Injection Molding vs Blow Molding: How B2B Cases Are Made
B2B cases use injection molding (95% of market) for precision and strength. Blow molding is cheaper but lower quality. Comparison for OEM buyers.
Direct answer: 95% of B2B protective cases use injection molding — high precision, strong walls, repeatable quality. Blow molding is cheaper but has thicker walls (wasted material), weaker corners, and limited color options. Kexin uses injection molding for all 7 series (0系/1系/6系/7系/8系/9系/拉杆) for consistent OEM quality.
Injection Molding Process
PP/ABS/PC pellets heated to 200-280°C, injected under 800-1500 bar pressure into steel mold, cooled 15-60 seconds, ejected. Cycle time: 30-90 seconds per part. Mold cost: USD 5,000-15,000 per case design. Wall thickness: 2.0-4.5mm (controlled). Tolerances: ±0.1-0.2mm.
Blow Molding Process
HDPE/LDPE pellets heated, air-blasted into hollow mold. Cycle time: 60-180 seconds. Mold cost: USD 1,000-3,000. Wall thickness: 3-8mm (variable, thicker at corners). Tolerances: ±0.5-1.0mm. Used for fuel tanks, water containers, low-cost storage boxes.
Why Injection Molding for Cases?
- Precision: ±0.1mm vs ±0.5mm for blow molding — critical for foam inserts, latches, hinges
- Wall thickness control: 2.0-4.5mm consistent vs 3-8mm variable — better impact absorption
- Material choice: PP, ABS, PC, nylon — vs HDPE/LDPE only for blow
- Surface finish: smooth, paintable, printable
- Color options: any Pantone (masterbatch) — vs limited colors for blow
Why Not Blow Molding?
Blow molding saves USD 4-12 per case (no expensive mold, faster cycle, less material). But for B2B: precision matters, IP ratings require controlled wall thickness, foam inserts need ±0.1mm tolerance, defense/military specs mandate injection. Blow molding is for non-critical applications (toys, packaging, fuel tanks).
Tooling Cost Comparison
| Process | Mold cost | Unit cost (500 MOQ) | Unit cost (10,000 MOQ) |
|---|---|---|---|
| Injection (PP/ABS/PC) | USD 5,000-15,000 | USD 18-40 | USD 15-25 |
| Blow (HDPE) | USD 1,000-3,000 | USD 12-20 | USD 8-12 |
FAQ
Can Kexin use recycled material for injection molding?
Yes. rPP and rABS work with injection molding, same precision as virgin. Mechanical properties: 10-15% lower impact resistance. Not recommended for MIL-STD-810H or precision inserts.
What about overmolding (TPU handle over PC shell)?
Overmolding combines two materials in one mold. Kexin offers TPU overmolded handles and latches for soft-touch grip. Tooling cost: +USD 3,000-5,000 per part. Lead time: +5-7 days. Common for premium 8系 cases.
How long do injection molds last?
Steel molds: 500,000-1,000,000 cycles. Aluminum molds: 100,000-200,000 cycles. Kexin uses hardened steel for 1M+ cycles. Molds are Kexin property (not customer's), so customer does not pay for mold storage or replacement.