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3D Printing and Bike Manufacturing

Being more than 100 years old, the bicycle as an invention has remained a vital mean of transportation to this day. In opposition to motor vehicles, bicycles are economical, healthy, versatile and environmentally friendly ways of quickly moving around. Their …

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Alejandro Auerbach

September 25, 2020

Being more than 100 years old, the bicycle as an invention has remained a vital mean of transportation to this day. In opposition to motor vehicles, bicycles are economical, healthy, versatile and environmentally friendly ways of quickly moving around. Their manufacturing techniques have come a long way, but what is the input 3D printing has to offer? In this article, we’ll mainly focus on what 3D printing can do to improve frame designs and manufacturing processes.

Bike Frame Manufacturing

When we’re talking about bicycle design, the essence is without a doubt the frame. The main goal when designing a bike is to get optimal mechanical properties for a given purpose. For example, mountain bikes must deal with impacts and constant cycles of stress, while racing bikes must be as light as possible to achieve high speed. So, deciding which material to use has a significant impact on the bike’s strength-weight ratio. Moreover, manufacturing costs and times are also vital factors.

Most manufacturing processes tend to be by hand; the following are key processes:

  1. Frame dimensioning through a CAD layout.
  2. Tubing selection according to diameters and thicknesses.
  3. Tube bending to get curved shapes.
  4. Tube machining for accomplishing desired lengths, joint matching and surfaces.
  5. Assembling the parts with the help of an adjustable jig.
  6. Joint welding

Steel and aluminium alloys are the traditional materials from which frames are made. Let’s review some details for each one:

Steel: It’s the main engineering material thanks to its versatility when it comes to alloys and manufacturing costs. Steel’s toughness enables the production of firm structures while allowing compliance at the same time. The main advantage of this material is that it’s easy to work with (Machining, bending, welding) and repair when needed. Now for its downside, steel is pretty heavy in comparison to other materials, not to mention its tendency to rust.

Aluminium: If you’re looking for a lighter option than steel, aluminium, which is 1/3 lighter, is an excellent choice. Since it’s not as strong as steel, aluminium’s tubing usually compensate with wider diameters, also it’s more likely to dent.

Full bicycle frame

Aerospace Grade Materials for Bikes

If we have to describe bike culture in one word, it would be customisation. As riders engage deeper into cycling as a hobby, or even as a way of life, looking for adjusting it to one’s specific needs leaves much more space for upgradings or even custom designs from scratch. So, the fact that there’re many manufacturers offering custom services makes complete sense.

The search for high-end possibilities gave rise to the “aerospace-grade” materials: Titanium and carbon fibre. Just as in the actual aerospace industry, bike manufacturers are looking to get optimal performances, but also, enter into a luxury niche (aesthetically speaking). Let’s briefly examine what makes these materials superior in performance when compared to traditional materials, but also why are they so much more expensive.

Titanium Frames

Depending on which alloy we are talking about here, titanium can either be tougher or weaker than steel. Despite the case, titanium has an exceptional strength-weight ratio (Lighter than steel, but heavier than aluminium). Furthermore, it has immunity to corrosion and it’s also cravingly aesthetic. So why are titanium bikes so expensive? Well, more than the material itself, it is the expenses of manufacturing. It requires huge amounts of energy to bend, quickly wears out machining tools and welding it requires specialised control environments and skill.    

Carbon Fibre Frames

They are formally known as carbon fibre reinforced polymer (CFRP). As the name reveals, this material is a combination of very strong strands of carbon arranged inside a resin matrix. In contrast to the other materials, carbon fibre is anisotropic, meaning that its mechanical properties vary according to fibre orientations.

If you properly orient it, this material can be stiffer than steel and, at the same time, lighter than aluminium. Countless possibilities are open for controlling specific mechanical properties thanks to said fibre orientation, fabric layering and fibre-resin ratio.

Manufacturers add other composites for even better performances. Kevlar, for example, can add shock-resistant properties to the frame, which compensates for carbon fibre’s brittleness.

All these complex characteristics that carbon has is something extraordinary, but it’s also this composite’s main drawback; manufacturing carbon fibre parts is in fact extremely labour intensive and time-consuming.

Markforged-Carbonfibre-bike-crank-Material
Markforged Carbon Fibre Bike Crank

3D Printing: Big steps for bike customisation

Perhaps, the main contribution that 3D printing introduced into the manufacturing world is the ability to reproduce effective customisations. And indeed, this article is making emphasis on how valuable is this aspect for bike design. The benefits of additive manufacturing in this industry are proving how far and wide human ingenuity can get.

Design flexibility

Manufacturing titanium and carbon fibre parts is not the headache it used to be now that we can have at our disposition 3D printers. The design flexibility that additive manufacturing provides opens a whole lot of possibilities for complex shapes, reducing production cost and times, and having control over accurate and optimisable digital data.

New paradigms arise on how manufacturing processes can be accomplished, for instance, in assemblies. Welding and assembling bike parts is a tricky aspect of bike manufacturing, mainly because of having to carefully join and align parts while taking into consideration several tolerances, which can lead to many errors. 3D printing has the advantage of consolidating many parts into one while reducing the need for frequent quality inspections. You can even skip the need for an assembly jig in certain conditions.

An exceptional example of this is the Nera E-Bike prototype by BigRep, a company that specialises in printing large parts. For this project, the design team took advantage of all the benefits that additive manufacturing has to offer to create something with new innovative concepts. Nera’s parts are entirely made in a 3D printer (Not counting electronics), but the best part is that its assembly only requires 15 parts!

Now, let’s review some solutions specifically for the “aerospace-grade” materials.

Formlabs Tough 1500 Resin Bike Pedals
FormLabs bike pedal

Titanium Solutions

Manufacturing titanium is a life changer in this industry, typical obstacles related to machining and welding, are gone. But instead, new possibilities like reproducing intricate, optimised, aesthetic and aerodynamic designs. The manufacturing technology of choice for this purpose is Selective Laser Melting (SLM), which not only benefits titanium processes but also more economical materials like aluminium.

Markforged offer a metal 3D printer known as the Metal X which unlike the others on the market uses traditional Fused Deposition Modeling (FDM) to print parts. Specifically they use thier own innovative technology Atomic Diffusion Additive Manufacturing (ADAM) by binding the metal powder in a plastic matrix which is then removed during the debinding and sintering process.

Nowadays, many companies use this advantage to make intricate parts like lugs and crankarms; some, even print the entire frame!

Carbon Fibre Solutions

Explaining what additive manufacturing can do for carbon fibre processes is not a straightforward issue, 3D printing solutions for composites can be endless, and it’s probably just in its infant stage. Nowadays, many 3D printing brands attempt to offer carbon fibre reinforced thermoplastics for FDMs as an alternative to traditional composite presentations.

But one of the main aspects that make composites exceptional materials is the proper continuity and optimal weaving of strands, and this is the issue with composite reinforced filaments. Composite fibres are chopped and distributed within the thermoplastic with no specific order. But some brands, like Markforged, figured ways for solving this issue with Continuous Fiber Fabrication (CFF) technology.

Markforged specialises in composite 3D printing, and one of their biggest successes is their printers wit CFF capabilities. These printers use two extruders, one for the thermoplastic, while the other one places the continuous fibre. Furthermore, their slicer software, Eiger, allows you to have control over the weaving patterns.

CFF is just one of many groundbreaking alternatives for improving composite part manufacturing techniques for bikes. With the design freedom that 3D printing offers, there’re many solutions to properly shape carbon fibre sheets with printed moulds and guides.

markforged-industrial-series-1
Markforged 3D Printer

Innovating and Maintaining

3D printing bike parts is not just about the manufacturing process of the bike itself but also for its maintenance and improvement. If you have an innovative mind and you’re also a cycling enthusiast, then a 3D printer can become a vital tool to create custom upgradings and accessories for your bike. You can even use reverse engineering to make any spare part you might need.

If you’re into biking culture and you have ideas for improving your experience, Solid Print3D is here to help you make it come true. For more information, please call Solid Print3D at 01926 333 777 or email at info@solidprint3d.co.uk

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