Mohammed Sarwar

The economic benefit of finish turning with coated carbide

Abstract Surface roughness values are an important consideration in component design and are increasingly specified on engineering drawings. A value of surface finish (roughness) may be specified so that expensive finishing processes are eliminated, thereby reducing costs, or alternatively to improve the mechanical properties of a component. The careful finishing of components can lead to longer life, improved efficiency and other benefits. The investigation reported in this paper was carried out on behalf of a medium sized engineering company who wished to learn whether a change from uncoated carbide to coated carbide could be economically justified for finish turning operations. It was desired to identify the most cost effective combination of cutting speed, feed and tool material for a finish turning operation, useful tool life being taken when the surface roughness deteriorated beyond a predetermined level. It is shown that the lowest cost per component is achieved by using the highest cutting speed possible on the lathes available within the company, coupled with the highest cutting tool feed rate commensurate with finish turning. Significantly however, it is shown that the lowest cost when machining with coated carbide is 30% less than when machining with uncoated carbide during finish turning operations.

Performance of titanium nitride-coated carbide-tipped circular saws when cutting stainless steel and mild steel

The use of TiN coatings on cutting tools for general ferrous machining applications to enhance tool life and increase productivity is now well established. However, application of coatings to the carbide-tipped cutting tools using the PVD process is a new activity. In this investigation a new experimental approach was used, in which TiN coatings were applied to carbide-tipped circular saw segments. The four cathode PVD technique was used for deposition at a low coating temperature. This results in a fine-grain, thin, hard film with excellent adherence to the substrate. When deposited on tools, coating acts as a chemical and thermal barrier between the tool and workpiece. Applications including machining mild steel and stainless steel benefit from the coating. Comparison between coated carbide-tipped circular saws and uncoated carbide-tipped circular saws is presented. The cutting test results have shown that TiN-coated carbide-tipped circular saws presented much better performance and longer tool life than the uncoated saws. This information will be useful in the development of a coating system applied to the carbide-tipped circular saw using PVD.

Forces, surface finish and friction characteristics in surface engineered single- and multiple-point cutting edges

Abstract Advanced surface engineering technologies (physical and chemical vapour deposition) have been successfully applied to high speed steel and carbide cutting tools, and the potential benefits in terms of both performance and longer tool life, are now well established. Although major achievements have been reported by many manufacturers and users, there are a number of applications where surface engineering has been unsuccessful. Considerable attention has been given to the film characteristics and the variables associated with its properties; however, very little attention has been directed towards the benefits to the tool user. In order to apply surface engineering technology effectively to cutting tools, the coater needs to have accurate information relating to cutting conditions, i.e. cutting forces, stress and temperature etc. The present paper describes results obtained with single- and multiple-point cutting tools with examples of failures, which should help the surface coater to appreciate the significance of the cutting conditions, and in particular the magnitude of the forces and stresses present during cutting processes. These results will assist the development of a systems approach to cutting tool technology and surface engineering with a view to developing an improved product.

An Engineering Research and Development Framework for the Challenges Faced by the Hotel Industry: Hong Kong Case Study

Most hotels in a commercialized city are now struggling to satisfy the rapid and dynamic changes of customers’ requirements. New concepts and approaches for design and development and operation of hotel systems are necessary to cope with these challenges, to maintain market competitiveness, and to secure long-term prosperity. The article examines the present customer requirements and future hotel industry development in a rapidly changing city. The article attempts to formulate strategies to deal with challenges from the utilization of advanced information and systems engineering perspective. An engineering research and development (R&D) framework composed of a customer-oriented approach, a manufacturing system-life-cycle, and artificial intelligence employed in computer integrated manufacturing and agile manufacturing is proposed. Each important aspect of the R&D framework is discussed in detail: the current problems of hotel design and operating concepts, the engineering principles of resolving encountered problems, and methods of facing the challenges.

Effect of substrate surface preparation on the performance and life of TiN-coated high speed steel circular saw blades

Advanced surface engineering technologies have been successfully applied to high speed steel and carbide single-point cutting tools. Limited benefits have been achieved when applying the same technologies to multipoint cutting tools of commercial quality. In this application, poor substrate surface preparation is a major contributor to premature failure of the tool. The current work investigates the effect of substrate surface preparation on the performance and tool life of titanium-nitride-coated high speed steel circular saw blades when machining tool steel under accelerated cutting conditions. Tests have been developed to allow the cutting action of a full circular saw blade to be replicated by simulation tests using a segment containing representative teeth. Segments which were untreated or had a TiN coating applied onto either a microblasted or a surface ground substrate were tested for performance and life at an accelerated cutting speed. Results indicate blade life improvements through careful preparation of the substrate surface prior to coating. Benefits of substrate surface preparation in enhancing the life of TiN-coated circular saw blades have been established. This information will be useful in developing a total systems approach by which advanced surface engineering and cutting tool technology can be jointly applied to develop an improved product.

Application of advanced surface engineering treatments to multi-point cutting edges

Hard coatings to arrest or slow down wear, improve productivity and produce quality products are now well established in single-point tools (HSS and carbide). However, the same is not true for multi-point cutting tools. The paper examines the progress made in low-value high-volume (bandsaws, holesaws) and high-value low-volume (circular saws, broach tools) products. Whilst some successes are reported there are some continuing disappointments in tool life improvement and performance owing to the lack of systems approach. The author gives examples of products and has identified parameters and processes which tool manufacturers and coaters should jointly address to fully exploit the advantages of surface engineering technologies. The paper should prove useful and be of interest to material suppliers, tool manufacturers and surface coaters.

The effect of substrate surface preparation on the wear and failure modes of TiN coated high speed steel circular saw blades

The effect of substrate surface preparation on the performance and tool life of titanium nitride (TiN) coated high speed steel circular saw blades has been shown to be significant [1]. The influence this has on the wear and failure characteristics of the blades is now considered. Previous work by the authors shows TiN coated high speed steel circular saw blades benefit from substrate surface preparation prior to treatment. Cutting test results show that blades which had undergone a microblasting process exhibited an increase in tool life. Using testing methods developed to simulate the cutting action of full circular saw blades by using representative saw segments, the effects of substrate surface preparation are further investigated by identifying and comparing the wear mechanisms that develop on circular saw teeth subject to various preparation/coating conditions. Assessment of the wear and failure mechanisms associated with each combination of substrate preparation/coating have been used to appraise the relative merits of the treatment, blade design and manufacturing process. The work will assist in the development of a systems approach that combines both cutting tool and surface engineering technologies with a view to developing an improved product.

The effect of product quality on the integrity of advanced surface engineering treatments applied to high speed steel circular saw blades

Advanced surface engineering technologies have been successfully applied to high speed steel drills and carbide single-point cutting tools, but, as yet, limited benefits have been realized when applying the same technologies to multi-point cutting tools of commercial quality. This paper discusses the factors that have limited the benefits of advanced surface engineering treatments when applied to high speed steel circular saw blades. Common manufacturing defects have been identified on the teeth of the blades. Tests which evaluate the blade performance throughout its useful life and examination by scanning electron microscopy (SEM) have shown that these defects adversely affect the performance and wear resistance of surface engineered blades. Further investigations suggest that significant improvements in coating integrity can be achieved through the careful preparation of the substrate surface and refinement of the cutting edge geometry prior to treatment. For this application, the need for refinement and enhancement of current manufacturing practices is demonstrated if the full benefits of advanced surface engineering are to be realized.

Wear of High Speed Steel Bi-Metal Bandsaw Blade when Cutting AvestaPolarit 17-7 Stainless Steel in the As-Cast State

This paper reports experimental data on the wear of high-speed steel bimetal bandsaw blades cutting austenitic 17-7 stainless steel bars. Several different methods of assessing the wear modes and mechanisms are evaluated; Cutting and thrust force components, Set width, Kerf width, “Out-of-square” cutting, Wear modes and mechanisms and Chip characteristics. The wear mode established in the current work when bandsawing austenitic stainless steel with a bimetal blade is flank and corner wear together with formation of a cutting edge radius. The cutting edge radius increases as the wear progresses, reaching 25-50 mm after 300 cut sections. The established wear mechanism for the initial stages of wear is mild adhesive wear of the flank surface together with built-up edge formation and break-down. As the wear reaches steady-state the mechanism is adhesive wear of the flank surface with tempering/softening of high-speed steel layers. When the wear reached the steady-state region the level of thrust and cutting force were equal and relatively high. The kerf width appears to be less than the total set width of the blade, meaning that there is compression of the set teeth as they pass through the kerf. There is segmented chip formation with an increasing amount of vibration as the teeth wear, probably due to the increasing size of cutting edge radius. This work should be of great interest to the tool designer and user associated with bandsaws.

Forces, wear modes, and mechanisms in bandsawing steel workpieces

Abstract Bandsawing is an important primary operation in a variety of industries, particularly steel suppliers who need to cut-off raw material for secondary processes. Bandsawing is a competitive method of cutting to size as it achieves a low kerf width, high metal removal rates, and good surface finish. One specific feature of the bandsaw metal-cutting operation is that the depth of cut per cutting edge is small (5–50 μm). Under conditions of low depth of cut and restricted chip formation, metal is removed by a complex combination of fragmented chips, ploughing, and some continuous conventional chips. The process of bandsawing is scientifically evaluated by measuring forces and associated parameters. Wear modes and mechanisms are also monitored, characterized, and their validity discussed.