Production planning and scheduling is often described in the abstract, which makes it sound more mysterious than it is. This piece walks through how it actually works, step by step, from a customer order to a precise sequence of jobs on the shop floor.
Step one: demand
Everything starts with demand, the answer to "what does the business need to produce". Demand comes from two sources: confirmed sales orders, which are known, and a forecast, which is an informed estimate of orders not yet placed. A make-to-order manufacturer leans on the first; a make-to-stock manufacturer leans on the second. Either way, demand is the input the whole process plans against, and if demand is captured badly, everything downstream inherits the error.
Step two: the high-level plan
Demand is turned into a high-level production plan, often expressed as a master production schedule. This states what finished products should be made, in what quantities, in which periods, over a horizon of weeks. It is not yet detailed enough to run the floor. Its job is to set the shape of production and to be a sane, achievable target before the detail is worked out.
Step three: MRP works out the requirements
The high-level plan then goes through MRP, material requirements planning. MRP takes each planned product and explodes it through its bill of materials, working out every component and sub-assembly needed and in what quantity. It compares that gross requirement against stock already on hand and supply already on order. What remains is the net requirement: the precise list of what must be manufactured and what must be purchased, and by when, so the plan can be met. MRP is the step that turns "make 500 of product A" into a full shopping and production list.
Step four: the capacity check
A plan that ignores capacity is a wish. So the requirements are checked against capacity, the real hours available on the machines and from the people. If the plan needs more capacity than exists in a period, that conflict has to be resolved now, by moving work earlier, adding a shift, subcontracting, or adjusting commitments, not discovered on the floor later. This step is what keeps the plan honest.
Step five: scheduling the detail
With requirements known and capacity confirmed, scheduling produces the detail: which job runs on which machine, in what sequence, starting when. This is where setup and changeover times, material readiness, and due dates are resolved into an exact order of work. The output is a schedule the shop floor can actually run from.
Step six: execution and feedback
The floor then executes the schedule, and reports back, what was completed, what was scrapped, what ran late, what broke down. That feedback is not the end of the process, it is the input to the next cycle. The reported reality updates stock, updates progress, and feeds the next round of planning.
Why it has to be a connected loop
The reason production planning and scheduling works as software rather than as a spreadsheet is that every step depends on the one before and feeds the one after, and reality keeps changing the inputs. Demand shifts, a delivery slips, a machine stops. In a connected system, a change re-runs the affected steps and the plan stays current. In a set of disconnected spreadsheets, a change quietly invalidates everything downstream and nobody has time to redo it all. The loop is the point. For how we approach manufacturing systems, see our manufacturing work.