Recast issues

[ghyman]

Our Trumpf 3030 (3000 watt) has been acting peculiar.

We have an on-site met lab and do our own in-house evaluation.
As our product line is nearly 100% aerospace, we are careful to keep recast under control.
Recently, (within the past 6 months,) we have started having problems with recast on .125" material.
The problem is that the depth of recast is variable from part to part, from as low as .0003" to as much as .0086". This variation exists in pats cut at the same time in the same section on a sheet, regardless of where on the sheet, or where in the machine.
The reason I say "peculiar" is because the problem exists on all of the materials we cut: Inconel, Stainless, Titanium, etc. ***but the same materials in other thicknesses show consistent recast of under .001"***
And by 'other thicknesses', I mean .050" - .188", including .100" and .156", on either side of the .125".
We have run through all of our ideas, and are no closer to solving this than when we started.
The lens was replaced 3-4 weeks ago (no help)
The gas nozzle and pressure are good
The resonator was replaced just over a year ago
Beam quality, optics, focus, etc were checked after the resonator was replaced and again when the lens was replaced.
We have tried with SprintLas 'on' and 'off'.
The variation shows up at the entry point as well as around the part profile.
Part geometry does not seem to matter, nor does approach distance or angle.
Any assistance or ideas would be greatly appreciated.

[Rodney Gold]

Have a look at this article , the solution may be there?
The Challenges of Laser Cutting

[ghyman]

Well, that was a good read, and good information.
Thanks, Rodney.
Unfortunately, nothing in there to help with our issue.

[Tweakie]

Have you tried physically measuring your set focal distance and confirming it is correct for the 0.125 material ?

Tweakie.

[ghyman]

Originally Posted by Tweakie Have you tried physically measuring your set focal distance and confirming it is correct for the 0.125 material ? Tweakie.

We replaced the lens last month; the focus *should* be correct, but I honestly had not considered that it might be off. That would certainly explain a lot.
I will check it out.

Good idea, Tweakie. Thanks.

[ghyman]

Originally Posted by Tweakie Have you tried physically measuring your set focal distance and confirming it is correct for the 0.125 material ? Tweakie.

No joy.
it's right at .100" into the material, (80% of sheet thickness) which is where we run it on everything.

I actually had my hopes up, too!

[Tweakie]

I suppose it was a long shot - but worth a try

Tweakie.

[ghyman]

General request:
Does anyone have a Trumpf 3030, who would be willing to cut some test coupons for us? We'll supply the material, the part geometry, and even a (reasonable) purchase order. All we ask is the parts, and whatever cutting data you are willing to supply.

I want to be certain our machine is actually doing something "wrong", and want to do a side-by-side comparison with another similar machine.

In my quest to solve this, I have come to the conclusion that no other company puts this much concern into recast; even the manufacturer stopped understanding the question when I said "No, not dross. Recast. No, not spatter. Recast. It's the layer of... No, not oxidation, either."

Originally Posted by Tweakie I suppose it was a long shot - but worth a try Tweakie.

Seriously, it was a great idea. We had not thought to check that.