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Up Topic Welding Industry / Technical Discussions / Rough Laser Welds Same Process as Good Welds?
- - By OBEWAN (***) Date 06-09-2012 13:41
We are launching a new laser welding system.

The old system is making fairly smooth welds on 1050 aluminum.

The new system is using the same laser system, same parameters, and making the same product, yet the welds have a crown and rough surface.

My first suspicion is that the systems are not identical.  I think maybe the machine builder has tampered with some laser settings.

But it can get deep.  I mean, we do have the abiity to edit pulse, wave shape, frequency, beam focusing, yada yada yada...

I am trying to keep it simple by sticking with focal length, watts, and travel speed.

But any thoughts on what might cause a rough weld?  I think it is a hermetic seal - just blowing the drawing OD limit on diamter with the weld crown.  (Circular weld)
Parent - - By OBEWAN (***) Date 06-09-2012 19:20
An update.  We do have an issue right now with different beam to work distances between the two systems.  And it really bothers me.  I have some data from the AWS publicatiion for Co2 lasers but we are using YAG.  It looks like due to system design constraints we may not be able to have the same beam to work distance on both systems.  I was not with this company for the design build phase of this system.

Am I hosed?  Do I need two different processes?  I know you will need some numbers, but is there a standard for maintaining beam to work distance for YAG?  I can only find Co2. I have not tried Google yet.

OB
Parent - - By OBEWAN (***) Date 06-09-2012 19:45 Edited 06-10-2012 01:53
I found Fig 6.21 in the AWS Standard C7.2 for YAGs.  Does anyone have any practical experience?  I think I can cobble together a table or matrix in Excel using this figure and some macro data I have on file.  More to follow tomorrow unless anyone has some input.  It is the weekend after all.  LOL

I am thinking this may be more travel speed related according to what I have read.  But we are using the same relative travel speeds on both systems but have not verified with a tach yet.  But, I may get beat up on travel speed if I try to slow down and may not make weld size if I drop watts.
Parent - - By 803056 (*****) Date 06-11-2012 02:43
Looks like you are the pioneer cutting a path for the rest of us on this one.

Keep us up dated.

Thanks - Al
Parent - - By OBEWAN (***) Date 06-11-2012 09:48
Yeah, I was afraid of that.  But, that was the mantra at my alma mater.  The yearbook is even called the Pioneer.
Parent - - By fschweighardt (***) Date 06-11-2012 10:50
What is your focal length on the 2 systems?  How big is the spot size on the system that works vs the system that doesnt?  You should be using argon for shielding, does it come from the same source?  You should be able to get lenses/mirrors to set the FL where you want it, despite different standoffs.
Parent - - By OBEWAN (***) Date 06-11-2012 15:02 Edited 06-12-2012 14:58
I don't have an exact number for the focal length on both systems yet.  But I am talking about beam to work distance if that is the same thing.  Our technicians just adjusted our system so that the beam to work distance will be identical for both systems.

The other good news is that all my macoro's this morning were good and also the OD measurements meet the drawing requirement.  So, if they beat me up it will be over a reduction in travel speed to get the weld crown a little smaller.  Plus, I may need to redo a few macros to verify that my process is still good after the adjustment to beam to work distance.

And we are using nitrogen instead of argon.  I would rather see argon but my hands are tied on this one due to cost plus other processes that are already qualified with nitrogen.

OB
Parent - - By fschweighardt (***) Date 06-12-2012 23:39
For me focal length is from the center of the final focusing lens/mirror to point of the smallest spot size.  If you have different lens to work distance and identical optics, your beam spot will not be the same, and could easily give different results.  Are you adding filler, or autogenous.
Parent - By OBEWAN (***) Date 06-13-2012 03:53
It is an autogenous weld.

And we have better results after moving the beam towork distance to be the same on both. And I found out the head is on an actuator so that it will move between our two different products so my major worries are gone I hope.

Steve
Parent - - By OBEWAN (***) Date 06-14-2012 11:44
We moved the focal length just 1mm and the issue is now resolved.  The weld size is 1/3 the prior size at the same parameter settings.  We meet spec on OD now and on min weld width but could maybe bring the power up a tad to get more centered above the min size.

I am really shocked at the drastic impact of a small difference in focal length.  I think it may be more severe than the data in the curve in the AWS standard for pulsed YAG's.  (But, we are using continuouos power.)

In my past job this was a non-issue because the laser operator and welding inspectors were trained to do their own set-up's for every production job.  We had WPQ's and WPS's but they were written to give a first set-up starting point from which the operator and welding inspctor adjusted parameters until a good macro test was obtained.  I had over 700 products to support with over 400 weld procedures and never had time to get to a laser focal length study.  But, I always wanted to.  It was just off the radar until now!  LOL
Parent - By OBEWAN (***) Date 06-27-2012 22:02
We discovered a severe gas shortage to be the source of most of our agony.  There may be an obstruction in the system even since we had to go to many times more flow and pressure to get smooth welds.
Up Topic Welding Industry / Technical Discussions / Rough Laser Welds Same Process as Good Welds?

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