution, microstructure, hardness, and residual stresses of the weld coupon were predicted using a thermo-metallurgical-mechanical model. The simulation incorporated a double-elliptical heat source for welding and an imposed thermal cycle model for pre- and post-weld heat treatments. Metallurgical analysis was performed utilizing a phase transformation model and Continuous Cooling Transformation diagram to estimate microstructural phase fractions and hardness. The mechanical analysis, based on the thermo-metallurgical profile and boundary conditions, evaluated weld distortion and residual stresses on weld coupon. Predicted results, including thermal cycles, fusion zone, distortion, hardness, and residual stresses, were validated against experimental data showed strong coherence.</div><div class="htmlview paragraph">This study demonstrates the efficacy of FEA tools in accurately predicting dissimilar weld properties, reinforcing their reliability for welding and repairing cast iron components in industrial applications.</div></div>

<div class="htmlview paragraph">ULTALITE<sup>®</sup> is a patented low cost Aluminium Metal Matrix Composite (Al-MMC) produced using flyash particles as the reinforcement particulate. The material is proven to possess higher stiffness, strength and wear resistance relative to the monolithic matrix alloy both at room and elevated temperatures.</div> <div class="htmlview paragraph">Cast Iron has been utilised in brake drums and disc rotors throughout the history of Automobile manufacturing. High density, rigorous machining due to imprecise casting and consequently, substantial production cycle times are few of the inherited drawbacks in utilising cast iron for brake drums. Utilisation of a material such as this is undoubtedly invaluable in eliminating majority of such shortcomings.</div> <div class="htmlview paragraph">In this paper, our focus is on the performance of automotive brake drums produced with this new material. Brake dynamometer test results are presented and analysed substantiating the suitability of the technology. Brake drums for testing purposes were produced by a squeeze casting method.</div> <div class="htmlview paragraph">Brake dynamometer tests were conducted in accordance with the SAE J2522 standard. The new AL-MMC drums with standard linings exhibit equivalent or better performance comparatively to OE Cast Iron drums at all times. Heat dissipation characteristics of these Al-MMC based brake drums are outstanding compared to OE Cast Iron brake drums and this is further proven by the Brake Dynamometer test results. Wear test results indicate superior wear characteristics compared to OE Cast Iron brake drums.</div> <div class="htmlview paragraph">Components made from this new material also possess characteristics such as less machining, stringent tolerances, less production time and substantial weight reductions partly due to the die casting fabrication process. Considering the tests results and evident benefits, we demonstrate that the investigated Al-MMC based brake drums are a potential substitute for OE Cast Iron brake drums.</div>

<div class="htmlview paragraph">A new brake disc rotor material has been developed that provides excellent resistance to heat cracks.</div> <div class="htmlview paragraph">Hair cracks have been found to develop in the surface of brake disc rotors as a result of repeated braking from high speed.</div> <div class="htmlview paragraph">The results of a finite element analysis revealed that these cracks are generated in the early stage of braking because of temperature differences between the surface and interior of the brake disc rotor.</div> <div class="htmlview paragraph">The newly developed cast iron has a high carbon and a low silicon content, which works to improve its thermal conductivity, and molybdenum has been added to prevent any decline in strength.</div> <div class="htmlview paragraph">The results of high speed braking tests show that the new material provides superior resistance to heat cracks.</div>

<div class="htmlview paragraph">There has been and continues to be a growing trend in world engines towards the use of ‘Bi-Metallic’ constructions, ie. engines which feature head and block castings of different materials. The use of aluminium cylinder heads with cast iron cylinder blocks is a typical arrangement.</div> <div class="htmlview paragraph"><span class="xref">Figure 1</span> indicates some of the significant differences in the physical properties of cast iron and aluminium. As can be seen, aluminium offers a number of advantages from an engine design viewpoint, notably weight saving and heat transfer efficiency.</div> <div class="htmlview paragraph">The use of aluminium can, however, result in a number of potential difficulties in terms of its effect on cylinder head gasket performance.</div> <div class="htmlview paragraph">This paper considers these difficulties with particular reference to ‘fluid sealing’. <figure id="F1" class="figure"><div class="graphic-wrapper"><img class="article-figure figure" src="840189_fig0001.jpg" alt="No Caption Available"/></div></figure></div>

<div class="htmlview paragraph">The system that will be presented consists of a Crawling Portable Robot (CPR) for drilling large air frame components as a part of the whole assembly process of fuselage or wing type sub-structures.</div> <div class="htmlview paragraph">Currently, the drilling of such components is massively fulfilled manually in a very labour intensive and “craft-based” manner. The operations are conducted in cramped, dangerous conditions and often involve unhealthy postures. The alternative to this situation consists in the use of large fixed-base multi-axis machines mounted upon a foundation on the shop floor.</div> <div class="htmlview paragraph">These machines are quite expensive, and also have a number of operational limitations. Because of their large working envelope, it is difficult for these machines to hold close tolerances over the entire range of all movement axes of the machine. Hence, there is a need to probe and calibrate the machine to the workpiece one or more times during work operations with the consequent negative impact in productivity. Moreover, the machines also require permanent floor space and require the structure that is to be processed to be brought to the machine with the non-productive transit time that is incurred in this process.</div> <div class="htmlview paragraph">The innovation presented seeks to improve upon the situation described above by providing a portable multi-axis drilling robot. The system consists in a robot that is stored in a wheeled station designed for that purpose. Whenever its services are needed, the storage carriage is brought to the component being assembled, and the robot is fixed to the aeronautic component by its own vacuum cups. After self-referencing with the aid of a vision system, the drilling work is done inside the robot working volume. Once this finished, the robot can move and relocate autonomously to the next working volume on the panel by means of a walking or crawling system. Once the work on the full component is finished, the robot is taken down from the panel and placed again in the storage station.</div>

<div class="section abstract"><div class="htmlview paragraph">A linerless aluminum (Al) engine block has potential to reduce the weight of an automotive engine and improve the fuel economy. However, the Al cylinder surface of an aluminum engine block is not usually strong enough to withstand the sliding wear against piston rings. A few surface processing technologies are used to protect the surface of cylinders. Among them, a thermal spraying coating, such as plasma transferred wire arc (PTWA) is already popular. Plasma electrolytic oxidation (PEO) coating is also proposed for increasing the wear resistance of aluminum-silicon (Al-Si) alloys and reducing the friction between the cylinder and piston. In this work, two different PEO coatings with a thickness of around 23 μm were prepared on an Al-Si alloy A356, and a high speed pin-on-disc tribometer was used to study the tribological behavior of the coatings at oil lubricant conditions. A cast iron sample was also used to do similar tribological tests for comparison. The coefficient of friction (COF) vs surface roughness (R<sub>a</sub>: 0.2 - 0.8 μm) and sliding speeds (up to 6.07 m/s) were particularly studied. The results show that the COF significantly decreased with the increase of sliding speeds, and a smoother coating surface generally exhibited a lower COF and a steeper descent rate of the COF. While such observations seem true for both PEO coatings and the cast iron sample, the polished PEO coatings can have a lower COF than cast iron. The study indicates that the Al-Si alloy with PEO coatings could be further explored as a feasible solution to reduce the weight and improve the fuel efficiency of an Al engine.</div></div>

<div class="htmlview paragraph">NI-ROD<span class="xref">*</span> FC 55 Cored Wire is a recently developed flux-cored wire specifically designed for automatic welding of various grades of cast irons. With the product, high-quality joints can for the first time be achieved in cast irons at rapid production rates.</div> <div class="htmlview paragraph">The flux-cored wire presents designers with many opportunities to obtain substantial cost savings. The use of economical cast irons can now be expanded to include parts that previously had to be designed in forged or cast steel to gain the required weldability. This report presents a description of the new cored wire and describes several examples of its use in the automotive, farm machinery, and other industries.</div>

<div class="htmlview paragraph">The 2.8 Liter 60° V-6 engine discussed here is an all new design made specifically for the 1980 Citation type of GM vehicle.</div> <div class="htmlview paragraph">This paper describes the technical features of the engine, and some of the development problems encountered and how they were solved. It also touches on the durability testing of the components and the total assembly.</div> <div class="htmlview paragraph">Paramount design goals for this engine were, from the outset, maximum reliability with minimum weight. Further, compactness of the total dressed engine assembly was dictated by size and configuration of the drive train compartment in the vehicle. Serviceability, tooling, and possible future displacement and material changes also were important factors.</div> <div class="htmlview paragraph">Extensive engine testing has demonstrated the desired reliability, as well as, very good power and specific fuel consumption. The overall weight, with the use of cast iron in both the cylinder heads and the block, fulfills the design goals.</div>

<div class="htmlview paragraph"><b>A</b>CHIEVEMENTS of the last ten years in increasing the power-weight ratio of aircraft engines are stated and contributing factors are analyzed. Aluminum alloys have replaced cast iron and steel for certain parts, not entirely because of their lower weight but because of a combination of properties which better fit them for the task. Similar considerations must govern the replacement of aluminum-base alloys by those of magnesium. The most promising immediate field for the magnesium alloys is said to lie in applications wherein strength and lightness are the main considerations and high-temperature properties are of secondary importance.</div> <div class="htmlview paragraph">Properties of magnesium castings and forgings are compared with those of castings and forgings of the aluminum alloys. Features of design are discussed which should receive special attention when changing a part from aluminum to magnesium.</div> <div class="htmlview paragraph">Machining practices for magnesium are covered in some detail. The author states that the present casting-alloys have proved commercially satisfactory as to corrosion for most types of land service. In saltwater service, especially in tropical countries, a certain amount of trouble has been encountered and some protective measures seem to be necessary. A recommended treatment for protection against corrosion is offered.</div> <div class="htmlview paragraph">Discussion of the paper touched on corrosion, including the effects of contact with wood and with gaskets; on machining and heat-treatment; and on the rapid improvement that is being made in magnesium.</div>

Machining time is a major performance criterion when it comes to high-speed machining. CAM software can help in estimating that time for a given strategy. But in practice, CAM-programmed feed rates are rarely achieved, especially where complex surface finishing is concerned. This means that machining time forecasts are often more than one step removed from reality. The reason behind this is that CAM routines do not take either the dynamic performances of the machines or their specific machining tolerances into account. The present article seeks to improve simulation of high-speed NC machine dynamic behaviour and machining time prediction, offering two models. The first contributes through enhanced simulation of three-axis paths in linear and circular interpolation, taking high-speed machine accelerations and jerks into account. The second model allows transition passages between blocks to be integrated in the simulation by adding in a polynomial transition path that caters for the true machining environment tolerances. Models are based on respect for path monitoring. Experimental validation shows the contribution of polynomial modelling of the transition passage due to the absence of a leap in acceleration. Simulation error on the machining time prediction remains below 1%.

<div class="section abstract"><div class="htmlview paragraph">Engine development activities are being driven forward primarily by the challenge of continuing to reduce CO<sub>2</sub> and exhaust emissions. From the piston/liner system it is well known that Lube Oil Consumption (LOC) is affected by the bore distortion occurrences within Internal Combustion Engines (ICE) that usually demands a redesign on the piston ring pack not in favor to reduce friction losses. This article shows a potential solution to reduce bore distortion and oil evaporation through more efficient heat dissipation from combustion chamber to engine cooling system in a modern aluminum Spark Ignition (SI) block. Electroplated nickel coating applied to the external cast iron surface previous to the casting process enable a metallurgical diffusion layer with the aluminum block material and therefore improve heat conductivity in fired operation conditions compared to conventional cast iron liners. The improvement of the heat dissipation rate reduced the bore distortion and therefore LOC as proven by engine tests. In this paper, results of engine dyno tests to build up LOC maps using Real Time Lube Oil Consumption (RTLOC) by mass spectrometry are presented. The application of nickel coated liners showed LOC reduction up to 75% in certain engine operation conditions. Detailed information about the coating and diffusion layer of Fe-Ni-Al is also presented by Energy Dispersive X- Ray (EDS) and Scanning Electron Microscope (SEM). Finally comparative analysis of bonding strength on aluminum blocks and thermal conductivity measurements by thermocouples installed on aluminum blocks engine test is presented to consolidate the nickel coating technology.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Wear and friction behavior of disc brakes are important properties of disc brake systems and are mainly addressed by appropriate selection and tuning of friction material. Disc material composition is often considered as “given”. The most common material used for brake discs is grey cast iron which can have carbon content between 2.5 to 4.2 percent. It is difficult to find in literature investigations related to the influence of cast iron material in combination with modern low-met friction material on wear and friction performance of disc brakes. In this work, the author will try to analyze impact of brake disc material properties on wear and friction performance.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The most used rotor material is gray cast iron (GCI), known for its susceptibility to corrosion. The impact of corrosion on the braking system is paramount, affecting both braking performance and the emission of particulate matter. The issue becomes more severe, especially when the brakes are left stationary or unused for extended durations in humid conditions, as seen with electric vehicles (EVs). Brake disc corrosion amplifies the risk of corrosion adhesion between contacting surfaces, leading to substantial damage, increased quantity and mass of non-exhaust particulate emissions, and decreased braking effectiveness. In addition, brake pads' friction material plays a crucial role in generating the necessary stopping force, creating friction that transforms kinetic energy into heat. However, heightened pressure during braking elevates rotor temperatures, contributing to the degradation of the friction material. This degradation manifests in decreased mechanical strength, heightened pad-to-rotor force, wear, and reduced braking efficiency. To address all these challenges and meet the stringent Euro7 particulate emission standards, we have developed controlled wear-resistant nitrocarburized layers on cast iron surfaces with customizable thicknesses, compositions, and porosity coupled with a new generation of post-oxidized layers referred to as Smart-ONC®. These layers, known for their remarkable "self-healing" capabilities, are formed through a controlled, in-situ post-oxidation process by incorporating additional metals into the oxide layer to enhance corrosion resistance and fortify the surface against damage and potential failures. the dyno tests validated the integrity of the FNC-Smart ONC (Ferritic nitrocarburizing-Smart oxidation of the nitrocarburized layer) layers, affirming their ability to preserve mechanical properties without experiencing wear, delamination, or cracking. Notably, FNC-Smart ONC discs demonstrate pad material accumulation, effectively sustaining braking performance as an additional protective interface between pads and discs.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Nowadays, more than in the recent decades, the design process for the body in white for passenger cars is driven by efficiency. This results in the enhanced usage of large-scale cast components made of aluminum, for the battery compartment, the front or rear body and other components. While the automotive industry is striving towards even larger structures made with so-called “Giga-Casting”, challenges in the casting and supply chain processes, but also maintenance and repair processes of these large structures, arise. Other tasks to solve might follow from controlling local microstructures, and thus the strength of the parts, when the flow length of the molten metal increases with component size, especially in relation to an increased fraction of recycled aluminum. Within the Fraunhofer-internal project “FutureCarProduction”, focus is directed towards understanding what drives efficiency, availability and sustainability of modern processes for the production of a car body. Moreover, the project addresses questions along the complete product chain of a car body, in terms of optimization of casting and joining, and quality assurance processes and seeks to give solutions for the efficiency and quality of different manufacturing processes. In the present paper, an overview of the project scope itself and the recent findings of “FutureCarProduction” are presented with a focus on the influences of higher fractions of secondary/recycled aluminum on the casting process, the occurring microstructure and defect situation in body in white components. This forms the basis for further investigations on the performance of different manufacturing and design opportunities for automotive components.</div></div>