Feasibility-Driven Assembly and Welding Planning for a Dual-Robot Steel Fabrication Cell

Assembling a welded steel structure with robots requires deciding whether an entire assembly—dozens of parts, each needing a collision-free pick-up, press-fit placement, and welding—is executable at all, and under which positioning of the workpiece. We describe and evaluate the planning system deployed in an industrial dual-robot fabrication cell. It replaces optimization with parallel feasibility simulation: candidate beam setups are simulated part by part in isolated containers, setup selection is posed as coverage maximization over the resulting feasibility sets, and the output is executable ABB RAPID code with inter-robot synchronization compiled in. On six fully swept production work orders, a single setup covers all parts only once, and the greedy setup pair matches the exhaustive optimum in five of six cases; on 250 further assembly designs from a second site, one setup suffices for 17% of work orders and the two-setup plan for 84%; the deployed within-class pair rule costs 10% of coverable parts. On 1580 archived welds, geometric torch pre-validation prunes the orientation space 8.3-fold, and 37.9% of CAD-specified welds are overhead as posed: repositioning, not planning, makes them weldable. A repeated planner-budget sweep shows coverage doubling along the budget axis. Floor records show 92.9% of installations and 96.4% of welds succeeding, while parts are left unattempted in 11 of 16 assemblies: coverage, not motion quality, binds throughput.