Innovation watch - Machining titanium components

 

Titanium has a high tensile strength and is light in weight but notoriously difficult to work with. Ed Mason has developed a way to machine the metal and has built a reputation for producing high-end custom-made parts for titanium bicycles.

Left: Finish-machined cranks installed on a mountain bike. Right: Two components designed by Ed Mason – a seat clamp and top cap. Ed custom anodises all the parts he makes in-house

 Ed Mason’s passion is to make things that he has designed himself. After graduating as a mechanical engineer, he gained on-the-job experience with manual machining, fabrication and welding at big UK engineering companies.

At home, Ed started building custom steel bicycle frames, as well as making, assembling, testing, and proving bespoke parts. His aim was to design parts that would be functional, easily serviceable and of high quality. The material he settled on was titanium: it ticked all the boxes he was looking for and has an inherent durability that permits him to make parts that last a lifetime.

Titanium alloys have a high tensile strength, are light in weight and have exceptional corrosion resistance. Ed works with 6-4 titanium, a material that has titanium alloyed with small amounts of aluminium and vanadium, typically 6% and 4% respectively, by weight.

Ed set up his machine shop, Dward Design, in Bath working on subtractive machining and machine-finishing additively manufactured components. He uses subtractive machining to shape titanium billets into custom-made bicycle parts. He applies his industrial CNC machine to fulfil contracts for hi-spec cycle parts that are made into bespoke titanium bicycles for companies such as Sturdy Cycles.

Titanium can’t be welded because of oxygen embrittlement and work-hardens very easily. It also has a thermal conductivity that results in tools heating up when working on the metal. Ed’s machining solutions, after much trial and error, lay in specific tooling and tailormade processes.

Ed’s tooling and cutting methods enable the heat generated in a cut to be carried away in the off-cuts, rather than remaining in the workpiece itself. Using tungsten carbide cutters enables him to achieve a higher cutting speed. He uses a strong coolant concentrate to help lubricate the workpiece, keeping the parts at a constant temperature and preventing thermal growth during machining.

Using a higher-strength material like titanium allows the framebuilder to use smaller diameter tubing for a bike than for an aluminium frame of equivalent weight. Riders say that titanium bikes have a specific ride quality over aluminium and carbon bikes. Ed sees this as a direct result of using smaller diameter tubing to reduce stiffness in targeted areas thereby allowing less of the vibration from the road to be transferred to the rider’s body. The last couple of years have been extremely busy for Ed. Cycling was one of the few activities allowed during the COVID- 19 pandemic and bicycle sales soared. This in turn led to a shortage of bicycles and bike parts in the UK. Lockdowns in countries that make bikes, the shortage of containers and dearth of HGV drivers has meant that the usual sources of bikes, frames and components have narrowed.

Ed does think that the technique he has honed could be other uses for other additively manufactured metals. He says: “I see applications for well-thought-out additive parts in semiconductor processes, where complex parts with organic geometry are required to be placed into pipework containing chemically harsh gases. In fact, any industry that needs strong, light, corrosion-free components like performance automotive and aerospace would benefit.”

Instagram: @dward_design


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