Airborne Explosion-Proof Box: From Multi-Supplier Risk to 99.5% Batch Qualification Rate

From Prototype Validation to Stable Mass Production for a High-Protection Aviation Battery Box

Airborne lithium battery storage boxes must do more than contain a battery. They need to reduce weight, resist extreme internal heat, protect surrounding equipment, and stay sealed under demanding aircraft installation conditions.

For this project, an aviation equipment customer needed to upgrade an airborne explosion-proof battery box. The product had to be lighter, more refined in appearance, and more reliable than similar products on the market.

The challenge was complex because the part was not made with one process. It required stainless steel sheet metal fabrication, PA material prototyping, injection molding, assembly, sealing control, and full performance testing.

Yijin Solution provided a one-stop manufacturing solution from design optimization and multi-process prototyping to mold development, mass production, and final quality verification. The final product achieved stable batch production with a 99.5% qualification rate, while the full development-to-production cycle was reduced by 30%.

Project Overview

Background: A High-Protection Box With Multi-Process Manufacturing Risk

The customer needed an upgraded explosion-proof storage box for lithium batteries used in airborne equipment. The product had to support aircraft installation, so weight, sealing, fire resistance, and thermal protection were all critical.

The structure included two main components. The inner liner was made from stainless steel sheet metal. The outer shell used PA material and needed to move from 3D-printed prototype samples to injection molded mass-production parts.

In a traditional supply chain, the customer would need to manage several suppliers: a design team, a sheet metal factory, a 3D printing supplier, a mold maker, and an injection molding factory. Each handoff could create delays, drawing misunderstandings, dimensional mismatches, or performance variations.

The customer wanted one manufacturing partner that could manage the full process. They needed a team that could optimize the design, build functional prototypes, test performance, prepare production tooling, and deliver stable batch parts under one workflow.

The Main Issues

1. Too Many Suppliers Increased Project Risk

The product involved sheet metal, 3D printing, injection molding, assembly, and testing. When these processes are split across different factories, communication becomes slow and errors become easier to miss.

A small mismatch between the stainless steel inner liner and PA outer shell could affect assembly, sealing, and final protection performance. For an airborne product, these risks were not acceptable.

2. Lightweighting and Protection Were Difficult to Balance

The customer needed a lighter box, but the product still had to meet strict fireproof, heat insulation, strength, and sealing requirements.

The key requirement was demanding: after a fully charged 300 Wh lithium battery combustion test, the internal structure had to resist temperatures above 1000°C while the outer surface temperature stayed at or below 70°C.

This required more than material selection. It needed structural optimization, heat insulation design, process control, and performance testing.

3. Prototype and Mass Production Consistency Was Hard to Guarantee

The early outer shell samples were made by 3D printing. The final production shells would be made by injection molding.

This created a common risk. If injection molding shrinkage were not considered early, the mass production parts could differ from the approved 3D-printed samples. That could lead to poor fit, sealing failure, or unstable performance after production transfer.

Why the Customer Selected Yijin Solution

The customer selected Yijin Solution because the project required more than a single manufacturing process.

Three capabilities were especially important.

First, Yijin Solution could manage Blechfertigung, 3D-Druck, mold making, injection molding, assembly, and quality inspection in one closed-loop workflow.

Second, our engineering team could optimize the design around weight reduction, heat insulation, sealing, and manufacturability before production began.

Third, the customer only needed to work with one project team. This reduced coordination risk and made it easier to move from prototype testing to stable mass production.

Yijin Solution’s Manufacturing Approach

High-protection aviation enclosures cannot be developed through trial and error alone. The structure, material, process, assembly, and testing plan must be connected from the beginning.

For this project, Yijin Solution built the workflow around four main goals: reduce weight, improve appearance, control heat transfer, and maintain reliable sealing.

1. Design Optimization for Lightweight Structure

The stainless steel inner liner was optimized to reduce wall thickness while keeping the required structural strength.

For the PA outer shell, Yijin Solution adjusted the wall thickness and reinforcement layout to reduce weight without weakening the enclosure. The team also improved the outer appearance with cleaner lines and a grid reinforcement structure.

This helped the product meet both functional and visual requirements for aviation equipment.

2. Fireproof and Heat Insulation Structure Design

To meet the thermal protection target, Yijin Solution designed a stainless steel honeycomb inner liner structure. This structure was combined with a high-temperature insulation layer to reduce heat transfer from the battery combustion area to the outside of the box.

The design was built around the customer’s core test condition: internal resistance to temperatures above 1000℃ and external temperature control at or below 70℃ after a fully charged 300Wh lithium battery combustion test.

Thermal performance was considered during the design stage, rather than treated as a final-stage adjustment.

3. Sealing Structure Optimization

The sealing surface and sealing components were optimized to support long-term protection.

The goal was to meet the customer’s requirement of no water overflow after 30 minutes of movement and 6 hours of standing. The design also had to remain practical for assembly and reliable during repeated use.

Yijin Solution reviewed the sealing structure together with the assembly process to reduce the risk of leakage caused by tolerance stack-up or poor part fit.

4. Prototype Manufacturing With Sheet Metal and 3D Printing

After the design was confirmed, Yijin Solution produced the first functional samples using in-house sheet metal fabrication and 3D printing.

The stainless steel inner liner was made through laser cutting, precision bending, and argon arc welding. The PA outer shell was produced by 3D printing for fast appearance and assembly verification.

Because both processes were completed internally, the team could quickly check the fit between the inner liner and outer shell after assembly. This helped confirm dimensional accuracy, appearance, and structure before moving to production tooling.

5. Performance Testing and Rapid Iteration

The prototype went through a full set of performance checks, including high-temperature fire resistance testing, 300Wh lithium battery combustion heat insulation testing, moving and standing water immersion sealing testing, and total weight verification.

During testing, the team found a minor deformation issue in the handle area under stress. Yijin Solution updated the 3D drawing within two working days by thickening the buckle base by 1.5 mm.

The updated sample was then produced and tested again. Since all key processes were handled in-house, the team did not need to wait for external factory scheduling.

6. Injection Mold Development and Production Transfer

After the prototype met the required standards, Yijin Solution began preparing the PA outer shell for injection molding.

Our mold workshop developed the injection mold in-house. The mold team then worked with our injection molding workshop to complete trial molding and parameter adjustment.

PA material shrinkage can change under different temperature and pressure conditions. To control this, the team completed six rounds of injection molding parameter fine-tuning.

As a result, the key dimensional deviation between the injection molded production parts and the earlier 3D printed samples was controlled within ±0.15 mm.

This helped maintain assembly accuracy and reduce the risk of performance loss during the shift from prototype to mass production.

7. Batch Production and Full-Process Quality Control

During mass production, Yijin Solution used parallel production across the sheet metal line and injection molding line.

The stainless steel inner liner process covered cutting, bending, welding, and surface treatment. The PA outer shell process covered injection molding, dimensional inspection, and assembly fit verification.

After final assembly, samples from each batch were tested for fire resistance, sealing, and weight. This ensured that production parts remained consistent with the approved prototype.

Yijin Solution also provided product testing reports and performance documentation with delivery.

Project Results

1. Fireproof and Heat Insulation Performance Met the Target

The final product met the customer’s thermal protection requirements.

The stainless steel honeycomb inner liner resisted internal temperatures above 1000°C. After a fully charged 300 Wh lithium battery combustion test, the external temperature of the box stayed controlled at or below 70℃.

This helped the product meet the fire safety requirements for airborne installation scenarios.

2. Sealing Performance Passed the Required Test

The enclosure passed the customer’s sealing test.

There was no water overflow after 30 minutes of movement and 6 hours of standing. This made the product suitable for complex airborne operating environments where reliable protection is required.

3. Weight and Appearance Were Improved

The final box achieved the customer’s weight reduction target while maintaining the required strength and protection level.

The reinforced dark outer shell also improved the product’s appearance. The combination of structural ribs and clean industrial styling made the product more suitable for aviation equipment use.

4. Development Efficiency Improved

By working with one manufacturing team, the customer avoided the need to coordinate separate suppliers for design, sheet metal fabrication, 3D printing, mold making, and injection molding.

Communication cost was reduced by 60%. The full cycle from solution design to mass production was shortened by 30%.

This helped the customer move faster from product iteration to onboard verification.

5. Batch Quality Stayed Stable

The batch product qualification rate reached 99.5%.

Sampling results showed consistent performance between the approved prototype and mass production parts. The project avoided common issues such as dimensional mismatch, process transfer deviation, and performance fluctuation.

After customer verification, the product passed onboard testing. The customer later entrusted Yijin Solution with long-term production for this series of explosion-proof battery boxes.

Customer Outcome

This project helped the customer reduce supplier coordination, shorten development time, and move a high-protection aviation enclosure from prototype validation to stable mass production.

Instead of managing separate suppliers for each process, the customer worked with one engineering and manufacturing team from start to finish.

For products that require multiple processes and strict performance control, this approach reduces risk at every stage: design, prototype, testing, mold development, production, and final inspection.

If you are developing a lightweight enclosure, explosion-proof box, or multi-process custom part, Yijin Solution can help review your design, optimize the manufacturing plan, and support the project from prototype to production. Contact us now.

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