There are many causes of deformation in aluminum part machining, which are related to material properties, part geometry, and production conditions. The main factors include: deformation caused by residual stress in the blank, deformation induced by cutting forces and cutting heat, and deformation due to clamping forces.

Process Measures to Reduce Machining Deformation

Reducing Residual Stress in Blanks

Natural or artificial aging, as well as vibration treatment, can partially eliminate residual stresses in blanks. Pre-machining is also an effective method. For bulky blanks with excessive stock allowance, post-machining deformation tends to be significant. By pre-machining to remove excess material and balance stock allowance, subsequent machining deformation can be reduced. Additionally, allowing the pre-machined blank to rest helps release residual stresses.

Improving Tool Cutting Performance

Tool material and geometric parameters significantly influence cutting forces and heat generation. Proper tool selection is crucial for minimizing part deformation.

Optimizing Tool Geometry

Rake Angle:

A larger rake angle (while maintaining edge strength) enhances cutting sharpness, reduces chip deformation, improves chip evacuation, and lowers cutting forces and temperatures. Negative rake angles should be avoided.

Clearance Angle:

The clearance angle directly affects flank wear and surface finish. For rough milling with heavy loads and high heat, a smaller clearance angle improves heat dissipation. For finish milling, a larger clearance angle reduces friction and elastic deformation.

Helix Angle:

A higher helix angle ensures smoother milling and reduces cutting resistance.

Lead Angle:

A smaller lead angle improves heat dissipation and lowers average cutting zone temperatures.

 

Enhancing Tool Structure

Reducing Teeth Count & Increasing Chip Space:

Aluminum’s high plasticity demands larger chip pockets. Tools with fewer teeth and wider gullets are preferred.

Precision Edge Honing:

The cutting edge roughness should be below Ra = 0.4 μm. Lightly honing new tools with a fine stone removes burrs and micro-serrations, reducing heat and deformation.

Strict Wear Control:

Tool wear increases surface roughness, cutting temperature, and part deformation. Wear limits should not exceed 0.2 mm to prevent built-up edge. Workpiece temperature should stay below 100°C to avoid distortion.

Optimizing Workpiece Fixturing

For thin-walled aluminum parts with low rigidity:

Axial Clamping for Bushings

Radial clamping (e.g., 3-jaw chucks) causes post-machining deformation. Instead, use a threaded mandrel inserted into the part’s bore, secured axially with a endplate and nut to maintain precision during OD machining.

Vacuum Chucks for Thin Plates

Uniform clamping force distribution paired with light cuts minimizes distortion.

Filling Method

Fill hollow parts with a low-melting filler (e.g., urea-potassium nitrate melt) to enhance rigidity during machining. Dissolve the filler post-process in water/alcohol.

Strategic Process Sequencing

High-speed machining with large stock or interrupted cuts may induce vibration. A typical CNC process flow:

Roughing → Semi-finishing → Corner Cleaning → Finishing

For high-precision parts, repeat semi-finishing before final passes. Post-roughing natural cooling relieves stresses. Leave 1–2 mm stock after roughing; maintain 0.2–0.5 mm uniform allowance in finishing to ensure stability, reduce deformation, and achieve high surface quality.

Operational Techniques to Minimize Machining Deformation

In addition to the aforementioned causes, operational methods play a crucial role in controlling deformation during aluminum part machining.

Symmetrical Machining for Large Stock Parts

For better heat dissipation, use alternating symmetrical machining. Example: A 90mm plate machined to 60mm achieves 0.3mm flatness when processed in alternating passes versus 5mm with consecutive machining.

Layered Machining for Multi-cavity Parts

Machine all cavities layer-by-layer simultaneously to ensure uniform stress distribution, preventing deformation from uneven forces.

Optimized Cutting Parameters

Adjust depth of cut (ap) with corresponding feed rate and spindle speed increases in CNC high-speed milling to balance productivity and reduced cutting forces.

Strategic Tool Path Selection

Use conventional milling for roughing (maximum removal rate) and climb milling for finishing (better surface quality with progressive chip thickness reduction).

Thin-wall Fixturing Technique

Before final passes, briefly release and reapply minimal clamping force to allow natural recovery, applying force along the part’s most rigid direction.

Cavity Machining Method

Avoid direct plunging; pre-drill or use helical entry paths to prevent chip packing and tool breakage.

結(jié)論

Aluminum part deformation stems from material properties, geometry, and processing conditions, primarily involving?blank residual stresses,cutting forces/heat,and clamping stresses.The integrated application of these process optimizations and operational techniques significantly reduces deformation, enhances precision and surface quality, providing reliable technical support for production.