2-1 Old Method according to the patent of EP 0489167 B1

• Old patent that the laser welding has not yet introduced the the seam welding.
• Lots of heat generated from welding point enough to burn all surface of tube.
• To protect the flux, it need to secure some distance from heat source.
• Big tube make the manufacturing process complicate.

2-2 Assumption of Bühler (PPT data)

• Up to date technology to make a seamless FCW from Europe.
• However still big tube to make the seam welding that make the process complicate.
• Also has small possibility to burn the flux since laser light can penetrate extremely small gap of the seam.

2-3 Double tube method from the Patent of US20150044506A1.

• To protect the flux, add one more tube to weld.
• Cause of the small tube diameter similar to the existing process, very simple to make a final products
• However some cumbersome works needed for double tube and some obstacles to adjust fill percent of flux

• Not to penetrate the laser beam to the flux, adjust the angle of laser.
• Or make the tube type of folded so the beam could not reach to the flux
• Could realize the simplest welding for seamless FCW.