Inverse tolerance design method of thin-walled blades in multi-stage machining process

The design tolerances of thin-walled blades in each machining stage are essential for the final machining accuracy. Currently, the tolerances for the finishing stage are usually directly specified by designers, while tolerance design for the intermediate stages relies mainly on machining experience and existing tolerance grade standards. However, due to the significant machining error accumulation effect of thin‑walled blades, conventional intermediate stage tolerance design methods often cause the final machining accuracy to exceed the design tolerance requirements, with non‑conformance rates in actual production reaching as high as 20%–40%. To address this issue, this paper proposes an inverse tolerance design method specifically tailored to the multi-stage machining process of thin‑walled blades. Taking aero‑engine high‑pressure compressor blades as an example, compared with the conventional empirical method, the proposed method tightens the roughing stage upper tolerance limit from 0.25 mm to 0.1399 mm (44.04% tightening) and the semi‑finishing stage upper limit from 0.10 mm to 0.0667 mm (33.30% tightening). In 15 validation experiments, all blades met the design tolerances (100% qualification) versus about 60% for the conventional ISO method. The method integrates an error propagation model based on Gaussian process regression with the Harris Hawks Optimization (HHO) algorithm for backward recursive tolerance design. The case study fully verifies the effectiveness and engineering practicality of the method. This is the first experimentally validated inverse tolerance design method specifically targeting the intermediate manufacturing stages of thin‑walled blades.