Working models of real operations: a clinic, an ambulance service, a warehouse, inspection lines, stockrooms, a machining cell. Open any of them in your browser, change a number, and run it.
Each model is a short chiaha-SLX file with its decisions as plain numbers at the top. Each model outside the showcase was checked run for run against an independent implementation of the same model before it went in; the warehouse showcase is newer and was reviewed for its logic. In the workspace they’re under Model, in the Showcase and Demo library groups.
A fulfillment center at the morning peak: pickers walk the aisles, totes queue on the conveyor, packers race the trucks. Change pickers, pack stations or batch size and see who makes the truck. Read the write-up.
Open it freeA 24-hour clinic over 365 days (7 of them warm-up). Arrival rates and MD/PA staffing change by hour, and patients share one FIFO line. The model reports wait times, long waits, the peak queue and patients seen per provider.
Open it freeEmergency calls (60% North, 40% South) are served by the nearest of two 2-ambulance bays, fall back to the other bay with a longer cross-zone round trip, and otherwise wait in one shared line, over one 1440-minute day.
Open it freeA machine makes one part every 5 minutes for an 8-hour shift. One inspector checks each part in Uniform(1,7) minutes, and 15% of parts are rejected. The model reports parts made, inspected, accepted and rejected, the reject rate, average and maximum wait, average time in system, and inspector utilization.
Open it freeOne technician serves three machines that break down at random during an 8-hour shift. The model reports breakdowns, repairs, the wait for the technician, travel and repair times, and technician utilization.
Open it freeTV sets arrive every Uniform(3.5,7.5) minutes and go to two inspectors (Uniform(5,10) minutes each). 15% fail and go to one adjuster (exponential, mean 30 minutes), then return to inspection, over one 480-minute shift.
Open it freeEach raw part splits into three sub-parts that go through three 2-machine groups at the same time, and the unit can leave only when all three are done. The model reports how long the earlier sub-parts wait at the assembly point for the last one, along with sojourn time and each group's utilization over a 40-hour run.
Open it freeA continuous-review (s, S) inventory: random daily demand, backorders, and a monitor that orders up to S whenever the inventory position drops below s, reporting mean on-hand, mean backorder, fill rate, orders and holding/backorder cost over 335 days after a 30-day warmup.
Open it freeAn (R, S) periodic-review inventory: every 7 days stock is ordered back up to 200, demand the shelf can't fill is lost, and the model reports mean on-hand stock, the spread of on-hand levels at each review, the lost-sales rate and costs over a year with a 30-day warmup.
Open it freeOne barber in a shop that holds at most 3 customers: when it is full, new arrivals wait outside and are let in first come, first served. The model reports arrivals, customers served, average time in the shop, and the longest line outside over an 8-hour day.
Open it freeOne shared FIFO line feeds two servers. Server A takes the customer at the front whenever A is free. Server B takes a customer only when B is free and more than 5 are waiting. The model reports L, Lq, W, maximum queue and the share of customers served by B over 100,000 seconds.
Open it freeOne barista and one espresso machine serve drip orders (2 min, barista only) and espresso orders (4 min holding barista and machine, then 1 min with the barista only). Espresso orders go first in the barista's line, and customers leave if the barista hasn't started their order within 5 minutes, over a 480-minute day.
Open it freeSix pallets circulate forever through load, machine and unload stations (one server each) for 48 hours. The model reports cycles, throughput per hour, average cycle time and the utilization of each station after a 2-hour warmup, and shows the machine running near 100% busy.
Open it freeThe classic textbook problems (barber shop, bank tellers, tool crib, machine breakdowns, customers who give up) each have their own page with the model, the GPSS deck where there is one, and results from 20 runs. Start with the example models page, which links to all of them.