One unit becomes many: cutting, splitting, taking apart
One unit becomes several that go on separately: a sheet cut into blanks, a casting split into two halves, a product taken apart into components that are reused, or a step that makes a second product besides the first.
Built in A field or setting does it directly.
How
Give the step that splits the unit Splits into (Factory data → Products → the operation; "splits_into": [{ "product": "blank", "qty": 4 }]). As the step finishes, that many units of each product are made and go on along their own product's route; the split-off products need operations of their own and machines that do them. They are carried from the splitting station to the nearest that does their first step, at the transport speed.
The unit ends at the split: it became the new units, and counts as made for its own demand but not as output. Tick Keeps unit ("keeps_unit": true) when it goes on as well (co-products: a step that makes the main part and a second one).
The demand sits on either side, as with an assembly's parts. On the unit (arrivals of sheets): the split-off products are made at its rate times the count. Or on the split-off products, when the unit has none of its own (300 small blocks a day, cut from large ones): the unit is released at the rate the most demanding of them needs (its demand / count), and any others it splits into are made alongside as co-products. Split-off products are never released by themselves. Splits of split-off products multiply through.
Build layout lays out every product the run makes, each at the rate it is made, in lines or work centres as for any product; the run then splits the units. The results give summary.splits (per product, the units split and what they made), and the demand check judges each product at its own rate.
The source may be paced in any way: its own arrivals, the project takt (each root paced by the takt then runs on even arrivals at its share, so the line's takt the build computes does not change the release), or an order list (the split-off products are sized for what the order makes of them). A split-off product with demand of its own and several sources (small blocks from large and from medium ones) takes an equal share of it from each.
Check
A sheet every 5 min is cut into four blanks (120 s on a panel saw); each blank is drilled (60 s) and deburred (50 s). Build layout buys one saw, one drill press and one bench (0.8 and 0.67 of a machine for the blanks at 85%). Over 40 h 479 sheets become 1,916 blanks, of which 1,913 are finished; no sheet counts as output, and both products meet their demand.