Material Change for Surveying Instrument Base Plate: Trial, Validation and Approval

A material change programme for an aluminium base plate carrying tribrach threads and levelling feet: why the change was needed, how the trial part was machined and tested, and how the new material was validated and approved.

Why the material was reviewed

The original material for an aluminium base plate carrying tribrach threads and levelling feet was either unavailable on a workable lead time or too expensive for the production quantity.

Any change had to keep the part performing exactly as before while still meeting thread accuracy to 5/8-11 with mounting faces flat within 0.02 mm.

Candidate and comparison

We shortlisted alternatives on strength, corrosion resistance, machinability and availability, then machined one trial part from the leading candidate.

Cutting data, tool wear, surface finish and dimensional behaviour were recorded so that the comparison was based on the same evidence as the original grade.

Machining behaviour

The candidate machined differently: different cutting speeds, different chip control and slightly different springback in thin sections.

We adjusted the finishing strategy and tool geometry for those differences rather than forcing the old parameters onto the new material.

Validation

The trial part was measured in full, finished as specified and, where the application required it, tested alongside a part made from the original material.

We supplied the customer with the results, the certificates and a clear statement of what changed and what did not.

Approval and follow-up

The change was approved and the first production batch shipped after 7 working days with the revised material.

We keep both grades qualified where the drawing allows it, which protects the customer against the next supply disruption.

Summary

This programme now runs against an agreed process sheet, and repeat orders are released without a new round of proving.