Factories and logistics
Industrial robots from arm selection to a complete workcell
Compare arm architectures, calculate an illustrative payload and read cycle time as a complete production sequence.
An industrial arm becomes useful when its tool, fixtures and surrounding equipment can complete a production operation. A specification for the arm alone leaves out where parts arrive, how they are held and how the process confirms an acceptable result.
The International Federation of Robotics describes industrial robots as automatically controlled, reprogrammable multipurpose manipulators with three or more programmable axes. The definition covers several mechanical architectures rather than one arm shape. [1]
Compare the required movement before comparing brands
Start with the path the tool must follow and the orientations it needs at each position. A useful application drawing includes the pickup area, working position, placement area and obstacles. Mechanical categories provide an initial shortlist; the selected model's workspace remains the deciding document. [1]
Scroll sideways for all columns.
| Architecture | Movement to examine | Application evidence to request |
|---|---|---|
| Articulated arm | Tool orientation around fixtures and equipment | Reach at every required orientation, collision clearance and tool loading |
| SCARA | Horizontal positioning and vertical insertion | Insertion stroke, orientation range and the specified assembly tolerance |
| Cartesian or gantry | Travel along linear axes | Axis travel, supporting structure and access above the work area |
| Parallel robot | Repeated movement within its configured workspace | Payload, permitted orientation and performance on the actual pick pattern |
Include the tool in the payload calculation
A worked example uses a 3 kg part, a 2 kg gripper and a 0.5 kg adapter. The carried mass is 5.5 kg. A brochure's part mass should not be compared directly with the arm rating while leaving the gripper out.
Universal Robots' documented payload setup defines payload as everything attached to the tool flange. It also asks for the center of gravity and describes changing the active payload after pickup and release. This is a documented example of a controller workflow, not a statement that a particular arm is suitable for the 5.5 kg assembly. [2]
The mass calculation is only a first check. As an illustrative statics calculation, 5.5 kg acting horizontally 0.2 m from a reference point produces about 10.8 N m under gravity, using 9.81 m/s². Acceleration adds further loading. An integrator must compare the actual center of gravity, moments and inertia against the selected manufacturer's limits. This calculation does not validate a workcell.
Count waiting and handoffs in the cycle
Imagine a machine-tending sequence with 8 seconds for pickup, 4 for travel, 12 for the machine operation and 6 for unloading and return. Assuming these steps happen sequentially, the nominal cycle is 30 seconds, or 120 parts per hour. These are teaching numbers.
Add a four-second wait for a door or machine-ready signal and the cycle becomes 34 seconds, about 106 parts per hour before rejects or interruptions. Overlapping operations would require a different timing model. Explain which steps overlap rather than adding or removing time without stating the assumption.
Separate the robot's movement time from the process time and the time spent waiting for another device. A faster arm cannot remove an unchanged processing step from this example.
Repeatability and accuracy answer different questions
Consider an illustrative positioning test. A tool repeatedly stops in a tight cluster, but that cluster is 2 mm away from the intended target. The system repeats its position well while retaining a target error. Tool calibration, fixture location and the measurement reference all matter to the finished operation.
Request the definition and conditions behind a manufacturer's positioning figure. Then specify the tolerance at the workpiece. A bare-arm figure cannot by itself account for a flexible gripper, a moving fixture or a process that deforms the part. Treat this as a measurement plan rather than a conversion between unlike specifications.
Write the brief an integrator can use
A practical brief describes the part and its variation, pickup and placement poses, desired accepted output, tool changes and the machine interface. Include the floor plan and the operator's access for replenishment, cleaning and fault recovery.
For the teaching example, ask the integrator to document how the cell confirms one part was picked, the machine is ready and the finished part was placed. Include recovery time and operator work in the comparison. Keep guarding, process hazards and risk assessment within the complete application review. This article provides engineering orientation and does not certify an installation.
Sources and scope
Sources were consulted for this revision. Manufacturer descriptions are identified in the text. Worked examples are illustrative calculations, not measurements from a TechniaHQRobot test.
- IFR industrial robot definition and architectures
Industrial robot terminology and mechanical categories.
- Universal Robots SW5.19 payload setup
Manufacturer instructions for payload mass, center of gravity and pickup/release changes. Examples here are not model selection or safety approval.