| 11. |
- Pejryd, Lars, 1955-, et al.
(author)
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Machine Tool Internal Encoders as Sensors for the Detection of Tool Wear
- 2012
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In: Procedia CIRP. - : Elsevier BV. - 2212-8271 .- 2212-8271. ; 4, s. 46-51
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Journal article (peer-reviewed)abstract
- Tool wear in machining changes the geometry of the cutting edges, which effect the direction and amplitudes of the cutting forcecomponents and the dynamics in the machining process. These changes in the forces and dynamics are picked up by the internalencoders and thus can be used for monitoring of changes in process conditions. This paper presents an approach for the monitoringof a multi-tooth milling process. The method is based on the direct measurement of the output from the position encoders availablein the machine tool and the application of advanced signal analysis methods.The paper investigates repeatability of the method developed and how to detect wear in an individual tooth in a milling cutter. Theresults of this work show that various signal features which correlate with tool wear can be extracted from the first few oscillatingcomponents, representing the low-frequency components, of the machine axes velocities. The responses from the position encodersexhibit good repeatability, especially short term repeatability while the long-term repeatability is more unreliable. A worn toothincreases the irregularity in the encoder responses and can be identified at an early stage of the cut.
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| 12. |
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| 13. |
- Pejryd, Lars, 1955-, et al.
(author)
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Minimization of chatter in machining by the use of mobile platform technologies
- 2012
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In: Proceedings of the 5th International Swedish Production Symposium, SPS12. - Linköping. - 9789175197524 ; , s. 179-189
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Conference paper (peer-reviewed)abstract
- The risk of vibration in machining can be estimated by identification of the transfer functions of the system. Traditionally the transfer functions may be identified through the use of an impact hammer and a force transducer. This technology needs wiring and therefore cannot be easily used in a production environment. Through the use of the sound that is picked up from the running process, the simplified stability diagram of the system can be deduced. Mobile platforms, like phones and pads can be used to record the sound of the process. The computational capability of these devices are now enough to render the possibility to include the theory and modelling into these devices to make it possible to analyze the process in question as it is running and from that give recommendations to modify the process for minimization of the chatter vibrations. The paper outlines the theoretical considerations and strategy employed to make it possible to develop a useful solution for end-users on the shop floor.
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| 14. |
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| 15. |
- Repo, Jari, et al.
(author)
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Measurement method for the identification of individual teeth in milling operations
- 2012
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In: CIRP - Journal of Manufacturing Science and Technology. - : Elsevier BV. - 1755-5817 .- 1878-0016. ; 5:1, s. 26-32
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Journal article (peer-reviewed)abstract
- Internal sensors already available in the machine tools may prove to be an interesting approach to monitor the machining process. Accurate determination of the position of the individual tooth on a milling cutter is important to be able to correlate the measured responses from the machine tool position encoders to the tooth or teeth that may be the cause of the response.The aim of the work presented in this paper is to develop a measurement method to identify the individual tooth on a milling cutter by their angular position relative to a specified 0-degree direction. If the lower and upper bounds of the cutting zone are known, together with the actual spindle position and the starting time of the cut, it will be possible to track and identify which teeth are within the cutting zone at a given time in the following off-line analysis of the responses. This may simplify the task of finding potential correlations between the state of individual teeth on the milling cutter with measured responses from various sensors during the milling process. The proposed method is based on a reflectance detector and uses accurate position information provided by the position encoders.A validation of the measurement method is also presented which shows that the error of the estimated angular position is approximately +/- 0.15 degrees for the validation setup used in this case.
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| 16. |
- Wanner, Bertil, 1963-, et al.
(author)
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Cutter Exit Effects during Milling of Thin-walled Inconel 718
- 2012
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In: Advanced Materials Research. - : Trans Tech Publications Inc.. - 1022-6680 .- 1662-8985. ; 590, s. 297-308, s. 297-308
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Journal article (peer-reviewed)abstract
- 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.
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| 17. |
- Wanner, Bertil, 1963-, et al.
(author)
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Milling Strategies for Thin-walled Components
- 2012
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In: Advanced Materials Research. - : Trans Tech Publications Inc.. - 1022-6680 .- 1662-8985. ; 498, s. 177-182, s. 177-182
-
Journal article (peer-reviewed)abstract
- 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.
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| 18. |
- Wanner, Bertil, 1963-, et al.
(author)
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Process Stability Strategies in Milling of Thin-walled Inconel 718
- 2012
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In: The 4th Manufacturing engineering society international conference (MESIC 2011). - : American Institute of Physics (AIP). - 9780735410176 ; , s. 465-472
-
Conference paper (peer-reviewed)abstract
- 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?
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