Comau Rebel-S6-0.45 vs Epson G3-251: Robot Comparison

IN A NUTSHELL

Comau Rebel-S6-0.45 vs Epson G3-251 is a choice about SCARA assembly and planar handling. Comau Rebel-S6-0.45 and Epson G3-251 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.

Comau Rebel-S6-0.45 vs Epson G3-251: quick verdict

Shortlist Comau Rebel-S6-0.45 for 6 kg planar handling within the selected 450 mm SCARA envelope. Shortlist Epson G3-251 for 3 kg maximum-load SCARA handling within the selected 250 mm horizontal 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 Comau Rebel-S6-0.45 against Epson G3-251. 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

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.

Comau Rebel-S6-0.45: design and configuration

The Comau Rebel-S6-0.45 is a 4-axis SCARA robot with a 6 kg payload and a horizontal reach of 450 mm, repeatable to ±0.02 mm in the X-Y plane. It offers a 200 mm vertical stroke, a Z-axis down force of 160 N and a robot weight of 20 kg, with base or wall mounting. Internal user wiring provides a 25-pin electrical connection and three pneumatic lines, and protection is IP10 with an IP54 option. The arm is driven by the Comau R1C-4 controller and is used for handling, assembly and machine tending. The Rebel-S6 is a four-axis SCARA robot, not a six-axis Racer. The arm-length suffix defines the planar envelope. Validate insertion stroke, spindle inertia and controller options for the quoted R1C-4 package; no arbitrary pitch or roll motion is assumed.

Epson G3-251: design and configuration

The Epson G3-251 is the named four-axis SCARA configuration with 3 kg maximum payload, 250 mm horizontal reach and ±0.008 mm XY repeatability. The reviewed control baseline is Epson RC700-A. 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 reviewed G or LS-B generation must be identified separately from later GX, LS-C or other replacements. A compact XY envelope can support closely spaced nests, but the complete spindle, tool and cable sweep still needs a fixture-specific simulation.

For this pair, Epson G3-251 offers 3 kg over the stated 250 mm reference, compared with 6 kg and 450 mm for Comau Rebel-S6-0.45 example. Comau Rebel-S6-0.45 has the larger stated distance by 200 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 3.6 kg below the Comau Rebel-S6-0.45 example’s nominal limit and 0.6 kg below Epson G3-251’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? Epson G3-251 is the lower-or-equal nominal payload choice in this pair. Comau Rebel-S6-0.45 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. Comau Rebel-S6-0.45 provides a stated 450 mm reference, while Epson G3-251 provides 250 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 Comau Rebel-S6-0.45 and Epson G3-251 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.

Precision and throughput: compare the same task

The comparison uses ±0.02 mm for Comau Rebel-S6-0.45 and ±0.008 mm for Epson G3-251. 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 Comau Rebel-S6-0.45 over Epson G3-251. Use a measured or validated application cycle before assigning a throughput benefit.

Programming, controls and production integration

Comau Rebel-S6-0.45 is paired here with Comau R1C-4, while Epson G3-251 uses Epson RC700-A. 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

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: Comau Rebel-S6-0.45 is listed from $18,000 and Epson G3-251 is listed from $9,000. Request configuration-specific quotations for Comau Rebel-S6-0.45 and Epson G3-251. 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

Advance Comau Rebel-S6-0.45 when 6 kg planar handling within the selected 450 mm SCARA envelope solves the real constraint and its selected configuration passes the load and access checks. Advance Epson G3-251 when 3 kg maximum-load SCARA handling within the selected 250 mm horizontal 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

Comau Rebel-S6-0.45 has 4 arm axes and Epson G3-251 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 Comau Rebel-S6-0.45 vs Epson G3-251, 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.

Frequently asked questions

Which robot is better for this application?

Comau Rebel-S6-0.45 is the stronger starting point for 6 kg planar handling within the selected 450 mm SCARA envelope, while Epson G3-251 is worth shortlisting for 3 kg maximum-load SCARA handling within the selected 250 mm horizontal 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 6 kg for the specified Comau Rebel-S6-0.45 example and 3 kg for Epson G3-251, subject to all documented load and orientation conditions. Include the tool, adapters, sensors and carried part. XY repeatability, Z stroke, spindle inertia and vertical pressing force are separate limits. Do not transfer a standard cycle time to the maximum load.

Does the stated reach guarantee access to my fixture?

No. The comparison gives 450 mm for Comau Rebel-S6-0.45 and 250 mm for Epson G3-251 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 ±0.02 mm for Comau Rebel-S6-0.45 scope and ±0.008 mm 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 Comau Rebel-S6-0.45 and Epson G3-251 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 Comau Rebel-S6-0.45 and Epson G3-251. 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

Read the Comau Rebel-S6-0.45 review

Read the Epson G3-251 review

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.