How to map a manufacturing process
A manufacturing map that begins at the works order begins too late. How to map the plan-to-make boundary, keep the routing out of the process, and draw re-planning as a route rather than an exception.
Mapping a manufacturing process means recording the decisions an organisation makes to get something built (demand, capacity, materials, release, execution) rather than the operations a part passes through.
The short version
- Look upstream of the shop floor for the constraint: capacity first, then materials.
- A routing belongs to the product; the process belongs to the organisation. Map one of them.
- Re-planning is a route on the diagram rather than an exception to it.
- A confirmed date from purchasing is a promise, not stock on a shelf.
- An MRP run inherits every error in the bills of material and the supplier lead times.
Starting at the works order starts too late
Most manufacturing maps open with a works order being released and close with a pallet being labelled. Everything in them is real, and almost none of it is where the disruption came from. Late orders are created upstream: the schedule was built on capacity nobody netted down, or on a material whose lead time nobody re-checked. A map bounded by the shop floor can only record the symptom arriving at the first work centre.
Two sequences compete for the same diagram and only one of them belongs there. A routing is the product's path: operation ten, operation twenty, work centres and standard times, held as master data and different for every part number. A process is the organisation's path: who commits capacity, who buys, who releases, who re-plans. Drawn together they produce a diagram too specific to plan with and too general to work to, and one that goes stale the next time engineering changes an operation.
The example below is production planning across five phases, from demand through to execution. The arrows pointing back up the sheet are the argument: "Re-phase" returns a capacity shortfall to "Build the master production schedule", and a breakdown late in execution sends the affected orders back to "Calculate capacity requirements". Neither is an exception bolted on to the process; between them they are how a plan gets made.
Demand plan to completed orders
Production planning end to end: twelve rows of deciding before a works order reaches the shop floor, and three arrows that come back to them.
Begin where the plan begins
"Demand plan received" opens the map, and the two rows after it reconcile the forecast against firm orders and build the master production schedule. Nothing has been bought and nothing has been made, and this is already the part most manufacturing maps leave out.
Capacity answers before materials
The load is calculated, "Capacity sufficient?" splits on "Short", and the gap decision offers subcontract, overtime, or a "Re-phase" arrow straight back into the schedule. The first two buy hours with money; re-phasing spends the delivery date, so the three exits are not equivalent.
Two loops before anything is cut
Requirements planning runs, and a shortfall raises a purchase requisition that comes back on "Date confirmed" to be re-checked rather than assumed. Orders are then sequenced, released, and materials issued against them. Every row so far precedes the first operation.
Execution feeds the plan back
Manufacture, a quality confirmation that records scrap, and progress monitoring ending in "Schedule still achievable?". The Breakdown exit does not stop on the shop floor: it re-plans the affected orders and re-enters the diagram at capacity, which is where the plan was set in the first place.
How it works
Put the boundary upstream of the works order
Start the map at the commitment that creates the work (a demand plan, a firm order, a replenishment signal) and end it at orders completed to plan. A map that opens at release can describe how the plant reacted to a bad plan, and nothing whatsoever about how that plan came to be made.
Decide whether you are mapping routing or decisions
If the answer is the operation sequence for one part number, that is a routing: it belongs in the works order and the master data, not in a process map. If the answer is who commits capacity, who buys, who releases and who re-plans, you are mapping the process. The two need different diagrams and different owners.
Type the planning rows in before the making rows
Fill the Box text column from the top in the order the decisions happen: reconcile demand, schedule, size the capacity, run the requirements, sequence, release. The making steps come last and there are fewer of them than planners expect, which is itself worth showing a plant manager.
Turn each constraint into a labelled question
Mark the capacity, materials and progress checks as questions: Shape reads Decision, Line to holds a row number per outcome, and Line text names those outcomes in the same sequence. State what the question measures (hours short, days late) on the decision itself, or every planner will apply their own threshold.
Point the recovery routes back up the sheet
A Line to number lower than the row holding it is how the diagram says re-plan. Send a capacity shortfall back to the schedule and a breakdown back to the capacity calculation. Then set Horizontal lane to the phase and Vertical lane to the owner, so the handoff to Materials / Purchasing is drawn instead of assumed.
Check it with a planner and a shift supervisor
Separately, and in that order. The planner corrects where the loops go; the supervisor tells you which of them happens weekly rather than never. Before either leaves, put a number on "Capacity sufficient?" (the hours short that count as "Short"), then agree at "How to close the gap?" which gap earns "Overtime" and which forces a "Re-phase".
Mistakes to avoid
Opening the map at works order release
The capacity call, the material commitment and the sequencing choice all happened before that point, and they are where late orders are created. A map starting on the shop floor documents the consequence and cannot reach the cause.
Drawing the routing as the process
Operation ten, operation twenty, machine by machine. It is accurate, it differs for every part number, and it is out of date before the map is approved. Leave it in the works order, where somebody is paid to maintain it.
Scrap recorded but never routed
The example logs scrap inside the quality confirmation without branching on it, which is a simplification. Where scrap triggers a re-make or a shortfall, give it a labelled exit and a route back, or the rework stays invisible.
Nameplate capacity in the plan
Rated hours ignore planned maintenance, changeovers and the downtime everyone expects. A schedule built on them looks feasible, fails in week two, and the map then reports that failure as a breakdown rather than as a planning error.
Map your own manufacturing process
Open the production planning example as your own chart and replace its capacity, materials and re-planning rules with yours.
Related guides
Frequently asked questions
What is a manufacturing process map?
A diagram of the decisions and handoffs that get a product built: how demand becomes a schedule, how capacity and materials are committed, how works orders are released, and what happens when any of that turns out to be wrong. It is not the operation sequence for a part: that is a routing, held in the works order. The distinction matters because the two change at very different rates, and a map mixing them has to be redrawn whenever a part number is added.
Where should a manufacturing process map start and end?
Wide enough at the front to include the people who set the numbers the plant is working to, and at the back to include the record that says whether the plan was met. Two things sit outside a factory-doors boundary: the capacity assumption and the supplier lead time. Both are settled weeks before release, by a demand planner and a buyer who never see the shop floor. Bound the map at the doors and every argument about a late order is conducted over a diagram that does not contain the decision being disputed.
What is the difference between a routing and a process map?
A routing lists the operations a specific part passes through, in sequence, with work centres and standard times, and there is one per part number in the production system. A process map shows what the organisation does (plan, commit, buy, release, make, review) and is the same map whatever is being built. Routings are maintained by manufacturing engineering and change constantly; a process map is approved and reviewed periodically. Calling one the other is why many manufacturing maps are never opened twice.
How do you show a machine breakdown on a process map?
As a labelled exit from a progress check, with a route back into planning rather than a note in the margin. In the example, monitoring feeds a decision whose Breakdown branch re-plans the affected orders and re-enters at the capacity calculation. Drawn that way a breakdown is a route the process already owns, and the argument about who re-sequences the queue and who tells the customer has been had before the machine stopped rather than during.