J-20 5th Generation Fighter VII

Michaelsinodef said:

Might also be why we have seen bigger production of the J20 from around the 2019ish.

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That is another important indication of J20 using 3D printing.

In the same 2012 presentation, Wang Huaming said
f22的机翼和机身连接件，**超复杂的钛合金构件，因为太复杂20、30万吨的水压机也做不出来。美国人就分成三个铸件，然后热等静压再焊接，铸件的性能很差，但美国人没办法，f22就是这样用的。
F-22 connector of wing and fuselage, complicated structure. It is made from three ingots (cast), then HIP (Hot Isostatic Pressing), then welded together. The property of casting is inherently bad. (Making it not lasting. Probably the reason that F-22 is not produced in numbers expected.)

Titanium welding may achieve good quality, it's input is casting which is inherently bad. So the final product is still bad. If there is any other choice (3D printing), CAC would not use casting+HIP+welding. Otherwise J-20 would end up as useless as F-22. PLAAF would have waited another year for 3D printing to be ready, or choose SAC to do it.

美国F-22飞机中尺寸最大的Ti6Al4V钛合金整体加强框,零件重量不足144 kg,而其毛坯模(cast ingot)锻件(forging)重达2796 kg,材料利用率不到4.90%,数控加工(CNC)周期长达半年以上
The central bulkheads are made by casting 2796 kg ingot, then pressed, then machined to only 144 kg. The CNC machining process takes more than half year.

If it takes more than half year to make a bulkhead, we would not be able to see the production speed of J20 that we are seeing.

That is nonsense, BTW. The F-22 (and other modern fighter) bulkheads are NOT cast parts, they are machined forgings. Sure, these start out as cast ingots (as do all metal semi-finished products, really...), but the forging process completely alters the material microstructure, which is why they aren't simply cast into final shape to begin with. Indeed, this is something 3D printing cannot emulate (yet), making them closer to cast parts or weld seams in mechanical properties. This calls into question the suitability (or at least the weight efficiency) of such parts for highly-loaded applications - like fighter jet bulkheads, for instance.

But yeah, as I've been saying previously, lead-time is a huge advantage for 3D printing. Depending on your industrial base, that could be worth a certain weight penalty, if you can keep it within reasonable bounds.

taxiya said:

That is another important indication of J20 using 3D printing.

In the same 2012 presentation, Wang Huaming said
f22的机翼和机身连接件，**超复杂的钛合金构件，因为太复杂20、30万吨的水压机也做不出来。美国人就分成三个铸件，然后热等静压再焊接，铸件的性能很差，但美国人没办法，f22就是这样用的。
F-22 connector of wing and fuselage, complicated structure. It is made from three ingots (cast), then HIP (Hot Isostatic Pressing), then welded together. The property of casting is inherently bad. (Making it not lasting. Probably the reason that F-22 is not produced in numbers expected.)

Titanium welding may achieve good quality, it's input is casting which is inherently bad. So the final product is still bad. If there is any other choice (3D printing), CAC would not use casting+HIP+welding. Otherwise J-20 would end up as useless as F-22. PLAAF would have waited another year for 3D printing to be ready, or choose SAC to do it.

美国F-22飞机中尺寸最大的Ti6Al4V钛合金整体加强框,零件重量不足144 kg,而其毛坯模(cast ingot)锻件(forging)重达2796 kg,材料利用率不到4.90%,数控加工(CNC)周期长达半年以上
The central bulkheads are made by casting 2796 kg ingot, then pressed, then machined to only 144 kg. The CNC machining process takes more than half year.

If it takes more than half year to make a bulkhead, we would not be able to see the production speed of J20 that we are seeing.

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I think whether 3D printing is used for J-20 bulkheads is a different question from whether those bulkheads have had their weights reduced. The former does not automatically confirm the latter. However, in theory so long as center of mass of the airframe is preserved it’s not unlikely for them to include as much weight savings as possible with minimal amounts of additional testing. But usually these kinds of changes to weight and structure follow an iteration of the model number, to be packaged together with other tests that have to be done for a new model iteration. Because the changes to production and the design from a mechanical performance standpoint are not trivial and can’t just be introduced to the production line on a whim.

Tirdent said:

That is nonsense, BTW. The F-22 (and other modern fighter) bulkheads are NOT cast parts, they are machined forgings. Sure, these start out as cast ingots (as do all metal semi-finished products, really...), but the forging process completely alters the material microstructure, which is why they aren't simply cast into final shape to begin with. Indeed, this is something 3D printing cannot emulate (yet), making them closer to cast parts or weld seams in mechanical properties. This calls into question the suitability (or at least the weight efficiency) of such parts for highly-loaded applications - like fighter jet bulkheads, for instance.

But yeah, as I've been saying previously, lead-time is a huge advantage for 3D printing. Depending on your industrial base, that could be worth a certain weight penalty, if you can keep it within reasonable bounds.

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Clearly 3D printed titanium is suitable enough for highly loaded applications like the C919’s wing spars and the FC-31’s bulkheads, since that’s where the technology is already being used.
Edit: But don’t take my word for it.

latenlazy said:

Clearly 3D printed titanium is suitable enough for highly loaded applications like the C919’s wing spars and the FC-31’s bulkheads, since that’s where the technology is already being used.
Edit: But don’t take my word for it.

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Oh yeah, because somebody says so in less than a minute, without stating how they are able to emulate the effect of mechanical pressure loading on material grain, that clinches it What kind of process is he even talking about - laser sintering, EBAM? What kind of forging are we comparing to?

I thought the 3D printed C919 part was a wing/body fairing longeron? Far smaller (though huge by 3D printing standards) and far lower stress than a wing spar.

There are ways of improving the strength of 3D printed parts to mitigate the inferior properties of the base material, by altering the geometry of the part. These take advantage of the ability to manufacture complex shapes that are unachievable by other methods, for example integrating traditionally separate parts into one or topological optimization of shaping.

The former is already done to a large extent in integrally machined fighter bulkheads, going even further (for example by integrating wing spars & fuselage bulkheads, as is claimed for the J-35) runs into real practical drawbacks. What do you do if the wing takes battle damage or even has a ground support vehicle accidentally run into it? Scrap the entire aircraft? There's a reason why that is not normally done, even though at least the Russians could conceivably achieve it, using conventional machined forgings and electron beam welding. Check out the construction of the Tu-160 wing-pivot carry-through, you could easily build a J-35-size fighter with integrated spars/bulkheads that way.

Topological optimization meanwhile offers genuine opportunities, but there's no sign of it on either the J-20 or J-35. Consider what the rivet patterns joining the wing skins to the following topologically optimized wing internal structure would look like:



By contrast, the J-20 and J-35 exhibit conventional straight lines and oval/circular man hole covers, like everybody else's fighters.

Tirdent said:

Oh yeah, because somebody says so in less than a minute, without stating how they are able to emulate the effect of mechanical pressure loading on material grain, that clinches it What kind of process is he even talking about - laser sintering, EBAM? What kind of forging are we comparing to?

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I mean, aren’t you also someone who just said so? At least that guy is being paid to actually touch and work on these technologies.

Tirdent said:

I thought the 3D printed C919 part was a wing/body fairing longeron? Far smaller (though huge by 3D printing standards) and far lower stress than a wing spar.

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All reporting on this says it was a wing spar.

Tirdent said:

The former is already done to a large extent in integrally machined fighter bulkheads, going even further (for example by integrating wing spars & fuselage bulkheads, as is claimed for the J-35) runs into real practical drawbacks. What do you do if the wing takes battle damage or even has a ground support vehicle accidentally run into it? Scrap the entire aircraft? There's a reason why that is not normally done, even though at least the Russians could conceivably achieve it, using conventional machined forgings and electron beam welding. Check out the construction of the Tu-160 wing-pivot carry-through, you could easily build a J-35-size fighter with integrated spars/bulkheads that way.

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I’m going to make the perhaps unwise assumption that SAC has done a whole lot more study and calculation of the construction of the J-35, and specifically the viability of its 3D printed integrated bulkhead-wing spar structures, than you or I have.

latenlazy said:

I mean, aren’t you also someone who just said so? At least that guy is being paid to actually touch and work on these technologies.

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He's also paid to sell them. As I said, the issue is far too involved to rely on a blanket statement such as this, especially when it's rather at odds with a first-principles consideration of how metal additive manufacturing works.

latenlazy said:

All reporting on this says it was a wing spar.

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If it's 3m long it's safe to say it isn't a wing spar for anything remotely C919 size (try 15m). It doesn't look much like a wing spar either (and the "C919 passenger airplane (above)" is in fact a CSeries/A220, which perhaps indicates the source's familiarity with the aerospace industry and its terminology).

latenlazy said:

I’m going to make the perhaps unwise assumption that SAC has done a whole lot more study and calculation of the construction of the J-35, and specifically the viability of its 3D printed integrated bulkhead-wing spar structures, than you or I have.

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More than us two? Nothing unwise about assuming that. More than the collective aerospace industries of the US, EU, Russia and Japan? None of these have adopted such a solution even in those cases where they demonstrably could have literally decades ago, without even resorting to 3D printing.

Again, there are first-principles reasons not to do so, which raises questions about how these problems are dealt with. "Magic" isn't really a satisfactory answer and, although I'll readily admit that absence of evidence is not evidence of absence, skepticism is thus warranted.

Tirdent said:

He's also paid to sell them. As I said, the issue is far too involved to rely on a blanket statement such as this, especially when it's rather at odds with a first-principles consideration of how metal additive manufacturing works.

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I seem to remember a time when you insisted that marketing oriented sources were more credible because customers kept them honest and accountable.

Tirdent said:

If it's 3m long it's safe to say it isn't wing spar for anything remotely C919 size (try 15m). It doesn't look much like a wing spar either (and the "C919 passenger airplane (above)" is in fact a CSeries/A220, which perhaps indicates the source's familiarity with the aerospace industry and its terminology).

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“Central spar” is the specific term I’m seeing. Even if it’s not the main spanwise spar that hardly means it’s not structurally significant.

Tirdent said:

More than us two? Nothing unwise about assuming that. More than the collective aerospace industries of the US, EU, Russia and Japan? None of these have adopted such a solution even in those cases where they demonstrably could have literally decades ago, without even resorting to 3D printing.

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Ah, so if the US, EU, Russia, or Japan don’t do it it’s therefore not valid or real? I’m sorry but what happened to the engineering and science speaking for itself?

Tirdent said:

Again, there are first-principles reasons not to do so, which raises questions about how these problems are dealt with. "Magic" isn't really a satisfactory answer and, although I'll readily admit that absence of evidence is not evidence of absence, skepticism is thus warranted.

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Unless you can give me the specific grain characteristics of the titanium that came out of the printer, or post printing treatment process for the part, or the force loading simulations for the whole part or the whole frame the part will be included in, your “first principle” reasons are mostly just a cover for judgment by conjecture. SAC will have done far more actual engineering legwork about the viability of their parts or their process than you or I ever could with appeals to “first principles” reasoning. “Magic” is not a satisfactory answer but neither are “first principles reasons” based on personal conjecture. And unless I’m missing something you are not an engineer at SAC directly in touch with all the details of their manufacturing process or the parts they’re making. The limitations of commonly found 3D printing processes for metallic parts are well known, but those limitations are not iron laws of nature, and it’s not like those limitations aren’t being worked on either.

Unless of course you’re suggesting that the engineers at SAC don’t in fact know what they’re doing and don’t employ some pretty rudimentary engineering practices when they design their planes and manufacturing processes. But it’s not magic for SAC to use 3D printed bulkheads in their airplanes. They’re just doing engineering that you and I don’t have more specific details on.

Aaaanyway.
Huitong's blog has image of J20 serials from various plaaf units.
9th brigade has serial codes documented in a range from 01 to 27.
1st brigade has serial codes from 02 to 18.
Three more brigades have just one serial documented.

So... would the range from 02 to 18 suggest there's not many more than 18 planes in said brigade?
Or would the 01 to 27 range suggest there's more than 24 planes in said brigade?

How often does PLAAF use gaps in their serials on purpose?

There's also the example of J16.
There the 98th brigade has serials document in a range from 03 to 33 AND there's another serial number which would correspond to 96. Which is quite weird.
The 7th brigade has serials ranging from 01 to 28 documented.
The 40th brigade has serials from 01 to 24 documented.
The 3rd brigade has serials from 01 to 29. Though there's a huge gap in between, from 07 to 20.

Assuming all those J16 brigades don't have gaps (ignoring the peculiar 96 serial for the moment) that would suggest most J16 brigades (if not all) have around 30 or even little over 30 planes each.

So with that precedent, it's also plausible J20 brigades could be bigger. It would appear plausible that current brigades featuring modern planes are made to be larger and that they have more planes. But do we have other indications pointing in that direction, that J20 brigades are in fact quite large?