In machining, tool life is the chief determinant of cost, tool changing frequency, machining efficiency, and machining precision. Application of a proper cutting edge with optimized geometry and suitable edge properties is an effective way to improve tool performance and machining quality. The majority of the reported work is limited to the effect of edge geometry on tool life. In this thesis, cutting edges were prepared using three different methods which were evaluated in terms of tool edge geometry produced, tool surface quality and topographies, edge hardness and residual stresses. Furthermore, the influence of cutting edge preparation techniques on the tool performance of uncoated tungsten carbide cutting inserts with different average cutting edge rounding (S¯), different form factor (K), as well as the different edge preparation methods used underwent experimental investigation through the orthogonal turning of AISI 4140 alloy steel. Results show that the performance of the prepared edge depends on the combined effect of micro-geometry and edge properties. For symmetric edges (K=1), the preferable range for S¯ was found to be 20 µm to 30 µm. Drag finishing was determined to be the best edge preparation process which is able to produce cutting edges with the best performance. The experimental investigations provided guidelines and evidence for future study of the cutting tool life and wear behavior of prepared cutting inserts and PVD-coated carbide inserts. / Thesis / Master of Applied Science (MASc)

The industrial development of metal cutting processes in gear manufacturing aims at continuously increasing productivity, including increased tool reliability. Basically, the parameters that have an influence on the cutting processes should be known and possible to control. Gear manufacturing is highly important for the automotive industry. The prevalent manufacturing method is gear hobbing with hobs consisting of solid Powder Metallurgical High Speed Steel (PM HSS) with Physical Vapor Deposited (PVD) coatings. The hob teeth have to be reconditioned before wear reaches such levels that the gear quality becomes impaired. Such wear often results in a total breakdown of the tool. One crucial reason for this is that hobbing processes for the present often lack reliability; which makes it difficult for the gear manufacturers to predict the tool wear on the hob teeth and decide when the tool should be replaced in order to avoid severe damages. A consequence of catastrophic tool wear is that it leads to an instantaneously changed geometry of the cutting edge, which in turn implies that the machined gears do not comply with the stipulated properties on the machined gear products. A single tooth milling test (STMT) with tools of PM-HSS in a conventional milling machine has been developed in this research project, aiming at characterizing the effect of tool preparation on the type of wear mechanism. The experience and conclusions from these tests may probably be transferred to real PM-HSS hob tooling (HT). The advantages of such a test, compared to a real gear hob test, are primarily the cost reductions and time saving aspects with respect to both the design and the manufacturing of the cutting teeth The research presented in this thesis is based on experimental investigations and theoretical studies of significant parameters, i.e. the surface roughness and edge rounding, contributing to the robust and reliable design of a PM-HSS cutting tool. The research work has in addition to, the development of the milling test method, also comprised development of measuring methods and a simulation model based on the Finite Element Model (FEM). / <p>QC 20121105</p>

Den ökande efterfrågan på högre produktkvalitet inom tillverkningsindustrin kräver hög stabilitet och lång livslängd på borrverktyg under borrningbearbetningsprocessen. En metod för att öka produktkvaliteten och därmed förlänga livslängden på borrverktyg är skäreggpreparering. Skäreggpreparering används för att skapa en kantgeometri som ger borrverktyget både en bättre styrka och högre tålighet mot slitage. Det mest förekommande slitaget på borrverktyg är fasförslitning och det utvecklas snabbt under den initiala slitningsperioden under borrens livslängd. Syftet med det här examensarbetet var att genom flerfaktorförsök undersöka hur skäreggprepareringsprocessen kan förbättras för att minska fasförslitning under den initiala slitningsperioden på belagda hårdmetallborrar. Skäreggprepareringsprocessen studerades som en fallstudie på Scania Motorbearbetning. Fallstudien genomfördes efter problemlösningsmetodiken DMAIC (Define, Measure, Analyse, Improve och Control) som inkorporerade försöksplanering, vilket medförde att två ytterligare faser tillkom: Pre-analyze och Experiment. Datainsamlingen bestod av både kvalitativ och kvantitativ data. Den kvalitativa datan erhölls från intervjuer under Measure-fasen och den kvantitativa datan erhölls från det genomförda experimentet under Experiment-fasen, som sedan analyserades i Analyze-fasen. Baserat på litteraturstudien, nulägesbeskrivningen och intervjuerna bestämdes försöksfaktorerna till processtid, borrens djup i slipmedel, rotationsriktning på rotor och rotationshastighet på spindel samt responsvariablerna till skäreggradie och total fasförslitning. Försöksfaktorerna testades i ett fullständigt tvånivåers faktorförsök med 4 faktorer och 4 centrumpunkter. Analysen av resultaten från experimentet visade att korrelationen mellan responsvariablerna var försumbar under den initiala slitningsperioden. Vidare identifierades inte några signifikanta effekter baserade på responsvariabeln total fasförslitning. Däremot kunde det konstateras att de försöksfaktorer som påverkade responsvariabeln skäreggradie var processtid, borrens djup i slipmedel och rotationsriktning på rotor. En optimeringsmodell togs fram i Improve-fasen för att optimera skäreggprepareringsprocessen med avseende på skäreggradie. Optimeringen utgick från att ha en stor skäreggradie under förutsättningen att den nuvarande processtiden halveras. Optimeringsmodellen kunde inte bekräftas, därför togs en rekommendation fram som beskriver stegen för att bekräfta den framtagna optimeringsmodellen. Vidare togs två ytterligare rekommendationer fram med syfte att undersöka skäreggprepareringsprocessen med avseende på andra typer av slitage samt undersöka verktygsslitage under verktygets fulla livslängd. I Control-fasen togs en kontrollplan fram som stöd för att kontrollera rekommendationerna. Avslutningsvis bidrog det här examensarbetet med nya insikter och slutsatser om utveckling av fasförslitningen under den initiala slitningsperioden under en borrs livslängd. / The increasing demand for higher product quality in the manufacturing industry requires high stability and long service life of drilling tools during the drilling process. One method of increasing product quality and thus extending the tool life for drills is cutting edge preparation. Cutting edge preparation is used to create an edge geometry that gives the drilling tool both better strength and higher resistance to wear. The most common wear on drill tools is flank wear that develops rapidly during the initial wear period of the drill's life. The purpose of this thesis was to investigate how the cutting edge preparation process can be improved by factorial design in order to reduce flank wear during the initial wear period on coated solid carbide drills. The cutting edge preparation process was studied as a case study at Scania's motor processing department. The case study followed problem-solving methodology DMAIC (Define, Measure, Analyze, Improve and Control) incorporating design of experiments. This resulted in two additional phases: Pre-Analyze and Experiment. Data collection consisted of both qualitative and quantitative data. The qualitative data were obtained from interviews during the Measure phase and the quantitative data was obtained from the experiment conducted during the Experiment phase, which was later analyzed in the Analyze phase.     Based on a literature study, current description, and interviews, the identified experimental factors were process time, depth in the grinding granulate, rotational direction of the rotor, and rotational speed of spindle. The identified response variables were cutting edge radius and total flank wear. The experimental factors were tested in a full two-level factorial design with 4 factors and 4 center points. The analysis of the results from the experiment showed that the correlation between the response variables was negligible during the initial wear period. Furthermore, no significant effects could be found based on the response variable total flank wear. However, it was found that the experimental factors that influenced the response variable cutting edge radius were process time, depth in grinding granulate, and direction of rotation of the rotor. An optimization model was developed during the Improve phase to optimize the cutting edge preparation process in regards to the cutting edge radius. The optimization was based on generating a large cutting edge radius and at the same time reducing the current process time by half. The optimization model could not be confirmed; therefore, a recommendation was developed outlining the steps to confirm the optimization model. Furthermore, two additional recommendations were made to investigate the cutting edge preparation process concerning other types of wear and to examine tool wear during the tool’s full life. A control plan was developed in the Control phase to help to control the recommendations. In conclusion, this thesis contributed new insights and conclusions on the development of flank wear during the initial wear period during the tool life.