Mitsubishi M80 Built-IN Spindle Motor SJ-2B6704TK

🔧 Mitsubishi SJ-2B6704TK – Description

The SJ-2B6704TK is a Mitsubishi Electric SJ-B Series built-in spindle motor used in CNC machine tools for high-torque, precision spindle drive applications. It is designed to be mounted directly inside the machine spindle, enabling a compact and rigid machining structure.

⚙️ Key Description

• Series: SJ-B Built-in Spindle Motor
• Type: Dual-coil built-in spindle motor (low-speed / high-speed winding)
• Application: CNC machining centers, heavy-duty milling and turning machines
• Drive compatibility: MDS-D2-SP-320 spindle drive unit

⚡ Functional Characteristics

• Supports coil changeover operation:
  • Low-speed coil → high torque cutting
  • High-speed coil → finishing / high RPM machining
• Designed for stable torque delivery under heavy load
• Suitable for continuous industrial operation with oil-cooled spindle systems

📊 Key Performance Overview

• Power output:
  • Continuous rating: 15 kW (low-speed coil) / 22 kW (high-speed coil)
  • Short-time rating: 22 kW (30 min) / 30 kW (30 min)
• Torque:
  • Continuous: 302 N·m / 175 N·m
  • Short-time: 442 N·m / 239 N·m
• Speed range:
  • Low-speed coil: ~475 r/min base
  • High-speed coil: up to 6000 r/min

🧩 Mechanical & Construction Details

• Rotor inertia: ~0.37 kg·m²
• Motor mass: ~83 kg (stator), ~49 kg (rotor)
• Stator diameter: ~Ø299.5 mm
• Rotor inner diameter: ~Ø130 mm
• Cooling: Liquid/oil cooling via spindle jacket required
• Cooling flow: ~15 L/min typical requirement

🏭 Typical Applications

The SJ-2B6704TK is commonly used in:

• CNC vertical machining centers (VMC)
• Heavy-duty metal cutting machines
• High-load industrial spindle systems
• Production machining requiring stable torque at low speed

⚠️ Summary

Compared to similar models (like SJ-2B6721TK), the SJ-2B6704TK provides slightly higher torque capacity and inertia, making it better suited for heavier cutting loads and stronger spindle stability, while still supporting high-speed finishing operations.