2026-09-21 · KeXinMaterials 編集チーム
ロトモールド vs 射出成形 保護ケース:B2B 製造選択 (2026)
ロトモールドと射出成形は世界中の保護ケースの大部分を生産しています。プロセスは異なるケース形状、表面仕上げ、工具経済、単価を提供します。B2B バイヤーはプロセスを調達プロファイルに合わせる必要があります。
2 つのプロセス、2 つの調達プロファイル
Rotomolding and injection molding are not interchangeable. Each suits specific case geometries and order volumes.
Rotational molding (rotomolding) uses a heated mould rotated on two axes. Powder resin coats the inside of the mould as it rotates, then fuses into a hollow shell. Suits large, complex geometries with uniform wall thickness. Lower tooling cost (USD 5,000-15,000) but longer cycle time (30-90 minutes per part).
Injection molding injects molten plastic into a closed mould under high pressure (1,000-2,000 PSI). Cycle time 30-120 seconds. Suits high-precision, small-to-medium geometries with tight tolerances. Higher tooling cost (USD 8,000-30,000) but very fast cycle time.
The economic crossover: rotomolding wins for low-volume large cases; injection molding wins for high-volume small-to-medium cases.
工具コストとリードタイム
Tooling cost is the dominant upfront decision. Rotomolding tools are cheaper but slower; injection tools are expensive but faster.
For B2B buyers below 500 pieces per SKU, rotomolding is cost-competitive with injection molding at low volumes because tooling cost is lower. Above 2,000 pieces, injection molding wins on cycle time and unit cost.
For complex large cases (>1.5m length), rotomolding is the only practical process. Injection molding cannot produce such large parts in a single shot due to platen size limits.
| Attribute | Rotomolding | Injection Molding |
|---|---|---|
| Tooling cost (single-cavity) | USD 5,000-15,000 | USD 8,000-30,000 |
| Tooling lead time | 25-40 days | 25-30 days |
| Cycle time per part | 30-90 minutes | 30-120 seconds |
| Wall thickness uniformity | Excellent (rotational symmetry) | Good (depends on mould design) |
| Surface finish | Orange peel, matte | Glossy, smooth, textured options |
| Material options | Polyethylene (PE) primarily | PP, ABS, PC, PA, POM, PE, etc. |
| Maximum case size | Very large (3m+ for industrial tanks) | Limited by platen size (typically <2m) |
| Setup / changeover cost | Low (rotomould oven swap) | Higher (injection mould swap) |
| Break-even volume | 500-2,000 pieces | 2,000-10,000 pieces |
| Common B2B applications | Industrial containers, large military cases, kayak hulls | Camera cases, instrument cases, drone cases, medical cases |
プロセス別材料選定
Rotomolding is dominated by polyethylene (PE). Injection molding works with a wider material portfolio.
Rotomolding: 95%+ of cases are polyethylene (PE). PE offers excellent impact resistance, low temperature brittleness resistance, and chemical resistance. PE rotomolded cases are the classic "Peli-style" protective case shell. Material cost USD 1.50-3.00/kg. Wall thickness 3-8mm typical.
Injection molding: works with PP, ABS, PC (polycarbonate), PA (nylon), POM (acetal), and glass-filled variants. PP is the workhorse for protective cases (similar to PE but stiffer). ABS for high-gloss surface finish. PC for high-impact clarity. PA for high-temperature applications.
For most B2B protective case applications (drone, military, medical, instrument), either PE rotomolding or PP/ABS injection molding works. The choice is usually driven by tooling cost and order volume, not material performance.
At KeXinMaterials we run 60+ injection moulding machines. PE rotomolding available via partner factories for large cases. PP + glass-filled PP + ABS standard for injection. PC + PA for premium SKUs.
ケース強度と IP 等級
Both processes can achieve IP67 / MIL-STD-810G. The process choice does not determine the certification.
IP67 rating depends on shell sealing design (O-ring groove + latch compression), not moulding process. Both rotomolded PE and injection-molded PP / ABS can be designed to IP67 spec.
MIL-STD-810G drop test depends on case geometry, wall thickness, and corner radius. Rotomolded cases typically have thicker walls (5-8mm) and uniform corner geometry. Injection-molded cases can have thinner walls (3-4mm) with strategic ribs for stiffness.
In practice, both processes can pass MIL-STD-810G with proper design. The 2010-2020 industry trend has been migration from rotomolding to injection molding for cases < 1.5m, due to lower per-part cost at high volumes and better surface finish for retail branding.
表面仕上げとブランド美学
Surface finish is the most visible difference. Rotomolding gives a matte "orange peel" texture; injection molding gives a smooth glossy or textured finish.
Rotomolding surface: matte, slightly rough, "orange peel" texture. Functional but not premium-looking. Difficult to add gloss or fine detail. Hot stamp logos work but silk-screen printing requires special surface prep.
Injection molding surface: smooth, glossy, can be moulded with texture (leather grain, brushed metal, etc.). Silk-screen printing and hot stamping both work well. UV-cured logos can be in-mould decorated. Higher perceived quality for consumer-facing brands.
For B2B programmes targeting industrial / defence / field service users, rotomolding's matte finish is acceptable and may even be preferred (less glare in field use). For consumer-facing brands (retail, photography, lifestyle), injection-moulding finish delivers premium aesthetics.
単価比較
Unit cost varies with size, material, order volume, and process. Here is a real comparison for representative case sizes.
Small case (300mm × 200mm × 150mm, IP67, 500-piece MOQ): rotomolding USD 65-95, injection molding USD 55-85. Injection wins slightly due to lower cycle time even at low volume.
Medium case (500mm × 350mm × 200mm, IP67, 1,000-piece MOQ): rotomolding USD 95-140, injection molding USD 85-130. Injection wins on cycle time.
Large case (1,200mm × 600mm × 400mm, IP67, 200-piece MOQ): rotomolding USD 250-380, injection molding N/A (too large for platen). Rotomolding wins by default.
Very large case (2,000mm × 1,000mm × 800mm, 100-piece MOQ): rotomolding USD 800-1,400, injection molding N/A. Rotomolding only option.
For 90% of protective cases (drone, military, medical, instrument, camera, tool, trolley), injection molding is the process of choice at volume. Rotomolding dominates large industrial and military cases.
B2B 調達決定
Match the process to your case size, order volume, and brand requirement.
- Small case (under 500mm length), 1,000+ piece MOQ: Injection molding wins. Faster cycle, lower unit cost, premium surface finish.
- Medium case (500-1,200mm length), 500+ piece MOQ: Injection molding if platen size supports it. Otherwise rotomolding.
- Large case (1,200-2,000mm length), any volume: Rotomolding only option. Tooling cost USD 5,000-15,000.
- Very large case (over 2,000mm length), any volume: Rotomolding only. Custom industrial case for military / aerospace / marine.
- Defence / industrial priority (matte finish OK): Rotomolding or injection molding both acceptable.
- Consumer / retail priority (premium finish needed): Injection molding preferred for surface finish and moulded texture options.
なぜ KeXinMaterials を選ぶのか
KeXinMaterials operates 60+ injection moulding machines for cases < 1.2m. We partner with rotomolding factories for larger cases.
For 90% of protective case sizes (under 1.2m), injection molding is our primary process. 60+ machines, 20+ patents, ISO 9001:2015 certified. 100-piece MOQ for custom OEM / ODM, 30-45 day lead time.
For large industrial cases (1.2m+), we partner with rotomolding factories in our supply chain. We handle mould design, project management, quality control, and export shipping. Single-point accountability for B2B buyers.
Material options: PP (workhorse), PE (rotomolding only), ABS (high-gloss), PC (clarity), PA (high-temp), glass-filled PP (stiffness), flame-retardant variants (UL94 V-0 for some applications).
Trade terms: EXW Shenzhen / FOB Shenzhen / FOB Ningbo. No DDP, no EU warehouse, no US warehouse. Every shipment direct from our 13,000 m² Guangdong facility or partner rotomolding facilities.
重要なポイント
- ロトモールド:USD 5K-15K 工具、30-90 分サイクル、大型 / 複雑ケース、PE のみ
- 射出成形:USD 8K-30K 工具、30-120 秒サイクル、中小ケース、PP/ABS/PC/PA
- 両方とも IP67 / MIL-STD-810G 達成可能 — プロセス選択は認証に依存しない
- 損益分岐点:500 個未満でロトモールド / 2,000 個超で射出成形
- 1.5m を超えるケースはロトモールドのみ
よくある質問
ロトモールドと射出成物の違いは何ですか?
ロトモールドは 2 軸で回転する加熱金型を使用します。粉末樹脂(通常 PE)が金型内側をコーティングし、中空シェルに融合してから冷却します。サイクル時間 30-90 分。工具コスト USD 5,000-15,000。射出成形は溶融プラスチック(PP、ABS、PC、PA、PE)を高圧下で閉じた金型に注入します。サイクル時間 30-120 秒。工具コスト USD 8,000-30,000。ロトモールドは肉厚均一の大規模な複雑形状に適し、射出成形は厳しい公差の高精度中小形状に適します。
保護ケースではどちらが安いですか:ロトモールドまたは射出成形?
注文量によって異なります。SKU あたり 500 個未満の場合、ロトモールドは工具コストが低いため競争力があります。2,000 個以上の場合、射出成形はサイクル時間がはるかに短いため勝ちます。中型ケースの 500 個 MOQ の場合、射出成形 USD 85-130 vs ロトモールド USD 95-140。1,000 個以上の場合、射出成形がリードを広げます。1.5m を超える大型ケースの場合、ロトモールドは量に関係なく唯一の実際的な選択肢です。
ロトモールドケースは IP67 と MIL-STD-810G を満たすことができますか?
はい。IP67 等級はシェルシーリング設計(O リング溝 + ラッチ圧縮)に依存し、成形プロセスには依存しません。ロトモールド PE と射出成形 PP/ABS の両方を IP67 仕様で設計できます。MIL-STD-810G 落下試験はケース形状、肉厚、コーナー半径に依存します。ロトモールドケースは通常、肉厚(5-8mm)が厚く、コーナー形状が均一であるため、落下試験に適しています。
ケースのロトモールドと射出成形ではどのような材料が使用されますか?
ロトモールド:95%+ のケースはポリエチレン(PE)です。PE は優れた耐衝撃性、低温脆性耐性、耐薬品性を提供します。材料コスト USD 1.50-3.00/kg。肉厚は通常 3-8mm。射出成形:PP(主力、PE と同様だがより剛性)、ABS(高光沢表面仕上げ)、PC(高衝撃透明度)、PA(高温)、POM(アセタール)、剛性のためのガラス充填変種で動作します。KeXinMaterials では 60+ 台の射出成形機が PP、ABS、PC、PA、ガラス充填 PP を稼働させています。
大型産業用ケースにはどちらが適していますか?
ロトモールドは大型産業用ケースの唯一の実際的なプロセスです。1.5m を超える長さのケースの場合、射出成形のプラテンサイズがシングルショット生産を制限します。ロトモールドは 3m+ の長さのケースを生産できます。一般的な産業用途には、軍用武器ケース、航空宇宙輸送ケース、海軍装備ケース、大型医療機器輸送ケース、産業タンク容器が含まれます。
B2B ケース調達でロトモールドと射出成形をどのように決定しますか?
決定マトリックス:小型ケース(500mm 未満)、1,000+ 個 MOQ → 射出成形。中型ケース(500-1,200mm)、500+ 個 MOQ → プラテンがサポートする場合は射出成形、そうでない場合はロトモールド。大型ケース(1,200-2,000mm)、任意の量 → ロトモールド。超大型ケース(2,000mm 超) → ロトモールドのみ。防衛 / 産業優先(マット仕上げ OK) → 両方許容。消費者 / 小売り優先(プレミアム仕上げ) → 射出成形を推奨。