Industrial Robot Types: A Guide to Articulated, SCARA, Delta, and Cobots

Types of Industrial Robots

Industrial robots are classified primarily by mechanical structure and kinematics. The dominant families—articulated, SCARA, delta (parallel), Cartesian (gantry), and collaborative robots (cobots)—each deliver different trade-offs in degrees of freedom (DOF), payload, speed, repeatability, and workspace geometry. Selecting the correct type requires matching those mechanical and performance characteristics to the application's tasks such as welding, high-speed pick-and-place, precision assembly, large-volume handling, or human-robot collaboration. Industry references and manufacturer datasheets summarize these trade-offs and provide baseline performance ranges used in system design and ROI analysis [2][4][7].

Articulated Robots

Articulated robots use rotary joints and typically provide 6 axes of motion (some systems add an external linear axis for reach or payload reasons). They offer the highest flexibility for complex paths, making them the preferred choice for multi-process applications such as arc/stick welding, automated painting, machine tending, assembly of complex geometries, and palletizing large payloads.

Key technical characteristics:

• Axes/DOF: Commonly 6, with some systems offering 7 or more when a linear base axis is added.
• Payload range: Wide—typical commercial models span about 3 kg to >1,000 kg; many general-purpose arms cover 5–500 kg classes [2][4].
• Repeatability: Typical repeatability lies between ±0.05 mm and ±0.1 mm for industrial-grade articulated arms; high-precision variants may improve on that [2][4].
• Workspace: Spherical or cylindrical work envelope, enabling reach around fixtures and parts.

Manufacturers and examples: ABB IRB series, FANUC M-series, KUKA KR series, and Yaskawa Motoman GP series. Control systems and integration options include KUKA KRC and FANUC R-30iB controllers; these support fieldbus connectivity (EtherCAT, PROFINET, EtherNet/IP) and vision integration. Articulated robots are best selected where path flexibility, torque, and payload dominate the selection criteria rather than absolute cycle speed [4][10].

SCARA Robots

SCARA (Selective Compliance Articulated Robot Arm) robots provide high-speed, high-precision motion primarily in the horizontal plane. They excel at vertical insertion tasks because of a rigid Z-axis combined with compliant X–Y positioning. SCARA arms are common in electronics assembly, surface-mount handling, medical device assembly, and small-part pick-and-place.

Key technical characteristics:

• Axes/DOF: Typically 3 rotational joints with a prismatic or rotational Z-axis — most commercial models are 4-axis systems.
• Payload: Typically 1–20 kg depending on arm size.
• Repeatability: SCARA robots commonly provide very high repeatability — often <10 microns (±0.01–0.03 mm) in top-class units, enabling precision insertion and micro-assembly [1][5][8].
• Speed: High horizontal speed with cycle rates up to ∼120 picks/min or more on short strokes.
• Workspace: Disc-shaped X–Y workspace with limited vertical travel.

Popular models include FANUC SR series and Mitsubishi MELFA RH-FR. SCARA robots provide a compact footprint and low inertia in horizontal motion; however, their limited Z travel and smaller overall workspace make them less suitable for tall or deeply nested fixtures [1][3][5].

Delta (Parallel) Robots

Delta robots use a parallel kinematic architecture: lightweight arms connect a fixed base to a moving end effector via parallelogram linkages, with motors mounted at the stationary frame. This arrangement minimizes the moving mass, enabling the highest available cycle rates for light-payload pick-and-place tasks.

Key technical characteristics:

• Axes/DOF: Usually 3 translational DOF with optional 4th axis for part orientation.
• Payload range: Typically light—about 0.5–8 kg depending on design; common commercial payloads are 1–3 kg.
• Repeatability: On the order of ±0.03–0.1 mm depending on size and configuration [1][3][4].
• Speed: Very high; common pick rates exceed 150 picks/min and some delta models report >500 picks/min (FANUC M-1iA family reports up to 550 picks/min in certain configurations) [1][6].
• Workspace: Dome-shaped workspace mounted overhead—best for conveyor-to-packaging transfer, sorting, and light part handling.

Delta robots such as ABB FlexPicker and FANUC M-1iA/M-3iA are standard in food, pharmaceutical, and consumer-goods packaging lines. The fixed motor placement lowers inertia and improves dynamic response, but high-speed parallel mechanisms can require more frequent maintenance (lubrication of parallelograms, checks on ball joints) and careful calibration for vision-guided pick accuracy [1][6].

Cartesian (Gantry) Robots

Cartesian robots (also called gantry robots) move along orthogonal linear axes (X–Y–Z) and produce a rectangular or cuboidal working volume. They are typically used where large coverage, linear accuracy, and predictable straight-line motion are required—examples include CNC machinery, large-part assembly, 3D printing gantries, and heavy-duty pick-and-place over extended areas.

Key technical characteristics:

• Axes/DOF: Usually 3 linear axes; additional rotary axes can be added at the end effector.
• Payload: Broad—small gantries handle a few kilograms; large industrial gantries handle 50 kg and above depending on structure.
• Repeatability: Typically ±0.01–0.05 mm for precision gantries; depends on ball-screw/linear guide quality [2][7].
• Workspace: Rectangular, scalable to very large sizes; ideal for large-platform automation.

Choose Cartesian systems when straight-line accuracy and scalability outweigh the need for compactness or multi-axis dexterity. They are mechanically simpler and often have lower lifecycle costs for large-area tasks [7].

Collaborative Robots (Cobots)

Collaborative robots are designed specifically to operate in proximal human environments with reduced guarding. They incorporate force-limiting, speed and separation monitoring, and safety-rated reduced-speed functions to allow safe human-robot collaboration when risk assessments and mitigation measures are in place.

Key technical characteristics:

• Axes/DOF: Commonly 6-axis arms derived from articulated designs, with software and sensors for safe operation.
• Payload: Modern cobots range from about 3 kg to 30 kg for the newest high-payload units (for example, Universal Robots' UR20/UR30 families extend payloads in the 20–30 kg class) [3].
• Repeatability: Typical values lie between ±0.03 mm and ±0.1 mm depending on model and payload [2][3].
• Safety features: Power and force limiting (PFL), speed and separation monitoring, collaborative stop, hand-guiding modes, and support for ISO/TS 15066 risk assessments.

Cobots from Universal Robots (UR series), ABB GoFa/Safety (and SWIFTI for lighter tasks), and FANUC CRX are commonly deployed for flexible assembly, inspection, and machine tending. For cage-free operation, ISO/TS 15066 requires a documented risk assessment and compliance with force/pressure limits; for example, ISO/TS 15066 provides guidance on contact force limits with human body regions (a commonly referenced upper contact force for certain body zones is around 140 N, depending on the contact area and duration) [3].

Standards and Safety Requirements

Safe robot integration requires adherence to multiple standards and national regulatory requirements. The most relevant standards for robot cell design and collaborative operation include:

• ISO 10218-1 and -2 (2011): Framework for industrial robot safety—covers robot design, installation, and protective measures. It defines safety functions, stopping distances, and classification for protective stops and reduced-speed conditions [3].
• ISO/TS 15066 (2016): Technical specification for collaborative robot operation that supplements ISO 10218. It specifies force and pressure limits for quasi-static and transient contact scenarios and requires documented risk assessments before cage-free deployment [3].
• IEC 60204-1: Safety of electrical equipment on machinery—the standard requires safe electrical practices, emergency stop circuits, and reliable control wiring for robot systems.
• ISA-101: HMI design guidance for operator interfaces, useful for designing control panels, teach pendants and operator screens for robot integration.
• IEEE 1872-2015: Provides an ontology and standard terminology for robotics—helpful in multi-vendor system documentation and interoperability [4].

Systems must also meet regional conformity markings (CE in Europe, UL/CSA for North America) and functional safety requirements that can include IEC 62061 or ISO 13849 for safety-related control systems. Adherence to these standards ensures that stopping distances, speed limits (for example collaborative speed thresholds on approach), and emergency stopping behaviors follow best practice and legal expectations [3][4].

Robot Selection Criteria

When choosing a robot type, match the application's dominant drivers—payload, cycle time, workspace geometry, repeatability, and operator interaction—to the robot's strengths:

• Payload: If required payload > 20 kg on a sustained basis, articulated arms or Cartesian gantries often work best; delta and SCARA are better for lightweight nets [2][3][6].
• Cycle time / speed: For per-part cycle times <1 s (very high throughput), delta robots are ideal; SCARA also excels on sub-second horizontal moves [1][3].
• Repeatability/precision: For sub-0.01 mm requirements, high-end SCARA or precision gantries are preferable; articulated arms offer good repeatability for many assembly tasks (±0.05–0.1 mm) [1][5].
• Workspace and reach: Choose articulated robots for complex 3D work envelopes; choose Cartesian for large rectangular areas; SCARA for compact planar work cells.
• Human interaction: For close-proximity or flexible workcells with frequent manual intervention, choose cobots that comply with ISO/TS 15066 and design safety functions accordingly [3].
• Integration and communications: Verify fieldbus compatibility (EtherCAT, EtherNet/IP, PROFINET) with existing PLC and machine controls; many modern models support ROS2 and vendor-specific integration toolchains [6].

Practical selection heuristics used by system integrators: payload >20 kg → articulated/gantry; cycle time <1 s on light parts → delta/SCARA; variable human interaction and reconfiguration → cobot. Vendor simulation tools (e.g., FANUC RoboGuide, KUKA.Sim) and pilot trials are standard practices to validate cycle time, reach, and collision envelopes before capital purchase [2][6].

Integration Best Practices

Successful robot integration follows engineered steps that reduce commissioning time and long-term downtime:

• Site preparation: Mount robots to stable foundations—vibration transmission should typically be minimized to <0.5 g for