SCARA Robots
Unlock high-speed precision for your mobile fleet. SCARA (Selective Compliance Assembly Robot Arm) technology combines rigid vertical strength with horizontal flexibility, making it the ideal manipulator for mobile platforms requiring rapid pick-and-place operations in dynamic environments.
Core Concepts
Selective Compliance
The defining feature of SCARA. The arm is rigid in the Z-axis (vertical) to tolerate heavy loads but flexible in the X-Y axes, allowing it to adjust slightly for hole misalignment during insertion tasks.
4-Axis Freedom
Unlike 6-axis arms, SCARAs typically operate with 4 degrees of freedom: X, Y, Z, and Theta (rotation). This simplified kinematics results in faster cycle times and easier programming for flat-plane operations.
High-Speed Operation
Due to their specialized joint configuration and lower moving mass, SCARA robots achieve higher accelerations and velocities than articulated arms, essential for high-throughput mobile fulfillment.
Repeatability
SCARA robots are renowned for excellent repeatability, often within 0.01mm to 0.05mm. This makes them perfect for tasks where the AGV parks and the arm must interact with precise docking stations.
Mobile Integration
When mounted on an AMR (Autonomous Mobile Robot), a SCARA creates a "Mobile Manipulator." This extends the robot's workspace from a single cell to the entire factory floor.
Compact Footprint
The cylindrical work envelope creates a compact operational area. This is critical for mobile robots navigating narrow warehouse aisles, ensuring the arm doesn't protrude dangerously during transport.
How It Works
The SCARA architecture is defined by two parallel rotary joints that provide compliance in the horizontal plane, coupled with a linear joint for vertical motion. This design mimics the human arm's ability to extend and retract while maintaining a rigid shoulder-to-elbow connection.
In a mobile robotics context, the SCARA arm is typically mounted on the top deck of an AMR. The base of the robot handles the "macro" movement (navigating the facility), while the SCARA arm handles the "micro" movement (precise interaction with inventory).
Because the vertical axis is rigid, these robots handle vertical loads—like pressing components into circuit boards or stacking heavy trays—far better than fully articulated arms of similar weight classes. This structural rigidity allows for faster settling times, meaning the robot stabilizes quickly after the AGV stops moving.
Technical Highlight: The "kidney-bean" shaped work envelope allows the robot to reach behind itself and around obstacles, maximizing the utility of the mobile platform without requiring the AGV to rotate perfectly into position.
Real-World Applications
Mobile Lab Automation
SCARA-equipped mobile robots traverse laboratory environments to transport microplates and test tubes between analyzing stations. The SCARA's precision ensures delicate vials are handled without spillage, while the mobile base links disparate automated islands.
Electronics & PCB Handling
In semiconductor facilities, mobile SCARAs move cassettes of wafers or PCBs. The robot's vertical stiffness is crucial here for accurately slotting cassettes into processing machines without vibration-induced damage.
Warehouse Bin Picking
Integrated with 3D vision systems, SCARAs on AGVs perform "goods-to-robot" picking. The AGV drives to a shelf, and the SCARA arm rapidly picks small consumer goods from bins to place them into order totes, replacing manual picking carts.
Machine Tending
A single mobile SCARA can tend to multiple CNC machines. The robot travels between units, loading raw materials and unloading finished parts. This maximizes machine utilization rates while reducing the need for a fixed robot at every station.
Frequently Asked Questions
What does SCARA actually stand for?
SCARA stands for Selective Compliance Assembly Robot Arm (or sometimes Selective Compliance Articulated Robot Arm). The "Selective Compliance" refers to the fact that the arm is slightly flexible in the X-Y horizontal plane (to aid in fitting parts together) but completely rigid in the Z vertical axis.
Why choose a SCARA over a 6-axis arm for an AGV?
SCARA robots are generally faster, more compact, and more cost-effective than 6-axis arms for flat-plane operations. If your mobile application mainly involves picking an object up and placing it down on a flat surface (pick-and-place), a SCARA offers better cycle times and consumes less battery power from the AGV.
What are the payload limitations for mobile SCARA robots?
Most standard SCARA robots handle payloads between 0.5kg and 20kg. While heavy-duty models exist, mobile applications typically stick to the 3kg–10kg range to maintain the stability of the AGV and conserve battery life. Heavy payloads on a fast-moving arm can tip a lightweight mobile base.
How does the robot handle power on a mobile platform?
Mobile SCARAs are usually DC-powered (24V or 48V) to integrate directly with the AGV's battery system. Efficient power management is critical; the robot controller often communicates with the AGV's BMS (Battery Management System) to ensure the arm parks safely before the battery is depleted.
Are SCARA robots safe to work alongside humans?
Traditional SCARA robots are fast and dangerous, requiring safety caging. However, modern "Cobot" (Collaborative) SCARA models exist that feature force-limiting sensors and rounded edges. For mobile applications in open aisles, safety laser scanners on the AGV usually dictate when the arm is allowed to move.
Can a SCARA robot reach items on different vertical shelf levels?
This is a limitation. The Z-stroke (vertical reach) of a SCARA is typically limited (e.g., 150mm to 400mm). To reach multiple shelf levels, the entire SCARA arm is often mounted on a vertical linear lift column attached to the AGV, allowing it to access inventory from floor to eye level.
How precise is the positioning when the AGV stops?
The SCARA itself is highly precise (±0.02mm), but the AGV stopping accuracy might be ±10mm. To solve this, Mobile Manipulators use "visual servoing" (onboard cameras) to detect fiducial markers on the workstation, allowing the arm to compensate for the AGV's parking inaccuracies dynamically.
What is the typical reach of a mobile SCARA?
Horizontal reach typically ranges from 300mm to 1000mm. For mobile robots navigating standard doorways (800mm width), a reach of 400mm–600mm is ideal to ensure the robot doesn't overhang the footprint of the AGV during transport.
Is programming a SCARA difficult?
Generally, SCARAs are easier to program than 6-axis arms because movements are often defined in a simple X-Y grid. Most modern controllers support ROS (Robot Operating System), making integration with the AGV's navigation stack seamless for developers.
What maintenance is required for mobile SCARAs?
Maintenance is relatively low compared to articulated arms. Key tasks include greasing the ball screw spline (the Z-axis shaft) and checking belt tensions. On mobile units, it is also important to regularly check cable management systems for wear caused by vibration during travel.
How does cost compare to other manipulator types?
SCARA robots are usually the most cost-effective option for assembly and pick-and-place tasks. They are significantly cheaper than Delta robots or 6-axis articulated arms of comparable payload, making them an attractive option for scaling large fleets of mobile manipulators.