Automotive Assembly Line Payload Validation

Case Study 1: Automotive Assembly Line Payload Validation

Scenario A Tier-1 automotive supplier in Stuttgart, Germany, integrated a new 6-axis collaborative robot (UR10e variant) into a battery module assembly cell. The robot must lift and precisely position aluminum battery trays weighing up to 32 kg while maintaining ±0.1 mm repeatability. Constraints included tight cycle time (≤18 s), existing floor-mounted safety fencing (no structural reinforcement allowed), and strict ISO/TS 15066 compliance requiring ≤150 N contact force during potential human interaction — necessitating conservative payload limits.

Given Data

• Maximum force the robot can exert (f_max): 4,850 N
• Weight of the robot arm (f_robot): 1,920 N
• Acceleration due to gravity (g): 9.807 m/s² (local calibrated value)

Calculation Using the Robot Payload Capacity Calculator’s underlying static equilibrium formula:

p_max = (f_max − f_robot) / g
p_max = (4850 N − 1920 N) / 9.807 m/s²
p_max = 2930 N / 9.807 m/s²
p_max ≈ 298.76 kg

However, this theoretical value ignores dynamic amplification, safety factors, and end-effector mass. Per ISO 10218-1, a minimum safety factor of 1.5 for payload is required for industrial robots in non-collaborative mode — but since this is a cobot operating in shared space, the integrator applied a conservative safety factor of 2.0 and subtracted the 12.3 kg end-effector (vacuum gripper + tooling):

• Adjusted allowable payload = 298.76 kg / 2.0 = 149.38 kg
• Net payload capacity = 149.38 kg − 12.3 kg = 137.1 kg

The required tray weight (32 kg) falls well within this margin.

Result and Decision The calculated net payload capacity (137.1 kg) comfortably exceeds the 32 kg tray requirement. The team selected the UR10e with reinforced wrist mounting and validated real-world performance via 72-hour stress testing under thermal cycling (15–40°C). No actuator overheating or positional drift was observed; cycle time remained stable at 17.3 ± 0.2 s.

Lesson Never equate theoretical payload capacity with operational payload — always de-rate for safety factors, end-effector mass, dynamics, and environmental conditions before final selection.