CNC Turning Machining Process: Un guide complet pour la fabrication de précision

In industrial production, why do automotive and aerospace industries rely on CNC tournant for cylindrical parts like engine shafts or fuel nozzles? The answer lies in the CNC turning machining process—a computer-controlled method that transforms raw metal bars into high-precision, uniform components with minimal human error. Contrairement au tournage manuel, which depends on operator skill, CNC turning ensures consistent quality across high-volume runs while handling complex geometries. Cet article décompose 6 core stages of the process, paramètres clés, sélection d'outils, contrôle de qualité, et applications du monde réel, helping you master every step for efficient, accurate part production.

What Is the CNC Turning Machining Process?

CNC Turning Machining Process is an additive-subtractive manufacturing method that uses Computer Numerical Control (CNC) systems to rotate a workpiece while a cutting tool shapes it into cylindrical or conical forms. The process removes excess material from the workpiece (typically metal bars, 5–100mm in diameter) to create features like outer circles, faces d'extrémité, rainures, fils de discussion, ou se rétrécir.

Think of it as a “digital lathe operator”: it follows pre-programmed G-code and M-code to control tool movement, vitesse de broche, and feed rate—executing repetitive tasks with micron-level accuracy (up to ±0.01mm) et 24/7 cohérence. It’s ideal for producing rotational parts, from small electronic connectors to large industrial shafts.

6 Core Stages of the CNC Turning Machining Process

Le processus suit une trajectoire linéaire, error-proof workflow—each stage builds on the last to ensure part quality. Vous trouverez ci-dessous une ventilation détaillée de chaque étape, with actionable tips and common pitfalls to avoid:

1. Analyse des processus (Le fondement du succès)

Process analysis is the first and most critical step—it defines how the part will be machined. Key tasks include:

• Part Drawing Interpretation: Extract critical details from 2D/3D drawings:
• Dimensional requirements (Par exemple, diamètre extérieur: 20± 0,02 mm, longueur: 100MM).
• Surface finish standards (Par exemple, Rampe < 1.6μm for visible areas).
• Type de matériau (Par exemple, alliage en aluminium 6061, acier inoxydable 304).
• Machining Content Selection: Decide which features to machine (Par exemple, trous, fils de discussion, rainures) and their order—follow the “from rough to fine” principle (roughing removes 80–90% of excess material first; finishing refines precision).
• Sequence Optimization: Avoid repositioning the workpiece unnecessarily. Par exemple:

1. Machine the outer circle → 2. Drill the center hole → 3. Cut threads → 4. Finish the end face.

Pitfall to Avoid: Skipping process analysis leads to tool collisions or out-of-tolerance parts. Par exemple, machining threads before drilling a center hole can cause the workpiece to vibrate, ruining thread accuracy.

2. Sélection d'outils (Match Tools to Material & Caractéristiques)

The right tool directly impacts machining efficiency and surface quality. Use this table to select tools based on material and feature type:

Exemple: Machining M8×1.25 threads on a stainless steel 304 shaft → Choose a 16IR 1.25 ISO threading insert with TiAlN coating (resists wear from stainless steel’s high hardness).

3. Réglage des paramètres de coupe (Vitesse d'équilibre, Alimentation, & Profondeur)

Paramètres de coupe (vitesse, taux d'alimentation, profondeur de coupe) determine how fast and accurately the part is machined. Below are optimized parameters for common materials:

Formula Tip: Calculate spindle speed (N, RPM) using N = (1000 × Vc) / (π × D), where D = workpiece diameter (MM). Par exemple, a 20mm aluminum shaft at Vc=180 m/min → N = (1000×180)/(3.14×20) ≈ 2866 RPM.

4. Programmation CNC (Translate Design to Machine Code)

Programming converts process analysis results into code the CNC machine understands. Key codes and a sample program for a simple shaft are shown below:

Sample Program for a 20mm×100mm Aluminum Shaft:

O0001 (Program Number)G21 G99 G97 (Metric units, feed per rev, constant speed)T0101 (Tool 01: External turning; Offset 01)M03 S2800 (Spindle on CW, 2800 rpm)M08 (Coolant on)G00 X25 Z2 (Rapid to start position)G71 U2 R1 (Roughing cycle: depth 2mm, retract 1mm)G71 P10 Q20 U0.2 W0.1 F0.2 (Finish allowance: X0.2mm, Z0.1mm; feed 0.2mm/rev)N10 G00 X18 Z2 (Start of roughing contour)G01 X20 Z0 F0.15 (Cut to Z0)Z-100 (Cut to length 100mm)N20 G01 X25 Z-100 (End of roughing contour)G70 P10 Q20 (Finishing cycle)G00 X100 Z100 (Rapid to safe position)M05 (Spindle off)M09 (Coolant off)M30 (Program end)

Astuce: Use simulation software (Par exemple, Mastercam, Fusion 360) to test programs before physical machining—this avoids tool collisions and overcuts.

5. Serrage de la pièce & Positionnement (Assurer la stabilité)

Proper clamping prevents workpiece vibration (a major cause of poor surface finish). Suivez ces directives:

• Chuck Selection:
• Three-jaw chucks for round workpieces (self-centering, configuration rapide).
• Four-jaw chucks for irregular shapes (adjustable jaws for precise centering).
• Tailstock Support: For long workpieces (length > 5× diameter), use a tailstock center to reduce bending. Par exemple, a 100mm-long, 20mm-diameter shaft needs tailstock support to avoid vibration during roughing.
• Runout Check: Use a dial indicator to measure radial runout (should be < 0.01MM). Excess runout (Par exemple, 0.05MM) causes uneven cutting, leading to out-of-tolerance diameters.

6. Test Cut Inspection & Réglage des paramètres (Validate Before Mass Production)

Never skip test cuts—they let you correct errors before wasting materials. Le processus comprend:

1. Test Cut Execution: Machine 1–2 sample parts using the programmed parameters.
2. Inspection dimensionnelle:

• Use calipers for outer diameters/lengths (accuracy ±0.02mm).
• Use a micrometer for precise measurements (Par exemple, pas de fil, groove width—accuracy ±0.001mm).
• Use a surface roughness tester to check Ra values (ensure they meet drawing requirements).

3. Réglage des paramètres:

• If surface finish is rough (Ra > 3.2μm): Réduire la vitesse d'avance de 20% or increase cutting speed.
• If diameter is too small (Par exemple, 19.98mm instead of 20mm): Increase the X-axis offset by 0.02mm.

Exemple: A test cut aluminum shaft has a diameter of 19.95mm (cible: 20± 0,02 mm). Adjust the X-offset by +0.05mm—subsequent parts will meet the target dimension.

Cas réel: Machining Aluminum Alloy 6061 Arbres

• Problème: An automotive supplier needs 10,000 aluminum shafts (20mm×100mm) avec:
• Diamètre extérieur: 20± 0,02 mm.
• Finition de surface: Rampe < 1.6µm.
• Temps de production: < 2 minutes par partie.
• CNC Solution:

1. Analyse des processus: Brouillage (ap=3mm) → Forage (center hole, φ3mm) → Finition (ap=0.2mm) → Deburring.
2. Outils: T01 (CCMT 09T304 carbide insert), T02 (φ3mm twist drill).
3. Paramètres: Vc=180 m/min, f=0.2mm/rev, N=2866 rpm.
4. Program: Use G71 roughing + G70 finishing cycles (reduces program length by 50%).

• Résultat:
• Précision dimensionnelle: 99.8% of parts meet 20±0.02mm.
• Temps de production: 1.8 minutes par partie (meets target).
• Vie de l'outil: Carbide inserts last 500 parties (reduces tool change time by 80%).

Perspective de la technologie Yigu

À la technologie Yigu, Nous voyons le CNC turning machining process as the backbone of precision cylindrical part production. Our CNC lathes (YG-T200) are optimized for this process: they have high-speed spindles (jusqu'à 6,000 RPM) for aluminum machining, smart tool offset systems (auto-corrects dimensional errors by ±0.005mm), and integrated coolant recycling (reduces waste by 30%). We’ve helped automotive clients cut production time by 35% and aerospace firms achieve ±0.008mm accuracy for critical parts. As Industry 4.0 advances, we’re adding AI-driven parameter optimization—our software now auto-suggests cutting speeds/feeds based on material, reducing operator skill requirements and ensuring consistent quality.

FAQ

1. Q: What’s the difference between rough turning and finish turning in the CNC turning process?

UN: Rough turning removes most excess material (80–90%) at high feed rates (0.15–0.3mm/rev) and large depths of cut (2–5 mm)—prioritizes speed over surface finish. Finish turning uses small depths (0.1–0,5mm) and slow feeds (0.05–0.15mm/rev)—prioritizes precision (± 0,01 mm) et surfaces lisses (Rampe < 1.6µm).

2. Q: How to avoid tool breakage during CNC turning of hard materials like stainless steel?

UN: Use these tips: 1) Choose TiAlN-coated carbide tools (résister à l'usure); 2) Réduire la profondeur de coupe (1–3mm for roughing); 3) Increase coolant flow (cools tool and workpiece); 4) Avoid interrupted cuts (Par exemple, machining grooves in hard spots).

3. Q: Can CNC turning machine non-metallic materials like plastic or wood?

UN: Oui! Pour les plastiques (Par exemple, Pom, Abs), Utiliser l'acier à grande vitesse (HSS) outils (empêche la fonte) and low cutting speeds (50–80 m/moi). For wood, use specialized woodturning tools (Par exemple, carbide-tipped scrapers) and high feeds (0.3–0.5mm/rev)—CNC turning produces smooth wooden parts like handles or decorative spindles.