Mitsubishi HC-SFS52BG1H Servo Motor — 500W | Brake + High-Precision Gearhead | 17-Bit Absolute Encoder | MELSERVO J2S

Not every servo axis is a simple point-to-point move on a flat surface. A significant share of real industrial applications — rotary tables, vertical clamping axes, angular positioners, inclined slides — place three hard requirements on the drive: adequate output torque at reduced shaft speed, mechanical holding between moves, and angular positioning accuracy that doesn't drift over time. The HC-SFS52BG1H addresses all three in a single factory-assembled unit: 500W HC-SFS medium-inertia motor, spring-applied electromagnetic brake, and G1H high-precision gearhead, shipped and mounted as one integrated assembly.

Specifications at a Glance

Why This Configuration Exists — and What It Solves

A 500W servo motor running at 2,000 rpm produces 2.39 Nm of continuous torque at the shaft. That figure is right for many applications, and entirely insufficient for others. A rotary table carrying a 30 kg fixture, a clamping cylinder pushing against significant spring-back force, a vertical ballscrew axis holding its own weight — these all require torque that the motor alone cannot deliver.

The G1H gearhead changes that equation. Gear reduction multiplies output torque proportionally to the gear ratio while dividing output speed by the same factor. A 1/20 ratio, for example, delivers up to 47.8 Nm of continuous torque at the gearhead output shaft — from the same 500W motor body. The machine gets the force it needs without stepping up to a larger, heavier, more expensive drive class.

What makes the G1H the right gearhead rather than the standard G1 is backlash control. Standard G1 general industrial gearheads are built for broad industrial use where some angular play at the output shaft is acceptable. G1H high-precision units are built to a tighter specification, with reduced backlash that carries the encoder's 131,072 ppr resolution effectively through to the gearbox output shaft. For index tables and angular positioning fixtures where degrees or fractions of a degree define part quality, that difference matters directly.

The electromagnetic brake completes the picture. A gearhead multiplies holding torque just as it multiplies driving torque — but only if the motor shaft is physically locked. Between moves, during power-down, at emergency stop: the brake holds the entire assembly at whatever position the servo last commanded, without servo current, without the amplifier being active.

The Brake: Fail-Safe by Design

The HC-SFS52BG1H brake is spring-engaged and electrically released. Apply 24V DC to the coil, the spring compresses, the shaft turns freely. Remove the voltage for any reason — intentional shutdown, power failure, safety circuit trip, emergency stop activation — the spring re-engages instantly and the shaft locks.

This is the fail-safe configuration that most machine safety standards require for vertical axes and gravity-loaded mechanisms. The brake does not depend on controller logic or amplifier availability to hold position; it holds by default and requires active energy to release.

Installation note: the brake coil requires a dedicated 24V DC supply wired to the motor's brake connector. This circuit is independent of the servo amplifier — the MR-J2S-60A and MR-J2S-60B amplifiers do not supply brake power directly. The 24V source and its interlock wiring must be included in the machine electrical design.

17-Bit Absolute Encoder — No Homing at Startup

The built-in encoder counts 131,072 positions per motor shaft revolution across the full multi-turn range, with the count retained through power-off cycles by a Mitsubishi A6BAT backup battery installed in the servo amplifier. Every startup — shift change, maintenance shutdown, emergency stop and recovery — the machine knows where it is without a homing sequence.

In a system with a G1H gearhead, this capability has added value: the output shaft position is fully determined from the motor encoder reading across all gear ratio configurations. No additional output-side feedback device is needed to know where the gearhead output shaft stands.

Compatible Amplifiers: MR-J2S-60A and MR-J2S-60B

The 60-series J2S amplifiers are the rated match for the HC-SFS52 motor family.

MR-J2S-60A — accepts pulse-train (differential or open-collector) or analog command input. Position, speed, and torque control modes are all supported. Setup via MR Configurator software over RS-232C or RS-422. Standard choice for PLC-based motion systems, standalone CNC applications, and any host that outputs pulse/direction commands.

MR-J2S-60B — SSCNET interface for Mitsubishi multi-axis motion controller systems (Q172D, Q173D, A172SHCPUN series). All axes share the synchronous SSCNET bus, enabling electronic gearing and coordinated multi-axis moves with tight inter-axis timing. Right choice for systems with multiple servo axes on a single Mitsubishi motion controller.

Gear Ratio Options and Selecting the Right Configuration

The G1H gearhead on the HC-SFS52B is offered in multiple ratio options — typically 1/5, 1/9, 1/12, 1/15, 1/20, and 1/25. Each ratio produces a different part number within the HC-SFS52BG1H family. When replacing an existing unit, the gear ratio must be confirmed from the original machine documentation or the gearhead nameplate before ordering. Installing a different ratio produces incorrect output speed and torque, and may cause motion profile errors or mechanical collision.

Output torque increases with ratio; output speed decreases proportionally. Motor speed at rated output torque is always 2,000 rpm regardless of ratio — the gearhead divides that speed to produce the required output rpm.

Where the HC-SFS52BG1H Gets Specified

Precision rotary index tables on machining centers — the G1H gearhead controls index angle accuracy; the brake locks the table during cutting; the absolute encoder eliminates the startup homing run on every shift change.

Vertical ballscrew axes with gravity loading — the brake prevents axis drop at power-down; the gear-multiplied torque handles the holding requirement without continuous servo current; IP65 motor protection handles the coolant environment.

Workpiece fixture tilting and angular positioning axes — tilted fixtures hold position at arbitrary angles, requiring both brake authority and gear-multiplied torque to resist gravity torque loading at all positions.

Automated welding positioners — headstock drives on positioners require precise angular indexing between weld passes, with the workpiece locked during welding without servo current.

CNC 4th-axis drives (A-axis, B-axis) — medium-power 4th axis applications on vertical machining centers, where 130mm motor body size, 500W power class, brake holding, and IP65 are all standard specification points.

HC-SFS52 Variant Summary

All variants share the same 500W output, 17-bit encoder, oil seal, and IP65 motor housing. The HC-SFS52BG1H is the correct selection when all three features — brake, high-precision gearhead, and straight shaft — are required simultaneously.

FAQ

Q1: What is the difference between the G1H and G1 gearhead on Mitsubishi HC-SFS motors?

Both are Mitsubishi factory-fitted reduction gearheads for the HC-SFS series, but they differ in precision level. The G1 is a general industrial gearhead suitable where moderate angular play at the output is acceptable. The G1H is the high-precision variant, built to tighter manufacturing tolerances with lower backlash — meaning the commanded servo position is more accurately reproduced at the gearhead output shaft. For rotary indexing, precision fixture drives, and any application where output shaft angular accuracy is a direct quality parameter, G1H is the correct specification.

Q2: Which servo amplifier is required for the HC-SFS52BG1H?

The HC-SFS52BG1H is matched to the MR-J2S-60A (for pulse-train or analog command input) or MR-J2S-60B (for SSCNET multi-axis network applications). Both are 500W-class amplifiers within Mitsubishi's MELSERVO J2S series. The electromagnetic brake requires a separate 24V DC power supply wired to the motor brake connector — the servo amplifier does not supply brake coil power directly.

Q3: How do I confirm the gear ratio of an HC-SFS52BG1H unit?

The gear ratio is part of the specific assembly configuration and must match the original machine design. Check the gearhead nameplate on the physical unit, or refer to the original machine bill of materials and electrical drawings. The ratio is not identifiable from the base part number HC-SFS52BG1H alone — a ratio suffix is appended in full catalog notation (e.g., 1/20). Ordering a replacement without confirming the ratio risks incorrect output speed and potential mechanical damage.

Q4: Does the absolute encoder retain position data if the machine power is cut unexpectedly?

Yes, provided the A6BAT lithium backup battery is installed in the servo amplifier's battery holder and is in good condition. With the battery present, multi-turn position data is preserved through any power interruption. The amplifier will display a battery voltage alarm when replacement is due. Without the battery, position data is lost at power-down and a reference return homing cycle is required before production can resume.

Q5: What protection rating applies to the gearhead section of the HC-SFS52BG1H?

The motor body carries IP65 — fully sealed against dust and protected against water jets from any direction. The gearhead section is rated IP44, which covers solid particles larger than 1mm and water splashing from any direction, but not direct water jets or coolant immersion. In machine tool environments with active coolant spray near the gearhead, a mechanical shield or coolant deflector should be incorporated into the installation design.