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Detektering borrbrott
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
2018 (Swedish)Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesisAlternative title
Detection of drill breakage (English)
Abstract [en]

The scope of the project was to recommend an automated method for the detection of drill breakage for Valmet in Sundsvall 120-spindle drilling machine. At present there is no system for automatic detection of drill breakage. The machine requires constant monitoring and drill breakage is detected visually by the operators. At occurrence of drill breakage, more or less large areas of undrilled holes result in manual post-processing. The purpose with an automated method is to reduce the need for monitoring and post-processing. Valmet has previously made an attempt for detection using sound analysis. The system was taken out of service due to high amount of false alarms. Primarily, systems based on sound- and vibration analysis, was evaluated to assess whether these could be used to detect drill breakage. The ambition was that after the experiment, prove whether and which methods are considered to operate in an automated system for the detection of drill breakage.The work was divided into three main parts: the collection of measurement data, the development of programs in Matlab and analysis of measured data. At the first part of the project, a series of measurements of sound and vibration were performed on the drilling machine for later analysis of the measurement results in Matlab. Two programs were developed in Matlab. One to perform FFT (Fast Fourier Transform) on short sequences, and one to find changes in the form of peaks in longer time signals. The purpose of the analysis was to try to discern if the drill breakage were registered when recording, which in turn gave rise to a change in the time signal and with any specific frequency.The result shows that the drill breakage can be detected with both sound and vibration which suggests that a system based on sound or vibration analysis can potentially be used for detection of drill breakage. However, the appearance of the change in the time signal for different drill breakage are not identical, and thus no specific frequency is obtained. Because measurements were made solely with one accelerometer and one microphone, the distance between a large amount of the drills and the measurement instruments was too long to register any drill breakage for these drills. This causes an uncertainty about the proportion of drill breakage that provides a sufficiently large difference in the signal to be detected.The recommendation to Valmet is to use a vibration-based system based on the measurements and analyzes made. The reason to analyze vibrations instead of sound, is that the signal processing is simplified due to the fact that vibrations are not so affected by the noise from industry premises that can lead to false alarms.

Place, publisher, year, edition, pages
2018. , p. 32
Series
MA ; 1813
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:umu:diva-149538OAI: oai:DiVA.org:umu-149538DiVA, id: diva2:1222571
External cooperation
ELE Engineering AB / Valmet i Sundsvall AB
Subject / course
Maskinteknik
Educational program
Bachelor of Science Engineering in Mechanical Engineering
Supervisors
Examiners
Available from: 2018-06-21 Created: 2018-06-21 Last updated: 2018-06-21Bibliographically approved

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