Cutting strategies for thin-walled parts processed by end mills

When using end mills to process thin-walled parts, the core problems such as easy deformation of the parts, large vibration and poor precision need to be solved through the comprehensive application of tool design, parameter optimization, process control and auxiliary means. The following are the sub-item strategies and key technical points:

First, optimization of tool design

Structural strengthening

Integrated design of tool handle and tool body: Reduces connection clearance and lowers vibration transmission (such as solid carbide tools).

Unequal pitch/unequal helix Angle: By asymmetrically arranging, the cutting force harmonics are dispersed to suppress vibration (for example: helix Angle difference of 5° to 10°).

Core diameter strengthening: Increase the core diameter of the tool body (such as 60% to 70% of the tool diameter) to enhance the bending stiffness.

Geometric parameter optimization

Rake Angle: 10° to 15° for aluminum alloys and 5° to 10° for steel parts, to balance the cutting force and strength.

Relief Angle: 8° to 12°, reducing friction and ensuring the strength of the cutting edge.

Edge treatment: T-shaped edge bands (width 0.05-0.1mm) or rounded edges (R0.02-0.05mm) are adopted to suppress burrs and enhance wear resistance.

Second, control of cutting parameters

Three-directional force balance

Axial force (Fz) control: Reduce the axial load by decreasing the cutting depth (ap≤0.2D, where D is the tool diameter).

Radial force (Fx/Fy) cancellation: By using a symmetrical tool path (such as in helical milling), the radial force directions are reversed to cancel out the deformation.

Parameter recommended value

Material type Cutting speed Vc (m/min) Feed per tooth fz (mm/z) Depth of cut ap (mm) Width of cut ae (mm)

Aluminum alloy: 200-400. 0.05-0.15. 0.1-0.3. 0.5-0.8

Steel parts: 80-150. 0.02-0.08. 0.05-0.2. 0.3-0.6

Dynamic adjustment

Real-time monitoring: The cutting status is monitored through power sensors or vibration sensors. When the limit is exceeded, the speed is automatically reduced or the machine stops.

Thermal compensation: Reserve a margin of 0.02 to 0.05mm for the finishing process after heat treatment to counteract thermal deformation.

Third, process path planning

Layered milling strategy

Equal-thickness layering: The cutting depth of each layer is 0.1 to 0.3mm, and the total cutting depth is ≤0.8 times the wall thickness.

Variable cutting depth layering: The cutting depth of the first layer is 0.1mm (to remove the oxide layer), and the subsequent layers are gradually increased to 0.3mm.

Knife passage method

Helical interpolation: The feed rate is reduced by 30% to 50%, reducing the plunge impact.

Row cutting to ring cutting: After row cutting, a ring cutting smooth knife is added to eliminate the connection marks.

Clamping optimization

Negative pressure adsorption: Vacuum degree ≥-80 kpa, in combination with sealing rubber strips to prevent air leakage.

Low-melting-point alloy filling: The cavity is filled with alloy with a melting point of 60 to 80℃, and then removed by heating after processing.

Fourth, vibration suppression technology

Active vibration reduction

Damping handle: Equipped with high-damping materials (such as tungsten alloy particles), it attenuates vibration energy.

Tuned mass damper (TMD) : Attach a mass block at the end of the tool handle and adjust it to 1/√2 times the natural frequency of the system.

Passive vibration reduction

Length-to-diameter ratio control: The tool overhang should be no more than 3 times the diameter. If necessary, use an extension rod for transition.

Preload optimization: The preload of the main shaft taper hole is increased by 10% to 15% to reduce the fit clearance.

Fifth, quality inspection and compensation

Online detection

Laser displacement sensor: Measures wall thickness changes with an accuracy of ±0.005mm.

Infrared thermal imaging: Monitor the temperature in the processing area and suspend cooling when the temperature exceeds the limit.

Error compensation

Thermal deformation compensation: Establish a temperature-deformation model and correct the G-code in real time.

Force deformation compensation: Predict deformation through finite element analysis and preset the amount of inverse deformation.

Sixth, verification of typical cases

Case: Processing thin-walled frames made of aviation aluminum alloy (wall thickness 1.2mm, contour accuracy 0.05mm)

Tool: φ6mm end mill with unequal pitch, core diameter 4.2mm

Parameters: Vc=250m/min, fz=0.08mm/z, ap=0.3mm, ae=4mm

Result: The surface roughness Ra is ≤0.8μm, the wall thickness tolerance is ±0.03mm, and the vibration amplitude decreases by 60%