Material Selection for Aerospace Aluminium Bracket: A Machining Case Study
A material selection case study for a structural bracket machined from 7075-T6 plate: why the original material was reviewed, what it was changed to, what that changed in machining and how the new specification was approved.
The original material
The customer had been producing a structural bracket machined from 7075-T6 plate in a material that met the specification but was slow to machine and expensive to buy.
The requirement on the drawing was 2 mm walls with a profile tolerance of plus or minus 0.05 mm, and any alternative had to meet it without a design change.
Why it was reviewed
Two drivers prompted the review: unit cost at the current volume and a delivery lead time that was affecting the assembly schedule.
We proposed an alternative with similar mechanical properties and better machinability.
Machining implications
The alternative allowed higher cutting speeds, longer tool life and a better as-machined surface finish.
We adjusted feeds, speeds and tool geometry to suit the new material and re-proved the cycle before releasing it.
Testing and approval
Sample parts were produced and measured, and the results were supplied with material certification for the customer's own testing.
The customer validated the parts in its application and approved the change in writing.
Long-term performance
Production has continued on the new material with stable dimensional results and no change to the inspection regime.
The change improved cost and lead time without altering the drawing, which is the safest kind of cost-down.
Summary
Every figure quoted here came from the inspection report supplied with the shipment, not from an estimate made at quotation stage.
