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On-line estimation of laser-drilled hole depth using a machine vision method.

Ho CC, He JJ, Liao TY - Sensors (Basel) (2012)

Bottom Line: Therefore, a low cost on-line inspection system is developed to increase productivity.A correlation between the cumulative size of the laser-induced plasma region and the depth of the hole is presented.The result indicates that the estimated depths of the laser-drilled holes were a linear function of the cumulative plasma size, with a high degree of confidence.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin 64002, Taiwan. HoChao@yuntech.edu.tw

ABSTRACT
The paper presents a novel method for monitoring and estimating the depth of a laser-drilled hole using machine vision. Through on-line image acquisition and analysis in laser machining processes, we could simultaneously obtain correlations between the machining processes and analyzed images. Based on the machine vision method, the depths of laser-machined holes could be estimated in real time. Therefore, a low cost on-line inspection system is developed to increase productivity. All of the processing work was performed in air under standard atmospheric conditions and gas assist was used. A correlation between the cumulative size of the laser-induced plasma region and the depth of the hole is presented. The result indicates that the estimated depths of the laser-drilled holes were a linear function of the cumulative plasma size, with a high degree of confidence. This research provides a novel machine vision-based method for estimating the depths of laser-drilled holes in real time.

No MeSH data available.


Related in: MedlinePlus

Plasma region of image of SS 420 (a) acquired by CMOS camera and (b) after binarization.
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f3-sensors-12-10148: Plasma region of image of SS 420 (a) acquired by CMOS camera and (b) after binarization.

Mentions: The laser-drilled machining, including breakthrough detection and blind hole depth analysis, were recorded and analyzed using 8-bit encoding and 120 × 120 pixel images. Through binarization during the image processing, we could determine the plasma emission region and calculate the total pixels of the plasma region. The images of aluminum and stainless steel after binarization are shown in Figure 2 and Figure 3, respectively. In breakthrough detection, the total pixels in the plasma region of a single image frame were recorded and analyzed. Breakthrough detection for laser drilling was successfully developed in a previous study [16]. Breakthrough detection can be briefly explained as follows. When a breakthrough occurs, the amount of plasma declines abruptly. The pixels in the plasma region of a single image frame would also decline abruptly and simultaneously at this time, as shown in Figure 4. Depth control and analysis for laser-drilled machining, the number of laser pulses is used to control the depth of a laser-drilled hole in the conventional control method. As the number of laser pulses increases, the depth of the hole would also increase. The conventional control method uses experience-based control rules to detect the completion of the ablation process off-line.


On-line estimation of laser-drilled hole depth using a machine vision method.

Ho CC, He JJ, Liao TY - Sensors (Basel) (2012)

Plasma region of image of SS 420 (a) acquired by CMOS camera and (b) after binarization.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472821&req=5

f3-sensors-12-10148: Plasma region of image of SS 420 (a) acquired by CMOS camera and (b) after binarization.
Mentions: The laser-drilled machining, including breakthrough detection and blind hole depth analysis, were recorded and analyzed using 8-bit encoding and 120 × 120 pixel images. Through binarization during the image processing, we could determine the plasma emission region and calculate the total pixels of the plasma region. The images of aluminum and stainless steel after binarization are shown in Figure 2 and Figure 3, respectively. In breakthrough detection, the total pixels in the plasma region of a single image frame were recorded and analyzed. Breakthrough detection for laser drilling was successfully developed in a previous study [16]. Breakthrough detection can be briefly explained as follows. When a breakthrough occurs, the amount of plasma declines abruptly. The pixels in the plasma region of a single image frame would also decline abruptly and simultaneously at this time, as shown in Figure 4. Depth control and analysis for laser-drilled machining, the number of laser pulses is used to control the depth of a laser-drilled hole in the conventional control method. As the number of laser pulses increases, the depth of the hole would also increase. The conventional control method uses experience-based control rules to detect the completion of the ablation process off-line.

Bottom Line: Therefore, a low cost on-line inspection system is developed to increase productivity.A correlation between the cumulative size of the laser-induced plasma region and the depth of the hole is presented.The result indicates that the estimated depths of the laser-drilled holes were a linear function of the cumulative plasma size, with a high degree of confidence.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin 64002, Taiwan. HoChao@yuntech.edu.tw

ABSTRACT
The paper presents a novel method for monitoring and estimating the depth of a laser-drilled hole using machine vision. Through on-line image acquisition and analysis in laser machining processes, we could simultaneously obtain correlations between the machining processes and analyzed images. Based on the machine vision method, the depths of laser-machined holes could be estimated in real time. Therefore, a low cost on-line inspection system is developed to increase productivity. All of the processing work was performed in air under standard atmospheric conditions and gas assist was used. A correlation between the cumulative size of the laser-induced plasma region and the depth of the hole is presented. The result indicates that the estimated depths of the laser-drilled holes were a linear function of the cumulative plasma size, with a high degree of confidence. This research provides a novel machine vision-based method for estimating the depths of laser-drilled holes in real time.

No MeSH data available.


Related in: MedlinePlus