Bonded Seams
Energy per metre is the seam variable, and it is inversely proportional to line speed. Running faster is a recipe change, not just a throughput change.
— J/m
Delivered into each metre of seam at the working speed
Energy comes from the measured generator draw, so the efficiency term carries everything lost in the stack, the horn and the anvil — measure it rather than assuming. Over-welding shows as a hard, brittle seam line and eventual burn-through, so there is an upper limit this arithmetic does not know about; find it by peel-testing a speed ladder.
Ultrasonic Sealing Energy Density & Speed Optimizer — free, with the formula and a worked example, at Textile School.