Mitsubishi M80 Built-IN Spindle Motor SJ-2B6721TK

🔧 Mitsubishi SJ-2B6721TK – Description (SJ-B Series Built-in Spindle Motor)

The SJ-2B6721TK is a high-capacity built-in spindle motor from Mitsubishi Electric’s SJ-B series, designed for CNC machine tool spindles where high torque at low speed and high stability under load are required.

It is a dual-coil (low-speed / high-speed) integrated spindle motor, used directly inside the machine spindle structure for compact, rigid, and high-performance machining systems.

⚙️ Key Description

• Series: SJ-B Built-in Spindle Motor
• Type: Dual winding (coil changeover: low-speed & high-speed)
• Application: Heavy-duty CNC machining centers, milling machines, high-load spindle systems
• Drive unit: Typically used with MDS-D2-SP-320 spindle drive

⚡ Functional Characteristics

• Designed for high-torque cutting at low speed
• Switchable operation between:
  • Low-speed coil → high torque rough machining
  • High-speed coil → finishing operations
• Built for continuous industrial duty with high thermal stability

📊 Key Performance Overview

• Power output:
  • Continuous: 18.5 kW (low-speed coil)
  • High-speed coil: 22 kW class
  • Short-time (30 min): 22 kW / 30 kW range
• Torque:
  • Continuous: 353 N·m (low-speed coil) / 140 N·m (high-speed coil)
  • Short-time: 420 N·m / 191 N·m
• Speed range:
  • Low-speed coil: 500–1500 r/min
  • High-speed coil: up to 6000 r/min

🧩 Mechanical & Construction Data

• Rotor inertia: ~0.283 kg·m²
• Motor mass: ~70 kg (stator), ~35 kg (rotor)
• Stator diameter: Ø299.5 mm
• Rotor inner diameter: Ø145 mm
• Frame length: ~390 mm (compact compared to similar models)

🌡️ Cooling & Operation Requirements

• Cooling type: Liquid cooling (oil jacket system required)
• Cooling capacity: ~5.2 kW heat dissipation requirement
• Flow rate: ~15 L/min
• Thermal class: Class F (155°C insulation system)

🏭 Typical Usage

The SJ-2B6721TK is commonly used in:

• Heavy-duty vertical machining centers (VMC)
• Large CNC milling machines
• High-load metal cutting operations
• Industrial production lines requiring stable spindle torque