Limits...
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

Workpiece (Al 5052) profile images at different process times (radiation energy is 200 mJ): (a–d) 50×.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3472821&req=5

f7-sensors-12-10148: Workpiece (Al 5052) profile images at different process times (radiation energy is 200 mJ): (a–d) 50×.

Mentions: The resulting profile images for laser-drilled machining using different process times, where the radiation energy of the pulse laser was 145 mJ, 175 mJ, and 200 mJ for aluminum and stainless steel are shown in Figures 5, 6, 7, 8, 9 and 10, respectively. It is obvious that the depth of the laser-drilled holes increases with the process time. The relation between the machining hole depth and pixel value of the laser-induced plasma region is shown in Figure 11. In all cases, the depth of the laser-drilled holes could be described by a monotonically increasing function, and for both materials the ablation depth rate increases with large laser energy. Since the heat transfer mechanism near the ablation zone was heavily affected by the thermal response of the materials to the incident laser pulses. The vaporization thermal properties is known to be affected by the material boiling temperature, which is lower in aluminum (Tvap = 2,740 K) than stainless steel (Tvap = 3,134 K), thus leading to an earlier ablation under the same incident laser pulses. There, a faster depth removal rate on the aluminum material than in steel material was observed at the ablation process as expected.


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

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

Workpiece (Al 5052) profile images at different process times (radiation energy is 200 mJ): (a–d) 50×.
© Copyright Policy
Related In: Results  -  Collection

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

f7-sensors-12-10148: Workpiece (Al 5052) profile images at different process times (radiation energy is 200 mJ): (a–d) 50×.
Mentions: The resulting profile images for laser-drilled machining using different process times, where the radiation energy of the pulse laser was 145 mJ, 175 mJ, and 200 mJ for aluminum and stainless steel are shown in Figures 5, 6, 7, 8, 9 and 10, respectively. It is obvious that the depth of the laser-drilled holes increases with the process time. The relation between the machining hole depth and pixel value of the laser-induced plasma region is shown in Figure 11. In all cases, the depth of the laser-drilled holes could be described by a monotonically increasing function, and for both materials the ablation depth rate increases with large laser energy. Since the heat transfer mechanism near the ablation zone was heavily affected by the thermal response of the materials to the incident laser pulses. The vaporization thermal properties is known to be affected by the material boiling temperature, which is lower in aluminum (Tvap = 2,740 K) than stainless steel (Tvap = 3,134 K), thus leading to an earlier ablation under the same incident laser pulses. There, a faster depth removal rate on the aluminum material than in steel material was observed at the ablation process as expected.

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