Epson GX4-B251 vs Mitsubishi Electric RH-3FRH: Robot Comparison
Updated: 4 hours ago
IN A NUTSHELL
🔎 THE KEY DIFFERENCE This is a load-versus-reach trade-off: Epson GX4-B251 has the higher stated load capacity, while Mitsubishi Electric RH-3FRH has the longer stated reach. Start with the constraint your task actually has. |
→ CONSIDER Epson GX4-B251 Consider it when additional load capacity matters more than extra reach. This article compares 4 kg with a published reach of 250 mm; include the gripper and part in the load. |
→ CONSIDER Mitsubishi Electric RH-3FRH Consider it when reaching farther matters more than the higher payload of the alternative. This article compares 3 kg with a published reach of 350 mm; include the gripper and part in the load. |
💡 THE TAKEAWAY For repetitive pick-and-place or assembly, check the actual vertical stroke and tool rotation as well as horizontal reach. Compare the same loaded cycle and installed quotation before deciding. |
Epson GX4-B251 vs Mitsubishi Electric RH-3FRH is a choice about SCARA assembly and planar handling. Epson GX4-B251 and Mitsubishi Electric RH-3FRH differ in their working envelope, loading assumptions and engineering ecosystem. A useful decision starts with the exact mechanism and process, then checks whether either robot can execute the required path with the real tool attached. This comparison separates documented specifications from application-level engineering judgments.
Epson GX4-B251 vs Mitsubishi Electric RH-3FRH: quick verdict
Shortlist Epson GX4-B251 for 4 kg maximum-load SCARA handling within the selected 250 mm horizontal envelope. Shortlist Mitsubishi Electric RH-3FRH for 3 kg planar handling within the selected 350 mm SCARA envelope. Both are four-axis SCARA candidates, so the decisive questions are planar access, vertical stroke, spindle inertia and the complete assembly cycle. Neither supplies independent tool pitch and roll.
The numerical comparison below uses Epson GX4-B251 against Mitsubishi Electric RH-3FRH. The stated model scope matters when comparing later revisions or differently equipped installations. Published repeatability describes return to a taught position under specified conditions; it does not establish complete-cell accuracy or prove a faster production cycle.
Specifications and exact configuration scope
Criterion | Epson GX4-B251 | Mitsubishi Electric RH-3FRH |
|---|---|---|
Comparison configuration | Epson GX4-B251 | Mitsubishi Electric RH-3FRH |
Payload used for comparison | 4 kg | 3 kg |
Reach / motion-area reference | 250 mm | 350 mm (selected short-arm reference) |
Axes | 4 | 4 |
Repeatability for this scope | ±0.008 mm | ±0.010 mm (XY reference) |
Controller reference | Epson RC700-E | CR800-03HD (standalone reference) |
Purchase-price basis | Configuration-specific quotation | Configuration-specific quotation |
Purchase pricing | From $11,000 (arm list price) | From $18,500 (arm list price) |
Read the reach row together with the geometric notes below. Manufacturers may specify an arm-link sum, a wrist-centre motion area or reach to the flange; those dimensions are not interchangeable. The table does not establish access to every point at every tool angle. Controller references identify reviewed packages, and actual compatibility must be confirmed by model, software version and region.
Epson GX4-B251: design and configuration
The Epson GX4-B251 is the named four-axis SCARA configuration with 4 kg maximum payload, 250 mm horizontal reach and ±0.008 mm XY repeatability. The reviewed control baseline is Epson RC700-E. Horizontal repeatability is not the Z-axis or rotational specification, and nominal cycle figures use a defined test load and path rather than every maximum load. Keep arm length, Z stroke, mounting direction and protection suffix tied to the full order code. Evaluate tool inertia, insertion stroke and any permitted vertical pressing force separately from payload. The newer GX-B controller and arm generation must not be blended with G-series or older GX revisions. A compact XY envelope can support closely spaced nests, but the complete spindle, tool and cable sweep still needs a fixture-specific simulation.
Mitsubishi Electric RH-3FRH: design and configuration
The Mitsubishi Electric RH-3FRH comparison uses the RH-3FRH3515-D short-arm reference: four SCARA axes, 3 kg maximum load and 350 mm horizontal reach. The standalone control reference is CR800-03HD. The family also contains 450 and 550 mm arms, different Z strokes, clean or oil-mist options and separately matched R/Q controller variants; none of those maxima are combined with this example. XY repeatability of ±0.010 mm is distinct from Z and rotation specifications. Confirm spindle stroke, tool inertia, pneumatic services and insertion loads independently of the mass rating. Four axes suit planar handling with controlled vertical travel, but they cannot provide arbitrary six-axis wrist pitch and roll. Evaluate the complete fixture layout, minimum approach height and recovery route, and use the exact order-code manual for the supplied arm/controller combination.
For this pair, Mitsubishi Electric RH-3FRH offers 3 kg over the stated 350 mm reference, compared with 4 kg and 250 mm for Epson GX4-B251 example. Mitsubishi Electric RH-3FRH has the larger stated distance by 100 mm, but this difference is only a preliminary layout indicator because reference points and joint envelopes can differ. Locate the actual fixture in each manufacturer model before treating this as usable extra working space.
Payload, tooling and a worked load example
Consider an illustrative total wrist load of 2.4 kg: a 0.6 kg tool and adapter package carrying a 1.8 kg part or product group. This arithmetic leaves 1.6 kg below the Epson GX4-B251 example’s nominal limit and 0.6 kg below Mitsubishi Electric RH-3FRH’s nominal limit. These are mass differences, not safety factors or a validated load approval. A heavy camera, valve block or retained material must be included before recalculating the total.
The example exposes the practical question: is the application limited by mass, by tool offset or by wrist rotation? Mitsubishi Electric RH-3FRH is the lower-or-equal nominal payload choice in this pair. Epson GX4-B251 offers more or equal headline mass capacity, but that alone cannot approve an eccentric fixture. Moving the same mass farther from the flange increases the moment, and spreading it increases rotational inertia. Manufacturer load diagrams and the actual centre of gravity govern the final allowable motion.
For the two SCARA configurations, model the tool inertia around the vertical spindle as well as total carried mass. A broad multi-part gripper can satisfy the mass limit while exceeding permitted rotational inertia. Set the controller load and inertia parameters for empty and loaded states, then check insertion stroke and any allowable vertical pressing force separately. Nominal cycle figures do not establish performance at maximum payload.
Reach, orientation and fixture access
Build the same cell model for both candidates: base height, machine opening, fixture datum, maximum part size, tool extension and access for maintenance. Epson GX4-B251 provides a stated 250 mm reference, while Mitsubishi Electric RH-3FRH provides 350 mm. Check the deepest production pose and the return path with the loaded tool. An arm that just touches the target at full extension may have little freedom left to turn, retract or avoid a door.
For SCARA assembly, check the full XY sweep, inner dead zone and Z stroke. A horizontal reach figure does not establish that the spindle can descend into the fixture without the tool body or cable loop colliding. Vertical pressing force is a separate limit from payload. Validate screwdriving or insertion forces, spindle inertia and settling with the real fixture. Neither robot gains six-axis pitch and roll freedom merely by having enough horizontal reach.
SCARA motion and assembly fit
The selected Epson GX4-B251 and Mitsubishi Electric RH-3FRH should be assessed on the same horizontal transfer, vertical insertion and rotation sequence. Smaller horizontal reach can support a compact bench; larger reach can serve more nests, but also changes the swept area and cable clearance. Check actual Z stroke and tool length against the lowest station and tallest obstruction. Compare XY repeatability with XY repeatability, while keeping Z and rotational values in their own units.
SCARA requirement | Epson GX4-B251 | Mitsubishi Electric RH-3FRH |
|---|---|---|
Horizontal scope | 250 mm selected example | 350 mm selected example |
Payload scope | 4 kg maximum for the named configuration | 3 kg maximum for the named configuration |
Z stroke and downforce | Confirm exact spindle and stroke option | Confirm exact spindle and stroke option |
Tool pitch and roll | No independent six-axis pitch/roll | No independent six-axis pitch/roll |
Acceptance path | Same transfer, insert, rotate and settle sequence | Same transfer, insert, rotate and settle sequence |
Precision and throughput: compare the same task
The comparison uses ±0.008 mm for Epson GX4-B251 and ±0.010 mm (XY reference) for Mitsubishi Electric RH-3FRH. These figures should be read in their documented configuration scope. Repeatability is not absolute accuracy, camera calibration accuracy or finished-part capability. Fixture variation, TCP calibration, thermal conditions and tool compliance can dominate the error at the process point, especially when the tool extends far from the flange.
Ask each integrator to execute the same representative path with the same payload model, tool length, process dwell and stop conditions. Report transfer time, settling time, process time and waiting time separately. Published standard cycles often use different loads and distances; dividing one catalogue cycle by another would not establish the production advantage of Epson GX4-B251 over Mitsubishi Electric RH-3FRH. Use a measured or validated application cycle before assigning a throughput benefit.
Programming, controls and production integration
Epson GX4-B251 is paired here with Epson RC700-E, while Mitsubishi Electric RH-3FRH uses CR800-03HD (standalone reference). Controller names identify the review baseline rather than a guarantee that all interface options are included. Compare the actual software revision, teaching workflow, diagnostic tools, fieldbus licences and recovery procedures. An existing trained team and reusable production code may outweigh a small dimensional advantage. Obtain a demonstration of the same machine handshake and interrupted-cycle recovery on both platforms.
Specify the PLC handshakes before ordering: cycle request, ready, busy, complete, fault, part present and recovery authorization. Define how an interrupted operation resumes without repeating a dangerous or quality-critical action. Vision, force sensing, fieldbus communication and external-axis coordination must be checked as explicit included or optional functions. An Ethernet connector does not by itself prove that a particular industrial protocol or software interface is licensed and supported.
Configuration and communication detail
Integration reference | Epson GX4-B251 | Mitsubishi Electric RH-3FRH |
|---|---|---|
Control package | Epson RC700-E | CR800-03HD (standalone reference) |
Documented interface baseline | Specify required interfaces in the delivered package | Specify required interfaces in the delivered package |
Programming baseline | Named platform software and supported API; confirm supplied version | Named platform software and supported API; confirm supplied version |
Integration acceptance | Test the actual machine handshake and controlled recovery | Test the same handshake and controlled recovery |
Protection, installation and maintenance
Match the precise protection package to the process. Standard, protected, cleanroom, foundry and washing configurations can have different seals, services and maintenance requirements. Do not transfer the best optional IP or cleanroom rating to an unprotected base model. Check the controller location, cable bend radius, available lifting access and base reactions with the installer.
Treat safe operation as a property of the complete task and installation. Include the tool, sharp workpiece edges, trapping points, dropped loads and machine access. These robot systems require task-specific safeguarding; payload or compact size does not establish safe unguarded operation. Plan tool replacement and fault recovery without dismantling the whole installation, and include connector access, lubrication and spare-cable replacement in the maintenance layout.
Price and lifecycle value
Published arm list prices: Epson GX4-B251 is listed from $11,000 and Mitsubishi Electric RH-3FRH is listed from $18,500. Request configuration-specific quotations for Epson GX4-B251 and Mitsubishi Electric RH-3FRH. An arm-only number is not the price of a commissioned production cell. Ask for separate line items for controller, pendant, communication options, end effector, safety equipment, installation, acceptance, training and warranty. Price changes, regional support and included software can reverse an apparent hardware-cost advantage. Compare the same delivered scope before calculating payback.
Compare the installed production scope: tool, fixtures, sensing, guarding, machine interface, programming, acceptance and training. For small-parts automation, include feeders, vision calibration, nests and rejected-part handling. Keep purchase cost and recurring support costs separate. No payback figure is defensible until the actual cycle, yield, utilization and installation quotation are known.
Selection and acceptance plan
Decision gate | Epson GX4-B251 | Mitsubishi Electric RH-3FRH |
|---|---|---|
Strongest documented fit | 4 kg maximum-load SCARA handling within the selected 250 mm horizontal envelope | 3 kg planar handling within the selected 350 mm SCARA envelope |
Main boundary | XY repeatability, Z stroke, spindle inertia and vertical pressing force are separate limits. Do not transfer a standard cycle time to the maximum load. | Four axes do not provide arbitrary wrist pitch and roll. |
Required approval | Exact Epson variant, tool load and validated process path | Exact competitor revision, tool load and validated process path |
Acceptance evidence | Agreed parts, path, quality and recovery results | The same agreed parts, path, quality and recovery results |
Advance Epson GX4-B251 when 4 kg maximum-load SCARA handling within the selected 250 mm horizontal envelope solves the real constraint and its selected configuration passes the load and access checks. Advance Mitsubishi Electric RH-3FRH when 3 kg planar handling within the selected 350 mm SCARA envelope provides the more suitable process arrangement. Reject either candidate if a mandatory pose, protection requirement or controller function cannot be demonstrated. A purchasing shortlist should preserve these conditions instead of converting a single catalogue advantage into a blanket recommendation.
Before acceptance, agree the representative parts, tool states, operating sequence and quality criteria with both suppliers. Demonstrate cold start, normal production, rejected parts, interrupted cycles and controlled recovery. Record the final tool data and software backup. This turns the comparison into a repeatable purchasing decision and helps prevent a later fixture change from invalidating the original robot selection.
Motion architecture and functionality
Epson GX4-B251 has 4 arm axes and Mitsubishi Electric RH-3FRH has 4 arm axes. A four-axis mechanism cannot independently supply every pitch and roll angle. Assess whether the tool must stay level or be presented at varying attitudes. Compare tool detection, sensing, machine I/O and recovery as separate delivered functions.
Industries and application fit
For Epson GX4-B251 vs Mitsubishi Electric RH-3FRH, use the actual part and process as the industry filter. Electronics assembly, component packaging and small mechanical assembly are plausible candidates when the required movement is primarily horizontal transfer plus vertical insertion. These are application-selection judgments, not claims that either exact model is installed at a named customer. A food, medical-device or clean-production application additionally requires the correct material, lubrication and protection package; the base model name does not establish hygienic or cleanroom compliance.
Selection issue | Epson GX4-B251 | Mitsubishi Electric RH-3FRH |
|---|---|---|
Tool and workpiece mass | 4 kg named scope; include the complete tool | 3 kg named scope; include the complete tool |
Working reference | 250 mm | 350 mm (selected short-arm reference) |
Main configuration boundary | XY repeatability, Z stroke, spindle inertia and vertical pressing force are separate limits. Do not transfer a standard cycle time to the maximum load. | Four axes do not provide arbitrary wrist pitch and roll. |
Process approval | Demonstrate the actual loaded path and recovery | Demonstrate the same loaded path and recovery |
Frequently asked questions
Which robot is better for this application?
Epson GX4-B251 is the stronger starting point for 4 kg maximum-load SCARA handling within the selected 250 mm horizontal envelope, while Mitsubishi Electric RH-3FRH is worth shortlisting for 3 kg planar handling within the selected 350 mm SCARA envelope. The final choice depends on the real loaded path, required protection, controls and acceptance results. Neither a higher payload nor a longer reach establishes a universal winner.
What payload should I use for the comparison?
Use 4 kg for the specified Epson GX4-B251 example and 3 kg for Mitsubishi Electric RH-3FRH, subject to all documented load and orientation conditions. Include the tool, adapters, sensors and carried part. Four axes do not provide arbitrary wrist pitch and roll.
Does the stated reach guarantee access to my fixture?
No. The comparison gives 250 mm for Epson GX4-B251 and 350 mm for Mitsubishi Electric RH-3FRH using the stated model references. Joint limits, reach reference points, wrist orientation, tool length and collisions determine whether the actual fixture is accessible. Simulate the full approach and exit path.
Can I use the best specifications from every family variant?
No. Keep each named model and revision intact. A different arm length, controller generation or protection option can change the relevant specification. Do not combine one version’s maximum payload with another version’s maximum reach.
Is repeatability the same as finished-part accuracy?
No. The stated values are ±0.008 mm for Epson GX4-B251 scope and ±0.010 mm (XY reference) for the competitor scope. Finished-part results also depend on fixtures, TCP calibration, sensing, thermal conditions and tool compliance. Validate the actual process instead of treating catalogue repeatability as a complete accuracy guarantee.
How should purchase prices be compared?
Use current written quotations for Epson GX4-B251 and Mitsubishi Electric RH-3FRH with the same arm, controller, software, tooling and commissioning scope. This comparison does not represent an ATC sales offer or stock confirmation. Historical review figures are not a substitute for a configuration-specific purchase quotation.
Can these robots operate safely next to people without guarding?
These specifications do not establish a safe unguarded installation. Assess the complete task, tool, load and machine interface, then implement and validate the required safeguarding and operating procedures. Do not infer collaborative operation from a compact arm, limited payload or education setting.
What should an acceptance test compare?
Use the same parts, actual tool load, fixture locations, path and quality criteria for Epson GX4-B251 and Mitsubishi Electric RH-3FRH. Check production timing, settling, interruptions and recovery. Include the most difficult loaded approach and retreat. Approve the exact delivered configuration and preserve its final settings.
Related ATC reviews
Specifications describe the model scope identified above. Purchase pricing requires a current configuration-specific quotation. Confirm current manufacturer documentation, local supply, controller compatibility and the exact configuration before purchase.
