Would you use a 3D printed stem?

Even if I understood the calculations I’d be nervous about something made from welded together powder, I think.

I Swedish but you’ll get the idea…

http://www.diva-portal.org/smash/get/diva2:1112547/FULLTEXT01.pdf

surely a) the medium cant possibly be strong enough and b) it would need machining for contact points between steerer and bars as well as threading.

That has got to be just a concept prototype.

the medium cant possibly be strong enough

A number of people are using it for Ti dropouts, BB shells etc so I can see it’s strong enough for some cycle applications and no reason it couldn’t be for this.

Yes, I expect some ‘finishing’ would be required to make it useable.

IIRC its already in use in F1, so if engineered properly (like any stem) it should be fine.

the medium cant possibly be strong enough

^ that picture is the plastic prototype. as far as i understand the abstract/ swedish the research was done on a metallic system (EBM).

Aesthetically marmite, prevents water pooling in BB, but bloody light & strong = not cheap.

http://www.miradapro.com/

The bb on that looks familiar………..

Charge were doing ti 5 years ago for dropouts.

no, it’s a daft way to make a stem

(it’s a daft way to make most things…)

When my son & I spoke with Mirada / Reynolds @ BeSpoked ’16 they are positive that 3D printing is in its infancy and will boom. He likened it to how in the past if you wanted something paper copied you’d pop into a shop with a photocopier (we all now have a paper printer at home), in the future you’ll be popping into a 3D print shop with whatever item you want duplicated in titanium, plastic, stainless etc, there will be one on every high street (probably most homes).

Those printed lugs….

Engineer 1: Triangles are strong.
Engineer 2: Yes, triangles are strong.
Engineer 1: So what do we need?
Engineer 2: Moar triangles!

in the future you’ll be popping into a 3D print shop with whatever item you want duplicated in titanium, plastic, stainless etc, there will be one on every high street.

Or like we have a combined scanner/printer at home, most homes will have a relatively simple, but robust, 3D printer.
You break the knob on your cooker, or lose a piece of lego, then download the file (for a modest fee!) and then print off your own.

Benefits are that you can do the most complex / intricate items with it, very small.

flexible 3D printed biodegradable stents, which can easily be customized for individual patients and provide life-saving support in the case of weak or clogged up arteries.

http://www.3ders.org/articles/20161012-northwestern-researchers-pioneer-custom-3d-printed-biodegradable-vascular-stents.html

On a plus note: titanium is cheaper than stainless steel 😀

Whilst the material of Ti may cost more, the cost to the customer is machine run time, & Ti can be printed far quicker than stainless steel.

Ive got access to various 3d metal and plastic printers (for a price) and imo its a solution looking for a problem.

They are doing trials with ALM/3D printing of qualified aircraft parts in titanium – if it works for those, bike parts are a trivial issue.

With the right in process verification AND real world design validation (not just FEA until the resulting material properties and variances are fully understood), I’d run a 3D printed stem no question.

Trusting just an FE model with no substantiation of material properties, on a “printer”, I’d be pretty worried.

I’m an aero design engineer, many 3D metallic parts flying, I’m trying to promote it in the company i’m currently working at, there’s so much you need to consider and account for, but there’s no reason not to trust 3D print if there’s the correct rigour behind it.

I would, if it was produced by a well recognised manufacturer, not so much an Alibaba special, but that could be said for any safety critical bike parts.

Not convinced that home 3D printing is going to be a huge thing. Maker Bot, (? could be another of the larger producers) are struggling apparently.

Ive got access to various 3d metal and plastic printers (for a price) and imo its a solution looking for a problem.

It’s looking at stuff with fresh eyes, if you’re looking to replicate machined parts it’s pointless, you’re trying to replicate subtractive manufacturing (deeply ingrained in the Engineering psyche) with additive, there’s zero benefit.

It’s definitely allowing me to design for function rather than design for subtractive manufacture, which just about any legacy design I’ve come across at my current place is. I’m readily combining parts, lightening parts and making them stronger in some instances.

^ Exactly. Being able to make printed parts that would be difficult if not impossible to machine. i.e. hollow/honeycomb filled structures. Being able to print in one piece a part that might have to be machined in 3 or 4 pieces and then welded together.

we can already buy stems for £20, that are light enough, and strong enough – what does 3d printing offer?

i appreciate that the thread has grown a little beyond the original brief,
so in that spirit – how do you validate this kind of thing:

you can’t put it in a plane until you can inspect it, and make a traceable pass/fail decision on it’s size, shape, integrity, microstructure, etc.

it’s a little premature to present 3d printing as an aerospace-ready technology.

hurdles, there are many.

I don’t see anything on that stem that couldn’t be done with subtractive manufacturing and forging… 3d printing is cool, and can do some genuinely interesting things with empty shapes, densities etc (how about a solid ti shell with a 30% honeycombed inner?) but for now it’s pointless just replicating standard shapes (might not always be the case). Stems are a nice simple thing to make.

I spoke to a chap at Renishaws about the Empire printed bike and the verdict was, cheaper in materials than making a ti bike out of tubes. But the machine that made it would otherwise have been making aviation or space industry parts that’d sell for massively more per hour/per gram so it was basically insane, when you can make a bike in a shed.

It would be interesting to see the stress test details on some of these printed parts and what they look like inside,core structure etc.

you can’t put it in a plane until you can inspect it, and make a traceable pass/fail decision on it’s size, shape, integrity, microstructure, etc.

it’s a little premature to present 3d printing as an aerospace-ready technology.

Don’t understand how you conclude the second from the first?

How does a part being manufactured by 3D printing /sintering preclude it from being put thought any of that?

deanfbm – Member
With the right in process verification AND real world design validation (not just FEA until the resulting material properties and variances are fully understood), I’d run a 3D printed stem no question.

Trusting just an FE model with no substantiation of material properties, on a “printer”, I’d be pretty worried.
This, plus if their publicity just showed a plot coloured by deflection I’d be worried – I’d definitely want to see (even theoretical) stress levels.

Really not a fan of that Mirada – if you’re going to have pretty swoopy sections, then you need to have a better way of joining them to tubes than rather agricultural welds. Bond it or something.

At the moment, most 3D printing in the bike industry is so people can say “look at us, we’re using 3D printing!” It’s a marketing gimmick. Especially that stem, which isn’t anything that couldn’t be made with conventional manufacturing.

I use 3D printing for one thing – a nylon belt drive cog that it’d be very expensive to make any other way. That’s what 3D printing is good for, not for making things just because you can.

[/Luddite]

it’s a little premature to present 3d printing as an aerospace-ready technology.

Not really – SpaceX have been using 3D printed rocket engines for ~3 years. I’ve seen them being made 😉

I’d ask them to make 2 and I’d try and smash the **** out of one until it broke or didn’t.

nedrapier – Member

How does a part being manufactured by 3D printing /sintering preclude it from being put thought any of that?

It’s my job, dimensional validation of internal surfaces* is an industry challenge, it’s fascinating. Metrology-grade ct scanning is probably where we’ll end up. However, normal ct scanning is a bit spendy, never mind one with an error-mapped granite chassis…

(Think £200/£300 per hour running costs, and 5hour scan times, to get an idea of validating each part)

(*the kind of sexy sweeping shapes and lattices that make additive-manufacture so legitimately appealing)

Ive got access to various 3d metal and plastic printers (for a price) and imo its a solution looking for a problem.

I see this a lot, industrial design graduates with a clever toy, but no real use beyond making pretty shapes.

I can’t help thinking most users get it arse about face, and the most useful applications for current 3D printing technologies are in tooling rather than “direct manufacturing” of the finished article…

Form inserts/consumable “tooling” for laminates, cheap PLA forms to do “lost wax” style sand casting, laser sintered injection moulding tools rather than spark eroded steel, producing a cheap mould for RIM with cold mixed rubbers and plastics to make usable small batch items…

Those are all sensible ways to use of “3D printing” to save money in production/prototyping, rather than Knocking out hugely expensive keyrings, bangles and pointless bicycle part just because you can…

If it’s not saving money over using traditional machining and doesn’t deliver a demonstrable mechanical benefit then you have to question the wisdom of using it…

I do low quantity stuff with mine- ideally I’d get it all injection moulded but that just doesn’t make any sense. Admittedly, it’s also a niche where people actually like that it’s 3d printed, sort of like endmill marks and steppy gradients in Hope- people wouldn’t be happy if they made them smoother 😆

Course, like everyone else with a small printer, what I mostly print is printer

PS, I would not use a stem printed by me, unless it was about the size of a breeze block.

You can’t say 3D printing is a solution looking for a problem. Its a process with its own pro’s and cons just like any other process and will be suited for some applications more than others. The company I work for has flown very large structural 3D printed components on test flights to prove the concept so there is no doubt 3D printed metal components can be made strong enough. the only thing preventing us from pressing it into production is the lack of consistency and repeatability of the process. When you buy metal to manufacture something from it will have a specification that tells you the mechanical properties of the metal. this will take into account all the potential imperfections that will be in the material. So as a design engineer that is what you design to. For 3D printing no such specifications exist and every part is different so the repeatability is not known and there are no controls. But as a process 3D printing offers significant opportunities and will revolutionise products in the future, but there is still some way to go yet before they are production ready.

Some parts may already be out there but they wont be major structural parts and things like Space X are experimental so they can over-engineer the components to ensure their structural integrity as the convenience of ease of quick design changes and quick manufacture is far more valuable to them at this stage. Once they start to freeze the design then they’ll be looking for efficiencies and that is where the repeatability issue will bite. Every gram of excess metal you have in the product is a gram of earning payload you can’t carry into space.

From a reputable company that does testing, yes.

It’s definitely allowing me to design for function rather than design for subtractive manufacture, which just about any legacy design I’ve come across at my current place is. I’m readily combining parts, lightening parts and making them stronger in some instances.

Engineering friends (real, not just a qualification) are saying they are having to completely change they way they conceptualise and design to take the fewer limitations on size, shape and structure into account. One of the older ones has likened it to when carbon fibre first appeared, they struggled to stop thinking in terms of tubes everywhere and embrace being able to do massively flared joints and alternative construction possibilities presented by the layup processes being developed.

I do this for a living.

3D printed titanium is already used for structural and systems applications in spacecraft and will be entered into service for safety critical, commercial aerospace structural applications later this year.

The processes and procedures used to ensure that the 32000 repeat operations needed to print a part from 25micron powder particles are extremely precise and have been validated over 0000s of builds and 000000’s of mechanical tests.

Rest assured that both the hollow dropouts (done by Airbus) and the motorbike (also done by Airbus) are based upon techniques developed for the aerospace industry. The topologically optimized structure for the motorbike above was performed by my previous intern on behalf of Airbus Apworks. The structure is designed by analysis and validated by repeat FEA, backed up by hand calcs. CT is used to inspect for defects and cracks are determined using dyepen, same as anything else.

andybrad – Member
Ive got access to various 3d metal and plastic printers (for a price) and imo its a solution looking for a problem.

Utter rubbish.

I’ve got 10 industrial 3D printers (5 metallic, 5 polymer) on site and am trained to use all of them. I’ve recently completed the a full multi-disciplinary optimisation of the main landing gear manifolds for an Airbus aircraft. The design freedom offered by 3D printing removes the need for complex internal machining, by fluidically optimising the flow within the manifold it reduces losses and cavitation in the structure, reducing stress. By reducing stress, we remove the need for structure to resist it and by removing un-needed structural mass, we save both material and beam time.

The result is a 70% decrease in mass, an 85% decrease in required machining setup operations, a 90% decrease in required machining tools, a 38% decrease in fluidic loss and (even after investment and certification costs) a potential £120m€ saving for the program… This part is under 750bar of dynamic pressure. I can provide you with hundreds of examples like this…Still think its a solution looking for a problem?

Would I ride a 3D printed Stem? Yes, if it were built by a reputable company who knew exactly what they were doing and what the quality of the feedstock was that they gave to the machine.

Bloody experts. 😆

NASA are trialling 3D printed rocket motor parts as well.

I thought I had ceased to be amazed at the depth of knowledge available on STW, but this thread has upped the ante. 🙂

All the whizzy aerospace examples are great.

I get that there are many industries & areas where 3-D printing comes into it’s own.
They are generally industries where performance requirements are high, low production numbers are required and costs are largely a minor concern.

But, for a production bike stem…..it seems to me like using the process because you can, not because you should.

At a place I used to work at, we had some prototype parts manufactured using “3d printing”. This was probably around 2003. Back then it was being touted as ‘the next big thing’ and people were talking about people having them in their homes etc in the very near future….that was almost 15 years ago & while I have no doubt that it will get there one day – I think we are still some time away from 3-D printing being common place.

Oh, and would I ride a 3D printed stem….? If it was done properly, then yes from a confidence point of view.
But, the cost involved would be stupidly expensive so I’ll just stick to some welded & machined bits of old tech stuff for the time being.

But, for a production bike stem…..it seems to me like using the process because you can, not because you should.

You have to unlearn what you have learned. Why does a bike stem look like they do? Because they’re made from a tube with two shorter bits of tube welded at each end. The design is completely dictated by ease of manufacture and availability of stock material. Now if you use some fancy pants design software that looks at the forces applied to a stem during use and come up with an idealised shape/form of a stem that purely and only manages the forces applied to it through use then you’d come up with a very different shape that will not be easy to manufacture using traditional processes. That is how 3D printing will transform engineering. You’ll see a lot more organic shapes and forms emerging, with thin webs of varying thicknesses where material only exists where it needs to and serves a specific function in the performance of the component.

wobbliscott – Member

You have to unlearn what you have learned. Why does a bike stem look like they do? Because they’re made from a tube with two shorter bits of tube welded at each end. The design is completely dictated by ease of manufacture and availability of stock material. Now if you use some fancy pants design software that looks at the forces applied to a stem during use and come up with an idealised shape/form of a stem that purely and only manages the forces applied to it through use then you’d come up with a very different shape that will not be easy to manufacture using traditional processes. That is how 3D printing will transform engineering. You’ll see a lot more organic shapes and forms emerging, with thin webs of varying thicknesses where material only exists where it needs to and serves a specific function in the performance of the component.

Yep. I know all that.
BUT, even so…..3-D printing is slow for production purposes.
How long would it take to manufacture a batch of 500 stems using a 3-D printer, compared to traditional techniques…..?
Consider that for a range of stem sizes the only bit that changes is the length of the main tube – so your BOM cost goes down on the faceplate, the steerer tube end etc. because you are buying them in quantities to suit your entire range of stems in that model….all that changes is the cut length of the main tube.

And, there is a reason tubes are used for structural components. They are bloody strong; bd^3/12 and all that.
So, you can fiddle around with intricate features all you want and you might make a stem that is a few percent lighter for a given strength, but it takes you 8 hours to manufacture on a 3-D printer and costs £400 – or you can accept the slight hit in weight & manufacture it using some welded tube.

Don’t get me wrong, I’m not poo-pooing the technology at all, but it needs to be applied to the right applications.
We used it at work recently to make a one off gas flow manifold that we wanted to try. There was no way it could have been done using traditional machining techniques, so we used an additive manufacturing technique (can’t remember exactly what we used; it was a colleague’s project not mine).
But for most of our stuff, 3-D printing wouldn’t be the right tool for the job.