3D-printed metal bike frame is light but strong

Feb 10, 2014 by Nancy Owano weblog
The entire bike frame was arranged in sections with the seat post bracket on one build plate and fabricated in one go

(Phys.org) —As a bicycle newsmaker, you can file this under 3D-printed projects and you can flag it as a uniquely light yet strong 3D-printed titanium bicycle frame. The frame, announced earlier this month, was manufactured out of a collaboration between two UK companies, Renishaw, a manufacturer of a metal-based additive manufacturing machine that prints metal parts, and Empire Cycles, a bicycle design and manufacturing company. The design is based on Empire's MX-6 mountain bike but optimized. Renishaw leveraged its 3D printed materials and technology process to deliver a light but sturdy frame. The key words in all this are "3d printing" and "metal." Quoted in Dezeen, Chris Williams, managing director of Empire Cycles, noted that while some carbon fiber bikes are light, this 3D printed frame is both light and more robust. "The durability of carbon fiber can't compare to a metal bike," he said.

Renishaw enabled the bike frame to be additively manufactured in in sections and then bonded together to create the titanium alloy frame. Renishaw's notes on titanium alloys point to high Ultimate Tensile Strength (UTS) of more than 900 MPa when processed using , and, the company said,"near perfect densities of greater than 99.7 percent are achieved."

The frame was made according to a process called topological optimization—-This is an approach that optimizes material layout within a given design space, for a given set of loads and boundary conditions so that the result meets performance targets. The implications for 3D printing are mentioned in solidThinking, which said that topology optimization "could be a critical motivator to create industrial designs specifically for additive manufacturing."

Renishaw also described the optimization process:

"Topological optimization software is the term given to programs that are used to determine the 'logical place' for material – normally using iterative steps and finite element analysis. Material is removed from areas of low stress until a design optimized for load bearing is evolved." The resulting model is light and strong. By working together, Renishaw and Empire Cycles were able to eliminate many of the downward facing surfaces that would otherwise have needed wasteful support structures.

Complete bike with 3D printed titanium alloy frame and seat post bracket

According to Renishaw, testing of the completed bicycle frame will continue, both in the laboratory and on the mountainside using portable sensors in partnership with Swansea University. The potential performance has not been completely explored yet, said the company, which hopes to continue to develop the project. "As no tooling is required, continual design improvements can be made easily; and as the component cost is based on volume and not complexity, some very light parts will be possible at minimal costs."

Explore further: Titanium powder used to 3D print automotive parts

More information: www.renishaw.com/en/first-meta… w-for-empire-cycles24154
www.dezeen.com/2014/02/07/worl… inted-bicycle-frame/

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User comments : 23

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antialias_physorg
4 / 5 (4) Feb 10, 2014
They might want to look into one (avian) bone structure. That might be able to shave off even more weight given a certain stability target.

The way it looks they're still only adding/removing material from a solid frame around a central hollow. That is a limitation that is not necessary with 3D printing.

But the approach itself is promising for all kinds of load bearing structures: From bridge supports to girders for buildings.
Doug_Huffman
1 / 5 (1) Feb 10, 2014
Two practical data were missed or avoided, practical for bike geeks; how much mass and how much cost.

Unfortunately Renishaw has designed to a niche (UCI dictated) market rather than to the broader performance market as might be seen Audax/Randonneuring.

The evolved shapes should be effective in most practical materials, that have other advantages than titanium's peculiar lack of reactivity - affordability and ease of fabrication.
laird
5 / 5 (1) Feb 10, 2014
Agreeing with Doug_Huffman, it would be great to know what the cost of printing the bike was, as a basis of comparison. It's likely quite high, but I'd imagine that professional bikers might be willing to pay for a bike completely optimized for their body, and extremely light and strong. Similar to how other exotic bike materials have a niche market.

Beyond that, it sounds like they've come up with software to optimize designs to take advantage of design options that are newly available to additive manufacturing. I can see that benefitting numerous devices, not just bicycles. Imagine if you could print a car that's stronger and lighter than traditional manufacturing, or aircraft. Or who knows - perhaps it could even be applied to traditional manufacturing, to make those designs more efficient?
Eikka
3 / 5 (1) Feb 10, 2014
high Ultimate Tensile Strength (UTS) of more than 900 MPa


The ultimate tensile strenght point refers to the highest point in stress-strain curve where the metal already behaves in a ductile way. You cannot design a part using UTS because the metal deforms irreversibly well before reaching that. Your part would bend.

The meaningful desing point is the yield strenght, which notes the point where the metal still behaves like a spring that returns to shape when the stress is removed.

Example: http://i.stack.imgur.com/kIOJo.png

When stressed beyond the yield strenght, the metal deforms and becomes work-hardened, which increases the yield strenght. Many alloys are very bendy before they are work-hardened by rolling or hammering or drawing etc.

Example: http://pictures.b...g@2x.png

I have yet to hear a good explaination to how 3D printed metals can achieve the same yield strenghts with the same metal alloys without work-hardening the metal.
TheGhostofOtto1923
1 / 5 (3) Feb 10, 2014
The way it looks they're still only adding/removing material from a solid frame around a central hollow. That is a limitation that is not necessary with 3D printing.
It is the birds, not the bicycles, which are limited. Engineers (real ones) know that the most efficient structural members have material located where stresses are best accommodated, which happens to be as far from the axis as is practical.
I have yet to hear a good explaination to how 3D printed metals can achieve the same yield strenghts with the same metal alloys without work-hardening the metal
They cant.
eric_in_chicago
4 / 5 (1) Feb 10, 2014
i see significant amounts of off the shelf parts on the bike... i want one with majority 3d printed parts..heheh

nice frame though.
antialias_physorg
3.7 / 5 (3) Feb 11, 2014
It is the birds, not the bicycles, which are limited. Engineers (real ones) know that the most efficient structural members have material located where stresses are best accommodated,

Well, maybe you should talk to real engineers. Stress is best distributed evenly. And as an article on physorg today points out:
http://phys.org/n...one.html
...real engineers are already looking at such structures.
FainAvis
2 / 5 (1) Feb 11, 2014
@eikka strenght [sic] ->strength
Doug_Huffman
4 / 5 (2) Feb 11, 2014
It is the birds, not the bicycles, which are limited. Engineers (real ones) know that the most efficient structural members have material located where stresses are best accommodated, which happens to be as far from the axis as is practical
Just so. Avian tube stiffening is inefficient. So much for un-Intelligent Design.
Eikka
5 / 5 (2) Feb 11, 2014
@eikka strenght [sic] ->strength


I don't understand what you're trying to say.

Well, maybe you should talk to real engineers. Stress is best distributed evenly.


The best solution is actually a matter of what you're trying to accomplish.

The lightest strongest structure is indeed produced as Otto described - with the materials at optimum distance from the axis of bending or torque. A tubular structure is light because it wastes no material where it's not needed - if you twist a bar of steel, 99% of the torque is carried by the material close to the surface, and the center is just dead weight.

But, the most optimized structure is also the weakest to other loads it is not specifically designed for. You can stand on an empty beercan and the micrometers thick walls will carry you, until someone pokes it with a finger.

So the bulk material is still needed to provide strenght against the unplanned forces, and the question is how to most efficiently provide for that.
TheGhostofOtto1923
2.7 / 5 (3) Feb 11, 2014
Well, maybe you should talk to real engineers. Stress is best distributed evenly. And as an article on physorg today blah
Animal structures are compromised by all sorts of accommodations for interior organs, muscle attachments, circulation, growth, as well as eccentric and distributed loading. Bicycles on the other hand are designed to accommodate loads at specific points on their structure.

STRESS occurs from either point loads, distributed loads, or torsion. Stress from operation is not 'distributed' on a bicycle frame, loads are. Economical design involves tubes which are best at resisting torsion and flexure. There is no need for structure inside a tube whatsoever.

Read a book. Take a course. Stop pretending.
TheGhostofOtto1923
1.5 / 5 (2) Feb 11, 2014
So the bulk material is still needed to provide strenght against the unplanned forces
Cannondale used relatively thin-walled aluminum tubing which was prone to damage from impacts. But riders were willing to live with this as Cannondale frames were the lightest and strongest for the money.

Here is a nice primer on bicycle frame design for software engrs with distorted self-awareness:
http://www.slowtw...ign.html
Jimee
not rated yet Feb 11, 2014
As we learn more, this will be a completely disruptive technology. A bit scary, but on the near horizon.
Doug_Huffman
not rated yet Feb 11, 2014
Beer cans; not even a finger touch is needed. I mass 250# and can stand on a beer can for as long as needed, but crush it with no obvious motion. A fun demonstration for an engineering class. To stand, I evenly distribute my weight with heavy soled boots, to crush I flex a bit, hidden in the catastrophe.

I ride recumbent and now an ICE trike Sprint 26.
TechnoCreed
3 / 5 (2) Feb 11, 2014
To put things in perspective here, printing is mainly reserved for prototypes. This seems to be more of a publicity stunt for 3D technologies than an actual marketable product. But hey, just look at it, it is a mountain bike! In mountain biking the frames are subjected to high impacts and torsion stresses and they usually weigh 12kg and up. So a 1,4kg frame is not an issue.
http://resources....ta=55480
TechnoCreed
5 / 5 (1) Feb 11, 2014
Oops, When I said they weigh 12Kg and up, I meant the whole bike, of course.
TheGhostofOtto1923
3 / 5 (2) Feb 12, 2014
To put things in perspective here, printing is mainly reserved for prototypes.
That was last year.
http://www.strata...n-series

-Please try to keep up.
TechnoCreed
5 / 5 (1) Feb 12, 2014
Well, my comment was not aiming at quality consideration (we have a good appreciation of it here), but at cost mitigation. Printing is not for mass market.
TheGhostofOtto1923
1 / 5 (1) Feb 12, 2014
Well, my comment was not aiming at quality consideration (we have a good appreciation of it here), but at cost mitigation. Printing is not for mass market.
Really. So why are they making production versions of 3d machines?

Direct digital manufacturing is already being used to manufacture dental and orthopedic implants and parts for the aerospace and defense industries.
TechnoCreed
5 / 5 (1) Feb 12, 2014
Really. So why are they making production versions of 3d machines?

Direct digital manufacturing is already being used to manufacture dental and orthopedic implants and parts for the aerospace and defense industries.

That is exactly what I meant, they are costly products for specific needs. Not for mass market.
antialias_physorg
4 / 5 (1) Feb 13, 2014
Not for mass market.

Then again you have to ask yourself: What product WOULDNT you like to be specific to your needs rather than off-the-shelf-standard?

The only reason we have a mass market in many areas is because producing what each person actually needs has, up to now, been vastly more expensive than producing something that is a one-size-does-not-quite-fit-all and telling everyone that that is "good enough".

We have to reevaluate whether a "mass market" is actually something we want to have - now that we have a viable option.

E.g. with bycicles I very much would like one that is tailored to my physique. Atheletes get that but at exorbitant costs per bike. If I could buy one that was completely fit to my specs at, say, no more than 25% additional cost then I'd buy that for sure.
TheGhostofOtto1923
1 / 5 (1) Feb 14, 2014
That is exactly what I meant, they are costly products for specific needs. Not for mass market
So what do you consider 'mass market'? You want steering wheels made this way?

Prosthetics and aerospace parts are billion dollar industries. They are traditionally very labor-intensive and currently employ 1000s of people. They ARE mass market.

"Just five years ago, there were little more than 50 commercially viable examples of 3D printing. But the market is starting to take off, growing at a clip of up to 35 percent annually. It is becoming price-competitive with traditional manufacturing techniques, especially ones for typical defense quantities."
TechnoCreed
not rated yet Feb 16, 2014
So what do you consider 'mass market'?

I guess it is all in the way you look at it. For sure, the technology itself is well positioned for a bright future.