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196. Assessment of Commonly Used Tool Life Models in Metal Cutting
Daniel Johansson1, Sören Hägglund2, Volodymyr Bushlya1, Jan-Eric Ståhl1
1Lund University, Sweden; 2Assessment of Commonly Used Tool
The ability to predict and model tool wear and excepted tool life in metal cutting is of great importance to secure robust, predictable and stabile manufacturing systems. Tool life models are used by tool manufactures to assist end users with optimal cutting data published in catalogues or online web assistance applications. A model dependent on cutting speed, depth of cut, feed and tool geometry describing the expected time the tool can be engaged with the work piece material producing parts within a given quality is needed. As tool manufactures are moving toward not only supplying tool inserts but also increasingly supporting the end user with cutting data recommendations and optimal tool solutions with online software, tool life modelling is becoming more important. The cost and environmental impact of collecting tool life data for an increasing amount of tool material, tool geometry and workpiece combinations calls for a generic tool life model that can handle this complexity in a cost efficient way.
A number of tool life models have been presented in literature over the last century but little effort has been made in judging their reliability. In this work, eleven different combinations of work piece materials and tool grades have been evaluated in wear test when turning with cemented carbide inserts. The most commonly used tool life models such as the Taylor model, the Extended Taylor model, the Coromant Turning model version 1 and the Colding model have been tested on the data and their accuracy is presented.
The different Taylor models are relatively accurate when used with caution and in smaller ranges of selected chip thickness. All models preform most accurate when using the Woxén equivalent chip thickness as base for the tool life model. When extended Taylor is used, it produces more accurate results when using equivalent chip thickness then when based on feed and depth of cut even though a fourth constant is introduced in the latter.
The traditional Taylor tool life model models the tool life with an average error of 17.9 %. The best preforming model is the Colding model which is most accurate in nine out of eleven combinations and has the lowest model error with an average model error of 4.0 %.
8. Too sharp for its own good – Tool edge deformation mechanisms in the initial stages of metal cutting
Sampsa Vili Antero Laakso1,2, Tao Zhao2, Mathias Agmell2, Andrewk Hrechuk3, Jan-Eric Ståhl2
1Aalto University, Sweden; 2Lund University, Ole Römers Väg 1, 223 63, Lund, Sweden; 3Institute for Superhard Materials, 04074 Kiev, Ukraine
Metal cutting simulations have become an important part of cutting tool design and the research in the field in general. One of the most important aspects of modeling is the accuracy of the tool geometry. 3D microscopy is used for measuring the tool edge radius with good accuracy. However, especially with sharp tools, i.e. small tool edge radii, the measurements, no matter how accurate, are not much of a use, since the initial wear, or deformation is so fast in the first 1-30 seconds into the cutting, that the tool geometry is significantly different than the one measured from the new tool. The average tool life is often set to 15 minutes. Therefore, the cutting simulations that only predict the tool behavior in the first seconds of its lifetime are not very useful in predicting the process variables throughout the tool life. Simulations with creep and elastic-plastic material model however, can predict the initial deformation of the tool. This tool shape can be then used in rigid tool model to predict the process variables in the steady wear region of the tool life. This paper presents simulation model for predicting the initial tool edge deformation for WC-10%Co tool while machining AISI 304 stainless steel. The novelty in this approach is the simultaneous coupled calculation of contact surface temperature and stress and change of the tool shape.
153. Machinability of Cobalt-based and Cobalt Chromium Molybdenum Alloys - A Review
Hainol Akbar Zaman1, Safian Sharif2, Dong-Won Kim3, Mohd Hasbullah Idris2, Mohd Azlan Suhaimi2, Z. Tumurkhuyag3
1Chonbuk National University, Korea, Republic of (South Korea); 2Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor Bahru, Malaysia.; 3Department of Industrial and Information Systems Engineering, Chonbuk National University, Jeonju 561-756, Republic of Korea.
Cobalt chrome molybdenum alloy is considered as one of the advanced materials which is widely gaining popularity in various engineering and medical applications. However, it is categorized as difficult to machine material due to its unique combination of properties which include high strength, toughness, wear resistance and low thermal conductivity. These properties tend to hinder the machinability of this alloy which results in rapid tool wear and shorter tool life. This paper presents a general review of the materials’ characteristics and properties together with their machinability assessment under various machining conditions. The trend of machining and future researches on cobalt-based and cobalt chromium molybdenum alloys are also discussed.