Mitsubishi HC-MFS13K AC Servo Motor — 100W Ultra-Low Inertia MELSERVO J2S | Keyed Shaft | New In Box | Fast Shipping

At 100W with a 40 × 40 mm flange, the Mitsubishi HC-MFS13K is one of the most compact servo motors in the MELSERVO J2S lineup — but compact does not mean compromised. Behind that small frame sits a 17-bit absolute encoder delivering 131,072 positions per revolution, an ultra-low inertia rotor built for high-frequency operation, and the keyed straight shaft that makes this specific variant the correct choice wherever the driven component requires a positive mechanical lock rather than a friction-only coupling interface. New in original Mitsubishi Electric packaging, ready for fast dispatch.

Technical Specifications

The K Shaft — Keyed for Positive Torque Transmission

The difference between the HC-MFS13 (plain straight shaft) and the HC-MFS13K is a single but meaningful mechanical feature: the keyed shaft. A machined keyway runs along the shaft length, accepting a standard parallel key that locks the coupling, pulley, or gear hub in the rotational direction while still allowing axial assembly and removal.

Where a plain shaft relies entirely on the clamping force of a split-hub coupling to prevent rotation between shaft and driven component, a keyed interface transmits torque through direct mechanical contact between key and keyway. For applications involving timing belt drives with keyed pulley bores, gear trains where a gear hub fits over the motor shaft, or any installation where the original machine design specifies a keyed shaft — the HC-MFS13K is the variant that installs correctly without modification.

Retrofit and replacement work is where this matters most. A machine that originally carried an HC-MFS13K requires another HC-MFS13K to restore the factory mechanical interface. Swapping in a plain shaft motor means modifying or replacing the coupling component — additional work, additional cost, additional downtime.

100W in a 40 mm Frame — Compact Without Compromise

The 40 × 40 mm mounting flange of the HC-MFS13K positions this motor at the small end of the HC-MFS series, yet the specification sheet is not modest. The 17-bit absolute encoder, IP55 housing, and ultra-low inertia rotor are the same quality standard found throughout Mitsubishi's MELSERVO J2S family regardless of power class.

At 0.32 Nm rated torque and 3,000 rpm rated speed, the HC-MFS13K serves the category of automation axes where the mechanical load is light, space is limited, and positioning accuracy is non-negotiable. Think insertion device tooling heads, small-axis assembly fixtures, label registration mechanisms, and multi-axis machine designs where several compact axes must coexist within a tight mechanical envelope.

The maximum torque of 0.96 Nm — three times rated — gives the motor the transient acceleration capacity to execute sharp motion profiles at the cycle rates these applications demand without sustained thermal stress. Ultra-low rotor inertia amplifies that acceleration further: a lighter rotor changes speed faster for the same applied torque, which is the underlying reason the HC-MFS series is designed specifically for high-frequency, short-travel positioning work.

17-Bit Absolute Encoder — 131,072 ppr, Instant Position at Startup

The HC-MFS13K ships from the factory with a 17-bit absolute optical encoder integrated into the motor body. Each shaft revolution is divided into 131,072 discrete positions, transmitted in real time to the servo amplifier via Mitsubishi's high-speed serial feedback link.

The absolute architecture means the encoder knows where the shaft is at all times — through power cycles, emergency stops, and planned shutdowns alike. With the backup battery installed in the servo amplifier, multi-turn absolute position is retained when the machine loses power. The practical result is a machine that starts up with all axis positions already confirmed, skipping the reference return routine that incremental encoder systems require at every power-on. For production equipment that cycles power multiple times per day, or machines where downtime has a direct cost, that startup time saving compounds into a meaningful operational advantage over a machine's service life.

Compatible Servo Amplifiers

The HC-MFS13K connects to the MR-J2S-10A (analog/pulse-train command) or MR-J2S-10B (SSCNET fiber-optic network command) servo amplifiers, both rated at 100W in the MELSERVO J2S platform. The K shaft variant does not affect amplifier selection — the electrical interface is identical to all HC-MFS13 variants.

For standalone single-axis positioning driven by a PLC or external controller via pulse train or analog reference, the MR-J2S-10A is the standard choice. For multi-axis machines where all axes are synchronized via SSCNET from a Mitsubishi A-series or Q-series motion controller, the MR-J2S-10B enables full networked coordination across all connected amplifiers.

Where the HC-MFS13K Is Used

The combination of 100W output, 40mm flange, ultra-low inertia, and keyed shaft puts the HC-MFS13K in a specific and well-populated application space:

Electronic assembly machines — component insertion heads, PCB transport axes, and small-travel positioning stages where the keyed shaft ensures a reliable coupling interface through high-cycle operation

Label applicators and registration systems — web tension and registration control axes where the coupling to a drive roller or timing pulley is a keyed interface by design

Multi-axis assembly fixtures — compact servo axes in machine designs where six, eight, or more independent axes must share a limited cabinet and machine volume, each with its own MR-J2S-10A amplifier

Packaging equipment — dosing, indexing, and portion-control axes where a 40mm motor fits within the spatial constraints of the machine structure and the driven mechanism requires a keyed connection

Semiconductor and flat panel handling — precision transport and alignment axes on wafer handling equipment and FPD assembly machines where position accuracy and repeatable settling are the primary requirements

HC-MFS13 Variant Comparison

All HC-MFS13 variants share the same 100W output, 17-bit absolute encoder, IP55 housing, and 40 × 40 mm flange. The selection between variants depends solely on shaft interface and brake requirements:

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

The HC-MFS13K is the correct specification for installations where the coupling component has a keyed bore and no shaft-locking holding brake is required. For vertical axes or safety-hold applications, the HC-MFS13BK adds the spring-applied electromagnetic brake to the same keyed shaft configuration.

FAQ

Q1: What is the difference between the HC-MFS13 and HC-MFS13K?

The only difference is the shaft configuration. The HC-MFS13 has a plain straight shaft that relies on clamp-type couplings for torque transmission. The HC-MFS13K has a keyed straight shaft with a machined keyway, allowing a parallel key to mechanically lock the coupling in the rotational direction. All electrical specifications, encoder, flange size, and IP rating are identical between the two variants.

Q2: Which servo amplifier is compatible with the HC-MFS13K?

The HC-MFS13K pairs with the MR-J2S-10A (for analog speed/torque commands or pulse-train position commands from an external PLC or controller) or MR-J2S-10B (for SSCNET multi-axis network applications). Both are 100W-rated within the MELSERVO J2S platform. The K shaft designation has no effect on amplifier compatibility.

Q3: Does the HC-MFS13K support absolute position retention through a power-off cycle?

Yes. The built-in encoder is an absolute type. With a Mitsubishi A6BAT battery installed in the servo amplifier, multi-turn position data is preserved when machine power is removed. At the next startup, axis position is immediately available — no reference return or homing sequence is required.

Q4: Should I choose HC-MFS13K or HC-MFS13BK for a vertical axis?

For vertical axes where the load must hold position safely when servo power is removed — or when a mechanical shaft lock is required during maintenance or emergency stop — the HC-MFS13BK is the correct choice. It adds a spring-applied electromagnetic brake that locks the shaft whenever brake coil voltage is absent. The HC-MFS13K has no brake and is suitable for horizontal or lightly loaded vertical axes where gravity load on the shaft is within acceptable limits without a mechanical hold.

Q5: What is the successor to the HC-MFS13K in Mitsubishi's current lineup?

The HC-MFS series belongs to Mitsubishi's MELSERVO J2S generation, which has been superseded by J4 and J5 series products. For new machine designs, Mitsubishi's current-generation equivalent in the 100W ultra-low inertia class is the HG-MR13 (MELSERVO J4 series), which offers a 22-bit encoder and updated amplifier compatibility (MR-J4 series). For maintenance and replacement on existing J2S-platform machines, the HC-MFS13K remains the correct and directly compatible specification.