レーザー切断 vs Plasma vs Waterjet: Which プロセス for Your Parts?

重要ポイント

• レーザー切断 delivers the best 精密 (±0.05–0.10 mm) on 板金 up to 12 mm thick — ideal for tight-tolerance ブラケット, enclosures, and thin-gauge parts.
• Plasma cutting is the cost-effective choice for thick steel plates (12–38 mm) where ±0.5 mm tolerance is acceptable — structural fabricators’ go-to process.
• Waterjet cutting handles virtually any 材料 (metals, composites, stone, glass) up to 200 mm thick with zero heat-affected zone — the only process for heat-sensitive or mixed-材料 jobs.
• Cost per part follows a clear hierarchy: plasma (lowest) → laser (mid) → waterjet (highest, due to abrasive consumables and slower speeds).
• For the typical DACH/EU industrial buyer sourcing 板金 from China: fiber laser covers 80% of parts. Plasma makes sense above 12 mm. Waterjet is a niche for exotic 材料s and zero-HAZ requirements.

Introduction: Three Cutting プロセスes, Three Different Physics

Ask five engineers which cutting process is “best” and you will get five different answers — because the right answer depends entirely on your 材料, 厚さ, tolerance requirements, and budget. Laser, plasma, and waterjet are fundamentally different technologies:

• レーザー切断 focuses a high-power fiber or CO₂ beam to melt and vaporize 材料 in a narrow kerf.
• Plasma cutting uses an electrically conductive gas (plasma arc) to melt 材料 and a high-velocity gas jet to blow it away.
• Waterjet cutting accelerates water mixed with garnet abrasive to supersonic speeds, eroding 材料 through kinetic energy — no heat involved.

This comparison guide is written for the industrial buyer sourcing from China — someone who needs to decide which process to specify on an RFQ, not someone shopping for a machine. We focus on outsourced manufacturing economics: what each process costs per part, how tight the 公差 can go, and which DFM constraints apply.

精密: When ±0.1 mm Matters

Fiber レーザー切断 is the 精密 champion among thermal cutting processes. Modern industrial fiber lasers (3–6 kW) hold ±0.05 mm on thin sheet (≤3 mm) and ±0.10–0.20 mm up to 6 mm. This is tight enough for most 板金 組立品 without secondary machining — ブラケット line up, enclosures close, bolt holes accept fasteners.

Waterjet comes close — ±0.10–0.25 mm — and actually exceeds laser on 材料s above 25 mm where laser taper degrades edge parallelism. Waterjet also produces zero taper on thick sections because the cutting stream is not conical like a focused laser beam.

Plasma delivers ±0.5–1.0 mm — adequate for structural steel, base plates, and heavy fabrication where bolt holes have generous clearance. If your part has locating dowels, press-fit features, or cosmetic surfaces, plasma is not your process.

最適な用途 tight 公差: Fiber laser on sheet ≤6 mm → ±0.05 mm achievable.
避けるべき場合： your tolerance is tighter than ±0.05 mm — that requires 出荷前に問題を発見します。 as a secondary step after cutting.

厚さ: Where Each プロセス Wins

材料 厚さ is the single biggest factor in process selection. Each cutting method has a “sweet spot” 厚さ range where it delivers the best balance of speed, quality, and cost.

最適な用途 板金 (≤12 mm): Fiber laser — the default choice for 80% of outsourced 板金 parts.
避けるべき場合： your plate is thicker than 20 mm and you are specifying laser — you are paying a premium for a process near its physical limit.

材料 互換性： What Each プロセス Can (and Cannot) Cut

レーザー切断 works on all 一般的な分野dustrial metals: mild steel, ステンレス鋼, アルミニウム, copper, and brass. However, highly reflective 材料s (copper, brass, polished アルミニウム) require fiber lasers with back-reflection protection — older CO₂ lasers can be damaged by reflected beam energy. Thick copper (>3 mm) is challenging even for fiber lasers due to thermal conductivity pulling heat away from the cut zone.

Plasma cutting is restricted to electrically conductive metals only: steel, ステンレス鋼, and アルミニウム. No plastics, no composites, no non-conductive 材料s. This is a hard physical limit — the plasma arc requires a conductive workpiece to complete the circuit.

Waterjet cutting is the universal option — it cuts virtually any 材料: all metals, composites (carbon fiber, G10/FR4), plastics, rubber, stone, granite, glass, ceramics, and even layered 材料s like metal-rubber-metal sandwiches. Because there is no heat, there is no HAZ, no 材料 hardening, and no toxic fumes from plastics or composites. This makes waterjet the go-to process for aerospace composites, armor plate, and food-grade stainless where heat damage or contamination is unacceptable.

Cost Breakdown: Price Per Part Hierarchy

When you are outsourcing cutting work to a Chinese manufacturer, the cost hierarchy is clear and consistent:

1. Plasma — lowest cost per part. Simple machine, low consumable cost (electrodes and nozzles), high cutting speed on thick plate. Ideal for structural steel parts where ±0.5 mm is fine.
2. Fiber laser — mid cost. より高い machine amortization but fast cutting speeds on 板金 (up to 5 m/min on 6 mm steel), low consumable cost (mainly assist gas — nitrogen or oxygen). The workhorse for 板金 in any 厚さ up to 12 mm.
3. Waterjet — highest cost. Slow cutting speeds (0.3–0.8 m/min on 6 mm steel), high consumable cost (garnet abrasive at ~0.5–1 kg/min, plus high-pressure pump maintenance), and significant water treatment overhead. Worth it only when HAZ must be zero or the 材料 cannot be cut any other way.

Rough cost multiples (same part, same 材料): If plasma costs €1 per part, expect laser at €2–3 and waterjet at €4–8. These are ballpark figures — actual pricing depends on part 複雑さ, nesting 効率, batch size, and the shop’s equipment amortization. But the hierarchy holds across suppliers and geographies.

最適な用途 budget: Plasma on thick steel ≥12 mm — you save 50–70% vs laser with acceptable 精密.
避けるべき場合： specifying waterjet for mild steel 板金 ≤6 mm — you are paying 4× the laser price for zero practical benefit.

Speed and Edge Quality: The Trade-Off

Cutting speed and edge quality are inversely correlated — the faster you cut, the rougher the edge. But the baseline quality differs dramatically between processes:

Fiber laser on 6 mm mild steel cuts at 3–5 meters per minute with an edge that typically needs no secondary finishing — smooth, minimal dross, and a narrow HAZ of 0.1–0.3 mm. The cut edge can be painted or powder-coated directly after deburring.

Plasma on the same 6 mm plate cuts at 1.5–3 m/min but produces a beveled edge (typically 1–3° from vertical) and a wider HAZ of 0.5–2 mm that hardens the edge. Structural parts that get welded anyway are fine. Parts with exposed edges usually need a 研削 pass — adding labor cost that can erase plasma’s upfront savings.

Waterjet is dramatically slower — 0.3–0.8 m/min on 6 mm steel — but produces a perfectly square, smooth edge with zero HAZ, zero hardening, and zero dross. The edge is ready for 溶接, 塗装, or 陽極酸化 with no secondary work. For thick sections (>25 mm), waterjet edge quality actually improves relative to the alternatives because it しません develop taper like a laser or bevel like plasma.

Decision Framework: Which プロセス for Your Parts?

Use this step-by-step decision tree to select the right cutting process for your next RFQ:

1. What is the 材料? If it is not metal (plastic, composite, stone, glass, rubber) → Waterjet. End of decision.
2. Is the 材料 thicker than 20 mm? If yes and HAZ is a concern → Waterjet. If yes and HAZ is acceptable → Plasma.
3. Is the 材料 between 12–20 mm? If tight tolerance (±0.2 mm) → Laser. If budget-constrained and ±0.5 mm is fine → Plasma.
4. Is the 材料 ≤12 mm? If you need 精密 (±0.1 mm or better) → Fiber laser. If the part is structural steel with generous 公差 and you are cutting high volume → compare Plasma pricing.
5. Does the part require zero HAZ? (Aerospace, food-grade, medical, heat-treated 材料 that cannot be re-hardened) → Waterjet, regardless of 厚さ.
6. Is the part アルミニウム, copper, or brass? Fiber laser can cut these but slows down and may require back-reflection protection. Plasma handles them well. Waterjet handles them perfectly. Get quotes for both laser and waterjet if 精密 is needed.

実際の事例： A Dutch industrial machinery builder needed 200 ブラケット in 8 mm S355 steel with ±0.3 mm hole positions. They initially specified waterjet “for quality” — quote came back at €18/part. We reviewed the drawing: HAZ was irrelevant (parts got welded and painted), ±0.3 mm was well within plasma capability, and the waterjet premium added €2,400 to the order for zero functional benefit. Plasma delivered the same functional result at €6/part — an €2,400 saving that went straight to the bottom line.

まとめ: Match the プロセス to the Part, Not the Prestige

The most expensive cutting process is the one you do not need. Fiber laser is the right answer for 80% of outsourced 板金 — fast, precise, cost-effective, and available at every serious fabrication shop. Plasma earns its place on thick steel where 公差 are generous and cost matters. Waterjet is the specialist — irreplaceable for exotic 材料s, zero-HAZ requirements, and ultra-thick sections where thermal processes physically cannot compete. The engineer who specifies the process based on the part’s actual requirements — not habit, not “best available” — gets the best parts at the best price.