L’industrie manufacturière compte deux poids lourds: fabrication soustractive (couper du matériel) et fabrication additive (construire couche par couche). Tous deux transforment les matières premières en pièces, mais ils fonctionnent de manière opposée, chacun avec des atouts uniques pour différents projets. Que vous fabriquiez un support métallique, un prototype en plastique, ou un outil médical complexe, choisir le mauvais peut faire perdre du temps, argent, ou ruiner les performances de votre pièce. This guide breaks down their differences, uses real-world cases to show how they work, and gives you a step-by-step way to pick the right one.
D'abord: What Are Subtractive and Additive Manufacturing?
Before comparing them, let’s get clear on what each process does. They’re opposites, and that’s why their uses vary so much.
Fabrication soustractive: “Cutting Down to Size”
Subtractive manufacturing starts with a solid block, plate, or rod of material (comme l'aluminium, acier, ou en plastique) and removes excess material to shape it. Think of carving a statue from a stone block—you take away what you don’t need until you get the design you want.
The most common subtractive method is Usinage CNC, which uses computer-controlled tools (exercices, moulins, tours) to cut with precision. Other subtractive processes include laser cutting (for 2D shapes), découpe au jet d'eau (for tough materials like metal), et GED (for tiny, detailed cuts).
Caractéristique clé: Relies on “removing” material—so the final part’s strength comes from the original solid material (no weak layers).
Fabrication additive: “Building Layer by Layer”
Fabrication additive (better known as 3D printing) builds parts from the bottom up, stacking thin layers of material (poudre, filament, or liquid resin) until the design is complete. Imagine stacking sheets of paper to make a 3D cube—each layer sticks to the one below.
Popular additive methods include:
- FDM (Modélisation des dépôts fondus): Uses plastic filament (like PLA or ABS) melted through a nozzle.
- SLS (Frittage sélectif au laser): Uses a laser to fuse nylon powder into parts.
- mjf (Fusion multi-jets en nylon HP): Uses liquid agents and heat to bond nylon powder.
- GDT (Fusion laser sélective): Uses a laser to melt metal powder (for metal parts like titanium implants).
Caractéristique clé: Relies on “adding” material—layers can create complex shapes, but they may leave weak spots between layers (called anisotropy).
Side-by-Side Comparison: Key Differences That Matter
To choose between them, you need to compare their performance on the factors that affect your project: coût, vitesse, options matérielles, et plus. The table below breaks down the critical differences (data from manufacturing industry studies and real-world quotes):
| Facteur | Fabrication soustractive (par ex., Usinage CNC) | Fabrication additive (par ex., 3D Impression) |
| Material Range | Wide—metals (aluminium, acier, titane), plastiques, bois, verre, pierre, mousse. | Limited—mostly plastics (nylon, PLA, ABS), some metals (titane, steel via SLM). |
| Résistance de la pièce | High—solid material means parts are isotropic (strong in all directions). No layer weaknesses. | Medium—parts are anisotropic (weaker along layer lines). SLM metal parts are strong but costly. |
| Precision/Tolerance | Very high—tolerances as tight as ±0.025 mm (great for tight-fit parts like gears). | Lower—tolerances down to ±0.1 mm (SLM/DMLS is better, but still not as tight as CNC). |
| Complexité | Best for simple-to-moderate shapes (trous, fils de discussion, surfaces planes). Struggles with hollow/lattice designs. | Best for complex shapes (treillis, intérieurs creux, organic curves). Can make designs CNC can’t. |
| Vitesse (Petits lots: 1–10 pièces) | Slower—setup takes time (sélection d'outils, machine programming). A metal bracket takes 2–4 hours. | Faster—no setup beyond uploading a CAD file. A plastic bracket takes 1–2 hours (FDM/MJF). |
| Vitesse (Grands lots: 100+ parties) | Faster—setup costs are spread over more parts. 100 metal brackets take 8–12 hours (CNC). | Slower—each part is built layer by layer. 100 plastic brackets take 20–30 hours (mjf). |
| Coût (Petits lots: 10 parties) | Higher—setup fees (\(50–)200) plus material waste. 10 aluminum brackets cost ~$150 total. | Lower—no setup fees, moins de déchets matériels. 10 plastic brackets (mjf) cost ~$80 total. |
| Coût (Grands lots: 100 parties) | Lower—setup fees spread out. 100 aluminum brackets cost ~$500 total. | Higher—layer-by-layer printing adds time/material costs. 100 plastic brackets (mjf) cost ~$600 total. |
| Déchets de matériaux | High—50–70% of raw material is cut away (chips/scraps). Some can be recycled, but most is waste. | Low—only uses material needed for the part. 3Impression D (SLS/MJF) reuses 50%+ of unused powder. |
| Post-traitement | Minimal—parts often have smooth finishes. May need sanding or polishing for aesthetics. | Required—parts have layer lines or loose powder. Needs cleaning (for SLS/MJF) or sanding (pour FDM). |
Real-World Cases: When to Use Each (And Why)
Numbers tell part of the story—but real projects show how these differences play out. Let’s look at three examples where the choice between subtractive and additive made or broke the project.
Cas 1: Metal Automotive Brackets (Large Batch)
A car parts supplier needed 500 aluminum brackets for a new SUV model.
- Additive Option (GDT): Each bracket would cost \(12 (metal powder is expensive), plus \)200 for setup. Total: \(12×500 + \)200 = $6,200. Délai de mise en œuvre: 2 semaines (layer-by-layer printing is slow for large batches).
- Subtractive Option (Usinage CNC): Each bracket cost \(5 (aluminum block is cheap), plus \)300 for setup. Total: \(5×500 + \)300 = $2,800. Délai de mise en œuvre: 3 jours (CNC is fast for repeatable parts).
Résultat: The supplier chose CNC machining—saved $3,400 and got parts 11 days faster. The brackets needed to be strong and fit tightly (tolerance ±0.05 mm)—CNC’s precision was perfect.
Cas 2: Custom Medical Surgical Guides (Petit lot)
Besoin d'une clinique dentaire 5 custom surgical guides (nylon PA12) for implant surgeries. Each guide had to fit a patient’s unique jaw shape (complexe, organic design).
- Subtractive Option (Usinage CNC): The complex shape would require custom tools (\(1,000 installation) et 10 hours of machining per guide. Total: \)1,000 + (\(50×5) = \)1,250. Délai de mise en œuvre: 1 semaine.
- Additive Option (mjf): No setup fees—just upload the patient’s 3D scan. Each guide took 2 hours to print. Total: \(30×5 = \)150. Délai de mise en œuvre: 2 jours.
Résultat: The clinic chose MJF—saved $1,100 and got guides 5 days faster. The guides didn’t need ultra-tight tolerances (±0.1 mm was enough), and MJF’s ability to make complex shapes was critical.
Cas 3: High-Temperature Engine Part (Métal, Petit lot)
An aerospace startup needed 3 titanium engine parts that could handle 600°C heat. The parts had a hollow interior to reduce weight (complex design).
- Subtractive Option (Usinage CNC): Titanium is hard to cut—tools would wear out fast (\(800 installation) and take 8 hours per part. The hollow interior would need extra steps (drilling from both sides). Total: \)800 + (\(100×3) = \)1,100. Délai de mise en œuvre: 5 jours.
- Additive Option (GDT): SLM melts titanium powder into the complex shape—no extra steps. Each part took 4 hours to print. Total: \(200×3 = \)600. Délai de mise en œuvre: 3 jours.
Résultat: The startup chose SLM—saved $500 and got parts with the exact hollow design they needed. SLM’s metal parts are strong enough for high heat, and the small batch made additive cost-effective.
Étape par étape: How to Choose Between Them for Your Project
Follow these 4 simple steps to pick the right process—no guesswork needed.
Étape 1: Define Your Project’s Core Needs
Start by asking:
- What material do you need? (Métal? Plastique? Bois?)
- How many parts do you need? (1–10? 100+?)
- How complex is the design? (Simple holes? Complex lattices?)
- What tolerance do you need? (±0,025 mm? ±0,1 mm?)
Exemple: If you need 200 steel brackets (simple design, tolerance ±0.05 mm), your core needs are “metal, large batch, simple shape, tight tolerance.”
Étape 2: Match Needs to Process Strengths
Use this cheat sheet to narrow down:
| Core Need | Best Process |
| Metal parts, large batch, simple shape | Soustractif (Usinage CNC) |
| Plastic parts, small batch, complex shape | Additive (MJF/SLS/FDM) |
| Metal parts, small batch, complex shape | Additive (GDT) |
| Wood/glass/stone parts (any batch) | Soustractif (CNC/Waterjet) |
| Tight tolerance (±0,025 mm) (any material) | Soustractif (CNC) |
Étape 3: Calculate Total Cost (Don’t Forget Hidden Fees)
Cost isn’t just per-part price—include setup fees, déchets matériels, et post-traitement:
- Soustractif: Add setup fees (\(50–)500) et déchets matériels (50–70% of raw material cost).
- Additive: Add post-processing costs (\(2–)10 per part for cleaning/sanding) et, for metal, higher material costs.
Exemple: 50 plastic parts (nylon PA12):
- Soustractif: \(2 par pièce + \)100 installation + \(50 material waste = \)250 total.
- Additive (mjf): \(3 par pièce + \)30 post-processing = $180 total.
Additive is cheaper here.
Étape 4: Test with a Prototype (If You’re Unsure)
If you’re on the fence, make a single prototype with both processes (if budget allows). Test the prototype for strength, ajuster, and finish—this will tell you which process works better for the final batch.
Tip: For plastic prototypes, use FDM (cheap, rapide). Pour les prototypes métalliques, use SLM (if complex) or CNC (if simple).
Yigu Technology’s Perspective on Subtractive vs. Fabrication additive
Chez Yigu Technologie, we don’t force one process—we match it to your project’s goals. For clients needing large batches of metal parts (comme les supports automobiles) or wood/glass components, we recommend CNC machining for its speed and cost savings. For small batches of complex plastic parts (like medical guides) or intricate metal parts (like aerospace components), we use 3D printing (MJF/SLM). We also help with prototypes: FDM for quick plastic tests, CNC for precise metal fits. Our team calculates total costs (installation, déchets, post-traitement) upfront, so you never have surprises. For us, the best process is the one that makes your part well, on time, and within budget.
FAQ
1. Can I use additive manufacturing for metal parts instead of subtractive?
Yes—but only if you have a small batch or complex design. GDT (impression 3D métal) makes great complex metal parts, but it’s 2–3x more expensive than CNC for large batches. For simple metal parts (like bolts) or batches over 50, CNC is cheaper and faster.
2. Is additive manufacturing always better for complex shapes?
Almost always—additive can make hollow lattices, organic curves, and internal features that CNC can’t reach. The only exception is if the complex shape can be split into simpler parts that CNC can make, then assembled. Par exemple, a complex plastic housing might be cheaper to CNC as two parts and glue together than to 3D print as one.
3. Which process produces less waste?
Additive manufacturing is far more efficient—SLS/MJF reuse 50%+ of unused powder, and FDM uses only the filament needed for the part. Subtractive manufacturing wastes 50–70% of raw material (chips/scraps), even with recycling. If sustainability is a priority, additive is the better choice.