Mitsubishi HC-SFS102K (HCSFS102K) — 1kW AC Servo Motor, Keyed Shaft, MELSERVO-J2S Series

Product Identification

Part Number: HC-SFS102K

Also Searched As: HCSFS102K, HC-SFS-102K

Series: Mitsubishi MELSERVO HC-SFS (J2-Super Generation)

Motor Type: AC Brushless Servo Motor — Keyed Shaft, No Brake

Condition: New In Box — One Year Guarantee

Product Overview

The Mitsubishi HC-SFS102K is a 1kW medium-inertia AC brushless servo motor from the MELSERVO-J2S platform — the same fundamental design used across a wide range of CNC machine tools, packaging lines, and general automation equipment that was built on Mitsubishi's J2-Super servo system. At 2,000 rpm rated speed and 4.78 Nm of continuous torque, it handles the kind of positioning and feed work that makes up the backbone of industrial motion control.

The "K" in the part number is the defining feature: a keyed shaft. Where the standard HC-SFS102 has a plain straight shaft, the HC-SFS102K includes a machined keyway. That keyway allows positive mechanical locking between the motor shaft and a coupled component — couplings, pulleys, or sprockets that require a key for torque transmission rather than friction clamping alone. In any application where slip under shock load is a concern, or where the driven component must be precisely clocked to a rotational reference on the shaft, the keyed variant is the correct choice.

No electromagnetic brake is fitted. The HC-SFS102K holds position through servo lock — the amplifier maintains current and closed-loop control to keep the axis stationary — and is not intended for vertical axes where load could fall on servo-off. For those applications, the HC-SFS102BK (keyed shaft plus brake) is the appropriate selection.

Technical Specifications

The Keyed Shaft: When and Why It Matters

Most servo motor couplings grip purely by friction — split clamp-style couplings, bellows couplings, and beam couplings all work this way, and for the vast majority of servo applications they work reliably. The straight shaft of the HC-SFS102 suits those setups perfectly.

The keyed shaft on the HC-SFS102K is specified when the driven component cannot rely on friction alone. A sprocket transmitting roller chain tension loads, a pulley on a timing belt drive with high pre-tension, a pinion gear in a rack-and-pinion axis — these are torque transmission points where the interface sees real shear forces. If the coupling slips, even fractionally, positioning accuracy degrades and the event can go undetected until the machine starts producing bad parts or a limit fault triggers. A key prevents that by creating a positive form-fit between shaft and hub.

Keyway matching matters during installation: the keyway in the motor shaft must be aligned with the keyway in the hub, the key must be the correct length and fit with minimal clearance, and the retaining fastener on the coupling hub must be properly torqued. Done correctly, a keyed connection is mechanically robust for the life of the motor. Done carelessly — oversized key, loose fit, or clocking errors — it introduces backlash and stress concentration at the keyway root. The HC-SFS102K ships with the keyway already machined; the key itself is sourced and fitted at installation.

17-Bit Absolute Encoder — Resolution That Changes the Equation

The HC-SFS102K uses the same 17-bit serial absolute encoder found across the HC-SFS family: 131,072 distinct positions per revolution, fed back to the amplifier through a high-speed serial link. That number is worth putting in context. The older HC-SF series used a 14-bit encoder delivering 16,384 ppr. The step to 17-bit is not simply a specification upgrade — it directly enabled the speed loop bandwidth improvement that defines the J2-Super generation.

At 1kW, this motor is often used in axes with moderate load inertia where the servo system is expected to respond quickly to small command changes. A feed axis that needs to follow a trajectory accurately, a turret that indexes through small angular increments, a tension-control roll where speed variations must be corrected in real time — all of these benefit from the amplifier's ability to compute velocity from a fine-resolution encoder rather than coarse-counting pulses and interpolating between them.

The absolute nature of the encoder means position is known the moment the control powers up. No reference return cycle, no lost position from a momentary power blip. The encoder retains its absolute position during power-off using a battery in the MR-J2S amplifier (the A6BAT lithium cell). As long as that battery is healthy, the axis resumes from an exact known position without any machine movement required.

HC-SFS Series Context — Where the 102K Sits

The HC-SFS family covers a power range from 500W to 7kW at the 2,000 rpm rated speed. The 1kW HC-SFS102K occupies the second position from the bottom of the standard range, above the 500W HC-SFS52K and below the 1.5kW HC-SFS152. Within that positioning it serves a distinct type of application: axes where 500W is genuinely marginal under worst-case load and duty cycle, but where going to 1.5kW or 2kW would create unnecessary cost, bulk, and amplifier expense.

In machine tool terms, that often means a second or auxiliary feed axis — a B-axis on a CNC lathe, a C-axis for simple spindle indexing, a subspindle feed axis, or a secondary servo on a multi-axis machining centre. In general industrial use, it covers conveyors, X-Y positioning tables, winding and tension axes, and pick-and-place gantries where the payload is modest but the duty cycle is continuous.

The 130 × 130mm flange matches the standard frame size for the 500W–1.5kW capacity range in the HC-SFS family. Motors that grow from 2kW upward move to the larger 176 × 176mm flange. For space-constrained machine designs, knowing the HC-SFS102K shares a flange size with 500W and 1.5kW siblings is useful: a design can accommodate future axis resizing without modifying the motor mounting arrangement.

HC-SFS 2000 rpm Family — Shaft Variants Available

Within the 1kW / 2000 rpm capacity point, Mitsubishi offered four shaft-and-brake combinations:

All four share the same rated output (1kW), torque (4.78 Nm rated / 14.4 Nm peak), encoder (17-bit, 131,072 ppr), flange (130×130mm), protection (IP65), and J2S amplifier compatibility. The choice between them depends entirely on the shaft coupling method and whether the axis requires a powered-off hold.

Broader HC-SFS 2000 rpm Range

Application Notes

CNC lathe C-axis and B-axis. Secondary servo axes on turning centres that handle spindle orientation, subspindle feed, or turret positioning often land in the 1kW range. These axes are typically horizontal or heavily counterbalanced, so a brake is unnecessary — the HC-SFS102K without brake is the cleaner, lower-cost solution.

Conveyor and indexing drives. Servo-driven conveyor sections and rotary indexing tables used in assembly automation see continuous-duty operation at moderate torque. Medium inertia, good thermal stability, and reliable low-speed torque — all characteristics of the HC-SFS class — are well matched to this work.

X-Y positioning tables. Flat-bed servo-driven positioning tables for laser processing, dispensing, or inspection work often use 1kW axes. The high encoder resolution directly benefits the following-error performance in interpolated XY moves.

Tension control and winding axes. Winders, uncoilers, and web tension control systems use servo motors in torque-control mode to regulate web tension. Low-speed torque stability — a strength of the J2S encoder-amplifier combination — matters considerably in these applications.

Pick-and-place and gantry loading. Single-axis pick-and-place systems and simple gantry loaders with light-to-moderate payloads use 1kW servo axes for the combination of speed and precision that pure pneumatic drives cannot match.

New In Box — One Year Guarantee

This HC-SFS102K is factory-sealed new-in-box stock — original Mitsubishi packaging, shaft and connector protection intact, never wired or powered. One year guarantee covers the motor against manufacturing defects and failures on arrival. For buyers sourcing a replacement for a machine that is currently down, or building a spare parts inventory for a fleet of machines running the J2S platform, new-in-box is the only condition that guarantees the motor has no prior history.

Frequently Asked Questions

Q1: What amplifiers are compatible with the HC-SFS102K?

The HC-SFS102K is designed for the MR-J2S-100 class of MELSERVO-J2S amplifiers, including the MR-J2S-100A (general-purpose pulse/analog), MR-J2S-100B (SSCNET bus), MR-J2S-100CP (built-in positioning), and MR-J2S-100CL (CC-Link interface). It is not compatible with MR-J2 first-generation amplifiers, which cannot read the J2S motor's 17-bit serial encoder, nor with MR-J3 or MR-J4 amplifiers without adaptation hardware.

Q2: What is the difference between the HC-SFS102K and the HC-SFS102?

The only difference is the shaft. The HC-SFS102 has a plain straight shaft for use with friction-clamp couplings. The HC-SFS102K has a machined keyway, allowing a positive key-and-keyway connection to the driven component. All other specifications — power, torque, encoder, flange, protection rating, and amplifier compatibility — are identical between the two models.

Q3: Does the HC-SFS102K have an electromagnetic brake?

No. The HC-SFS102K does not include a brake. Position on a stationary axis is maintained by servo lock (the amplifier keeps the control loop active and holds the axis with motor current). If the axis is vertical or requires a fail-safe mechanical hold when the servo is de-energised, the HC-SFS102BK (keyed shaft with electromagnetic brake) is the correct model to specify instead.

Q4: The encoder is described as "absolute" — does it need a battery?

Yes. The 17-bit serial absolute encoder requires a battery to retain position data during power-off. The battery is the A6BAT lithium cell, installed in the MR-J2S servo amplifier — not in the motor itself. When the battery is healthy, the axis knows its exact position the moment the control powers up, eliminating the need for a homing cycle. A low-battery alarm on the amplifier indicates the battery should be replaced at the next planned maintenance window.

Q5: Can the HC-SFS102K replace an HC-SF102K from the earlier J2 series?

The mounting dimensions are the same, and the keyed shaft geometry is compatible. However, the HC-SFS102K uses a 17-bit serial encoder that requires an MR-J2S amplifier — it will not communicate with an original MR-J2 amplifier. If the machine is running MR-J2 amplifiers, both the motor and amplifier need to be updated together. If it is already running MR-J2S amplifiers, the HC-SFS102K is a direct mechanical replacement with no other changes required beyond parameter verification in MR Configurator.