One New Mitsubishi Servo Motor HC-SF502 HCSF502 HC-SF502 New In Box Factory Sealed

Mitsubishi HC-SF502 (HCSF502) — 5kW AC Servo Motor, Straight Shaft, No Brake, MELSERVO J2 Series

Product Identification

Part Number: HC-SF502

Also Searched As: HCSF502, HC-SF-502

Series: Mitsubishi MELSERVO HC-SF (J2 Generation)

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

Condition: New In Box, Factory Sealed

Overview

The Mitsubishi HC-SF502 is the 5kW straight-shaft, no-brake motor from the original MELSERVO J2 HC-SF family — a medium-inertia AC brushless servo motor rated at 2,000 rpm, 23.9 Nm continuous, and 71.6 Nm peak. It occupies the second-largest capacity point in the HC-SF 2000 rpm range, sitting between the 3.5kW HC-SF352 and the top-of-range HC-SF702, and it covers the axis requirements that fall clearly above mid-range capacity without demanding the electrical infrastructure of a 7kW system.

Straight shaft, no brake. Two specification choices, both deliberate. The straight shaft matches the friction-clamp and split-clamp coupling designs standard in high-performance CNC axis ballscrew drives and direct-coupled mechanisms. The absence of a brake reflects an application design where the load is horizontally supported, gravity does not act in the direction of shaft rotation, and position hold at rest comes from amplifier servo lock rather than a mechanical spring device. No brake means no relay, no MBR sequencing, no brake coil wiring, and no additional panel overhead on an axis that has no use for any of it.

As a first-generation J2 motor, the HC-SF502 carries the 14-bit serial absolute encoder at 16,384 ppr and is compatible with both the original MR-J2-500 amplifiers and the later MR-J2S-500 platform. That dual-generation compatibility is the HC-SF502's practical defining advantage: for the large installed base of production machines running MR-J2-500 hardware, this is the only 5kW straight-shaft no-brake motor that can replace the original without requiring an amplifier upgrade at the same time.

Technical Specifications

5kW and 23.9 Nm: The Axis That Needs This Capacity

The HC-SF502 exists because some machine axes genuinely need more than 3.5kW and do not need 7kW. The gap between those two capacity points is wider than it looks on paper. The HC-SF352 delivers 16.7 Nm continuously; the HC-SF502 delivers 23.9 Nm. That is a 43% increase in sustained torque output at the shaft — enough to determine whether an axis stays within its thermal budget during a production shift or approaches overload.

What pushes an axis into that gap? Sustained heavy cutting. Large workpiece and fixture mass on a ballscrew-fed table. A high rapid traverse requirement combined with frequent acceleration cycles where the inertial torque demand is consistently high. A transfer mechanism cycling at production rates under significant load. Any of these, and the duty-cycle analysis that precedes motor selection will show that the 3.5kW motor runs at thermal margin while the 5kW motor runs comfortably within it.

The 71.6 Nm peak — three times the continuous figure — is the amplifier's acceleration resource. Bringing a loaded machine table from rest to rapid traverse speed in the minimum possible time requires substantially more torque than sustaining a cutting feedrate. The 71.6 Nm peak covers that demand, with the motor returning to the continuous operating region once the rapid move is complete and the cutting operation begins. This is the duty profile the HC-SF502 is designed for: brief, high-torque transients bracketing sustained operation well within the continuous rating.

The 7.5 kVA power facility demand is the system electrical footprint. Panel design, cable sizing, fusing, and contactor selection all key off this number alongside the 25A rated current. For axes with frequent, high-energy deceleration events — heavy table axes stopping from maximum rapid traverse speed — the MR-J2 or MR-J2S-500 amplifier's regenerative function returns deceleration energy to the DC bus, and regenerative resistor capacity should be confirmed as part of the system design.

Straight Shaft: Coupling Design at 5kW

The friction-clamp coupling hub on the HC-SF502's straight shaft must be selected, specified, and installed for the peak torque figure — 71.6 Nm — not the rated continuous torque. On a servo axis, the worst-case torque demand occurs during acceleration and deceleration transients, and these can happen repeatedly across a production shift. A coupling that handles the 23.9 Nm continuous load adequately but is marginal at 71.6 Nm will eventually slip under an aggressive rapid traverse cycle.

Slip on a 5kW CNC axis is not a minor event. Lost position on a large machining centre table means dimensional errors on the workpiece, at minimum. More seriously, on a machine with active position loop monitoring, a slip event causes a following error alarm and an emergency stop — stopping production in a way that is difficult to diagnose without close inspection of the shaft-to-coupling interface.

The selection process starts at the peak torque. The coupling must be rated to transmit 71.6 Nm under the service factor appropriate for reversing servo axis duty. Hub bore diameter and tolerance, shaft OD finish, and clamping fastener torque all contribute to the final achievable clamp force. Shortchanging any of these reduces the available friction torque at the interface.

For applications where the coupling design of the driven mechanism incorporates a keyway — timing belt pulleys, gear hubs, sprocket drives, or any interface requiring a positive key-and-hub connection — the HC-SF502K (keyed shaft, no brake) is the parallel variant. The HC-SF502 is for friction-clamp coupling interfaces where a plain shaft OD is the correct interface.

Hub installation guidance: use the shaft-end threaded hole to draw the hub axially onto the shaft with a drawbolt, washer, and nut seated against the hub face. Do not hammer or press-drive the hub onto the shaft. At this motor's frame size and mass, axial impact during hub installation transmits through the shaft to the encoder disc and bearing assembly at the motor's rear. The result is encoder damage that rarely triggers an immediate fault — it surfaces weeks or months later as intermittent encoder alarms under vibration, which are genuinely difficult to trace back to their origin. The drawbolt method adds thirty seconds to the installation and eliminates this failure mode entirely.

No Brake: When Servo Lock Is Sufficient

The HC-SF502 holds axis position at rest through the amplifier's closed-loop servo lock function. The position loop remains active, monitoring the encoder continuously, and supplies corrective current to maintain zero following error. For horizontal axes where no net force acts in the direction of shaft rotation when the servo is in hold state, this is reliable, accurate, and sufficient.

Adding a brake to this axis would provide no functional improvement in position hold quality. What it would add is 24V DC brake coil wiring, a relay and surge absorber in the control panel, an MBR interlock output circuit in the machine's safety logic, a brake sequencing requirement in the axis commissioning procedure, and periodic inspection of the brake disc friction surface as part of preventive maintenance. None of that overhead translates into any operational benefit on an axis where the load sits still when the servo is in hold.

The calculus changes on axes where gravity or load imbalance acts in the direction of shaft rotation when servo current is removed. A vertical Z-column carrying a spindle head, an inclined feed axis, a gravity-loaded shuttle mechanism — these axes belong to the HC-SF502B (straight shaft with spring-applied brake). The brake is a safety-critical device on those axes, not an upgrade; its absence would be a machine design error.

For a machine with multiple 5kW axes, correctly identifying which axes need the brake and which do not produces the simplest, most maintainable electrical design. The HC-SF502 is the correct choice for every 5kW axis in the machine where the load analysis confirms that brake hold is not needed.

J2 Generation Encoder: Capability and the Compatibility Advantage

The HC-SF502 uses the 14-bit serial absolute encoder at 16,384 positions per revolution, the standard feedback device across the original J2 HC-SF family. Serial absolute means the encoder transmits a digital position word to the amplifier at each sample period — not analog sine/cosine signals — and maintains a multi-turn absolute counter through power-off events via battery backup in the servo amplifier.

For the applications the HC-SF502 was designed for — CNC machine tool feed axes, large transfer drives, and industrial automation axes in the 5kW capacity bracket — 14-bit resolution is fully capable. Machine tool positioning tolerances, following-error limits, and velocity control quality on these axes are determined by multiple factors, of which encoder resolution is one. The 16,384 ppr figure is more than adequate for the vast majority of J2-era and J2S-era axis requirements at this power level.

The A6BAT lithium battery in the servo amplifier maintains the multi-turn absolute counter through any power interruption — overnight shutdown, alarm trip, emergency stop, or power fault. Machine restart after any of these events restores the absolute axis position without a reference return cycle. The battery lives in the amplifier, not the motor, and is replaced at the amplifier during planned maintenance. Replace it at the first low-battery alarm from the amplifier; a fully depleted A6BAT means the absolute counter is lost and a reference return is required before production can resume.

The dual-generation amplifier compatibility is the HC-SF502's most important practical characteristic. Because the 14-bit J2 encoder predates the J2S platform, it is readable by both amplifier generations without any parameter setting changes or hardware adaptation:

• MR-J2-500A / MR-J2-500B — Original J2 amplifiers. Full compatibility.
• MR-J2S-500A / MR-J2S-500B / MR-J2S-500CP — J2-Super amplifiers. Fully backward-compatible.

The HC-SFS502 (17-bit J2S encoder) runs on MR-J2S-500 amplifiers only — connecting it to an original MR-J2-500 amplifier causes an encoder protocol fault and the axis will not operate. The HC-SF502 has no such restriction. For the substantial number of machines built during the J2 era with MR-J2-500 amplifiers still in service, the HC-SF502 is the correct and only valid sourcing target for a like-for-like motor replacement.

HC-SF502 vs HC-SFS502: The Sourcing Decision

Mechanical output is identical. Mounting is identical. One verification determines the correct sourcing choice: read the amplifier nameplate in the machine. MR-J2-500 (without S) — source the HC-SF502, no amplifier change needed. MR-J2S-500 — either motor is compatible; the HC-SFS502 offers higher encoder resolution, the HC-SF502 is a fully valid alternative where J2S resolution is not a driving requirement.

HC-SF 2000 rpm Family — 5kW in the Range

The HC-SF502 shares the 176 × 176 mm flange with every motor from 2kW through 7kW in the HC-SF 2000 rpm range. Within each capacity point, the full suffix matrix covers all shaft-and-brake combinations: no suffix (straight, no brake), B (straight with brake), K (keyed, no brake), and BK (keyed with brake). All four share the same flange, encoder protocol, and amplifier compatibility. The shaft type and brake presence do not affect amplifier selection at any capacity point.

Typical Applications

Large CNC machining centre primary feed axes. The X and Y table axes on large-format vertical and horizontal machining centres moving substantial workpiece and fixture assemblies are the defining application for the HC-SF502. These are horizontal axes — no brake needed — at 5kW capacity. The sustained cutting torque demand on a large VMC table pushing through heavy cuts can easily exceed what 3.5kW handles comfortably. The HC-SF502's 23.9 Nm continuous provides the necessary thermal headroom.

HMC pallet shuttle drives. Horizontal machining centre pallet changers transfer loaded pallets between the machining position and the setup station. Pallet masses on medium-to-large HMCs can reach several hundred kilograms, and the shuttle must cycle repeatedly at production rates. The HC-SF502's 23.9 Nm continuous and 71.6 Nm peak handles the sustained transfer load and the acceleration torque demand without approaching thermal limits.

Travelling-column and bridge machining centre axes. On travelling-column machining centres, the column traversal axis moves a large, heavy structural casting along linear guideways over long strokes. The combination of high inertia and high rapid traverse speed makes this a 5kW application on medium-format machines, and the straight-shaft coupling interface suits the high-stiffness disc coupling designs used on these axes.

Large CNC lathe Z-axis carriage drives. Heavy-duty CNC turning centre Z-axis carriage drives moving a large turret and carriage assembly under sustained cutting loads need 5kW capacity to maintain constant cutting velocity during deep turning operations. The straight shaft suits the coupling designs used between servo motor and ballscrew on large lathe Z-axes.

Legacy J2-era machine maintenance and replacement. Perhaps the most direct application: a production machine currently running a failed or worn HC-SF502, with MR-J2-500 amplifiers installed. The HC-SF502 new-in-box replaces the original motor directly, restoring full axis function without any amplifier change, parameter re-engineering, or additional commissioning complexity. For maintenance teams managing fleets of J2-era machines, in-stock new-in-box availability at this capacity is an immediate production recovery solution.

New In Box, Factory Sealed

Factory sealed means original Mitsubishi packaging with all protective elements undisturbed — outer carton intact, inner foam support in place, shaft-end protective cap installed, encoder and power connector ports covered, and oil seal in as-manufactured condition. No prior installation, no thermal history, no bearing load from previous service. At the weight typical of the 5kW HC-SF frame class, the motor ships in packaging suited to its mass, protecting the shaft, oil seal, and encoder assembly through transit.

For a machine currently stopped waiting on this motor, in-stock new-in-box cuts directly through repair turnaround time and delivers a known-condition unit with no variables from previous service events. For planned maintenance inventory on multi-machine operations where this capacity appears on several axes, factory-sealed stock provides consistent, directly commissionable units.

Stored under stable temperature and low-humidity conditions away from vibration, factory-sealed HC-SF502 stock maintains full specification over multiple years. Beyond five years in storage, a pre-commissioning slow shaft rotation as part of the installation inspection helps redistribute bearing grease before first power-up.

Frequently Asked Questions

Q1: Which amplifiers are compatible with the HC-SF502?

The HC-SF502 is compatible with both J2-generation and J2-Super amplifiers at the 500 class. Confirmed compatible models are MR-J2-500A and MR-J2-500B (original J2 generation), and MR-J2S-500A, MR-J2S-500B, and MR-J2S-500CP (J2-Super generation). The 14-bit J2 encoder is readable by both platforms without modification. The HC-SF502 is not compatible with MR-J3 or MR-J4 amplifiers, which use a different encoder interface.

Q2: What is the difference between the HC-SF502 and the HC-SFS502?

Both motors deliver 23.9 Nm continuously and 71.6 Nm peak on a 176 × 176 mm flange with a straight shaft and no brake — physically interchangeable at the mounting face. The difference is the encoder generation: the HC-SF502 uses a 14-bit encoder (16,384 ppr) and works with MR-J2 and MR-J2S amplifiers. The HC-SFS502 uses a 17-bit encoder (131,072 ppr) and requires MR-J2S amplifiers only. If the machine runs original MR-J2-500 amplifiers, source the HC-SF502. If it runs MR-J2S-500, either motor is compatible.

Q3: Why does the HC-SF502 have no electromagnetic brake?

The HC-SF502 is designed for horizontal axes and drives where amplifier servo lock provides adequate position hold at all stop conditions. On these axes, adding a brake introduces relay wiring, MBR sequencing requirements, and panel components that serve no functional purpose. For axes where gravity or load imbalance acts in the direction of shaft rotation on servo-off — vertical Z-columns, inclined slides, unbalanced loads — the correct motor is the HC-SF502B (straight shaft with spring-applied electromagnetic brake). The no-brake specification is an engineering choice, not a cost reduction.

Q4: Where is the absolute encoder battery, and what happens if it depletes?

The Mitsubishi A6BAT lithium battery that backs the 14-bit absolute encoder's multi-turn position counter is located inside the servo amplifier — not in the motor. It retains absolute position through any power interruption as long as it remains charged. Replace the A6BAT when the amplifier displays its low-battery warning alarm. If the battery fully depletes, the multi-turn position counter resets to zero and the machine requires a reference return cycle before production can resume. Under normal conditions the A6BAT lasts several years, but replacement interval depends on ambient temperature and how often the machine is powered off.

Q5: Can the HC-SF502 be used to replace an HC-SF502B if the brake variant is unavailable?

Mechanically the motors share the same flange and shaft, but they are not interchangeable without reassessing the axis safety design. The HC-SF502B has a spring-applied fail-safe brake; the HC-SF502 does not. If the machine's safety design requires mechanical hold on that axis — because it is a vertical axis, carries a gravity load, or the machine's risk assessment specified a brake — substituting the no-brake HC-SF502 removes a safety function. That substitution should only be made after a formal review of the axis safety requirements confirms the change is acceptable. For like-for-like replacement of a B-suffix motor, source the B-suffix variant.