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Edge Geometry Effects on Entry Phase by Forces and Vibrations
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0003-3876-2361
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Intermittent machining is in general strongly related to the large impacts in the entry phase and related vibrations. The influence of the impact forces and vibrations on the cutting process is dependent on workpiece material, structural properties of the tool-workpiece system, cutting edge geometries and cutting parameters. Cutting forces adopt generally a periodic behaviour that gives rise to forced vibrations. In addition, self-induced vibrations may arise because of lowrigidity and insufficient damping in the tool-workpiece system at specific cutting parameters. The ability of the cutting tool to carry the loads during the entry phase and minimize the vibrations is often the key parameter for an effective machining operation.This research work is based on the experiments, analytical studies and modelling. It was carried out through six main studies beginning with a force build-up analysis of the cutting edge entry into the workpiece in intermittent turning. This was followed by a second study, concentrated on modelling of the entry phase which has partly been explored through experiments and theory developed in the first study.

The third part was focused on the influence of the radial depth of cut upon the entry of the cutting edge into the workpiece in a face milling application. The methodology for the identification of unfavourable radial depth of cut is also addressed herein. Next, effects of the cutting edge on the vibrations in an end milling application were investigated. This study was related to a contouring operation with the maximum chip thickness in the entry phase when machining steel, ISO P material.

The results of this work provide some general recommendations when milling this type of workpiece material. After that, the focus was set on the dynamic cutting forces in milling. The force developments over a tooth engagement in milling showed to be strongly dependent on the cutting edge geometry. A significant difference between highly positive versus highly negative geometry was found.

The implication of this phenomena on the stress state in the cutting edge and some practical issues were analysed. Finally, the role of the helix angle on the dynamic response of a workpiece was investigated. The modelling technique using force simulation and computation of the dynamic response by means of modal analysis was presented. Extensive experimental work was conducted to compare the modelling and experimentally obtained results. The modelling results showed a similar trend as the experimental results. The influence of helix angle on the cutting forces and the dynamic response was explained in detail.The research conducted in this work contributes to the deeper understanding of the influence of the cutting edge geometry and the cutting parameters on the force build up process during the entry phase. The presented studies investigate the force magnitudes, force rates and dynamic behaviour of the tools and workpieces when machining at the challenging entry conditions. The methodologies applied are focused on the physical quantities as forces and vibrations rather than the experimental studies that evaluate tool life. The methods and results of the research work are of great interest for the design of the cutting tools and optimization of the cutting processes.

Place, publisher, year, edition, pages
Trollhättan: University West , 2020. , p. 133
Series
PhD Thesis: University West ; 32
Keywords [en]
Entry; Cutting force; Cutting edge geometry; Acceleration
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-14852ISBN: 978-91-88847-46-1 (print)ISBN: 978-91-88847-45-4 (electronic)OAI: oai:DiVA.org:hv-14852DiVA, id: diva2:1385181
Public defence
2020-02-06, C208, 10:00 (English)
Opponent
Supervisors
Available from: 2020-01-15 Created: 2020-01-13
List of papers
1. Influence of cutting edge geometry on force build-up process in intermittent turning
Open this publication in new window or tab >>Influence of cutting edge geometry on force build-up process in intermittent turning
2016 (English)In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 46, p. 364-367Article in journal (Refereed) Published
Abstract [en]

In the intermittent turning and milling processes, during the entry phase the cutting edges are subjected to high impact loads that can give rise to dynamical and strength issues which in general cause tool life reduction. In this study the effect of geometrical features of the cutting tool on the force generation during the entry phase is investigated. Cutting forces are measured by a stiff dynamometer at a high sampling frequency. In addition, the chip load area is analyzed and related to the measured cutting force. The results show that micro-geometrical features, in particular the protection chamfer, significantly affect the force generation during the entry phase.

Keywords
Cutting, force, edge, chip, turning, dynamic
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-9324 (URN)10.1016/j.procir.2016.04.013 (DOI)000417327600086 ()2-s2.0-84978786104 (Scopus ID)
Conference
7th HPC 2016 – CIRP Conference on High Performance Cutting, Chemnitz, Germany, May 31-June 2, 2016
Available from: 2016-04-25 Created: 2016-04-25 Last updated: 2020-02-07Bibliographically approved
2. Modeling of Force Build-up Process and Optimization of Tool Geometry when Intermittent Turning
Open this publication in new window or tab >>Modeling of Force Build-up Process and Optimization of Tool Geometry when Intermittent Turning
2017 (English)In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 58, p. 393-398Article in journal (Refereed) Published
Abstract [en]

Intermittent turning the slotted workpieces is always accompanied with a high impact load of the machine tool during the entry phase of the cutting edge. The process leads to a strong dynamic response of the system and results in vibrations arose and potential tool life and surface finish issues. The present study addresses the modeling of cutting force build-up process with further optimization of cutting edge geometry where tooltip overshoot during the tool entry is selected as an objective function. The model takes into consideration the interaction between three units of the machine tool such as a tool, toolpost, and workpiece as well as an influence of the process on the system's dynamics.

Keywords
Intermittent machining, force buid-up, optimization, cutting edge geometry, dynamic response
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-12254 (URN)10.1016/j.procir.2017.03.241 (DOI)
Conference
16th CIRP Conference on Modelling of Machining Operations (16th CIRP CMMO)
Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2020-01-13Bibliographically approved
3. Influence of radial depth of cut on entry conditions and dynamics in face milling application
Open this publication in new window or tab >>Influence of radial depth of cut on entry conditions and dynamics in face milling application
Show others...
2017 (English)In: Journal of Superhard Materials, ISSN 1063-4576, Vol. 39, no 4, p. 259-270Article in journal (Refereed) Published
Abstract [en]

The choice of milling cutter geometry and appropriate cutting data for certain milling application is of vital importance for successful machining results. Unfavorable selection of cutting conditions might give rise to high load impacts that cause severe cutting edge damage. Under some circumstances the radial depth of cut in combination with milling cutter geometry might give unfavorable entry conditions in terms of cutting forces and vibration amplitudes. This phenomenon is originated from the geometrical features that affect the rise time of the cutting edge engagement into workpiece at different radial depths of cut. As the radial depth of cut is often an important parameter, particularly when machining difficult-to-cut materials, it is important to explore the driving mechanism behind vibrations generation. In this study, acceleration of the workpiece is measured for different radial depths of cut and cutting edge geometries. The influence of the radial depth of cut on the dynamical behavior is evaluated in time and frequency domains. The results for different radial depths of cut and cutting geometries are quantified using the root mean square value of acceleration. The outcome of this research study can be used both for the better cutting data recommendations and improved tool design.

Place, publisher, year, edition, pages
New York: Allerton Press, 2017
Keywords
milling entry, radial depth, cutting edge, cutting force, vibration
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-11769 (URN)10.3103/S1063457617040062 (DOI)000409936100006 ()2-s2.0-85029210912 (Scopus ID)
Funder
Knowledge Foundation
Available from: 2017-10-20 Created: 2017-10-20 Last updated: 2020-01-13Bibliographically approved
4. Experimental analysis of cutting edge effects on vibrations in end milling
Open this publication in new window or tab >>Experimental analysis of cutting edge effects on vibrations in end milling
2019 (English)In: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 24, p. 66-74Article in journal (Refereed) Published
Abstract [en]

The ability to minimize vibrations in milling by the selection of cutting edge geometry and appropriate cutting conditions is an important asset in the optimization of the cutting process. This paper presents a measurement method and a signal processing technique to characterize and quantify the magnitude of the vibrations in an end milling application. Developed methods are then used to investigate the effects of various cutting edge geometries on vibrations in end milling. The experiments are carried out with five cutting edge geometries that are frequently used in machining industry for a wide range of milling applications. The results show that a modest protection chamfer combined with a relatively high rake angle has, for the most of cutting conditions, a reducing effect on vibration magnitudes. Furthermore, dynamics of a highly positive versus a highly negative cutting geometry is explored in time domain and its dependency on cutting conditions is presented. The results give concrete indications about the most optimal cutting edge geometry and cutting conditions in terms of dynamic behavior of the tool.

Keywords
Milling, Acceleration, Cutting edge, Frequency spectrum, Rake angle, Chamfer
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13735 (URN)10.1016/j.cirpj.2018.11.001 (DOI)000460558000007 ()2-s2.0-85057229226 (Scopus ID)
Funder
Knowledge Foundation
Note

Funders: Seco Tools

Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2020-02-04Bibliographically approved
5. Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries
Open this publication in new window or tab >>Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries
2019 (English)In: International Journal on Interactive Design and Manufacturing, ISSN 1955-2513, E-ISSN 1955-2505, Vol. 13, no 2, p. 557-565Article in journal (Refereed) Published
Abstract [en]

Understanding the influence of the cutting edge geometry on the development of cutting forces during the milling process is of high importance in order to predict the mechanical loads on the cutting edge as well as the dynamic behavior on the milling tool. The work conducted in this study involves the force development over the entire engagement of a flute in milling, from peak force during the entry phase until the exit phase. The results show a significant difference in the behavior of the cutting process for a highly positive versus a highly negative cutting edge geometry. The negative edge geometry gives rise to larger force magnitudes and very similar developments of the tangential and radial cutting force. The positive cutting edge geometry produces considerably different developments of the tangential and radial cutting force. In case of positive cutting edge geometry, the radial cutting force increases while the uncut chip thickness decreases directly after the entry phase; reaching the peak value after a certain delay. The radial force fluctuation is significantly higher for the positive cutting edge geometry. The understanding of such behavior is important for modelling of the milling process, the design of the cutting edge and the interactive design of digital applications for the selection of the cutting parameters.

Keywords
Milling, Cutting force, Cutting edge geometry, Frequency spectrum, RMS
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13302 (URN)10.1007/s12008-018-0513-5 (DOI)000468115700013 ()2-s2.0-85058211299 (Scopus ID)
Funder
Knowledge Foundation
Note

Funders: Seco Tools

Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2020-02-03Bibliographically approved

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