Having researched the question of the Chinese bulkhead and wing beam a bit more, I have to admit that I'm on the fence now - I might be prepared to accept that they are 3D printed and ready for use in production aircraft. What I continue to doubt is that there is a weight reduction, I'll explain below (though most of the points I have made before in one post or another).
Why believe the claim that the parts are 3D printed and ready for use but reject the claim about weight savings when they come from the same source, the manufacture themselves?
Sciaky is neither a he or a she, they are a US-based manufacturer of metal 3D printers. Their biggest machine can handle parts about the same size as the Chinese samples we've been discussing and Airbus has been playing around with a smaller variant based on the same technology. I've since learned that Airbus have also been cooperating with the Chinese Uni since 2014, perhaps you were aware of this and that's what confused you?
Oops. When I was reading your original source for whatever reason I thought Sciaky was a person. In my defense it was very late when I wrote the reply. Also, somehow misread 5m parts as 3m parts. That said, the relative point still stands. China was ahead by a few years.
Regarding the accuracy of Western assessments of Chinese technology you are barking up the wrong tree - I don't disagree, hence my emphasis on the fact that I am expressly NOT holding China's 3D printer industry to a different standard than anybody else's. I also concur that China is at the forefront of the additive manufacturing race (their big machine beat Sciaky's by two years, closed loop control system and all!), I am just skeptical about them being THAT far ahead of the pack.
I'm just making the point. Not necessarily suggesting that you think otherwise.
I didn't - I made the point that for a highly loaded part of straightforward shape such as a fighter bulkhead, it will be load bearing requirements which drive part thickness, not manufacturing capability (and that this has been the case for a while). So unless you adopt a novel approach to shaping (e.g. something hollow or an integrated truss structure), using 3D printing to make it will drastically drive down cost and manufacturing time but hardly affect weight at all. A solid piece of Xcm³ of titanium is going to weigh Ykg, no matter how it came to be that shape.
"Modern high-speed milling can handle material thicknesses so low that making a full depth bulkhead that thin is nonsense (if load requirements are so low, simply stiffening a semi-monocoque skin with a frame is probably preferable, as in an airliner fuselage)."
That's what I was referring to when I said you made the point about mills being able to machine thinner parts than before.
Anyways, I think our disagreement here boils down to whether you can mill a titanium bulkhead to the minimal amount of material needed for the amount of load it must handle. As I keep saying, how much load a part can handle involves a lot more than how much material there is. Load bearing requirements drive thickness *dependent* on the capabilities of your process technologies and materials of the time. When either changes, achievable thickness can change too.
I think we can also use a bit of clarification over what we mean when we talk about "parts thickness". When I refer to "thickness", I'm specifically talking about shape features like, for example, how deep troughs in the structure can be or how thin rib structures are. Compare, for example, the two bulkheads below. The top two are the F-22's, and the bottom is presumably the J-31's.
We're not debating "something" though, we're discussing fighter bulkheads - and it's a fairly safe bet you'll want the best material properties obtainable for this particular application.
Do we have reason to believe fighter bulkheads *must* use the *strongest* form achievable of some material (strength is not a monolithic property either, and which strength properties you need is highly dependent on the context of their use)? As I understand it, what matters for planes is ultimately strength to weight ratio, not strength alone, and costs play a limiting factor as well.
Absolutely true (and I have been saying things to that effect all along), but for this to be relevant here it amounts to you claiming that the bulkhead sample you've shown is of a geometry which could not be made by forging and machining. I would roundly disagree with that - I don't see anything unconventional there which would support such an assessment. And the microstructures part after all is precisely what I mean by material properties - that aspect continues to favour forgings currently.
Judge for yourself based on the pictures I posted above, but if you're going to go with an eye test, do you have enough expertise to know what to look for? Is an eye test good enough to refute the claims of the manufacture?
I've been hearing that the F-22's bulkheads are two pieces that have to be welded together. Maybe being able to print the bulkhead as a single piece is a part of weight advantage?
Regardless of how strong forging is, microstructures are still only one part of the equation, and 3D printing doesn't need to be the best if it can be good enough.
So where would the weight saving over a machined forging be coming from in the above examples, if we accept that they're 3D printed? Same material, geometry which is achievable with traditional processes, likely somewhat inferior material properties which might require greater thickness in places than the conventional analogue to bear the same load. There's no question that 3D printing the conventionally shaped parts would be dramatically faster and less expensive (factors important enough that they may well clinch the deal all by themselves), but lighter?
Another case in point:
Handsome weight saving, but only obtainable by completely rethinking the shape.
On a different note:
LOL! Talk about being blinkered - on the General Dynamics web site where I found the F-16 gun data there is actually a page for the F-22 gun system which I somehow failed to notice.
So a total of 170kg (empty feed + gun), but on the other hand EOTS weight is actually a bit less than 100kg:
Nonetheless, it shows that by applying a bit of common sense and technical judgement you can get the general trend right even without having the exact figures, and the two errors (such as the relevance of a couple dozen kg one way or the other is, for a ~21t estimate) do cancel out to a large degree.
If you really want to, absent the judgement of technical expertise you can find any number of general reasonable rationales for why a claim can't be true. As I've said repeatedly though, the claims made by the manufacture aren't ambiguous. You can take it or leave it.
