材料選定は通常、CNC 部品のコスト、重量、被削性、最終性能に影響を与える最大の単一決定です。本ガイドは ADFCNC が日々加工している材料と、それぞれの適用先 — 工場の現場視点で執筆 — を解説します。
How to think about material choice
Most material decisions can be reduced to four questions, in order:
- Mechanical requirements — yield strength, fatigue, stiffness, weight target, operating temperature.
- Environment — corrosion, chemicals, UV, food/medical contact, sterilisation cycles.
- Machinability and cost — how fast it cuts, how much the bar stock costs, what tooling wear to expect.
- Finishing and downstream processes — does it anodise, plate, weld, paint, glue?
Aluminium alloys — the workhorses
Aluminium dominates CNC work because it cuts fast, takes a beautiful surface, anodises in any colour, and weighs a third as much as steel. For most consumer and industrial parts, the question is which aluminium alloy, not whether to use aluminium.
| Alloy | Yield (MPa) | Best for | Trade-off |
|---|---|---|---|
| 6061-T6 | 276 | General-purpose: housings, brackets, fixtures | Moderate strength; most common |
| 6063-T5 | 215 | Extruded profiles, decorative anodised parts | Softer; slightly worse machined finish |
| 7075-T6 | 503 | Aerospace, motorsport, structural | Harder to machine, less corrosion resistant, anodises poorly |
| 2024-T351 | 345 | Aerospace skin, fatigue-loaded parts | Susceptible to stress corrosion; usually clad |
| 5052 | 193 | Marine, sheet-metal-style folded brackets | Lower strength but excellent corrosion resistance |
| MIC-6 / cast tool | 170 | Vacuum chucks, optical bases, tooling plates | Stable but heavy; rarely used for end-use parts |
Carbon and stainless steels
When strength, fatigue resistance or corrosion in aggressive environments matters, steel is the answer. Three families cover almost everything we machine:
Carbon & alloy steels
- 1018, 1045 — cheap, weldable, easy to machine. Good for shafts, jigs, low-stress brackets.
- 4140, 4340 — pre-hardened or heat-treatable to ~50 HRC. Used for gears, drive shafts, tool holders.
- Will rust without coating — plate, paint or oil.
Stainless steels
- 303 — free-machining, but worse corrosion resistance and not weldable.
- 304 — the default food/marine grade.
- 316L — superior corrosion resistance, medical-implant grade.
- 17-4PH — precipitation-hardened, ~40 HRC, aerospace and pumps.
- 15-5PH — similar to 17-4 with better transverse properties.
For surface treatment of steel parts, see our surface finishing services — passivation for stainless, black oxide for tool steel, electroless nickel for carbon steel.
Titanium and superalloys
Titanium and nickel superalloys are the answer when no other material works — typically aerospace, medical implants, downhole oil tools and high-end motorsport.
| Material | Strength | Density (g/cm³) | Typical use |
|---|---|---|---|
| Ti-6Al-4V (Grade 5) | 895 MPa | 4.43 | Aerospace structural, bicycle frames, surgical implants |
| CP Titanium (Grade 2) | 275 MPa | 4.51 | Chemical processing, marine |
| Inconel 718 | 1240 MPa | 8.19 | Jet engine hot section, downhole tools |
| Inconel 625 | 760 MPa | 8.44 | Marine seawater, chemical processing |
| Hastelloy C-276 | 690 MPa | 8.89 | Worst-case chemical environments |
| Monel 400 | 241 MPa | 8.80 | Seawater, hydrofluoric acid |
Brass, bronze and copper
Copper-based alloys are niche but indispensable for electrical, plumbing and decorative work.
- C360 brass (free-machining). Cuts like butter, ideal for valves, fittings, electrical components and decorative hardware.
- C932 bearing bronze. Self-lubricating; bushings, gears, marine fittings.
- C110 (oxygen-free copper). Best electrical and thermal conductivity; bus bars, heat sinks, RF.
- Beryllium copper (C17200). Springs, non-sparking tools, EMI gaskets — but requires careful handling due to dust hazards.
Engineering plastics
CNC-machined plastics fill applications where metal is too heavy, too conductive or too expensive. Sheet stock and extruded rod are routinely turned and milled to ±0.05 mm tolerances.
| Material | Strengths | Watch out for |
|---|---|---|
| Delrin / POM | Low friction, dimensional stability, machines cleanly | Difficult to glue; weak in UV |
| Nylon (PA6, PA66) | Wear resistance, gears, bushings | Absorbs moisture and grows ~2% |
| PTFE (Teflon) | Chemical inert, very low friction, –200 to +260°C | Soft, creeps under load |
| Polycarbonate (PC) | Optical clarity, impact resistance | Scratches easily; chemical sensitive |
| Acrylic (PMMA) | Optical clarity, easy to polish | Brittle, not for impact |
| PEEK | Aerospace/medical, –60 to +250°C, autoclavable | Very expensive (~$300/kg bar stock) |
| UHMW-PE | Wear resistance, chemical inert, food-safe | Difficult to machine to tight tolerance |
For micro-features in plastics — sub-millimetre walls, optical surfaces — see our micro-machining services.
Materials at a glance
A condensed reference for selecting a starting material based on your top requirement:
| Top requirement | Start with | Upgrade path |
|---|---|---|
| Cheap and good enough | 6061 aluminium | 7075 → 17-4PH |
| Strength-to-weight | 7075 aluminium | Ti-6Al-4V |
| Corrosion resistance | 316L stainless | Hastelloy C-276 / Monel |
| Wear resistance, low friction | Hardened 4140 + DLC coat | Tool steel (D2, A2) |
| Heat resistance (>500°C) | Inconel 625 | Inconel 718, Waspaloy |
| Electrical conductivity | C110 copper | Silver-plated copper |
| Thermal conductivity (heat sinks) | 6061 aluminium | C110 copper |
| Optical clarity | Acrylic (PMMA) | Polycarbonate |
| Food contact / sterilisation | 316L stainless | PEEK for plastics |
| Magnetic permeability needed | 1018 carbon steel | 4140 hardened |
| Non-magnetic (MRI rooms) | 316L stainless or Ti | Beryllium copper |
Material × finish compatibility
The chosen surface finish often constrains the material. Always check both before locking the design:
| Finish | Compatible materials | Not compatible |
|---|---|---|
| Type-II anodising (decorative + protection) | 6061, 6063, 5052 | 7075 (poor cosmetic finish) |
| Type-III hard anodising | 6061, 7075, 2024 | 5xxx series (some grades) |
| Bead blasting | Most metals and plastics | Anything that must remain optical |
| Powder coating | Aluminium, steel, stainless | Plastics (heat-sensitive) |
| Electropolishing | Stainless 316L, 304 | Carbon steel |
| Black oxide | Carbon and tool steels | Stainless (only specific grades) |
| PVD coating | Stainless, tool steel, carbide | Aluminium (substrate softens at coating temp) |
Read more about specific finishes in surface finishing and PVD coating.
よくあるご質問
- アルミ 6061 が圧倒的。バー材が安価で、速く切削でき、あらゆる標準仕上げを受け入れます。ADFCNC の産業用作業の約 70％ は 6061 です。
- ほとんどは可能ですが、異なる工具で。チタンとニッケル系スーパーアロイは遅い切削速度と鋭い工具が必要です。マグネシウムは特殊な消火対策が必要です。
- 実用上：Ti-6Al-4V は疲労を含めると 7075 アルミをわずかに上回ります。純粋な引張強度対重量では現代のカーボンファイバー複合材が勝ります。
- アルマイトの色は合金、浴の化学、時間に依存します。同一バッチ = 良好な一致。異なるバッチ = 若干の変動。クリティカルな作業は単一バッチで処理する必要があります。
- 部品が湿気、塩、化学物質に継続的に晒される場合はステンレス。乾燥した屋内環境では亜鉛メッキ／塗装炭素鋼が遥かに安価です。
- 多くの場合いいえ。3D プリントされた Ti-6Al-4V 部品は CNC 加工されたものとは異なる材料グレードです。認証された航空宇宙や医療作業では、別途認定なしには代替できません。CNC vs 3D プリント比較を参照してください。
- はい — 一般的な合金 (6061、7075、304、316L、Ti グレード 5、Delrin、PEEK) を在庫しており、完全な材料試験報告書 (MTR) と適合証明書と共に特殊材料を調達できます。
最も安価な CNC 加工材料は？
同じ機械ですべての材料を加工できますか？
最高の強度重量比を持つ材料は？
アルマイト処理アルミはバッチ間で色が揃いますか？
ステンレスかメッキ鋼か？
3D プリント材料は CNC 加工と互換性がありますか？
ADFCNC は私のために材料を調達できますか？
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CNC Machining Services
Multi-material CNC service across aluminium, steels, titanium, brass, and engineering plastics.
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Upload CAD — engineers review material choice and machinability.
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著者について
ADFCNC Engineering Team
Senior CNC Application Engineers
Our application engineering team brings 15+ years of combined experience producing precision components for aerospace, medical, robotics and industrial automation customers.
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