Automotive Prototyping


We were asked to machine the prototypes of large, aluminium battery trays developed for a new electric SUV. Lightweight is a critical demand of all Electric Vehicles but that comes with its own set of problems as tolerances are tighter and demands more complex as parts become smaller, thinner and more structural. 

Being structural components battery cages are a particular issue as, being large, they are a principal target of lightweighting whilst battery design is constantly seeking to increase power densities, by incorporating more batteries, at the expense of structural support. 

As with all prototypes, the time frame was exceptionally tight.


The OEM had designed a battery tray which formed a part of the vehicle 

approximately 1m in length and 0.6m in width with wall thicknesses of 3mm. As with all automotive work tolerances were exacting because of the requirement for aesthetics and the need to dovetail perfectly with the rest of the assembly. 

We were also required to develop a machining strategy for production of the component. A machining strategy encompasses everything from programming and tool selection to operations and fixturing.

Initial Challenges Faced

The tight tolerances were made more demanding by the twisting/ distorting of the component in the heat treating process. No single component were alike and to achieve a balance or at least a happy medium would test our fixture design skills.

Selecting the correct tooling was particularly difficult within the given time frame as high quality form and speciality tooling takes time to source. As the final product was heat treated there was a high level of wear on tooling.

Fixturing for this item was a challenge due to datum specifics on all 5 different operations. And getting specialist fixturing made and designed within the time frame was an impossibility if normal avenues were used. 

Specific Challenges Faced

Deforming of cast part within cast tolerance but not within the allowable machining tolerances. This in turn caused an overlapping of material preventing the true datum’s required to be achieved. 

The twisting and or flexing of the component prevented true machining surfaces to be mis aligned making components unusable at its design and cast stage. Due to this twist, references between all 5 sides to datum were unachievable.

Solutions Presented

A combination of both modular and insert type fixturing were manufactured. Each part would almost be an individual datum setup. This fixture design allowed us to easily set each part up based on the inconsistency of the component with ease using a multiple datum shift probing strategy. 


The EV battery cage has become a huge learning experience for us and has underpinned other work we have been able to do for a number of other EV companies. This is an area that continues to develop and one in which we believe we have made some serious contributions to machining knowledge.