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Strategies for Reducing Vibrations during Milling of Thin-walled Components
University West, Department of Engineering Science, Division of Mechanical Engineering. (PTW)
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Factors such as environmental requirements and fuel efficiency have pushed aerospace industry to develop reduced-weight engine designs and thereby light-weight and thin-walled components. As component wall thickness gets thinner and the mechanical structures weaker, the structure becomes more sensitive for vibrations during milling operations. Demands on cost efficiency increase and new ways of improving milling operations must follow.

Historically, there have been two “schools” explaining vibrations in milling. One states that the entry angle in which the cutting insert hits the work piece is of greater importance than the exit angle. The other states that the way the cutter leaves the work piece is of greater importance than the cutter entry. In an effort to shed some light over this issue, a substantial amount of experiments were conducted. Evaluations were carried out using different tools, different tool-to-workpiece offset positions, and varying workpiece wall overhang. The resultant force, the force components, and system vibrations have been analyzed.

The first part of this work shows the differences in force behavior for three tool-to-workpiece geometries while varying the wall overhang of the workpiece. The second part studies the force behavior during the exit phase for five different tool-to-workpiece offset positions while the overhang is held constant. The workpiece alloy throughout this work is Inconel 718.

As a result of the project a spread sheet milling stability prediction model is developed and presented. It is based on available research in chatter theory and predicts the stability for a given set of variable input parameters.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 96 p.
Keyword [en]
Milling, vibrations, chatter, stability, prediction, thin-wall, Inconel 718.
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-4955ISBN: 978-91-7501-322-0 (print)OAI: oai:DiVA.org:hv-4955DiVA: diva2:580980
Presentation
2012-12-07, KTH Royal Institute of Technolgy, Brinellvägen 68, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2012-12-28 Created: 2012-12-27 Last updated: 2015-10-02Bibliographically approved
List of papers
1. Process Stability Strategies in Milling of Thin-walled Inconel 718
Open this publication in new window or tab >>Process Stability Strategies in Milling of Thin-walled Inconel 718
2012 (English)In: The 4th Manufacturing engineering society international conference (MESIC 2011): 21–23 September 2011, Cadiz, Spain / [ed] M. Marcos, J. Salguero, American Institute of Physics (AIP), 2012, Vol. 1431, 465-472 p.Conference paper, Published paper (Refereed)
Abstract [en]

Trends in Aerospace development have led to thin-walled, reduced-weight engine designs. The demands in manufacturing have forced production speeds and material removal rates (MRR) to increase. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter free process. The results show the differences in force response for three geometries while varying the height overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper gives guidelines on how to accomplish robust machining practices. It also answers the following questions: How critical is the choice of offset between tool and workpiece during milling setup? And what effects do the entry and exit of cut have on system vibrations?

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2012
Series
AIP Conference Proceedings, ISSN 1551-7616 ; 1431/1
Keyword
Thin-wall, Inconel 718, chatter, machining vibrations
National Category
Engineering and Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-4330 (URN)10.1063/1.4707597 (DOI)000307644700054 ()2-s2.0-84863327648 (Scopus ID)978-0-7354-1017-6 (ISBN)
Conference
The 4th Manufacturing engineering society international conference
Available from: 2012-05-31 Created: 2012-05-21 Last updated: 2016-11-21Bibliographically approved
2. Milling Strategies for Thin-walled Components
Open this publication in new window or tab >>Milling Strategies for Thin-walled Components
2012 (English)In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 498, 177-182 p.Article in journal (Refereed) Published
Abstract [en]

Recent developments in the Aerospace industry have led to thin-walled, reduced-weight engine designs. Due to demands in manufacturing, production speeds and material removal rates (MRR) have increased. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter-free process. The results show the differences in force response for three geometries while varying the overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper outlines certain robust machining practices. It also analyzes the criticality of the choice of offset between tool and workpiece during milling setup as well as the effects that the entry and exit of cut have on system vibrations.

Place, publisher, year, edition, pages
Switzerland: Trans Tech Publications Inc., 2012
Keyword
Thin-wall, Inconel 718, chatter, machining vibrations
National Category
Engineering and Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-4329 (URN)10.4028/www.scientific.net/AMR.498.177 (DOI)2-s2.0-84860254349 (Scopus ID)
Available from: 2012-05-31 Created: 2012-05-21 Last updated: 2016-11-21Bibliographically approved
3. Cutter Exit Effects during Milling of Thin-walled Inconel 718
Open this publication in new window or tab >>Cutter Exit Effects during Milling of Thin-walled Inconel 718
2012 (English)In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 590, 297-308 p.Article in journal (Refereed) Published
Abstract [en]

During milling of thin-walled components, chatter vibrations give rise to process issues. These include dimensional inaccuracy, damaged and scrap parts, and damaged cutting tools. This, in turn, leads to loss of production time with increasing cost as a consequence. This paper identifies the force profile during a single cut milling process. It focuses on the exit and post-exit behavior of the cut and discusses the process dynamics. The force profiles of various tool-to-workpiece positions are analyzed as regards the exit and post exit phases. A standard on-the-market cutter and a specially designed zero rake cutter are used in the investigation. Finally, a time-domain simulation of the force is performed and compared to the experimental results. The study concludes that a small change in exit angle may result in a considerable improvement in cutting behavior. In addition, the tool position should be chosen so that the cutter exits in the least flexible direction possible for the workpiece.

Place, publisher, year, edition, pages
Schweiz: Trans Tech Publications Inc., 2012
Keyword
Chatter vibrations, Thin wall, Inconel 718, Process stability, Exit angle
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-4686 (URN)10.4028/www.scientific.net/AMR.590.297 (DOI)2-s2.0-84870671318 (Scopus ID)
Available from: 2012-12-21 Created: 2012-09-26 Last updated: 2016-11-21Bibliographically approved

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