3D printed pistons

[e36jon]

Greetings all

I tossed some more images that I stumbled across in my previous post. Hopefully the additional info helps.

The 'heavy diesel' piston with the sodium filled cooling channels got me thinking about the hot section vanes in a jet engine. Those hot section vanes are investment cast in steel with complex internal cooling passages. So, are we doing anything with 3D printing that can't be done via. existing technology? Casting and 3D have similar requirements for getting the core/excess powder out of the finished part, so no real advantage there. In steel or aluminum there isn't an advantage one way or the other from a material POV. 3D printing is a win when more exotic alloys are involved as many of those can't be cast easily. Does it come down to just the 'rapid' part of the equation?

Cheers,

Jon

[subcritical71]

Greetings all

I tossed some more images that I stumbled across in my previous post. Hopefully the additional info helps.

The 'heavy diesel' piston with the sodium filled cooling channels got me thinking about the hot section vanes in a jet engine. Those hot section vanes are investment cast in steel with complex internal cooling passages. So, are we doing anything with 3D printing that can't be done via. existing technology? Casting and 3D have similar requirements for getting the core/excess powder out of the finished part, so no real advantage there. In steel or aluminum there isn't an advantage one way or the other from a material POV. 3D printing is a win when more exotic alloys are involved as many of those can't be cast easily. Does it come down to just the 'rapid' part of the equation?

Cheers,

Jon

Actually, in the jet and power engine world 3D printing is utilized because you can create very complex cooling air arrangements which are not possible by using cores cores on cast parts.

[e36jon]

Subcritical1 points out that 3D printing tech is already in use for turbine blades due to the complex internal geometry needed for cooling the blades in the hot section of the engine. I went searching and was surprised to find one certified example and several in the development pipeline. I had assumed printing tech would not be viable due to high-temp creep which drove the development of monocrystaline structure for hot section blades, something that can only be accomplished with casting. I'll just go sit in the corner now...

Actually, the turbine blades have at least one case that substantiates an earlier claim: GE has been able to substitute a TiAL alloy for a nickel alloy steel alloy using 3D printing with a 50% weight savings. The part would have been overly difficult / impossible to cast with the TiAL alloy. So, 3D printing can allow for materials that would have otherwise been impossible to use for a given application.

Lastly, as I ate my lunch, I remembered one of my own barriers to using casting for parts, having an overly complicated core. The cores for casting have to also be made somehow, often by casting, which I have failed to fully think through as I was designing a part. Even factoring in the ability to combine multiple pieces into a final core it can still be impossible or overly expensive to accomplish. 3D printing can generate cores and so allows a hybrid of a direct printed metal part...

OK, like I said, I'll be in the corner...

Jon

[subcritical71]

The technology is still in its early phase, I can’t wait to see what the next 10 years produce. Siemens have also created rotating parts for, I believe, a ~30 MW turbine. They reduced the time to test from 2 years to only 2 months by not having to do the investment castings. So there are also other benefits which aren’t so obvious.

[strad]

I still want to understand why the shown piston has a bubbly looking crown and how that affects flame propagation.

[Zynerji]

https://polymaker.com/product/polycast/

[e36jon]

I still want to understand why the shown piston has a bubbly looking crown and how that affects flame propagation.

This is what the pistons looked like after 200 hours on the dyno, so maybe that will partially answer your question:



Cheers,

Jon

[e36jon]

A question for the tech-geeks: What would be your dream material for a piston?

These pistons were made with the exact same Mahle aluminum alloy M174+ that the existing forged pistons used, the only difference being that the printed pistons started with a powder. I haven't seen anything about the end result having any different metallurgical properties than a casting of the same alloy.

In another thread (That I can't find now) there was a discussion of beryllium pistons used in F1 before such exotic solutions were banned. Although fantastically lightweight the material properties weren't ideal, with brittleness being an issue.

So, in the wild and crazy world of powder metallurgy, where things exist that never could have before, is there some amazing material that we could be using instead of aluminum? Is there some superior aluminum alloy that we can now use because we no longer have to cast or forge it?

[strad]

I'm thinking beryllium is one of the metals banned because of health concerns.

[Hoffman900]

You need something that is light, but strong enough not to deform the ring lands, and be plastic enough to absorb tiny amounts of debris / detonation. It also can't promote micro-welding of the rings (or be able to accept coatings / a process to help harden the ring lands and be super smooth). It also needs to be able to have high cycle limits and be able to dissipate heat.

It's a tough task and it needs to be looked at holistically with piston oil squirters as well as ring and even bore / block technology. Also, combustion characteristics factor in as does cycle times (are we talking something that needs to survive 5 seconds under full load, or thousands of miles?).

[e36jon]

I'm thinking beryllium is one of the metals banned because of health concerns.

You are not wrong. Ditto for magnesium being a fire hazard. And now that we are talking about powders a lot of formerly benign materials become a hazard due to particle size. The photos I found of the GE turbine blades being made out of TiAl had the machine operator wearing a full respirator... For the purposes of this discussion of what super-zippy material could work I propose we ignore personal safety with the assumption that any concerns could be addressed.

With regards to Hoffman900's remarks I would propose that we focus on an application similar to what Porsche just did, pistons for a very high performance turbo road car / endurance racing car. Porsche is saying they saved 10% on weight with the 3D design, even with the new cooling channels, so that gives us a target (I never did find actual weights for anything though.).

[Ringleheim]

What about nanotechnology?

When will something like a piston be "built" as a single, integral thing, put together an atom at a time?

[Tommy Cookers]

I'm thinking beryllium is one of the metals banned because of health concerns. :?:

afaik beryllium (a few still say it's not a metal) is a bit like Pluto .....

so-called beryllium/aluminium alloys are these days classified as MMCs
improved coherence via the Be particle production giving improved engineering properties (still not an alloy)

but (presumably) this coherence is lost by additive manufacturing - or we would be hearing all about it

btw
F1 'tungsten' is actually (so-called) THA tungsten heavy alloy(s) - but these are (presumably) MMCs not alloys
Meehanite (CI) is engendered only by a trace addition of cerium to the pour
and what about the zirconium in the modern magnesium alloys ?

[e36jon]

Tommy Cookers: Great post. I hadn't really considered how challenged our existing vocabulary would be with all of this new technology. I have seen 'PM' for 'Powdered Metal' used as a prefix and then a reference to 'alloy' after that. In the case of the Pankl Ti Cosworth conrod that I have, which is a PM Ti alloy that couldn't be made any other way (Sorry, I lost the exact alloy description...), I don't think they could have used it if it was a MMC. F1 had banned composites for engine components, right? This is me guessing / speculating / wondering as I am no expert on this.

Within the PM world my understanding is this (See earlier comment about not being an expert): The 'alloying' part of the process happens at a very fine, almost molecular level. This is necessary to get the actual material properties. The creation of the powders that are then used to either create billets of the new material or for feed-stock for 3D printers is happening on a much much larger scale. 100,000X? So, the 3D printer is welding together balls (The powder) of the new alloy. All this to say that the BeAl alloy, if it could be made into a powder, would probably work in the 3D printer. The GE turbine blades being made in the TiAl material had to do a bunch of work to get that material to actually work. They had to sort out a bunch of process details to finally get usable parts. So, BeAl may be absent because it can't be made into a powder, or it doesn't work well with the 3D printing process, or? At least we know what to get you for Christmas ;VP ...

[strad]

Guess we have discussed this before: viewtopic.php?f=6&t=509&start=15

Banned after that season after protests from Ferrari. Beryllium is perfect for the job, but is expensive and the dust is very unhealthy to inhale.

beryllium is radioactive. there are 12 different forms of beryllium. the form used by F1 teams did emit x-rays.