Analysis of Key Requirements for Injection Mold Process of Energy Storage Battery Wiring Harness Isolation Cover

In energy storage battery systems, wire harness isolation covers, as crucial components ensuring electrical safety, providing insulation, and structural support, are widely used in high-voltage scenarios such as new energy vehicle power battery packs and energy storage container systems. Due to the precision structure, high electrical insulation requirements, and limited assembly space of this component, its injection molding places extremely high demands on mold technology. This article systematically analyzes the core technical aspects of injection molding processes for wire harness isolation covers, including material selection, mold structure design, gate layout, demolding design, and mold temperature control systems.

Injection Molding Process for Energy Storage Wiring Harness Insulation Panels

I. Material Characteristics of Wiring Harness Insulation Panels

Wire harness insulation panels are mostly made of modified PBT, PA66, PP, and other engineering plastics, typically requiring the following characteristics:

High insulation (breakdown voltage ≥ 20kV/mm)

Good heat resistance (heat distortion temperature ≥ 150℃)

Flame retardant rating UL94 V-0

High dimensional stability and low water absorption (<0.3%)

Taking PBT-GF30 (30% glass fiber reinforced PBT) as an example, its flowability is moderate (MFR approximately 10-30 g/10min), and its shrinkage rate is approximately 0.2-0.5%. However, the glass fiber reinforcement introduces anisotropy, making it prone to warping or internal stress. Therefore, the rheological properties of the material, the molding temperature window, and the curing behavior must be comprehensively considered during mold design.

II. Mold Cavity Design and Wall Thickness Control for Wire Harness Isolator Plates

Wire harness isolation plates are mostly thin-walled structures (usually 1.5~2.5mm thick), but some areas, such as fixing clips, isolation ribs, and wire groove positioning areas, need to be thickened. Therefore, the mold cavity must have the following characteristics:

Uniform wall thickness design: Avoid shrinkage marks and cold runner marks caused by sudden changes in local thickness.

Reasonable rib structure: The height of the reinforcing ribs should be ≤ 2.5 times the main wall thickness, and the width should be 0.5 times the wall thickness to avoid excessive thickness leading to filling difficulties or uneven cooling.

Avoid sharp corners: All internal and external corners should have a 0.5~1mm radius to avoid stress concentration and poor material flow.

Multi-cavity design in the same mold (e.g., 2/4 cavity): Strict balanced runner design is required to avoid inconsistent filling between cavities.

III. Gate Layout and Runner System Design for Wire Harness Isolator Plates

Since the cover plate structure is generally over 100mm in size, irregular in shape, and includes slots, reinforcing ribs, and overlay structures, gate design is crucial. Key points include:

Main runners and branch runners should use fully enclosed cold slug wells to prevent cold material from entering the cavity.

Side-mounted or submarine gates are commonly used in cover plate structures, offering advantages such as automatic shearing and concealed gate marks.

Avoid weakened weld lines caused by single-point injection: CAE mold flow analysis is required, with multiple injection points or ring gates placed around ribs and slots.

Appropriate gate size design: Taking PBT-GF30 as an example, a gate cross-section of 3×1.5mm is recommended. Too small a size will result in insufficient filling, while too large a size will cause stringing and warping.

IV. Optimization of the Wire Harness Isolator Demolding System Design

Considering the complex shape of the cover plate and the numerous snap-fit ​​parts, the demolding design must balance efficiency and structural integrity. Key points include:

A combination of angled ejector and side core-pulling structure: suitable for designs with undercut slots. The core-pulling stroke control accuracy must be <0.1mm.

The angled ejector angle should be controlled between 8° and 15° to avoid jamming or insufficient sliding.

**Reasonable Draft Angle Design:** ≥1.5° for external surfaces and ≥2° for internal holes, especially important for glass fiber reinforced materials to prevent surface scratches.

**Ejector Pin Layout:** Evenly distributed ejector pins to avoid concentrated thrust causing part deformation. For larger flat areas, a push-plate structure is recommended.

**V. Precision Temperature Control System for Wire Harness Isolator Molds:**

**The cover plate is relatively thin and sensitive to molding temperature fluctuations, especially in glass fiber reinforced materials where temperature differences can easily cause warping.** Therefore, the mold temperature control system must have the following design features:

**Full-coverage Water Circuit System:** Ensure uniform cavity temperature, especially by enhancing cooling channels in rib areas or areas with dense reinforcement.

**Independent Circuit Control:** For multi-cavity molds or irregularly shaped structures, multiple temperature control units should be used, with a temperature deviation ≤2℃.

**Temperature Control Medium Selection:** A mold temperature controller combined with 85~120℃ water temperature control is recommended. If the material requires high crystallinity, oil heating to above 140℃ is necessary.

** The introduction of rapid cooling technology (such as variable frequency water cooling + high thermal conductivity alloy inserts) can shorten the molding cycle by 15-25%.

VI. Mold Life and Maintainability Requirements for Wire Harness Isolation Plates

Energy storage batteries typically need to meet an IP67 or higher protection rating. As a protective component, the cover plate requires high dimensional accuracy, and the sealing ring groove must be free of burrs. Therefore, the mold life and precision requirements are as follows:

Mold Steel Selection: High-hardness, corrosion-resistant materials such as S136 and H13 are recommended.

Mold Machining Accuracy: Cavity surface roughness Ra < 0.4μm, sealing surface Ra < 0.2μm.

Moving mold and fixed mold guiding accuracy control ≤ ±0.005mm to ensure assembly accuracy.

Regular Maintenance Plan: Clean the mold surface after 5000 injection cycles, and replace easily worn ejector pins and core-pulling sliders after 10,000 cycles.

The injection mold process for wire harness isolation plates requires high precision and necessitates coordinated design across multiple dimensions, including materials, structure, demolding, and temperature control. Through systematic CAE simulation, optimized mold construction, and rigorous temperature control strategies, product consistency and molding efficiency can be significantly improved, ensuring the safety and reliability of energy storage systems. In the future, with the miniaturization and modularization of energy storage devices, the precision molding requirements for separator covers will become even more stringent, necessitating continuous upgrades and intelligentization of injection molding processes. By strictly controlling these key process requirements, Donghao Plastics can produce high-quality, high-performance energy storage battery harnesses and separator covers, meeting customer needs in various application fields and further enhancing its competitiveness.