Map the Payload-Reach Envelope

Robot arm datasheets print two headline numbers: payload capacity and repeatability. Both are real specifications, and both are misleading on their own. A robot that carries 20 kg at its base cannot carry 20 kg at full reach, because moment loading cuts capacity as the arm extends. A robot that repeats to 0.02mm in a warmed-up lab cannot repeat to 0.02mm under production load after two hours of duty cycling. The combination of payload and reach defines a performance envelope, and that envelope is what determines which applications the robot can actually serve.

Payload and reach together determine which arm can do the job. This interactive plots three reference arms on a payload-reach grid: the Universal Robots UR10e (12.5 kg, 1,300mm), the UR20 (20 kg, 1,750mm), and the Fanuc M-20iD (Fanuc; 20 kg, 1,810mm). Four application zones are overlaid: electronics assembly, bin picking, machine tending, and palletizing. Drag the payload and reach sliders and a marker moves across the chart, reporting whether your point falls inside any of the three arms' envelopes and inside any of the application zones.

Envelope curves are linearized from the published UR10e, UR20, and FANUC M-20iD datasheets. The deflection estimate uses a simplified cantilever-beam approximation calibrated to match published cobot-class deflection data. Stiffness is treated as a single composite constant across all three arms, which understates how much stiffer the FANUC M-20iD is thanks to its heavier structure. Joint backlash, thermal expansion, and the difference between rated and field performance are not modeled; consult Universal Robots' thermal compensation application notes before promising datasheet accuracy in deployment.

Start at the defaults (10 kg, 1,300mm) and notice that your point sits inside both the UR10e and UR20 envelopes, on the boundary between machine tending and bin picking. Then push payload to 20 kg at 1,700mm. The UR10e drops out entirely, but the UR20 envelope still covers you because Universal Robots redesigned the arm specifically to open this region. Drag further, to 40 kg at 2,000mm, and no standard cobot applies; the palletizing application zone extends there, but covering it requires a heavier industrial arm or a custom solution. That transition is where a mechanical redesign creates a market, not where marketing finds one.