Mitsubishi HC-SFS202BK (HCSFS202BK) — 2kW AC Servo Motor, Keyed Shaft + Brake, MELSERVO-J2S Series

Product Identification

Part Number: HC-SFS202BK

Also Searched As: HCSFS202BK, HC-SFS-202BK

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

Motor Type: AC Brushless Servo Motor — Keyed Shaft with Electromagnetic Brake, 2000 rpm

Condition: New In Box, Factory Sealed

Overview

The Mitsubishi HC-SFS202BK is a 2kW medium-inertia AC brushless servo motor from the MELSERVO-J2S platform, combining two features that define this exact variant: a machined keyway on the drive shaft and a spring-applied electromagnetic brake. At 9.55 Nm continuous rated torque with a 28.6 Nm peak, it delivers the acceleration capacity and steady-state output needed for the broad middle range of machine tool and automation drive applications — axes that require more than a small-capacity servo can offer but where a 3.5kW or larger motor would be oversized and harder to justify on cost and panel space.

Why this specific combination? The keyed shaft and the brake answer two separate questions in the application design, and this variant satisfies both at once. The keyway provides a positive mechanical connection between shaft and driven component — a timing belt pulley, a gear hub, a ballscrew coupling — ensuring that the torque path through the interface does not depend on friction alone. The brake provides the fail-safe axis hold that is mandatory whenever servo power loss means the load is free to move in an uncontrolled direction.

Backed by the J2-Super platform's 17-bit serial absolute encoder, the HC-SFS202BK feeds 131,072 positions per revolution of feedback to the MR-J2S amplifier. The position loop runs on fine-grained data, and the absolute function retains full multi-turn position between power cycles — no homing sequence required after any shutdown, alarm reset, or power interruption.

Technical Specifications

Two Features, Two Problems Solved

The Keyed Shaft

A keyway is a small detail with significant mechanical consequences. On a straight-shaft motor, the coupling hub transmits torque through friction: the clamping load between hub bore and shaft OD must be large enough to carry the peak torque under the worst operating condition — a sudden reversal at maximum feed, an emergency deceleration from rapid traverse, a shock load from an aggressive cut. If the clamp is insufficient, the hub slips. Slip on a servo axis means lost position, and lost position on a CNC machine means scrapped parts.

The keyway on the HC-SFS202BK changes the torque transmission mechanism entirely. The key occupies a matched slot in both the shaft and the hub bore; under load, it bears in shear across the key cross-section. Torque passes through the key directly, independent of any friction contribution from the hub clamp. This is why keyways are standard in timing belt drives, chain sprocket applications, and any coupling design where the load is cyclic, reversing, or subject to shock — applications where a friction-only interface would require significantly higher clamping forces to remain reliable over time.

One installation point that applies at this frame size: always fit the hub using the shaft-end threaded hole rather than pressing or driving the hub on by force. A drawbolt through the threaded hole pulls the hub squarely onto the shaft without imparting axial shock. Impact loads during hub installation travel through the shaft to the encoder disc at the motor's rear and can cause subtle encoder damage that does not trigger an immediate fault but shortens encoder service life and may cause intermittent feedback alarms under vibration.

The Electromagnetic Brake

The brake on the HC-SFS202BK is spring-applied: mechanical spring pressure engages the friction disc against the brake plate, and 24V DC to the coil holds it open, allowing free shaft rotation. Remove the 24V — at any point, for any reason — and the spring closes immediately. No control logic required, no signal from the amplifier needed, no delay. That is what fail-safe means in this context: the default state is locked, and power is required to keep it open.

For a 2kW axis carrying a load with any meaningful gravitational component — a vertical tool slide, an overhanging arm, a Z-axis with an unbalanced spindle head — that default-locked characteristic is exactly what safe machine design requires. The axis holds position through e-stops, power outages, alarm trips, and maintenance shutdown sequences.

Proper brake sequencing through the MR-J2S amplifier's MBR (electromagnetic brake interlock) output is essential. The MBR signal delays brake engagement until the amplifier has confirmed that axis velocity has fallen below a safe threshold after deceleration. Wiring the brake relay directly from an e-stop contact — without the MBR interlock in the circuit — will cause the spring to engage against a rotating shaft. At 2kW and 28.6 Nm peak, the resulting impact accelerates brake wear and can produce mechanical shock loads in the driven mechanism. The MBR interlock is not optional; it is how the brake is designed to be used.

17-Bit Encoder: Fine-Grained Feedback at 2000 rpm

The J2-Super generation encoder upgrade from 14-bit (16,384 ppr in the HC-SF series) to 17-bit (131,072 ppr in the HC-SFS series) was not incremental. Eight times more positions per revolution feeds noticeably finer data into every part of the control loop.

At 2,000 rpm — the rated speed of the HC-SFS202BK — the encoder transmits position updates that resolve much smaller angular steps than the older 14-bit device could. The MR-J2S amplifier uses this data for three purposes simultaneously: velocity estimation for the speed loop, following-error calculation for the position loop, and commutation phase reference for the current vector. Better data in each calculation means the loops can be tuned to higher bandwidth while remaining stable, and higher bandwidth means faster error correction and better disturbance rejection during the working cycle.

The absolute multi-turn counter keeps doing its job silently in the background. Backed by the A6BAT lithium battery in the MR-J2S amplifier, it accumulates shaft rotation data through any power event and holds it indefinitely as long as the battery remains healthy. On the next power-up — whether after a planned overnight shutdown, an emergency stop recovery, or a power fault — the axis reads its current absolute position and reports it to the controller without any reference return movement. For machines that run continuous production shifts or have tight restart time requirements, eliminating the homing cycle saves measurable production time across a year of operation.

Amplifier Compatibility

The HC-SFS202BK pairs with the MR-J2S-200 class amplifier. Three interface variants cover the main system architectures used in MELSERVO-J2S installations:

MR-J2S-200A handles analog and pulse-train command inputs — the standard choice for CNC systems and PLCs using step/direction or ±10V analog velocity command. It supports position, speed, and torque control modes and includes the RS-232C interface for MR Configurator setup software.

MR-J2S-200B connects to Mitsubishi motion controllers via SSCNET fiber-optic serial bus. In multi-axis systems where all axes are coordinated through an A-series or Q-series motion controller, the B-type amplifier receives trajectory data over the network and executes it locally. The fiber-optic bus eliminates encoder cable runs between the controller and each amplifier — position feedback loops back through the same network.

MR-J2S-200CP incorporates a built-in point table for standalone positioning. Up to 31 positions can be programmed directly into the amplifier using MR Configurator, with I/O commands selecting target points and triggering moves. This variant suits machines where a dedicated motion controller is unnecessary and a simple indexed positioning function is sufficient.

The HC-SFS202BK is not compatible with first-generation MR-J2-200 amplifiers (which cannot read the 17-bit J2S encoder), nor with MR-J3 or MR-J4 amplifiers, which use a different encoder interface. For machines running original MR-J2 amplifiers, the HC-SF202BK (J2-generation motor with 14-bit encoder) is the correct alternative.

HC-SFS Series 2000 rpm — Where the 202BK Fits

The HC-SFS202BK sits at the bottom of the 176 × 176 mm flange range — the same physical mounting footprint as the 352, 502, and 702 motors above it. This matters for machine designers planning upgrade paths or maintaining flange-standardised designs across multiple axes: the bolt pattern and pilot diameter do not change between 2kW and 7kW within this flange class.

At each capacity point, the variant suffix indicates shaft type and brake:

• No suffix / B = straight shaft / straight shaft with brake
• K / BK = keyed shaft / keyed shaft with brake

The HC-SFS202BK is therefore the keyed-shaft, brake-equipped version at 2kW — the configuration for axes that need both features simultaneously.

Typical Applications

VMC and HMC secondary positioning axes. On vertical and horizontal machining centres, secondary axes — rotary table drives, B-axis trunnions, pallet clamping mechanisms — commonly use 2kW servo motors in the medium-inertia class. The keyed shaft suits direct gear mesh or timing belt drives common in rotary axis designs; the brake holds the axis mechanically between index positions during the cutting portion of the cycle.

Automated assembly station indexing. Servo-driven rotary index tables in assembly automation cycle rapidly through fixed angular positions, dwell at each station while assembly operations occur, then index again. The brake holds the table during the dwell without relying on servo torque — and the absolute encoder confirms exact angular position at every station without a reference return at shift start.

Packaging machine servo axes. Film drives, cross-seal mechanisms, and product infeed axes on packaging lines use 2kW servo drives in continuous high-cycle operation. Timing belt interfaces on these axes typically require keyed shafts on the drive pulley to prevent belt tension from rotating the pulley hub. The IP65 rating handles the wash-down environments common in food and pharmaceutical packaging.

Cartesian robot joint drives. Multi-axis Cartesian and SCARA robot systems use medium-capacity servo motors on the primary translation and rotation axes. The keyed shaft suits the precision shaft couplings common in robot joint design; the brake provides safe position hold during teach mode and power-down sequences.

CNC lathe turret indexing. Servo-driven turret indexing on CNC turning centres requires fast, accurate angular positioning followed by firm mechanical hold while the selected tool operates under cutting force. At 9.55 Nm continuous and 28.6 Nm peak, the HC-SFS202BK handles standard multi-position turret inertia and provides the holding torque needed to resist cutting loads between index cycles.

New In Box, Factory Sealed

This HC-SFS202BK arrives in its original Mitsubishi packaging — outer carton sealed, internal foam packing undisturbed, shaft-end protective cap and all connector covers in place. Factory-sealed means no prior installation, no accumulated thermal history in the windings, no bearing wear from previous use. The oil seal at the shaft through-point and the IP65 housing protection are both in as-manufactured condition.

For production machinery waiting on this part to resume operation, in-stock new-in-box means immediate shipment rather than repair turnaround time. For planned maintenance stock, factory-sealed units store reliably under proper conditions — stable temperature, low humidity, no vibration — for multiple years. Beyond five years of storage, slow manual shaft rotation as part of a pre-installation check helps redistribute bearing grease before first power-up.

Frequently Asked Questions

Q1: Which amplifiers are compatible with the HC-SFS202BK?

The HC-SFS202BK requires a MR-J2S-200 class amplifier from the MELSERVO-J2S platform. The three main variants are the MR-J2S-200A (general-purpose analog/pulse command), MR-J2S-200B (SSCNET fiber-optic bus for Mitsubishi motion controllers), and MR-J2S-200CP (built-in positioning function). All support the 17-bit serial encoder. This motor is not compatible with original MR-J2-200 amplifiers or with MR-J3 / MR-J4 amplifiers.

Q2: What is the difference between the HC-SFS202BK and the HC-SFS202B?

The two motors are identical in every specification — 2kW, 9.55 Nm rated, 28.6 Nm peak, 17-bit encoder, 176 × 176 mm flange, same amplifier requirements, same IP65 rating. The only difference is the shaft. The HC-SFS202B has a plain straight shaft for friction-clamp couplings. The HC-SFS202BK has a machined keyway for positive key-and-hub torque transmission. Choose based entirely on the coupling interface required by the driven mechanism.

Q3: Is the electromagnetic brake strong enough to hold the axis under gravity load?

The brake is a fail-safe holding device rated to hold the motor shaft stationary under the axis's static load at rest — provided the unbalanced gravitational torque at the motor shaft does not exceed approximately 70% of the motor's rated torque (roughly 6.7 Nm for this motor). This threshold comes from Mitsubishi's published guidance for vertical axis applications. For loads producing higher unbalanced torque, supplemental counterbalancing should be used alongside the brake rather than relying on the brake alone.

Q4: What battery does the 17-bit encoder require, and where is it installed?

The absolute encoder retains multi-turn position through power-off using a Mitsubishi A6BAT lithium battery, which is installed inside the MR-J2S servo amplifier — not in the motor. A healthy battery preserves absolute position indefinitely through any power interruption, eliminating homing cycles on restart. When the amplifier shows a low-battery alarm, replace the A6BAT during the next planned maintenance window before full discharge causes loss of absolute position.

Q5: Can the HC-SFS202BK replace a HC-SFS152BK if a higher-capacity motor is needed?

Both motors use the same MR-J2S amplifier platform and carry the 17-bit absolute encoder, but they require different amplifier ratings — the HC-SFS152BK pairs with MR-J2S-200 (which also covers the 202), while a capacity upgrade means confirming the existing amplifier can handle the 2kW motor's rated current. More importantly, replacing a 1.5kW motor with a 2kW motor also changes the 176 mm flange size versus the 130 mm flange on the HC-SFS152BK — these are not the same flange size. The 202BK uses a 176 × 176 mm flange; the 152BK uses a 130 × 130 mm flange. A motor swap between these two capacity points requires changes to the motor mounting plate, not just the amplifier parameters.