3D printing in metals

This is a new topic dedicated to 3DP metal printing mainly by outside commercial firms

3D printing has been around for a long time and many of us have our own printer at home. Home brewed filament printing is useful but has it's limitations. There are now a growing number of commercial outfits who offer high precision laser based 3DP printing in both plastics and metals, at competitive prices. The range of printable metals and the quality of the printed items is improving every day and prices are dropping.

There are some model engine parts which are difficult (approaching impossible) to make by traditional methods. For example, thin wall exhaust manifolds (headers) and pipework. I chose to explore the 3DP printed metal route rather than attempt a difficult fabrication. I designed each of the parts in 2D CAD, that's all I have available. Petertha kindly converted my 2D drawings into 3D models and from the 3D models provided me with the .STL printing files.

Almost all of the 3DP printing firms offer an instant quote service: upload a .STL file, select a material and your required quantity, within minutes they send back a price. You can explore all the different materials for comparisons. But beware, not all commercial printers stick with their initial quote, some reassess their quote when you show an interest in ordering some prints.

My current preferred supplier is  ProtoTi.com  based in Hong Kong. They held to their instant on-line quote. I was very impressed with their prices and service. I placed an order for these parts to be laser printed in Aluminium just before Christmas. 10 days later, a small parcel was delivered to my doorstep containing, a pair of exhaust headers, a pair of coolant pipes and the crankcase breather pipe. Wow, that's impressive by any stretch of the imagination. 






The coolant and vent pipes have a very thin wall thickness of only 0.8mm whereas the exhaust pipe wall is a little thicker at 1.2mm. All the pipes printed perfectly. They were bead blasted by ProtoTi to produce a casting like appearance. The laser printed aluminium appears to be fused (melted) into one homogeneous part which needs little or no further machine work.





I did notice a slight warping at the ends of long slender exhaust pipes, probably due to cooling after the laser melting process. I guess, a sacrificial bar across the ends of the four flanges would help prevent this movement.

Overall I am very impressed with the quality and service provided by ProtoTI. 10 days from order to delivery, all for $37 plus $15 for delivery. I will certainly use them again.


Below you can see the coolant pipes and crankcase vent pipes threading their way across the top side of the engine. The side view shows the exhaust manifold loosely in place. There is a slight interference between the rear engine mounting block and the rearmost wiggly down pipe. A few strokes of a file on the engine mount block will sort that out.






That's all for this visit to Vixen's Den

Cheers 

Mike

Your pipes are looking good Mike. If you were doing it again would you have used this method for those parts you made the moulds and waxes for and farmed out the investment casting? I bet it would be cheaper.

I also had a similar turn around with parts ordered just before Xmas arriving in 10days. As I only needed the one item I played with the minimum job cost on the instant quote and got six for the ame price as one. Parts arrived Monday and I've just finished the engine.

I would not want to do a whole engine this way as I still enjoy the machining both manual and CNC but treated just like another tool it can be used when it is the most suitable for the job in hand.

Jason

Back in December 1997, when I did all the pattern making, molds and waxes for the Jupiter engine, 3DP was not an available option. The investment casting cost for one inlet manifold was £25 each.

I think we can safely say that 3DP metal printing has come of age and costs are spiraling down, Each of the W165 exhaust headers cost only $11 each. The coolant pipes only $3 each. 3DP produces a part equal to any investment casting in terms of looks and quality. Furthermore, going directly from 3D CAD to finished printed part cuts out so many steps (and risks) associated with the investment casting route. I think investment casting is effectively dead.

What can you say about the machine-ability, strength and thread holding capacity of your 3DP parts. Is it similar to stock materials? I believe you have machined S316 and aluminium printed parts. The reason I ask, is because of the bad experience I had with the aluminium casting for my Westbury Seal. The cast aluminium engine block was so weak and soft that the cylinder head studs ripped out of the casting. That was the first and only casting I have ever used to build an engine, every other engine was made from stock materials of known strength and quality.

Mike

As I told Mike, I'm super happy with the outcome & pleased to have contributed a tiny part of this project. I agree 3DP metal appears to be a game changer. I suspect the 917 snake pit would be much the same except more. Having a full 3D model from the get-go is a big advantage. Once the pipe paths are known in 3D space, its not particularly difficult loft pipe sections along them. The slightly tricky bit here was the starting point, working from 2D Front & Side views of original drawing file to derive the path around silhouette obstructions, maintaining clearances etc. I'm not into CNC but I'm still shocked at how far Mike has pushed 2D-CAD & 2.5D-CNC on this engine to the results you see. That requires old school mental visualization of finished parts from 2D sections. A few niggly issues importing 2D format drawings into a 3D app, but most of this was just learning the nuances. I have already put those new found skills into my bag of tricks.

Interesting things can happen in the area when pipes 'come together' in the Siamese/manifold area from their various orientations. In this 4-pipe case the convergence occurred on one plane which makes cleaner sections. But resultant internal sharp corners or thin features may result & the printers may have a final say with their tools / constraints. A different engine with a different bowl of spaghetti may incur different challenges, all part of the model engineering fun. For CAD nerds, I found it better to model the entire manifold in solid including the varied fillet 'welds', then 'shell' the solid header from open ends to prescribed wall thickness. If that operation doesn't fail, its a good sign you have a compliant solid. I want to point out another nice Mike touch, the variable chamfer on the flanges like the FS.

This could go on & on. One could add extra boss material on all the welds & hand carve what end up looking like FS welds with its slight irregularities & surface imperfections. (I suppose could be modelled in 3D too, but that would require some noodling). Same goes for upsets or collars where pipes were nestled or joined even if cosmetic. Some FS pipes look to be made from straight + curve sections, mitered, welded, yes hammer massaged. So to be faithful to the FS, the CAD model should use similar geometry even though its tempting to make flowy spline curves. Obviously regular plastic 3DP parts could be made more locally to confirm things beforehand. I suppose, like casting, it may be beneficial to add sacrificial material here in there in certain areas if distortion is a fact of life, but that is trickier to assess until the parts are delivered. Well, that's enough CAD talk, lets enjoy the engine build on the home stretch.

The 316 stainles sparts only had through holes so I can't say what it would take a thread like but drilling seemed very similar to solid needing more pressure on the quill handle than say a free cutting mild steel.

The aluminium I have just had done again is mostly through holes though the air/exhaust was tapped M4 x 0.5 but the pipe connector does not put much load onto the thread so hard to say what the pull out strength is. Printed holes did come out a bit undersize eg the shank of a  2.7mm drill fitted a 3mm CAD hole.

I'm not worried about modeling the pipes
.just making them.

Dave

Thanks for all your inputs.

I would like to move all this 3DP discussion from the W165 build log into a more appropriate 3DP topic. Can anyone suggest the best existing topic name to use?

Mike

Additive Machining would be my suggestion.

Quote from: JasonbThe 316 stainles sparts only had through holes so I can't say what it would take a thread like but drilling seemed very similar to solid needing more pressure on the quill handle than say a free cutting mild steel.

The aluminium I have just had done again is mostly through holes though the air/exhaust was tapped M4 x 0.5 but the pipe connector does not put much load onto the thread so hard to say what the pull out strength is. Printed holes did come out a bit undersize eg the shank of a  2.7mm drill fitted a 3mm CAD hole.

On my next order (or one of yours?) we could get have them print a test coupon in aluminium and S316. (say 6mm diameter by 50mm long) We could then drill and tap it, turn and mill it, bash and bend it to get a fuller understanding of the mechanical properties of the various printed materials compared to equivalent bar stock.

Mike

Lovely result for those Headers etc. 

Wonder if Future 3D Prints should have a little more Meat on the Flanges (or other strategic places) so they could be sanded, filed or milled to fully flatness @ the Gasket Interface 

I remember some of my old thoughts from some years back during another Hike yesterday .... and wondered if that could solve one of your other Problems Mike ...?

So I have just sketched it in Alibre - here you see both Parts Cut in Half (for illustration).
It is basically a Punch and Die Tool. You put a length of precision ground Steel in the Die - Heat the part above the Die to between Red and White Hot. Put the Punch down over the Die and give it a Bloody good wack with a Hammer.

The Precision Ground part (the Valve Stem) should hopefully still be straight and perfectly round as before and the Hot Part should have been converted into the Valve Head.

I haven't included any Ejector or other specific Improvements (that might be needed) as this is only a 'Thought in the Air' - that you or others can play with and see if we can make the Creation of (Poppet) Valves a lot Easier in slightly bigger quantities 

Per               

ps  Happy New Year Everybody 

I have allowed a "machining allowance" on the prints much like you would for a casting pattern. Not such an issue for parts like Mike's manifold but for rotating and sliding surfaces it is a must.

In consideration of exhaust flow, what is the internal surface finish like on 3DP mfd. small bore U shaped bent pipe?

Do they use supports in there and if so how are they cleaned out?

Quote from: vtsteamIn consideration of exhaust flow, what is the internal surface finish like on 3DP mfd. small bore U shaped bent pipe?

Do they use supports in there and if so how are they cleaned out?

Hello Steve,

Photographing the inside of a model exhaust manifold is not the easiest of things to do.





However you should be able to see the internal surfaces and mitered edges are sharp and crisp, almost as smooth as the external surfaces. However, the outside has had the benefit of bead blasting, unlike the insides. Metal 3DP printing is achieved by a laser selectively melting a bed of aluminium powder, the compacted powder provides the support during printing.

Hope this helps

Mike

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?

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