Guidelines For Deformation Control in The Machining Of Power Battery Cover Plates And Aluminum Alloy Components

In the field of power battery manufacturing, key components such as Power Battery Cover Plates, Aluminum Cover Plates for Batteries, Prismatic Lithium Battery Lids, and Lithium-ion Battery Cover Plates extensively utilize thin-walled aluminum alloy structures. Due to the characteristics of aluminum alloys, such as high thermal conductivity, high coefficient of thermal expansion, and insufficient rigidity, deformation is easily generated during the machining of battery casing components such as top lids for prismatic battery cells, aluminum battery box covers, and LFP Safety Cover Sets. This deformation affects sealing performance, matching accuracy, and welding quality.

 

To improve the manufacturing stability of components such as Battery Cover Plates and Copper and Aluminum Bimetal Bipolar Plates, the following systematically summarizes effective methods to reduce machining deformation from the aspects of materials, processes, cutting tools, clamping, and operation techniques.
 

 

Deformation of thin-walled components such as power battery covers, top covers, and terminal blocks mainly originates from three aspects:

1. Relief of Internal Stress in the Blank

Applicable to: Prismatic Lithium Battery Annexe / Lithium Battery Top Cap

Free forging or large extrusion parts generate significant residual stress during the forming process.

As material is removed during cutting, the redistribution of internal stress leads to part deformation.

 

2. Cutting Force and Cutting Heat

The extrusion of material by the cutting tool causes localized heat concentration, exacerbating surface deformation.

This has a particularly significant impact on thin-walled aluminum battery covers.

 

3. Elastic Deformation Caused by the Clamping Method

Unstable clamping can cause uneven stress on the parts.

After loosening the clamp, the parts spring back, leading to dimensional deviations.

 

 

1. Reducing Internal Stress in the Blank

Applicable to: Aluminum Battery Cover Plate / Lithium-ion Battery Cover Plates

The following methods can effectively reduce internal stress and improve dimensional accuracy:

Natural Aging / Artificial Aging: Gradually release stress in the blank under stable conditions.

Vibration Aging: Use low-frequency vibration to accelerate internal stress equalization.

Pre-machining Method: Remove excess material → let stand for a period of time → perform secondary machining to ensure more complete stress release.

 

2. Optimizing Tools and Cutting Parameters

(1) Tool Geometry Selection

A larger rake angle is preferable: It reduces cutting deformation and improves chip removal.

Small clearance angle for roughing; large clearance angle for finishing to balance cutting edge strength and surface quality.

A larger helix angle is preferable: Suitable for high-speed cutting, improving machining stability.

Reduce principal cutting edge angle: Lowers the temperature in the cutting zone, reducing thermal deformation.

(2) Tool Structure Optimization

Reduce the number of teeth and increase the chip groove to improve chip removal efficiency.

Control the cutting edge roughness to Ra≤0.4μm.

Strictly control tool wear to ≤0.2mm to avoid built-up edge formation.

(This tool solution is also applicable to the machining of structural parts such as Copper Pressed Components and Copper and Aluminum Bimetal Bipolar Plate.)

 

3. Enhanced Clamping Structure Design

Applicable to: the top lid for a prismatic battery cell / prismatic battery can cover

Clamping methods that effectively reduce deformation include:

Axial end face clamping: Prevents thin-walled parts from being radially compressed.

Vacuum chuck clamping: Evenly distributed, less likely to cause plate deformation, very suitable for aluminum battery cover machining.

Internal filling method: Inject a fusible medium into the thin-walled part to increase rigidity, then dissolve and pour it out after machining.

 

4. Process Planning and Machining Sequence Optimization

Power battery covers are thin-walled sealing parts, and the scientific arrangement of processes is crucial.

Reasonable Process Flow:

Roughing → Semi-finishing → Corner Clearing → Finishing

Add a second semi-finishing step if necessary to release intermediate stress.

Maintain uniform finishing allowance, generally controlled within 0.2–0.5mm.
 

 

1. Symmetrical Machining to Reduce Heat Concentration

For example, machining an aluminum plate from 90mm to 60mm:

A single cut may cause planar deformation of up to 5mm.

Layered symmetrical cutting can control the deformation to within 0.3mm.

 

2. Layered Machining of Multi-Cavity Structures

Such as LFP Safety Cover Sets or multi-cavity prismatic battery lids

Cannot be machined cavity by cavity, otherwise uneven stress distribution can easily lead to warping;

Multiple cavities need to be machined simultaneously in layers.

 

3. Controlling Cutting Force and Cutting Heat

Reducing the depth of cut, increasing the feed rate, and spindle speed are more suitable for high-speed CNC machining.

Climb milling is recommended for finishing to reduce work hardening and surface stress.

 

4. Optimize Tool Path and Clamping Tightness

Appropriately loosen the clamp before finishing → allow the part to spring back naturally → then lightly press to secure it, which can significantly reduce final deformation.

The clamping force should be as small as possible, and the direction of the force should be reasonable.

 

5. Avoid "straight-down cutting" when machining cavities

It is recommended to drill a tool hole first or use a helical tool path to reduce heat buildup and the risk of tool breakage.

 

 

Applied to the following products: Power Battery Cover Plate / Aluminum Battery Box Cover / Prismatic Lithium Battery Lid / Lithium Battery Top Cap / LFP Safety Cover Set

 

Reducing deformation should be comprehensively controlled from the following aspects:

 

Reducing internal stress in the blank (aging and pre-machining)

Optimizing tools and cutting parameters

Adopting advanced clamping structures (vacuum fixtures, filling methods)

Rationally planning processes and tool path strategies

Operating techniques based on cavity structure and thin-wall characteristics

 

Through these measures, the manufacturing precision, appearance quality, and welding sealing performance of power battery cover plates and related aluminum alloy structural components can be significantly improved, providing a solid guarantee for the safety and reliability of power battery systems.