A Tier 1 EV charging component program — custom flame-retardant TPU compound, monolithic molding and in-house tooling, delivering 500,000+ units a year with a 0% field failure rate.
Key results: 500,000+ units / year · 6 weeks DFM to SOP · 0% field failure rate · 10,000+ tether flex cycles
The Challenge: One Part, No Assembly Points
A leading Chinese NEV manufacturer (Tier 1) needed a charging port dust cover that survives outdoor exposure — UV, temperature swings from -40°C to 120°C, rain and repeated insertions — with one hard requirement: the cover body and anti-loss tether molded as a single monolithic part. Multi-piece assembled covers had failed in the field at the connection points, breaking the IP67 seal and exposing high-voltage charging components to moisture.
The part also had to meet automotive fire safety (UL94 V-0), stay flexible in winter, recover quickly after compression, and carry a premium VDI matte finish with metallic speckle — all at production scale.
The Solution: Compound, Mold and Process Under One Roof
- Custom polyether-based FR-TPU — halogen-free flame retardants dispersed in the polymer matrix: UL94 V-0 without sacrificing elasticity.
- Monolithic design — cap body and tether molded as one piece, eliminating assembly joints and their failure modes.
- In-house Class 101 tooling with ±0.05 mm machining tolerance and multi-point balanced gating to fill thick-to-thin geometry without weld lines.
- Closed-loop cavity-pressure control keeps Cpk high and every batch inside ±0.05 mm.
- VDI fine-grain matte texture with UV-stabilizer speckle, reproduced by controlled mold temperature.
Critical Risks, Engineered Out
Flame-Retardant vs Elasticity
FR additives raise Shore hardness and limit elasticity — the cap needs both a V-0 rating and flexible, quick-recovering sealing. The custom polyether-based FR-TPU compound disperses halogen-free flame retardants in the polymer matrix, holding UL94 V-0 while keeping the seal flexible.
Thick-to-Thin Flow Balance
The thick cap body transitions into a thin anti-loss tether — polymer flow fronts must fill deep ribs and bosses without weld lines or trapped gas. Multi-point balanced gating and closed-loop cavity-pressure monitoring keep fill balanced across the cavity on every cycle.
Texture & Aesthetic Consistency
The metallic-speckled VDI matte finish must match modern EV interior standards — inconsistent mold temperature erases or ghosts the texture. Controlled mold temperature and cavity pressure reproduce the VDI fine-grain texture and UV-stabilizer speckle batch after batch.
Validation: Verified, Not Claimed
| Test | Result |
|---|---|
| Fire safety | UL94 V-0, halogen-free |
| Ingress protection | IP67, validated after thermal aging |
| Tether durability | 10,000+ flex cycles at -40°C to 120°C, no tear at the root |
| Compression set | Recovers in seconds after 72 h compression — IP67 seal maintained |
| Surface | Batch-level friction test on VDI texture; metallic speckle consistent |
| Field results | 0% failure rate in deployment |
The Result: Lower TCO, Zero Assembly Failure Points
Monolithic molding removed the assembly step and its failure points. In-house material compounding and mold making eliminated supply-chain fragmentation — the “Under One Roof” model lowered the customer’s total cost of ownership while keeping 500,000+ units a year within spec, from DFM to SOP in six weeks.
The same material, tooling and process capability is available for your EV charging protection program — port covers, gun covers, seals and custom components.
