Robot reach and work envelope: reading the numbers correctly

What the reach figure measures

Reach is the maximum distance from the robot’s base axis to a reference point on the arm, and manufacturers do not all use the same reference point. ABB publishes two figures for GoFa 5: 950 mm to the wrist centre and 1,050 mm to the tool flange. Universal Robots publishes a single 850 mm figure for UR5e.

Before comparing arms, establish what each figure measures. The 100 mm gap between ABB’s two reference points on the same arm is larger than many differences between competing products.

From reach to work envelope

The work envelope is the three-dimensional volume that the reference point can reach. Link lengths set its outer boundary and joint limits shape what happens inside it, including which approach directions and reorientations are possible.

What shrinks the usable volume

A tool adds length beyond the flange, which extends some reach but changes where the arm can approach from. Tasks that need the tool held at a fixed orientation, such as pointing straight down, can use only part of the reachable volume. Near the edge of the envelope the arm also approaches configurations where small tool movements need large joint movements.

Mounting changes the picture too. Both manufacturers allow mounting in any orientation, so a wall or ceiling mount can put the envelope where the work is instead of moving the work to the robot.

How to check a layout

Use the manufacturer’s dimensioned drawings or simulation model with your real tool, check every required pose at its required orientation and keep clearance from the envelope boundary. A published reach figure is enough to shortlist arms, not to sign off a cell.

• UR5e full specifications
• ABB GoFa 5 full specifications
• UR5e vs ABB GoFa 5, compared row by row