1. Typical deep-cavity thin-walled parts are shown in Figure 1, and their machining difficulties are as follows:

Figure 1

(1) Poor Tool Rigidity

The deeper the cavity of the part being machined, the poorer the rigidity of the part; the longer the tool extends from the machine tool clamp, the poorer the rigidity of the tool. The tool clamping length is shown in Figure 2. Generally, the tool extension length L should not exceed three times the tool diameter D. For example, if the tool diameter is 10mm, the extension length should ideally be controlled within 30mm. This principle is primarily based on considerations of tool rigidity and cutting stability. An excessively long extension length reduces tool rigidity, increases the likelihood of vibration and deflection, and thereby affects machining accuracy and surface quality.

Figure 2

(2) Cutting Vibration

The thinner the part, the lower its rigidity, making it more prone to phenomena such as vibration and chipping during machining. The cutting edge of the tool is susceptible to chipping, significantly reducing its service life and inadvertently increasing machining costs.

1. Technical Requirements

For rotating deep-cavity thin-walled parts, taking the blisk as an example, dynamic balance must be ensured after machining. Generally, the dynamic balance accuracy of the blisk is selected as grade G6.3 or G2.5. The profile tolerance of the blades is typically required to be ±0.07mm, the blade thickness tolerance is required to be ±0.15mm, and the surface roughness value of the blades is Ra=0.8μm.

1. Product Processing Solutions

During rough machining, the overall rigidity of the blisk is relatively good, and with a unilateral allowance of 1 mm in thickness, the difficulty of rough machining is not significant. However, during semi-finishing and finishing, the blades are largely exposed between each other, resulting in poor rigidity of the blades. Additionally, due to the considerable depth of the blades, the tool clamping length must be sufficiently long to ensure machining reaches the root of the blades, which severely compromises the rigidity of the tool. To address these machining challenges, the following aspects are primarily considered

(1)   An extended slender taper HSK tool holder (see Figure 3) is adopted to minimize tool overhang and enhance tool rigidity.

Figure 3

(2)   When precision machining the blades, apply plasticine (see Figure 4). The plasticine serves as a vibration damping material, absorbing vibrations generated by the ball-nose cutter during the blade cutting process.

Figure 4

（3）Selection of Ball End Tools. A φ10mm four-flute ball end mill with a chisel edge is used, made of carbide, with a cutting edge length of 15mm. The tool's rake angle is approximately 16°, making it relatively sharp, resulting in lower cutting resistance and relatively reduced vibration during operation.

The End

Addressing the machining challenges of deep-cavity thin-walled parts, the process was optimized by refining tool paths and cutting methods. Through physical approaches, the tool's rake angle and the number of cutting edges were appropriately increased to collectively reduce cutting resistance. Additionally, modeling clay was used to wrap the front section of the blade, serving as a vibration-damping measure to decrease blade vibration. This approach successfully resolved the part's machining difficulties and contributed valuable experience.