Mitsubishi HC-SF202K (HCSF202K) — 2kW AC Servo Motor, Keyed Shaft, No Brake, MELSERVO J2 Series

Product Identification

Part Number: HC-SF202K

Also Searched As: HCSF202K, HC-SF-202K

Series: Mitsubishi MELSERVO HC-SF (J2 Generation)

Motor Type: AC Brushless Servo Motor — Keyed Shaft, No Brake, 2000 rpm

Condition: New In Box, Factory Sealed

Overview

The Mitsubishi HC-SF202K is a 2kW medium-inertia AC brushless servo motor from the original MELSERVO J2 platform, rated at 2,000 rpm with 9.55 Nm continuous torque and a machined keyway on the drive shaft. No electromagnetic brake is fitted. It is the specification for horizontal axes, gear-coupled drives, timing belt mechanisms, and any 2kW J2-generation application where a positive shaft-to-coupling connection matters and mechanical hold on servo-off is not required.

Within the J2 HC-SF family, the "K" suffix means one thing only: the drive shaft has a machined keyway. Everything else about the motor — output power, torque ratings, encoder, flange dimensions, amplifier requirements — is shared with the straight-shaft HC-SF202. The shaft configuration change is purely about the coupling interface, and it is the right choice whenever the mechanical design of the driven side requires a key-and-keyway torque path rather than a friction-only clamp interface.

Two facts about the HC-SF202K are practically important for anyone sourcing a replacement. First, as a J2-generation motor with a 14-bit encoder, it is compatible with both the original MR-J2-200 amplifiers and the later MR-J2S-200 platform — broader amplifier coverage than the J2S-generation HC-SFS202K, which requires MR-J2S hardware. Second, the 176 × 176 mm flange is shared with every motor in the HC-SF/SFS 2kW-through-7kW range, making like-for-like physical swaps straightforward within that capacity bracket.

Technical Specifications

The Keyed Shaft: What It Solves at 2kW

The torque path through a shaft-to-hub connection determines how reliable the joint is over the life of the machine. A plain straight shaft relies entirely on friction between the shaft OD and the hub bore — the clamping force must be high enough to resist the peak torque without any slip under the worst condition the axis will ever encounter. That worst condition on a servo axis is rarely the steady-state cutting torque; it is more often a sudden reversal, a rapid deceleration from maximum traverse speed, or a shock input from an interrupted cut or an abrupt axis stop command.

The keyway machined into the HC-SF202K shaft changes that calculation. The key occupies matching slots in both the shaft and the hub bore, transmitting torque directly through the key's shear cross-section rather than through friction alone. Under cyclic loading, reversing torque, and shock inputs — conditions that gradually induce micro-slip in marginally clamped friction interfaces — the keyed connection remains stable. Position is not lost, the coupling does not drift, and the shaft does not develop wear marks from fretting between hub and shaft OD.

At 9.55 Nm continuous and 28.6 Nm peak, those loads are real. The 28.6 Nm peak represents the torque demand during the acceleration phase of an axis move — the moment when the amplifier commands maximum current to bring a loaded axis up to rapid traverse speed. A coupling hub fitted to the plain straight shaft at marginal clamping force may handle the steady-state torque without incident for months, then slip once during an aggressive acceleration sequence and introduce a position error that only becomes visible as a machined dimension offset.

The keyway is the preventive measure. Driven pulleys, sprockets, gear hubs, and precision couplings where angular position between shaft and driven component must be maintained — these are the interfaces that belong on a keyed shaft, and the HC-SF202K is the correct specification for them.

One installation point that applies to all HC-SF motors with keyways: use the shaft-end threaded hole and a drawbolt to pull the hub axially onto the shaft rather than hammering or pressing it on. Impact loads during hub installation travel along the shaft to the encoder disc and bearing assembly at the motor's rear. The resulting encoder damage is not always immediate — it often surfaces later as intermittent position alarms or erratic encoder readings under vibration load, which are difficult to diagnose and trace back to the original installation event.

No Brake: The Right Configuration for These Axes

The absence of an electromagnetic brake on the HC-SF202K is a specification, not an omission. For horizontal axes where no gravitational or asymmetric force acts in the direction of motor shaft rotation, servo lock — the amplifier's closed-loop position hold with motor current active — is sufficient at all stop conditions. Adding a brake on these axes introduces wiring complexity, a relay and surge absorber in the panel, additional 24V DC current draw, and MBR interlock sequencing in the machine's safety logic, all for a mechanical function that the application never actually needs.

The HC-SF202K belongs on axes where that description fits: table X and Y feeds on machining centres, horizontal transfer drives, belt and chain conveyor axes, and gear-driven auxiliary mechanisms where the load is mechanically supported against gravity and servo lock is adequate between moves and at rest.

Where the picture is different — vertical axes, gravity-loaded arms, unbalanced mechanisms that would drift on servo-off — the correct motor is the HC-SF202BK, which adds the spring-applied electromagnetic brake to the same keyed shaft configuration. The mechanical output specifications are identical; the brake is the only addition, and it is there specifically for those applications.

Across a multi-axis machine with eight, twelve, or sixteen servo axes, the HC-SF202K contributes to a simpler electrical system on every axis that does not require brake functionality. That simplicity has real value during commissioning, troubleshooting, and long-term maintenance.

J2 Generation Encoder: Capability and Compatibility

The HC-SF202K uses the J2 platform's 14-bit serial absolute encoder at 16,384 positions per revolution. This is a serial digital feedback device — position data is transmitted as a serial signal to the amplifier, not as analog sine/cosine pairs — and it includes the absolute multi-turn counter backed by battery power.

At 2kW and 2,000 rpm, 14-bit resolution is fully capable for the applications this motor serves. Machine tool feed axes, conveyor positioning, indexing drives, and gear-driven automation mechanisms all operate with position tolerances well within what 16,384 ppr can resolve. The practical limitation of 14-bit versus 17-bit encoding appears most clearly at very low feed rates, in slow contouring operations, or in direct-drive applications where the encoder's resolution at the load point is the primary constraint on velocity smoothness. For the great majority of J2-era machine tool axis applications, this is not a binding constraint.

The absolute multi-turn counter retains position data between power cycles using the A6BAT lithium battery inside the servo amplifier. Position survives any power interruption — overnight shutdown, alarm trip, e-stop — and the axis comes up in its correct absolute position on the next power-on without any reference return movement. Replace the A6BAT at the amplifier's low-battery warning, before full depletion causes loss of the stored absolute position.

The amplifier compatibility story is the HC-SF202K's practical strength. Because the 14-bit J2 encoder predates the J2S platform, it is readable by two generations of Mitsubishi amplifiers:

• MR-J2-200A / MR-J2-200B — Original J2-generation amplifiers. Full compatibility, no restrictions, no parameter workarounds.
• MR-J2S-200A / MR-J2S-200B / MR-J2S-200CP — J2-Super amplifiers. Fully backward-compatible with the J2 encoder.

The HC-SFS202K (J2S generation, 17-bit) runs on MR-J2S-200 amplifiers only. The HC-SF202K runs on both. For machines currently operating with original MR-J2-200 amplifiers — a substantial installed base in machine tools produced throughout the J2 era — the HC-SF202K is the correct sourcing target, and no amplifier upgrade is required alongside the motor replacement.

HC-SF vs HC-SFS at 2kW: The Practical Replacement Decision

Every time a 2kW J2-family keyed-shaft motor requires replacement, the same comparison arises. Both the HC-SF202K and the HC-SFS202K deliver 9.55 Nm continuous, 28.6 Nm peak, on a 176 × 176 mm flange, with a keyed shaft and no brake. The output is the same. The mounting is the same. The shaft interface is the same.

The decision comes down to a single verification: what amplifier is installed in the machine? Check the amplifier nameplate. If it reads MR-J2-200 (without the S), source the HC-SF202K — the HC-SFS202K will fault on encoder error and will not operate. If it reads MR-J2S-200, either motor works; the HC-SFS202K offers higher resolution feedback, but the HC-SF202K is a fully valid alternative that avoids any risk of compatibility uncertainty on older machines.

HC-SF 2000 rpm Family — 2kW in Context

The HC-SF202K marks the transition from the 130 × 130 mm flange group to the 176 × 176 mm flange group within the HC-SF 2000 rpm range. From 2kW upward, all motors in this family share the larger flange, and within each capacity bracket the keyed and straight-shaft variants share the same mounting bolt pattern. Brake and shaft-type suffix differences do not affect the flange interface.

Typical Applications

Timing belt drive axes. Machine tool axes using toothed timing belt drives between the servo motor and the ballscrew or rack input require a keyed drive pulley. Belt tension combined with cyclic tooth engagement loads create exactly the conditions where a keyed shaft connection prevents drive pulley rotation relative to the motor shaft. The HC-SF202K's 9.55 Nm continuous rating handles mid-range machine tool axis loads at rated belt speeds within a comfortable operating margin.

Gear-coupled rotary axes. CNC 4th-axis drive units, rotary table worm gear inputs, and gear-train auxiliary axes use servo motors with keyed shafts on the motor-side gear hub for a positive, play-free torque connection. The HC-SF202K provides the 2kW capacity and keyed interface that these designs require, with full compatibility for the MR-J2 amplifiers originally specified in a large proportion of the machines that use them.

Chain and sprocket transfer drives. Automated transfer systems using chain and sprocket drives on servo-controlled indexing axes specify keyed sprockets to prevent the drive sprocket from rotating relative to the motor shaft under the impulsive loads that characterise chain engagement. The HC-SF202K suits horizontal transfer conveyors, pallet transfer systems, and workpiece indexing mechanisms of this type at 2kW capacity.

Legacy machine tool maintenance. The HC-SF202K's dual amplifier compatibility makes it the first-choice sourcing target for machines built during the J2 era that run MR-J2-200 amplifiers. Rather than sourcing the motor and simultaneously upgrading the amplifier to MR-J2S — a more complex and expensive intervention — the HC-SF202K drops in directly against the existing hardware. For maintenance teams supporting fleets of J2-era machines, this matters practically.

High-cycle packaging and labelling axes. Servo-driven timing belt axes on packaging lines — product infeed, label applicator drives, carton forming stations — run at high cycle rates with moderate torque loads. The keyed shaft suits the timing belt pulley interface, and the J2-era absolute encoder provides the register accuracy required for consistent product-to-label alignment without a homing cycle after every e-stop or machine restart.

New In Box, Factory Sealed

Factory sealed means original Mitsubishi packaging with everything undisturbed — the key slot on the shaft is protected by the shaft-end cap, all connector ports are covered, the oil seal is in as-manufactured condition, and internal foam packing is intact. The motor has never been installed, never powered, and has no thermal or mechanical history to account for.

For a machine currently waiting on this part to resume production, in-stock new-in-box means no repair turnaround and no uncertainty about prior service condition. The motor ships ready for direct installation. For planned maintenance spares inventory, factory-sealed stock stores well over several years under stable, dry conditions with no vibration. Beyond five years in storage, a pre-commissioning slow shaft rotation helps redistribute bearing grease before first power-up.

Frequently Asked Questions

Q1: Which amplifiers are compatible with the HC-SF202K?

The HC-SF202K is compatible with both the original J2-generation and J2-Super (J2S) amplifiers at the 200 class. Confirmed compatible models are MR-J2-200A and MR-J2-200B (original J2 generation), and MR-J2S-200A, MR-J2S-200B, and MR-J2S-200CP (J2-Super generation). The J2-generation 14-bit encoder is readable by both platforms. The HC-SF202K is not compatible with MR-J3 or MR-J4 amplifiers, which use a different encoder interface.

Q2: What is the difference between the HC-SF202K and the HC-SFS202K?

Both motors deliver 9.55 Nm continuously, 28.6 Nm peak, on a 176 × 176 mm flange with a keyed shaft and no brake — mechanically interchangeable at the mount. The difference is the encoder generation: the HC-SF202K uses a 14-bit encoder (16,384 ppr) and works with MR-J2 and MR-J2S amplifiers. The HC-SFS202K uses a 17-bit encoder (131,072 ppr) and requires MR-J2S amplifiers only. If the machine runs original MR-J2-200 amplifiers, source the HC-SF202K. If it runs MR-J2S-200, either motor is compatible.

Q3: What is the difference between the HC-SF202K and the HC-SF202 (straight shaft)?

The two motors are electrically and mechanically identical in every respect except the shaft. The HC-SF202 has a plain straight shaft for friction-clamp couplings. The HC-SF202K has a machined keyway for positive key-and-hub torque transmission. Same rated output, same torque figures, same encoder, same amplifier compatibility, same flange. Select between them based solely on the coupling design of the driven mechanism — there is no performance difference between the two under correctly installed conditions.

Q4: What is the difference between the HC-SF202K and the HC-SF202BK?

Again, a single-feature difference: the HC-SF202BK adds a spring-applied electromagnetic brake. Everything else — keyed shaft, 2kW, 9.55 Nm, 28.6 Nm peak, 14-bit encoder, 176 × 176 mm flange, amplifier compatibility — is identical. The no-brake HC-SF202K is correct for horizontal axes and any application where servo lock provides sufficient hold at all stop conditions. The HC-SF202BK is necessary for vertical axes, gravity-loaded mechanisms, or any application where safe machine design requires fail-safe mechanical hold when servo power is removed.

Q5: Does the HC-SF202K include a key for the keyway?

Mitsubishi's standard practice across the HC-SF keyed-shaft range is to supply the motor without a key — the keyway is machined into the shaft, but the key itself is not included in the motor packaging. Verify the shaft keyway dimensions against the driven hub before ordering a key, and select a key with the correct width, height, and length tolerances for the hub and the application's torque and duty cycle. Refer to the Mitsubishi servo motor instruction manual for the HC-SF202 series shaft and keyway dimensions.