Mitsubishi HC-MFS13B AC Servo Motor — 100W Ultra-Low Inertia MELSERVO J2S, with Electromagnetic Brake, New In Box Factory Sealed

Space is tight. Cycle times are short. Position accuracy has no margin for error. These are the conditions the Mitsubishi HC-MFS13B was designed for. At 100W with ultra-low rotor inertia, a 40 × 40 mm frame footprint, a built-in electromagnetic brake, and a 17-bit absolute encoder generating 131,072 positions per revolution, this motor is a precision instrument for the kind of high-frequency, compact-axis automation where larger motors simply don't fit the application. This listing is for a brand-new, factory-sealed unit in original Mitsubishi Electric packaging.

Technical Specifications

Ultra-Low Inertia — What It Changes in Practice

The defining characteristic of the HC-MFS series is not its power rating — it's the rotor's moment of inertia. Ultra-low inertia means the motor can accelerate and decelerate extremely rapidly in response to servo amplifier commands, with minimal energy wasted overcoming the motor's own rotating mass.

In practical terms, this translates directly to shorter positioning settle times, tighter control of high-speed indexing moves, and the ability to execute dense motion profiles — dozens or hundreds of precise moves per minute — without the thermal and dynamic penalties that higher-inertia motors incur at the same duty cycle. The application note on this motor says it plainly: suitable for high-frequency operation, with insertion devices and assembly machines cited as primary examples.

For machine builders designing pick-and-place modules, electronic component placement heads, label applicators, or any axis that executes a large number of short-travel precision moves per hour, the inertia characteristic of the motor is as important as the torque rating — and the HC-MFS13B is specifically engineered to excel in that regime.

Electromagnetic Brake — The "B" in HC-MFS13B

Every HC-MFS13B includes a spring-applied electromagnetic brake integrated into the motor body. The operating principle is fail-safe: the brake applies (locks the shaft) when the coil is de-energized, and releases when voltage is applied to the brake coil. This is the correct configuration for:

Vertical axes — where a load must hold position safely when servo power is removed, either during normal stops or on emergency power loss. Without a brake, a de-energized vertical axis freefalls.

Hold-to-position requirements — applications where the motor must lock a position between motion cycles without continuous drive power, such as clamping mechanisms, shuttle stops, or indexing detents.

Safety compliance — machine designs where axis immobility during maintenance access or guard-open conditions is a machine safety requirement.

The electromagnetic brake does not replace a regenerative braking function during deceleration — it is a mechanical holding device, not a dynamic braking device. It engages after the axis has been brought to rest, locking the shaft mechanically.

17-Bit Absolute Encoder — 131,072 ppr, Zero-Homing Operation

The built-in encoder delivers 131,072 discrete positions per shaft revolution via a high-speed serial link to the servo amplifier. Being absolute in nature, it maintains position knowledge through power cycles — with a battery installed in the servo amplifier, the motor knows exactly where it is when the machine starts, without executing a reference return.

On a machine with many axes, eliminating the homing routine from the startup sequence is a consistent time saving on every power cycle. On an assembly machine with six or eight small servo axes, that adds up meaningfully across a production year.

40 × 40 mm Frame — Compact by Design

The HC-MFS13B mounts on a 40 × 40 mm flange — one of the smallest standard servo motor flanges in the MELSERVO family. This physical scale is well-matched to the mechanisms that need a 100W drive: lightweight tooling heads, small-travel linear stages driven by compact ball screws, multi-axis assembly fixtures where space between axes is limited, and machine designs where motor mass itself is a consideration.

The compact frame also keeps the motor's moment of inertia low from a system perspective — a lighter motor means the machine structure supporting it doesn't need to be as stiff, which benefits machine cost and design flexibility.

Compatible Servo Amplifiers

The HC-MFS13B is paired with the MR-J2S-10A (analog/pulse-train command, single-axis) or MR-J2S-10B (SSCNET network command) servo amplifiers, both rated at 100W within the MELSERVO J2S family.

For multi-axis machine designs where all axes are coordinated via SSCNET from a Mitsubishi motion controller (Q-series or A-series), the MR-J2S-10B allows the HC-MFS13B to participate in a synchronized multi-axis network without individual per-axis command wiring. For simpler single-axis installations or integration with third-party PLCs via pulse train or analog, the MR-J2S-10A is the appropriate choice.

Application Areas

The HC-MFS13B appears on BOMs for a specific category of high-frequency, precision automation equipment:

Electronic component insertion and placement — the motor's ultra-low inertia and compact size suit the high-cycle, short-travel axes on PCB assembly and component handling equipment

Assembly machines — rotary and linear indexing axes on small-parts assembly stations where multiple servo axes must execute precise, rapid moves in tight mechanical proximity

Packaging and labeling equipment — registration and positioning axes on label applicators, blister pack lines, and flow wrapping machines where accurate position at high throughput is essential

Semiconductor handling — wafer and substrate transport axes where low inertia and high positioning repeatability are more critical than raw torque output

Pick-and-place robots — wrist and end-effector joints on small SCARA and Cartesian robots where low axis inertia improves dynamic performance at the tool center point

HC-MFS13B in the HC-MFS Variant Lineup

Within the HC-MFS13 family, the suffix tells you the exact configuration:

• HC-MFS13 — straight shaft, no brake
• HC-MFS13B — straight shaft, with electromagnetic brake (this listing)
• HC-MFS13K — keyed shaft, no brake
• HC-MFS13BK — keyed shaft, with electromagnetic brake

All variants share the same 100W output, 17-bit absolute encoder, IP55 housing, and 40 × 40 mm flange.

FAQ

Q1: What servo amplifier should be paired with the HC-MFS13B?

The HC-MFS13B requires the MR-J2S-10A (for analog/pulse-train command interfaces) or MR-J2S-10B (for SSCNET multi-axis network applications). Both amplifiers are rated at 100W and are the correct match for this motor within the MELSERVO J2S platform. Choice between A and B type depends on whether the machine uses independent axis control or a networked multi-axis motion controller.

Q2: What does the electromagnetic brake do, and when does it engage?

The brake in the HC-MFS13B is a spring-applied, power-off type: it locks the shaft mechanically when the brake coil voltage is removed, and releases when voltage is applied. It is primarily used on vertical axes to hold position safely when servo power is off, and on applications requiring a mechanical shaft lock between motion cycles. It is not designed for dynamic deceleration — it engages only after the axis is at rest.

Q3: Does the HC-MFS13B support absolute position retention through a power-off cycle?

Yes. The 17-bit encoder is an absolute type. With a battery (Mitsubishi A6BAT) installed in the servo amplifier, multi-turn position data is preserved when mains power is off. On the next startup, the axis position is known immediately — no homing or reference return cycle is required.

Q4: What is the difference between HC-MFS13B and the newer Mitsubishi 100W motors like the HG-MR13B?

The HC-MFS13B is part of the MELSERVO J2S generation, while the HG-MR13B belongs to the newer J4 series. The HG-MR13B offers a higher-resolution 22-bit encoder (4,194,304 ppr vs. 131,072 ppr), an IP65 rating vs. IP55, and updated amplifier compatibility (MR-J4 series). The HC-MFS13B remains the correct replacement part for existing J2S-platform machines and for spare parts inventory on installed equipment.

Q5: What is the IP55 rating and what does it protect against?

IP55 provides complete dust protection (first digit 5 — dust-protected) and protection against low-pressure water jets from any direction (second digit 5). The rating applies to the motor body excluding the shaft penetration and connector interface. For machine environments with coolant splash, light wash-down, or general industrial particulate exposure, IP55 is appropriate for most installations when the motor is mounted per Mitsubishi's installation guidelines.