Modelling guide
Scrap, yield and OEE
An inspection rejects a share of units for good (a leak test, a final check), and the factory must still deliver the good units its customers ask for.
Built in A field or setting does it directly.
When
You want good output, yield and each station's OEE.
How
On the product's operations:
- Set
scrap_probability(0.1) on the step that rejects units (Product table → Scrap). As that step finishes, that share of units is scrapped: the unit leaves at that station, is counted as scrapped and never as output. - Each scrapped unit is replaced at once by a new unit of the same product for the same demand, so orders and arrivals are still met in good units. Its varied dimensions are drawn again.
- Build layout sizes the scrapping step and every step before it for the extra units, 1 / (1 − s) for each scrap point s at or after it; the steps after it see only good units.
- The results give
summary.scrapped,summary.yield(good / (good + scrapped)) and, per station,scrappedandoee: availability (not stopped for breakdowns, maintenance or its crew) × performance (working while available; waiting for units, blocked and short of parts count against it) × quality (finished and not scrapped there).
- A share on a part a feeder makes works the same way: the part is made again for the same parent, and the feeder is sized for it.
- At a breakdown: a machine's
failure_scrap_probability(Hardware → Scrapped at a breakdown) scraps that share of the units on it when it breaks down (withreliability_modeon). - After a wait: an operation with
max_wait_s/max_wait_untilandmax_wait_scrap: true(Product table → Over max wait: Scrapped) scraps a unit still queued for the later step when the limit runs out (work centres and job shops).
Scrapped units go to a scrap bin beside the station and can come back as raw material: see Scrap bins and recycling.
Check
Pumps are assembled, sealed and leak tested; the test rejects 10% for good. Pumps are ordered every 10 minutes on average for 40 hours. About 25 pumps are scrapped and replaced, every order is still met, and assembly and sealing get a second station for the extra pumps while the test, which does them at 240 s, keeps one.