Short answer: Process end effectors — welding torches, spot welding guns, spray bells, cutting heads — differ from grippers in one decisive way: the tool is not holding the workpiece, it is performing the manufacturing process on it. Selection therefore starts from process parameters (current, wire feed, atomisation, beam or jet) and only then asks which robot can carry the tool through the required path at the required orientation. The robot is, in a real sense, the tool's positioning accessory.
Arc welding: torch, feeder and the neck problem
A robotic arc welding package combines the torch, a wire feeder, the power source and dress-out cabling, and its daily behaviour is decided by unglamorous details: torch neck geometry decides which joints the robot can reach; the feeder's placement decides wire behaviour on long runs; anti-spatter and reaming stations decide how much operator attention a shift needs. Buyers should evaluate the package as the integrator delivers it — torch, source, feeder, positioner and fume extraction as one system — because weld quality problems rarely respect component boundaries.
Consumables and positioners: the rest of the package
Process tools consume. Arc welding burns through contact tips, liners, nozzles and shielding gas; painting consumes filters, bell cups and cleaning solvent; cutting consumes optics protection, nozzles and abrasives. None of these is expensive alone, but together they form a running-cost line that belongs in the cell budget from the first year, with the consumption rates taken from the integrator's reference installations rather than estimated hopefully. The other half of most process packages is the positioner — the servo table or headstock that presents the part to the tool at the right angle. Positioners are end effectors' silent partners: a two-axis positioner often improves weld quality and cycle time more than a larger robot would, because the best torch angle is the one the part offers, not the one the arm can reach.
Spot welding: the weight problem
Resistance spot welding guns are the heavyweights of the end-effector world: the gun carries a transformer and must press electrodes together with controlled force, so gun mass and its centre of gravity consume a large share of the robot's payload and shape the whole cell design. Servo-electric guns have been displacing pneumatic ones because force and tip position are programmable and gentler on panels — but the selection question remains physical: can this robot carry this gun, at this reach, at this cycle time, for this many spots per body? Automotive body shops answer it with simulation before metal is cut; smaller users should at least insist on the same arithmetic in writing.
Painting: explosion protection and the bell
Paint robots work in booths full of solvent vapour, so the tools and arms are designed for explosive atmospheres — purged, sealed and certified accordingly, which is why painting robots are a specialist product family rather than general arms with a spray gun bolted on. Makers such as FANUC maintain dedicated paint robot lines for exactly this reason. The applicator — usually a rotary bell — decides finish quality through atomisation and electrostatic wrap, and the hidden operating cost is cleaning: colour changes and bell maintenance dominate the non-painting minutes of a paint cell's life. Process questions (paint type, colour-change frequency, part mix) therefore size the tool long before payload does.
Cutting: laser, plasma and water
Cutting heads divide by energy source. Laser cutting heads need beam delivery, focusing optics and standoff control, and reward the robot with intricate 3D profiles in formed parts. Plasma trades edge quality for thickness and cost. Waterjet cuts cold — no heat-affected zone — at the price of abrasive handling and slower speeds. In all three, the robot's path accuracy at process speed, not its static repeatability, is the figure that decides cut quality; and the extraction, guarding and (for laser) enclosure around the cell are line items as real as the head itself.
The integrator is part of the tool
Process cells are where the directory's system integrators earn their margin most visibly: the process knowledge — weld schedules, paint parameters, cutting feeds — lives in the integrator's commissioning team, not in any catalogue. When comparing suppliers, compare process evidence: sample parts made on your material, with your finish specification, measured your way. The factory-side view of the same decision, for welding specifically, is covered in our guide to welding robots in metal fabrication; this article stays with the tools themselves, which are catalogued in the end effectors section of the directory.
Frequently asked questions
How do process end effectors differ from grippers?
A gripper holds the workpiece; a process tool performs the manufacturing operation on it — welding, painting or cutting. Selection therefore starts from process parameters and only then checks which robot can carry the tool through the path.
Why are spot welding guns such a design constraint?
A spot welding gun carries a transformer and must apply controlled electrode force, so it is heavy and its mass sits far from the robot's wrist. Gun weight and centre of gravity consume payload and shape the cell layout and cycle time.
Why are painting robots a separate product family?
Paint booths contain solvent vapour, so paint robots are sealed, purged and certified for explosive atmospheres, and their rotary bell applicators are specialised for atomisation and finish quality. They are not general-purpose arms with a spray gun attached.
What should I ask a process-cell supplier to prove?
Ask for sample parts: your material, your finish or weld specification, measured your way, before committing. Process knowledge sits with the integrator's commissioning team, and samples are the evidence that survives a sales meeting.