SCARA robots cover payload tiers from 1 kg to 20 kg across a 300-850 mm reach envelope, with repeatability clustering between ±0.010 mm and ±0.040 mm depending on arm length and price class [S3][S4][S5][S7][S10]. Buyers should map the application's worst-case part mass, footprint, and cycle-time budget to a specific model family before quoting a controller or vision option.
For a 4-axis selective-compliance arm, the four decision axes are reach, payload, Z-stroke, and environmental rating (IP65 / food-grade / cleanroom). Cross-check those four numbers against the workcell's conveyor pitch, part-fixture height, and washdown or dust exposure before shortlisting. Refer to the SCARA robot encyclopedia entry for the kinematic definition and a comparison against Cartesian and delta alternatives.
Reach Tiers and Work-Envelope Geometry
Table-top SCARAs cluster into three reach bands: 350-400 mm compact cells, 500-700 mm mid-range work envelopes, and 750-850 mm long-reach cells that bridge SCARA into light-cartesian territory [S3][S6][S7][S8][S9]. The Delta DRS50L/DRS70L series covers 500 mm and 700 mm arm-length variants with J1+J2 composite speeds of 4400-5500 mm/s and J3 Z-axis stroke options of 200 mm or 300 mm [S3]. Omron's i4-650H/750H/850H line extends the upper band with 210 mm or 410 mm Z-axis stroke and IP65-rated or food-grade variants, paired with EtherCAT connectivity to the NJ501-R controller [S7].
Yamaha's YK-XG platform uses an X=250 mm / Y=150 mm inner-link geometry inside a 350 mm total arm length, with R-axis unlimited rotation (±360°) and AC servo motors from 50 W on the Z-axis to 200 W on the shoulder [S9]. TM Robotics' THE600 publishes full-length 600 mm geometry (325 mm first arm + 275 mm second arm) with J1/J2 angles of ±140°/±152° and a composite maximum speed of 8.017 m/s [S8]. Work-envelope selection should subtract at least 50 mm of safety margin from the nominal reach to keep the part away from joint hard-stops during fast moves.
Payload Classes: 1-3 kg, 6 kg, 12 kg, 20 kg
Payload capability divides into four operational tiers. The 1-3 kg tier covers electronics pick-and-place, small-part feeders, and laboratory automation; Epson's T3-B and T6-B series sit here, with the T3-B publishing arm length around 400 mm and a built-in controller that runs on 110 V or 220 V without an encoder battery [S6]. The 6 kg mid-tier handles screw-driving, dispensing, and small assembly, populated by the Omron i4H and the Yamaha YK600XGLP, the latter rated to 2 kg payload in the YK-XG catalog but expandable with the 200 W shoulder servo [S7][S9].
The 12 kg tier addresses larger fastener torque, heavier dispensing, and small-part palletizing. Mitsubishi's RH-12FH series is the documented example, with reach options typically 700-1000 mm and repeatability of ±0.015 mm in the standard RH-F line [S5]. The 20 kg top tier — including FANUC's heavy-payload SCARAs — supports heavier end-of-arm tooling, larger vacuum grippers, and multi-part handling, while still occupying a pedestal-mount footprint with a 360° work envelope [S10]. Delta's DRS50L6SS1BN002 publishes a 2 kg rated / 6 kg maximum payload split, illustrating how vendors separate continuous-duty from peak capability on the same model [S3].
Repeatability and Cycle-Time Benchmarks
Repeatability for mainstream SCARAs falls in the ±0.010 mm to ±0.040 mm band, with sub-10 micron capability reserved for ultra-precision cells [S4]. Mitsubishi's RH-F line quotes ±0.010 mm to ±0.015 mm across the standard reach range, while Yamaha's YK-XG and TM Robotics' THE600 publish cycle times of 0.31 s and standard arch-motion cycle times in the 2-3 s range respectively [S5][S8]. Shibaura Machine's TH350 is documented at 2.9 s cycle completion for 1-2 kg payload in benchmark arch-motion tests [S4].
The cycle-time number buyers should demand from the vendor is the standard arch-motion benchmark: 300 mm horizontal, 25 mm vertical round-trip, with a 1 kg or 2 kg payload. Epson defines this explicitly for the T3-B and warns that payload center-of-gravity offset must be entered via the INERTIA command when the part mass sits off Joint 4 [S6]. A faster-rated servo will not deliver that 2-3 s cycle if the Z-stroke is longer than the application actually needs, so keep the published arch-motion number and the actual workcell geometry paired in the spec sheet.
Controller Integration and Fieldbus
Controller choice is a hidden selection driver because it determines programming language, fieldbus, and synchronization with surrounding axes. Omron's i4H line integrates via EtherCAT to the NJ501-R controller and programs through IEC 61131-3 languages or the V+ scripting environment, which shortens commissioning for plants already standardized on Omron PLCs [S7]. Mitsubishi's RH-FH variants coordinate with the CRnD-700 controller for synchronized motion with linear axes — useful when the SCARA hands a part to a linear guide slide or a crossed-roller guide stage downstream [S5].
Epson's T3-B and T6-B embed the controller inside the arm, eliminating a separate cabinet and supporting 110 V or 220 V input without an encoder battery, which simplifies retrofit installs where the original cabinet space is gone [S6]. ABB's SCARA family ships with the RobotStudio offline programming suite and an AR viewer mobile app, so plants already running articulated robot cells on ABB controllers can extend the same toolchain to a 4-axis pick-and-place cell without retraining the integration team [S1]. Yamaha's YK-XG series is controlled by the RCX340 or RCX240S, with operation supported through programming, I/O point trace, remote command, or RS-232C [S9].
Environmental Ratings and Cleanroom / Food-Grade Options
SCARAs increasingly ship with IP65 dust-and-water protection, food-grade grease, and cleanroom-classified variants because pharma, food, and semiconductor back-end lines are the fastest-growing installed base. Omron's i4-650H/750H/850H datasheet explicitly lists IP65 and Food Grade models as ordering options, signalling that the seals and lubricants are validated for washdown and incidental food contact rather than added as a field retrofit [S7]. FANUC's SCARA line extends the same logic with two documented environmental options across 3 kg, 6 kg, 12 kg, and 20 kg payload classes, with all pedestal-mount models supporting a 360° work envelope [S10].
For a buyer weighing cleanroom classification, the right question is whether the vendor publishes an ISO 14644 class rating or only an IP code. IP65 covers ingress but says nothing about particulate emission under motion, so a semiconductor back-end line should request the cleanroom-specific variant rather than assume an IP65 standard model will pass particle-count testing. ABB's RobotStudio and AR viewer tooling is platform-agnostic across ABB's SCARA, AGV, and AMR portfolios, which helps plants consolidating simulation across multiple robot classes [S1].
Selection Criteria: Matching Application to Model Family
A four-criterion comparison clarifies the shortlist. (1) Reach: sub-500 mm favors Epson T-series and Yamaha YK-XG 350 mm; 500-700 mm covers most Delta DRS and Omron i4H; 750-850 mm targets the long-reach Omron i4-850H and TM Robotics THE600. (2) Payload: under 3 kg → Epson T3-B; 6 kg → Delta DRS50L6, Omron i4-650H, Yamaha YK600XGLP; 12 kg → Mitsubishi RH-12FH; 20 kg → FANUC heavy-payload SCARA. (3) Repeatability: ±0.010-0.015 mm → Mitsubishi RH-F and Shibaura-class precision; ±0.020-0.040 mm → mainstream mid-payload lines. (4) Environment: IP65/food-grade → Omron i4H and FANUC's environmental options; cleanroom → vendor-published ISO 14644 variant only. [S5]
Skip the SCARA category entirely when the application needs long vertical travel beyond ~410 mm Z-stroke, true 6-axis articulation around an obstacle, or mobile manipulation. In those cases, the articulated robot arm class or an AGV / AMR with a manipulator is a more honest specification. For an electronics conveyor-handling cell with high throughput, also cross-reference the surrounding material-handling equipment; the roller conveyor selection for electronics handling spec map pairs naturally with a 500-700 mm reach SCARA at 4400-5500 mm/s composite J1+J2 speed.
Who Should NOT Choose a Mainstream Mid-Payload SCARA
A buyer needing more than ~5 kg continuous payload with a 410 mm Z-stroke is at the edge of the mid-payload envelope and should step up to a 12 kg or 20 kg class rather than over-rate a 6 kg model. The DRS50L6SS1BN002 split rating of 2 kg rated / 6 kg maximum is a warning, not a target: continuous duty at the 6 kg maximum will accelerate shoulder-servo wear and invalidate the cycle-time benchmark, because arch-motion cycle times are published at 1-2 kg payload [S3]. The Mitsubishi RH-FH line at 12 kg handles heavier end-of-arm tooling, including larger vacuum grippers, and gives margin for moment-arm offsets that a 6 kg arm cannot absorb.
Buyers who need under 1 kg payload on a 400 mm arm, with an embedded controller for a tight cabinet, should also look away from the 6-12 kg tier. The Epson T3-B with a built-in controller, 400 mm arm, 110/220 V input, and no encoder battery is the honest spec for that niche, not a 6 kg model running at 10% load [S6]. Track for 2026-08: vendor announcements extending food-grade lubrication and ISO 14644 cleanroom certification further into the 12 kg class, and IEC 61131-3 harmonization between Omron's NJ501-R, Mitsubishi's CRnD-700, and ABB's RobotStudio toolchain so multi-vendor cells share one programming model [S1][S5][S7].