Porosity in Laser Weld

Date 01-13-2004 16:27

You did not mention the type of laser or mode your using to weld with but at first glance your still in the key hole parameter mode as you “ pull back” this would mean that the key hole has closed ( change in focal point) but you have not ramped down the power density enough to prevent a rather violently stirred weld pool from rapid solidification ( kind of the same effect as crater fill on an arc weld). Assuming of course that you have venting on the part and this is not the back pressure “spitting” the weld pool back at you. Also the more sluggish high nickel precipitated hardened alloys do not flow as well as some other materials. Have you qualified the laser schedule on another part before or is this a new job and a first time problem?

By kylel Date 01-13-2004 17:01

The machine is a Nd:YAG 800W. Program mode is Robotic performing a keyhole weld in a HAST X material. Unfortunately, we would like to try Ramping down but the software book is not "right". We have been unable to reach the writer to see how to perform this function correctly. What we do now is increase the focal size to decrease the intensity at the start/stop point. This has been an ongoing problem in our FPI area due to the spec. class of this LBW .

By arcblue (*)

Date 01-13-2004 18:00

Bench a little to pass FPI ;) works all the time....

Seriously, this is a power density adjustment issue. If you cannot adjust the power than your are stuck with more rework ( hand blend and re inspection) to meet your spec.

If you can change the spot diameter then work on a more gradual change in focus point by a combination of travel speed variation (increase) and change (pull back) on stand off distance.

These are all minor tweaks to reduce the net effect of the beam on the surface of the part.

Sorry to put it this way but you need to be in control of your process. By what ever means it takes to do it right the first time, it is so much cheaper in the long run even if you hire a off line programmer to fix your program.

By Serg Date 02-25-2004 14:00

Hi,
Can I ask you a few questions?
What material are you trying to weld?
Do you use a safe medium? What?