コンテンツへスキップ 
What Is POM Injection Molding and Why Is It So Widely Used?
- POM（ポリオキシメチレン）は、低摩擦で剛性の高いエンジニアリング熱可塑性プラスチックであり、精密部品に最適です。
- ホモポリマーPOMはより高い強度を提供し、コポリマーPOMは加工性が良く、熱安定性に優れています。
- ホルムアルデヒドのガス発生や部品の不良を防ぐため、シリンダー温度は220°C以下に保ってください。
- POMの1.8〜2.5%収縮を管理するために、均一な1.0〜3.5 mmの肉厚で設計します。
- POMの自然潤滑性は、自己潤滑式ギアやベアリングの最適な選択肢となっています。
POM射出成形とは、ポリオキシメチレン（ポリアセタール）を成形するプロセスであり、 engineering thermoplastic1—を精密部品へ成形します。POMは、軽量でありながら金属のような剛性を備えることから、当社では「金属代替プラスチック」と呼んでいます。
If you are comparing vendors or planning procurement, our injection molding supplier sourcing guide covers RFQ prep, qualification, and commercial risk checks.
POM comes in two main types: homopolymer (such as DuPont’s Delrin) and copolymer (such as Celanese’s Celcon or BASF’s Ultraform). Homopolymer POM offers slightly higher mechanical strength and stiffness, while copolymer POM provides better thermal stability and easier processing with less centerline porosity.
The global demand for POM injection molded parts continues to grow, driven by the automotive industry’s push for lighter components and the electronics sector’s need for dimensionally stable housings. POM’s self-lubricating properties make it ideal for moving parts that would otherwise require metal-to-metal contact with added lubricants.
What Are the Key Properties That Make POM Ideal for Injection Molding?
POMを射出成形に理想的とする主要な特性は、このセクションで説明する主要なカテゴリーまたはオプションです。POMは、以下の点で理想的です： 射出成形 それは、高い引張強度（65～70 MPa）、低摩擦（0.20～0.35の摩擦係数）、優れた creep resistance2、および最小限の吸湿性——これらは、当社が加工する最も汎用性の高いエンジニアリングプラスチックの一つであることを可能にする特性です。
| プロパティ | POM Homopolymer | POM Copolymer | 単位 |
|---|---|---|---|
| 引張強度 | 65–70 | 58–65 | MPa |
| 曲げ弾性率 | 2,800–3,200 | 2,500–2,900 | MPa |
| 破断伸度 | 25–45 | 40–75 | % |
| Impact Strength (Izod, notched) | 65–80 | 50–65 | J/m |
| 融点 | 175 | 165 | °C |
| HDT at 1.8 MPa | 110 | 100 | °C |
| Coefficient of Friction | 0.20–0.35 | 0.25–0.38 | - |
| 金型 縮み3 | 1.8–2.5 | 1.8–2.2 | % |
| Water Absorption (24h) | 0.20 | 0.22 | % |
POMを際立たせる特性の一つは、そのクリープ抵抗です。持続的な荷重下で変形する多くのプラスチックとは異なり、POMは高温下での連続応力下でも形状を維持します。当社では、負荷下で10,000時間以上作動するPOM製ギアをテストし、0.3 mm未満の寸法変化を確認しました。
「POMの低い吸湿性は、精密部品用として最も寸法安定性の高いプラスチックの一つとなっています。」真
With only 0.20% water absorption in 24 hours, POM maintains tight tolerances even in humid environments. This is why it’s the go-to material for precision gears, bearings, and instrument housings.
「POMはナイロンのように大量の水分を吸収するため、成形前には常に予備乾燥が必要です。」偽
POM has very low water absorption (0.20–0.22% in 24 hours), far less than nylon’s 1.5–2.8%. While pre-drying at 80°C for 2–4 hours is recommended for optimal surface finish, POM is far less moisture-sensitive than polyamides.
What Are the Optimal Processing Parameters for POM Injection Molding?
最適なPOM成形には、シリンダー温度175～210°C、金型温度80～120°C、射出圧力70～120 MPaが必要です。これらのパラメータを適切に設定することが、完璧な部品と不良品の分かれ目となります。
| パラメータ | Homopolymer POM | Copolymer POM | 備考 |
|---|---|---|---|
| Barrel Temp (rear) | 180–190°C | 175–185°C | Avoid exceeding 220°C |
| Barrel Temp (middle) | 190–200°C | 185–195°C | Gradual increase |
| Barrel Temp (front) | 200–210°C | 190–205°C | Nozzle 5°C lower |
| 金型温度 | 80–120°C | 80–110°C | Higher = better crystallinity |
| 射出圧力 | 80–120 MPa | 70–110 MPa | Adjust for wall thickness |
| 保持圧力 | 50–80% of injection | 50–75% of injection | Critical for shrinkage |
| 射出速度 | ミディアム | Medium to medium-high | Too fast causes off-gassing |
| 背圧 | 5–15 MPa | 5–10 MPa | Minimize residence time |
| 冷却時間 | 15–40s | 15–35s | Depends on wall thickness |
| Drying | 80°C / 2–4h | 80°C / 2–4h | Recommended, not critical |
In our experience, the most common mistake with POM is overheating. When POM degrades thermally, it releases formaldehyde gas, which causes bubbles, splay marks, and a pungent smell. We keep barrel temperatures strictly below 220°C and minimize residence time in the barrel to under 5 minutes.
当社の上海工場では、90Tから1850Tまでの射出成形機47台を稼働しており、複数のPOMグレードを含む400以上の材料を加工しています。この設備範囲により、微小な精密歯車から大きな自動車部品まで、POM部品を成形できます。
Mold temperature plays a crucial role in POM part quality. We typically run molds at 90–100°C for most parts. Higher mold temperatures (up to 120°C) improve crystallinity, surface finish, and dimensional stability, but extend cycle time. For gears and precision components, we always go higher.
What Are Common POM Injection Molding Defects and How to Solve Them?
最も一般的なPOMの不良は、シンクマーク、反り、中心部ボイド、スプレーです。これらは温度と圧力を制御することで防止できます。以下に具体的な解決策を示します。
| 欠陥 | Root Cause | ソリューション |
|---|---|---|
| シンクマーク | Insufficient holding pressure; thick sections | Increase holding pressure/time; reduce wall thickness; add coring |
| 反り | Uneven cooling; differential shrinkage | Uniform wall thickness; optimize cooling channels; adjust mold temp |
| Centerline Porosity | Thick walls; insufficient packing (homopolymer) | Use copolymer POM; increase holding pressure; reduce wall thickness |
| Splay/Silver Streaks | Moisture; thermal degradation | 1.8–2.5 % (流れ方向)、1.6–2.0 % (クロスフロー) |
| Formaldehyde Off-gassing | Overheating above 220°C | Reduce barrel temperature; minimize residence time; purge regularly |
| Brittle Parts | Over-crystallization; contamination | Reduce mold temperature; check material purity |
| フラッシュ | Excessive injection pressure; worn mold | Reduce pressure; repair mold parting surfaces |
当社が特に注意を払うPOM特有の欠陥の一つは、中心部ボイドです。これは主に肉厚断面を持つホモポリマーPOM部品で発生します。外殻が固化・結晶化している間に中心部はまだ溶融状態であり、中心部が収縮する際に内部から引き離されることで内部ボイドが生じます。コポリマーPOMへの変更や、中空化した設計への変更により、ほとんどの場合この問題は解消されます。
What Applications Rely on POM Injection Molded Parts?
POM injection molded parts are found in virtually every industry that demands precision, durability, and low friction. The material’s unique combination of properties makes it irreplaceable in many applications.
Automotive (40% of POM consumption): Fuel system components (fuel sender units, fuel caps), seat belt mechanisms, door lock systems, window regulator gears, HVAC actuator gears, and interior trim clips. We’ve produced fuel rail clips for a major German OEM running 500,000+ cycles without a single failure.
コンシューマー・エレクトロニクス Keyboard mechanisms, printer gears, fan bearings, zipper sliders, and pen mechanisms. POM’s snap-fit capability and spring-back properties make it perfect for clips and latches in electronic devices.
Industrial: Conveyor chain links, pump impellers, valve bodies, bearing bushings, and spring elements. POM’s fatigue resistance handles millions of load cycles in industrial automation equipment.
「POMの自然潤滑性は、外部潤滑なしで作動するギアやベアリングに最適なプラスチックの一つとなっています。」真
POM has a coefficient of friction of 0.20–0.35, one of the lowest among engineering plastics. POM-on-POM and POM-on-metal contact surfaces perform well without lubrication, making it the material of choice for self-lubricating gears, bearings, and sliding mechanisms.
「POMは優れた耐紫外線性を備えているため、屋外用途にも適しています。」偽
POM has poor UV resistance and degrades when exposed to prolonged sunlight. Outdoor POM parts require UV stabilizer additives or protective coatings. For purely outdoor applications, materials like ASA or UV-stabilized ABS are better choices.
医療機器 Inhaler mechanisms, insulin pen components, and surgical instrument handles. Medical-grade POM (FDA-compliant copolymer) provides the precision and chemical resistance needed in healthcare.
Plumbing and Hardware: Faucet cartridges, valve stems, tap handles, and pipe fittings. POM’s resistance to hot water (up to 80°C continuous) and cleaning chemicals makes it ideal for plumbing applications.
How Should You Design Parts for POM Injection Molding?
POM部品の主要な設計ルールは、均一な1.0～3.5 mmの肉厚、0.5°～1.5°の片側抜き勾配、および50～60%のリブ対肉厚比であり、これにより1.8～2.5%の収縮を管理します。 射出成形金型.
| Design Parameter | 推奨値 | Why It Matters |
|---|---|---|
| 壁厚 | 1.0–3.5 mm (uniform) | Prevents sink marks and centerline porosity |
| ドラフト角度 | 0.5°–1.5° per side | POM shrinks onto cores; needs more draft than ABS |
| Rib Thickness | 50–60% of wall | Prevents sink marks on opposite surface |
| リブの高さ | ≤ 3× wall thickness | Taller ribs are hard to fill and eject |
| Corner Radius | ≥ 0.5 mm (0.25× wall) | Sharp corners cause stress concentration |
| Boss OD | 2× screw diameter | Prevents cracking during screw insertion |
| Snap-Fit Strain | ≤ 4% (single use), ≤ 2% (repeated) | POM’s fatigue limit for living hinges |
| Shrinkage Allowance | 1.8–2.5% (flow), 1.6–2.0% (cross-flow) | POM射出成形：アセタール成形の完全ガイド |
当社の設計レビューにおいて、POM部品に関する最大の問題は肉厚の不均一です。肉厚部分と薄肉部分が接合する場合、肉厚部分は冷却が遅れ、収縮差が生じて反りやシンクマークの原因となります。肉厚部分は必ず中空化し、部品全体の肉厚変動を±10%以内に保つことを常にお勧めします。
POM is one of the best plastics for snap-fits and living hinges due to its excellent spring-back properties. However, we recommend limiting strain to 4% for single-use snaps and 2% for repeated assembly/disassembly. For gear teeth, we apply 0.02–0.04 mm per tooth profile compensation for shrinkage to hit AGMA quality grades.
How Does Mold Design Affect POM Part Quality?
POMにとって最も重要な金型設計要素は、ゲートの配置、冷却の均一性、そしてベンティングです。POMの高い収縮率とホルムアルデヒドのガス発生は、精密な金型設計を必須とします。
ゲートデザイン： We prefer sub-gate or pin-gate designs for POM parts because they allow automatic degating and leave minimal witness marks. For gears, diaphragm gates provide the most uniform fill and minimize weld lines in the tooth area. Gate size should be 50–70% of wall thickness.
冷却システム Uniform cooling is critical for POM. Temperature variation across the mold surface should stay within ±5°C. We use conformal cooling channels for complex geometries and beryllium copper inserts for areas that need faster heat extraction. For gears, we often use circular cooling channels that follow the gear profile.
排気： POMは加工中にホルムアルデヒドガスを発生させるため、適切なベンティングが不可欠です。ベントの深さは0.01〜0.02 mmにする必要があります（POMは粘度が低く、深いベントではフラッシュが発生します）。ウェルドラインの位置と金型流動解析で特定された最後に充填される領域のすべてにベントを配置します。
退場： POM’s high shrinkage means parts grip tightly onto cores. We design generous draft angles (0.5°–1.5°), use multiple ejector pins distributed evenly, and sometimes apply mold release coatings to core surfaces. For deep-draw parts, air-assisted ejection prevents vacuum lock.
Frequently Asked Questions About POM Injection Molding
Can POM be painted or plated?
POM has very low surface energy, making it difficult to paint or plate without surface treatment. Flame treatment, plasma treatment, or chemical etching can improve adhesion. However, for decorative parts, we usually recommend switching to ABS or PC/ABS, which accept paint and plating much more readily.
What is the difference between POM homopolymer and copolymer?
Homopolymer POM (like Delrin) offers 5–10% higher mechanical strength and stiffness but is more prone to centerline porosity in thick sections and has a narrower processing window. Copolymer POM (like Celcon or Ultraform) processes more easily, has better chemical resistance, and is less likely to degrade thermally. For most applications, we recommend copolymer.
Does POM need to be dried before molding?
POM’s low moisture absorption (0.20%) means drying is recommended but not strictly required for most applications. We pre-dry at 80°C for 2–4 hours as standard practice to ensure optimal surface quality. For critical cosmetic parts, drying is essential.
Is POM FDA-approved for food contact?
Yes, certain copolymer POM grades (such as Celcon M90 and Hostaform C9021) are FDA-compliant for food contact applications. Always verify the specific grade’s FDA status with the resin supplier before production.
What causes the white residue on POM mold surfaces?
The white deposit is formaldehyde and trioxane oligomers released during POM processing. Regular mold cleaning (every 4–8 hours of production), adequate venting, and keeping barrel temperatures below 215°C minimize this buildup. Some shops use mold-cleaning compounds designed specifically for POM residue.
How does POM compare to nylon for gear applications?
POM is generally preferred over nylon for gears because it has lower moisture absorption (0.2% vs. 2.5%), better dimensional stability, lower coefficient of friction, and more consistent mechanical properties across humidity ranges. Nylon offers higher impact strength and better high-temperature performance. For gears running in wet or humid environments, POM is the clear winner.
What Are the Key Takeaways for POM Injection Molding?
POM injection molding is a proven manufacturing process for producing high-precision, low-friction, and dimensionally stable plastic parts. Whether you’re designing gears for an automotive transmission or clips for consumer electronics, POM delivers the mechanical performance of metal at a fraction of the cost and weight. The keys to success are controlling processing temperatures below 220°C, designing for uniform wall thickness to manage 1.8–2.5% shrinkage, and ensuring adequate mold venting to handle formaldehyde off-gassing.
ZetarMoldでは、自動車、産業用、民生用を含む様々な用途において、20年以上にわたりPOMの加工を手掛けてきました。当社のチームは、DFMレビューや金型設計から量産、品質検査まで全てを担当します。POM射出成形部品を必要とするプロジェクトに取り組んでいる場合、無料のDFMレビューと見積もりのために、当社のエンジニアリングチームまでご連絡ください。総合的な概要については、当社の「射出成形完全ガイド」をご覧ください。
射出成形プロジェクトの見積もりを取得する
Get competitive pricing, DFM feedback, and production timeline from ZetarMold’s engineering team.
Request a Free Quote →
EN 
ES 
FR 
DE 
PT 
AR 
RU 
JA 
KO 
IT 
NL 
TR 
PL 