Mitsubishi HC-SFS121B AC Servo Motor — New In Box, Factory Sealed

Condition: Brand New · Original Packaging · Factory Sealed

Part Number: HC-SFS121B

Series: HC-SFS | Compatible Amplifiers: MR-J2S / MR-J3 / MR-J4

Overview

High torque. Low speed. Built-in brake.

The Mitsubishi HC-SFS121B is a 1.2 kW AC servo motor rated at 1,000 rpm — the low-speed, high-torque configuration in the HC-SFS 1.2 kW range. At 1,000 rpm, it produces approximately 11.5 N·m of continuous torque, making it the right choice for applications that need sustained rotational force rather than high traverse speed. The integrated electromagnetic brake adds mechanical position holding the moment power is removed — no external brake unit, no additional wiring complexity.

Shipped new, sealed, and uninstalled in its original Mitsubishi factory carton. No field history. No rework. Every seal intact.

Key Specifications

Low Speed, High Torque — Where It Counts

Most servo motor selections default to the 2,000 rpm or 3,000 rpm variants. The HC-SFS121B exists for the applications where that assumption doesn't hold — where the load demands sustained torque at lower speed, and where spinning faster simply means gearing losses and mechanical complexity with no real benefit.

At 1,000 rpm with 11.5 N·m of continuous torque, this motor is directly suited to:

• Direct-drive and low-reduction-ratio gearbox configurations that can't efficiently step down from a higher-speed motor
• Heavy-load rotary tables and indexing mechanisms that need torque to start and hold position, not speed
• Welding positioners and tilt axes where controlled, steady rotation under load is the core requirement
• Clamping and press axes that operate in short, high-force strokes at moderate speed

Pairing that torque capability with an integrated electromagnetic brake makes the 121B particularly well-matched to vertical or gravity-loaded axes. When power cuts — by design or by fault — the spring-applied brake engages automatically, locking the shaft without drawing current or depending on the amplifier's dynamic brake function.

Built to Last in Real Production Environments

Absolute position, always. The 17-bit encoder retains position data across power cycles. After a restart, an e-stop, or an outage, the servo system knows exactly where the axis is — no homing routine required. In multi-shift operations, that translates directly to faster production restarts.

Sealed against contamination. IP65 shaft sealing is rated to resist water jets and dust ingress at the shaft entry point — relevant in press rooms, grinding cells, and any environment where airborne particulates or coolant mist are a constant presence.

Thermal resilience for long runs. Class F insulation handles higher sustained operating temperatures than Class B equivalents, adding margin in applications running extended duty cycles without dedicated motor cooling.

Cross-generation amplifier compatibility. The HC-SFS121B runs on MR-J2S, MR-J3, and MR-J4 amplifiers. For facilities managing equipment across multiple generations, that compatibility simplifies both spares stocking and system upgrades.

Where This Motor Gets Installed

Rotary Tables & Indexers — Applications where the table carries significant mass and needs smooth, controlled rotation with reliable stop-and-hold behavior between positions.

Welding & Cutting Positioners — Controlled rotation of workpieces during welding or plasma cutting, where speed consistency under varying load affects weld or cut quality.

Vertical Lift & Z-Axis Drives — Axes where a mechanical brake on power loss is a fundamental safety requirement, not an optional feature.

Injection Molding Clamping Axes — Clamping mechanisms that apply sustained force at low speed during the hold phase of the molding cycle.

Conveyor & Transfer Systems — Inclined or vertical conveyor drives where the load must be held in place when the system is stopped or powered down.

Frequently Asked Questions

Q1: What does the "B" suffix mean in HC-SFS121B?

A: It indicates the motor includes a built-in electromagnetic brake. The brake is spring-applied and electrically released — it engages automatically when power is cut, holding the shaft in position without requiring a separate brake module or external wiring.

Q2: How is the HC-SFS121B different from the HC-SFS122B?

A: Both are 1.2 kW motors with an integrated brake. The HC-SFS121B is rated at 1,000 rpm with approximately 11.5 N·m continuous torque. The HC-SFS122B runs at 2,000 rpm with roughly half the continuous torque. The 121B is the correct choice when the application needs high torque at low speed; the 122B suits faster axis traversal at moderate load.

Q3: Which servo amplifiers are compatible with this motor?

A: The HC-SFS121B is compatible with Mitsubishi MR-J2S, MR-J3, and MR-J4 series servo amplifiers. Confirm the amplifier's rated output matches the motor's 1.2 kW / 200V specification, and ensure the brake power supply connections are correctly configured in the amplifier wiring.

Q4: Is the electromagnetic brake suitable for dynamic stopping?

A: No. The built-in brake is a holding brake — designed to lock the shaft when the motor is stationary, not to stop a rotating load. Using it as a dynamic brake accelerates wear significantly. Dynamic deceleration should be handled by the servo amplifier; the mechanical brake engages only after the axis has come to a stop.

Q5: What does "New In Box, Factory Sealed" mean for this listing?

A: The motor has never been powered on, installed, or field-tested. It remains in its original Mitsubishi packaging with all factory seals and documentation intact — the same condition it left the production facility in. No refurbishment, relabeling, or reconditioning has taken place.