Understanding Robot Technical Specifications
A plain-English guide to payload, reach, accuracy, degrees of freedom, safety ratings, and everything else on a robot datasheet.
18 min read · Last updated January 2026
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Why specifications matter
Robot datasheets contain dozens of technical parameters. Selecting a robot that doesn't meet your application requirements — or grossly over-specifying — are both costly mistakes.
Under-specifying means the robot fails at your application, requires costly modifications, or needs replacing. Over-specifying means you pay for capability you don't use — industrial robot arms cost 2–5× more than collaborative robots and require safety infrastructure.
Key principle: Always match specs to your worst-case application scenario, not the typical case. If your heaviest part weighs 4kg, you need at least a 5kg payload robot — never operate at 100% of rated capacity.
Payload capacity
What it means: The maximum weight the robot can carry at its end-of-arm, measured in kilograms (kg).
| Payload Range | Typical Applications | Robot Type |
|---|---|---|
| 0.5–3 kg | Electronics assembly, lab automation | Cobot, SCARA |
| 3–10 kg | Light assembly, machine tending | Cobot, light industrial arm |
| 10–50 kg | General assembly, packaging, welding | Industrial arm |
| 50–500 kg | Palletising, heavy part handling | Heavy industrial arm |
| 500+ kg | Automotive body panels, casting | Gantry, heavy industrial |
Practical rule of thumb
Include the weight of your end-of-arm tooling (gripper, suction cup, weld gun) in your payload calculation. A 2 kg gripper handling a 3 kg part requires a robot rated for at least 5–6 kg.
Reach and workspace
What it means: The maximum distance from the robot's base to its end-of-arm tool, and the total volume within which it can operate.
Reach (mm)
Maximum radial distance from the robot base centre to the wrist flange. Compare this to the distance between your pick and place points.
Vertical reach (mm)
How high and how low the robot can reach. Critical for applications involving floor-level conveyor and elevated placement.
Working envelope
The 3D volume the robot can access. Always map your application layout onto the robot's working envelope diagram before purchasing.
Minimum reach
The zone too close to the robot for it to operate safely. Applications near the robot base require careful workspace planning.
Speed and cycle time
What it means: How fast the robot moves (m/s or degrees/s per axis) and how quickly it completes a full operation cycle.
Joint speed (deg/s)
Maximum angular velocity of each axis. Higher joint speeds enable faster cycle times, but speed must be balanced against accuracy and payload.
TCP speed (m/s)
Speed of the Tool Centre Point (TCP) — the most practically useful speed metric. Compare against your required throughput.
Cycle time (seconds)
The time to complete one full pick-and-place or operation cycle. Use this to calculate throughput: cycles per hour = 3600 ÷ cycle time.
Acceleration (m/s²)
How quickly the robot reaches full speed. High acceleration is important for short-distance, high-frequency operations like assembly.
Accuracy vs repeatability
These two terms are often confused but mean very different things for your application.
Accuracy (±mm)
How close the robot gets to a commanded absolute position in space. Affected by joint calibration and temperature drift.
Typical range: ±0.1mm – ±1mm
Critical for: Assembly to a fixed coordinate system, seam welding following a path
Repeatability (±mm)
How consistently the robot returns to a taught position. Usually much better than accuracy. This is the spec you see on most datasheets.
Typical range: ±0.01mm – ±0.1mm
Critical for: Pick and place, machine tending, packaging
For most industrial applications, repeatability is the relevant spec. You teach the robot the positions; it then needs to return to those positions consistently. Absolute accuracy matters most when integrating with external vision systems or CNC machines.
Degrees of freedom (DOF)
DOF = the number of independent axes of motion. More axes = more flexibility but also more complexity and cost.
4 DOF
SCARA robots
Pick and place, palletising — fast and accurate for simple motion patterns
6 DOF
Standard industrial arm
Welding, painting, assembly, machine tending — the most versatile configuration
7 DOF
Collaborative robots
Human-adjacent work — the extra axis enables arm obstacle avoidance and natural motion
Safety ratings and IP protection
IP Rating (Ingress Protection)
Describes protection against dust and liquids. Format: IP followed by two digits. IP54 = dust protected, splash resistant. IP67 = dust tight, immersion to 1m. For food/washdown: IP69K.
Safety Category (EN 13849)
Rates the safety of the control system: Category B (basic) to Category 4 (highest integrity). Most collaborative robots are Category 3/PLd or higher.
CE / UL marking
CE marking is required for sale in the EU/UK. UL listing is required for North America. Verify the complete robot cell (not just the arm) has appropriate certification.
Collaborative safety (ISO/TS 15066)
Defines four collaborative operation modes: safety-rated monitored stop, hand guiding, speed and separation monitoring, power and force limiting (PFL). Most cobots use PFL.
Integration requirements
Beyond the robot itself, check these integration requirements before purchasing:
Communication protocols
EtherCAT, PROFINET, EtherNet/IP, Modbus TCP. Verify compatibility with your existing PLC or WMS.
I/O capacity
Number of digital and analogue I/O signals available. Required for gripper control, sensors, and external devices.
Software ecosystem
Programming language (TP, URScript, KRL), simulation tools, and cloud connectivity options.
Power supply
Input voltage (200–480V 3-phase for industrial, 200–240V 1-phase for cobots), power consumption, and UPS requirements.
Footprint and mounting
Floor footprint, ceiling mount capability, and clearance required around the cell.
Weight
Important for ceiling-mounted and mobile applications. Heavy robots (200kg+) may require structural floor reinforcement.
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