CNC加工 vs. 3Dプリンティング vs. 射出成形：正しい製造方法の選び方

CNC これは、選択肢を比較したり、限界を確認したり、リスクの少ないプロセスを選定したりする必要がある場合、実用的な工学上のテーマとなります。.

This cnc machining vs 3d printing vs injection molding comparison guide explains practical material, design, manufacturing, and sourcing considerations for Nylon Plastic readers.

最終更新日2026年4月17日

Choosing between CNC machining, 3D printing, and injection molding is a critical decision that affects cost, lead time, part quality, and production volume. Here’s a practical framework for making the right choice for your project.

Production Volume: The Primary Decision Factor

射出成形： Most cost-effective above 1,000+ units. High upfront tooling cost (USD 3,000-30,000+) but extremely low per-unit cost at scale.

CNC Machining: Ideal for 1-500 units. No tooling cost, fast turnaround, and excellent precision. Per-unit cost is constant regardless of volume.

3Dプリント： Most economical for 1-50 units. No tooling required, design freedom is unlimited, but per-unit cost doesn’t decrease significantly with volume.

素材オプション

CNC Machining: Works with virtually any machinable material — metals, plastics, composites. Full material properties are preserved since parts are machined from solid stock.

3Dプリント： Limited to available filament/resin/powder materials. Some material properties are anisotropic (direction-dependent) due to layer-by-layer deposition.

射出成形： Thousands of material grades available in pellet form. Can mold engineered polymers, glass fiber composites, and metal injection molding powders.

Precision and Surface Finish

CNC Machining: ±0.01mm tolerance capability, Ra 0.8-3.2µm surface finish as machined. Post-processing (polishing, anodizing) available for superior finishes.

3Dプリント： ±0.1-0.3mm typical tolerance. Layer lines visible on most technologies. Some processes (SLA/DLP) offer smoother surfaces.

射出成形： ±0.05-0.1mm tolerance. As-molded surface depends on mold quality; high-polish molds produce mirror-finish parts.

Lead Time Comparison

• CNC Machining: 3-7 days for prototypes
• 3D Printing: 1-3 days for most parts
• Injection Molding: 4-8 weeks including tooling (rapid tooling: 2-3 weeks)

設計の複雑さ

3Dプリンティング offers the greatest design freedom — complex geometries, internal channels, and organic shapes are possible without additional cost. CNC加工 is limited by tool access and undercut restrictions. 射出成形 requires draft angles, uniform wall thickness, and consideration of part ejection.

When to Use Each Method

• CNC Machining: Functional prototypes, low-volume production, tight tolerance parts, metal components
• 3Dプリント： Concept models, complex geometries, small batch functional parts, jigs and fixtures
• 射出成形： High-volume production, cosmetic parts, consistent quality across thousands of units

A Combined Approach Is Common

Many manufacturers use a staged approach: 3D printing for initial prototypes, CNC machining for functional testing, and injection molding for final production. At Nylonplastic, we offer all three services in-house with integrated quality control, allowing you to transition seamlessly between manufacturing methods.