3D printing in metals

[Vixen]

Thank you Mike!    That does help. And Just to get an idea of the scale of the photos, what is the diameter of that pipe?

Hello Steve,
The exhaust pipes are all 11mm OD and 8.6mm ID with 1.2mm wall thickness.

Cheers   

Mike:

[Jasonb]

You could do a flywheel in Stainless so you have some decent weight and that would also suit a bare metal rim.

Cost may be high so an alternative may be to combine a printed spoke pattern with a rim cut from thick wall steel tube

I just tried it with a Stuart 7" flywheel which would cost you £71.00 from stuarts inc delivery. 3D printed in 316 Stainless would be £74.00 delivered so about the same

[Vixen]

Is it practical to do something like a flywheel at 6" to 8" diameter?

It would be practical to print something 6" to 8" diameter in any of the available metals. Aluminium, steel and Stainless are the most common. Brass and bronze is also available from a limited number of 3D print firms. You pay for the amount of metal powder consumed, not the complexity of the shape. Most do an instant quote so you can see what you are letting yourself in for. Jason has just posted some cost comparisons.

A 6" to 8" flywheel spinning at speed will produce significant centrifugal (bursting) force. I would question (check) the suitability of 3DP Laser melted/ fused metal with your chosen 3DP print firm. They will know all about the mechanical properties of their bulk printed metals. I believe you would be safer (maybe cheaper) making your flywheel from round bar stock or a good quality casting.

Mike

[AlexS]

Great parts been printed Mike!

[Jasonb]

I was thinking steam engine flywheels when I said they would be OK to print as those are more likely to be where printing is an advantage to forming fancy spoke patterns so speed is not going to be great. Probably get spun faster in the lathe to clean up the rim than it will eventually run on an engine.

Higher speed IC engine flywheels may want a bit more thought about strength but they do tend to be less fancy so more suited to cutting from solid. The built up printed inner and solid rim would again help keep things together. The other thing is that you would need to be making a large IC engine to get upto 8" diameter. Hit and miss or other old style engines would be that sort of size but speed is not going to be that high on those compared to a straight six or V8.

[AVTUR]

Mike

Other than ProtoTi, what friendly printers are there?

AVTUR

[Jasonb]

I use Craftcloud3d.com who are German based but the quotes come up from all over the world and posted from source. China are usually the cheapest, Hong Kong mid point and Europe the most expensive.

Interestingly I have had stuff done by ProtoTi but they came from China

Edit ProtoTi are in Shenzhen in China, photos from their website match those on the link from Craftcloud

[Vixen]

Hello John,

There are literally hundreds of firms offering laser 3DP. Ask Goggle

Laser 3DP in plastic materials is a well established industrial service, rows of expensive top end printers row after row. Fill them with powder, upload the .STP file and the machine does the rest. Now they have added dedicated metal printers to the row, the process remains much the same.

Jason uses a clearing house called  Craftcloud3d.com  They search the world for the best (lowest ?) quote. China is often the most competitively priced. I went direct to   ProtoTi.com  because I heard they had a good, reliable reputation.

Mike (AVGAS)

[AVTUR]

Mike & Jason

Many thanks. I will take a good look over the next few days.

AVTUR

[Jasonb]

The question of thread pull out was raised earlier. As I said I had not used many threads that are under load but took this video today.

The thread is metric fine M4 x 0.5. The male thread in the chuck approx 3mm long so 0.75D engagement length, Hole was drilled 3.5mm. The two chucks weigh 10.7kg, if someone wants to work out the loading I'd be happy to hear the value. BTW the part was printed on it's side just like in the video so the forces are pulling the layers apart.

<a href="https://www.youtube.com/watch?v=zSeL2acqw5A" target="_blank">http://www.youtube.com/watch?v=zSeL2acqw5A</a>

[petertha]

From Gemini The Fibber. Sorry, I wish there was a convenient way to just paste it's text, but doesn't seem to cooperate with its formatting so here are screen grabs. I'm not sure if the printers publish strength values but anyway this is what Gemini had to say.

[Vixen]

The Mercedes W165 exhaust headers demonstrate that CNC machining dimensional accuracy and 3DP printing dimensional accuracy to be very similar.

Aluminium parts (AlSi10Mg) parts from 3D printing will be stronger but less ductile than an equivalent wrought aluminium. I was therefore a little concerned that the lower ductility could cause problems with straightening the post printing warp (bend) in the exhaust pipes. However, I found the  typical elongation to failure values for As-printed AlSi10Mg were typically ~4-6% in the worst direction, due to grain structure. The slight bending I applied to correct the warp is comfortably within these limits.   

Cheers

Mike

[Jasonb]

Thanks Peter, though the part was Aluminium not steel and the threads cut not part of the print.

Mike I'm not so sure about dimensional accuracy being the same for CNC & 3DP.

The holes in that part were all 7-10% undersize. eg 3mm hole came out at 2.7mm, 4mm hole between 3.6 and 3.7mm.

The base was drawn at 28 x 17 but measures 28.23 x 17.16. Possibly more had it not been blasted.

I can do a lot better than that with my CNC or manual machines.

[Vixen]

Hello Jason,

Interesting dimensional observation.

All the through holes in my parts were undersize and had to be opened with a clearance drill. The metal felt hard, crisp and granular, quite unlike bar stock.

My dimensional observations were based on the 16 exhaust flange holes lining up perfectly with the 16 pre-machined flange holes in the cylinder head. OK, I only fitted bolts to the outside row, cos I ran out of screws.

It could be that the laser melting process adds a little to the outside and inside of the printed part, hence oversize base and undersize holes. However, I found the actual hole positions to be good.

We need more than our two samples to fully understand 3DP.

Lifting a 10.7KG lump with just 3mm engagement of a M4 x 0,5 (fine) thread in the 3DP aluminium was impressive. I will have few concerns about the strength of tapped holes in 3DP aluminium. From what we have both found regarding hole size, a printed thread would probably need to be chased with a hand tap anyway.

Cheers

Mike

[petertha]

Thanks Peter, though the part was Aluminium not steel and the threads cut not part of the print.

Thanks, I missed that aluminum detail in my query, which makes the 3DP strength all the more impressive.
Regarding the cut vs printed threads, I understood that's what you did, but I wasn't quite sure what Gemini was getting at. Maybe print roughness is not providing the same finished thread seat & fails by some other mechanism or equivalent diameter?
Not to belabor but it suggesting a very high stripping force assuming 3DP aluminum. It even suggests 'much stronger than cast aluminum. More test weight! LOL