Machined Hollow and Thin-Walled Drone Engine Component with 0.02 mm Runout Control

About Product

This product involves the pre-production validation of a critical drone engine component. At this stage, production volumes are relatively low, but rapid design verification and process optimization are essential. The machining process must consistently achieve drawing specifications while maintaining stable anodizing quality and predictable dimensional control after surface treatment.

The part serves as a core structural component within the drone engine assembly. Acting as the front-end mounting and positioning interface, it provides precise alignment, structural connection, and protection for the rotating system. Its dimensional accuracy and geometric consistency directly influence assembly coaxiality, rotor stability, vibration performance, and overall power transmission efficiency.

Part Structure Analysis

The part is a hollow, thin-walled ring structure with uneven wall thickness and weak rigidity areas, making it sensitive to deformation during machining. Key areas include assembly datum and mating surfaces with a strict runout tolerance of 0.02mm.

At the same time, the part has strict requirements for geometric tolerances and dimensional consistency after anodizing. The machining process must not only ensure dimensional accuracy but also take into account the impact of post-processing on structural stability. The overall machining quality directly affects the operational reliability and working condition adaptability of the drone engine.

Key Machining Considerations and Process Solutions

Although the part appears relatively simple in geometry, its hollow, thin-walled structure, stringent runout requirements, and tight post-anodizing dimensional tolerances created multiple manufacturing challenges.

1. Thin-Wall Deformation Control During Turning and 5-Axis Machining

The structural component is a hollow thin-walled structure with an outer diameter of Ø75.635–75.650 mm and an inner bore of Ø26.975–26.990 mm, resulting in an average wall thickness of approximately 24.33 mm. Due to its low overall rigidity, the cutting forces during turning and clamping forces during milling can easily cause radial or localized deformation. At the same time, under a small-batch production model, both machining efficiency and deformation control must be considered, significantly increasing the complexity of process integration.

Solution: Optimized Process Sequencing and Dedicated Fixture Design

A combined process route of “CNC turning (roughing) → stress relief → CNC turning (finishing) → 5-axis milling for features” was adopted.

To address these challenges, the engineering team also optimized the integration of turning and milling processes. A natural aging stress-relief step at room temperature was added after rough turning to effectively release residual stresses generated during machining.

During 5-axis milling, considering the characteristics of the thin-walled structure, a dedicated flexible fixture was designed. Based on the drawing datum, a 6-point uniform clamping method was applied to distribute clamping forces evenly and prevent localized deformation.

In addition, strict control was maintained over cutting forces during both turning and milling, as well as clamping torque throughout the process. These measures systematically reduced deformation risks at the process source.

2. Achieving Stable Runout Control on Critical Assembly Features

The part’s core assembly reference surface and mating end face are critical machining areas with strict runout requirements. The reference surface is only 1.3 mm, which is relatively small, and the runout measurement instrument can only perform single-point detection, unable to conduct multi-point measurements to determine cylindrical runout, inherently introducing significant measurement errors. Coupled with the reference deviation from secondary clamping and the low rigidity of the part’s hollow thin-walled structure, it becomes difficult to accurately control radial and axial runout tolerances during machining.

Solution: Unified Datum Strategy and In-Process Runout Verification

To address the challenges in runout control, the drawing A datum is uniformly used as the sole machining reference for turning and milling, minimizing reference conversion errors. A customized vibration-damping fixture is designed, combined with an on-machine, in-process detection system to enable multi-point runout measurement of the reference surface, allowing real-time monitoring and fine adjustment of the machining status. For the critical mating surfaces, a stepwise process of “rough machining → semi-finishing → stress relief → finishing” is applied, improving runout control capability from the process source.

3. Controlling Post-Anodizing Dimensions Within Tight Tolerances

The structural component requires Type II matte black anodizing, but the AL7075-T6 material exhibits poor anodizing performance. Conventional anodized film thickness is 0.01–0.015 mm (12 ± 4 µm) and uneven, and chemical corrosion during the anodizing process can easily cause dimensional deviations.

In addition, the heat generated during anodizing can induce secondary deformation. The parts’ critical mating dimensions require tight tolerances (0.015 mm), and conventional machining without accurately pre-reserved compensation can easily result in dimensions exceeding limits after anodizing. Ensuring stable and controllable tolerances is especially critical for small-batch production.

Solution: Anodizing Compensation Engineering and Multi-Stage Quality Control

Specialized anodizing tests were first conducted on AL7075-T6 to calibrate stable process parameters, including time, water temperature, and dyeing duration, achieving precise control of the anodized film thickness at 0.010 ± 0.001 mm with uniform coverage. Based on measured corrosion loss data from testing, a dedicated compensation database was established.

For the parts’ critical mating dimensions and key surfaces, the exact anodizing corrosion compensation amount and reserved locations were calculated. During finishing, machining is performed according to “final anodized dimension + compensation”, while pre-treatment processes were optimized to reduce residual stress – induced deformation during anodizing. A three-level inspection process—“final machining inspection → pre-anodizing recheck → full post-anodizing measurement”—ensures that the parts’ critical dimensions meet the 0.015 mm tolerance requirement after anodizing.

Results and Feedback

WayKen successfully delivered these parts with all critical dimensions, runout requirements, and anodized surface specifications achieved. The customer was highly satisfied with the dimensional consistency, deformation control, and overall machining quality of the parts.

From process development and precision machining to surface finishing and final inspection, WayKen provides a complete machining solution for high-precision components. Whether for prototypes, engineering validation builds, or low-volume production, our team can help customers achieve reliable dimensional accuracy, stable quality, and fast project turnaround.