A Process Flow Diagram (PFD), also called a process flow chart, is a sequenced picture of every step a product passes through, from receiving to shipping: operations, inspections, moves, storage, outside processes, rework, repair and scrap. It is the starting point of process planning, because the PFMEA analyses its steps and the Control Plan controls them.
The AIAG Advanced Product Quality Planning (APQP) manual, 3rd edition, asks for a preliminary process flow chart in phase 1 (plan and define) and a process flow chart in phase 3 (process design and development). Its Appendix A-6 checklist asks whether the flow covers receiving to shipping, is linked to the PFMEA and Control Plan, identifies special-characteristic stations, describes how product moves, and defines how reworked product is inspected and where it re-enters the flow.
Most flow charts are drawn with ASME-style symbols: a circle for an operation, a square for an inspection, an arrow for transport and a triangle for storage. The PFMEA and the Control Plan both refer to the flow's operation numbers, which is why those numbers have to agree across all three documents.
Five problems process and quality engineers describe in their own words, and what changes when the flow is the single definition of the process.
From the first preliminary sketch to a released revision that the PFMEA, Control Plan and PPAP all point to.
APQP 1.10 · Preliminary flow chart
Create the Process Flow Diagram in a process project, as a preliminary flow chart if the process is still an assumption, or import an existing process flow table from Excel.
Steps
Add steps in the table or directly in the diagram, by mouse or keyboard. Each step has a type, an operation number, equipment, station and cycle time, and can carry sub-steps such as 30.1 and 30.2.
Connections
Draw the main flow, then add rework loops, repair branches, returns to the flow and scrap exits. Rebuild main flow connects the steps in table order in one click; Auto layout redraws the diagram.
Structure
Record the 4M work elements of each step and link the product characteristics made or checked there and the process parameters controlled there, from the characteristic register. Special characteristics show their symbol at the station.
Controls
Attach error-proofing devices with their verification method and frequency, link master samples, and list the incoming materials and suppliers used at each step. Steps that hand product to another process are linked to that process.
Checks
Run checks lists every finding with its source reference. Fix applies a one-click repair where one exists, such as adding the missing Receiving step, renumbering duplicate numbers or connecting the steps in order. Findings other than MUST errors can be waived with a reason.
APQP 3.3 · Release
Promote the preliminary chart to the Process Flow Diagram, keeping its steps and history. Release freezes a revision, through an approval route with electronic signature when one is set up; a later edit marks the flow as changed after release.
Each capability is tied to a decision your team is already trying to make.
Edit in whichever view suits the conversation. Add, connect and reorder steps directly in the diagram — by mouse or keyboard — and the table changes with it. Auto layout keeps it readable; export to PNG or SVG when a customer asks for the picture.
A process step is never retyped. The same step anchors the failure chains in the PFMEA and the rows in the Control Plan, so "OP 30" means one thing everywhere. Renumbering previews every old and new operation number before you apply it, and renaming a step used by a released PFMEA or Control Plan flags it for review.
Man, machine, material and environment captured per step, ready to become the cause level of the PFMEA. The structure analysis is done once, at the point where the process is actually being described.
Link the product and process characteristics each step creates or affects, straight from the characteristic register, along with incoming materials. Special characteristics keep their classification symbol at the station and in the Control Plan.
Model the flow the plant really runs — sub-steps, rework loops, repair stations and scrap exits — not just the happy path. Rework steps are carried into the risk analysis and the Control Plan instead of being forgotten.
Every poka-yoke device recorded against the step it protects, with the master samples used to verify it. Verification becomes a Control Plan row — so the device that prevents the defect is itself under control.
Unreachable steps, rework loops that never return, a flow with no receiving or shipping step: Run checks lists every finding, and a Fix button repairs the common ones. Start with a preliminary flow chart in APQP phase 1 and promote it to the Process Flow Diagram in phase 3.
Operation numbers follow fixed rules. A new step at the end takes the highest number plus 10. A step inserted between OP 30 and OP 40 takes the free number half-way between, 35, or, if there is no room, the highest number plus 10. A sub-step of OP 30 becomes 30.1, then 30.2. Numbers that differ only by spaces, letter case or leading zeros, such as 010 and 10, are flagged as duplicates.
| Step | Old | New | What happens |
|---|---|---|---|
| Press bearing into housing | Old30 | New30 | What happensUnchanged |
| Check press force | Old30.1 | New30.1 | What happensSub-step follows its parent |
| Visual check of bearing seat | Old35 | New40 | What happensInserted step moves onto the grid |
| Insert shaft | Old40 | New50 | What happensShifted by one place |
| End-of-line test | Old50 | New60 | What happensShifted by one place |
The flow holds the steps; the other documents point to them instead of copying them.
The PFMEA structure is built from the in-scope steps and their 4M work elements. Building a PFMEA from a foundation FMEA adds any missing steps to the flow, and editing a step clears the PFMEA's completion mark.
Control Plan rows are generated per step and characteristic, with rework rows for rework steps and a verification row for each error-proofing device. Operation number, name and machine are read from the step.
The preliminary flow chart and process flow chart deliverables read their status from the flow, and the A-6 flow chart checklist answers questions from its checks.
The Process Flow Diagram element of a PPAP submission links to the flow's current released revision, and PPAP master samples come from the sample register.
A CAPA records the process step where the problem arises, and its prevention step can flag the Process Flow Diagram for review.
Build the steps, connections, work elements, characteristic links and error-proofing devices, run the checks, waive findings with a reason and release the flow.
Hold the same editing, waiver and release rights for their project, and decide the change requests that rename or insert steps.
Edit the flow alongside the PFMEA and run the checks; release and waivers stay with the engineers and the project lead.
When an approval route is set up for the flow, each named approver approves their step with an electronic signature before the revision is released.
Every project role can open the flow, see its findings and history, and download the Excel export.
| Zometric Process Flow Diagram vs a drawing or spreadsheet | Drawing tool or spreadsheet | Zometric Process Flow Diagram |
|---|---|---|
| Steps | Drawn once, retyped into the PFMEA and Control Plan | One record per step, used by the PFMEA and Control Plan |
| Renumbering | Edited by hand in every document | Previewed, applied once, followed by the linked documents |
| Rework and repair | Arrows with no meaning to other documents | Typed paths, checked for return and re-inspection |
| Diagram and table | Two files that drift apart | Two views of the same data, exported to PNG, SVG or PDF |
| Checks | None | 14 flow rules, with one-click fixes for common gaps |
| Error-proofing | A separate list, if any | Devices and master samples at the step, verified in the Control Plan |
| History | File versions | Every change recorded with who, when and why; released revisions frozen |
| APQP status | Typed into a tracker | Read from the flow's own state |
Import a process flow table with one row per operation. Next, rework, return, repair and scrap columns become connections; characteristics and incoming materials are linked.
Download the flow as a formatted workbook: header block, symbol, equipment, characteristics, next and rework steps, and PFMEA and Control Plan scope per step.
Save the diagram as PNG or SVG, or open an A3 landscape print view with the document header and save it as PDF.
Steps, connections, work elements, characteristic links and the diagram data are available through the REST API, including bulk edit, reorder and renumber.
Straight answers to the questions teams ask before a demo.
In practice they are the same document: a sequenced picture of every step from receiving to shipping. The AIAG APQP manual, 3rd edition, calls it a process flow chart and expects a preliminary version in phase 1 and a full version in phase 3. Zometric keeps both as one document: you start with a preliminary flow chart and promote it, keeping its steps and history.
Each process step is a single record. The PFMEA builds its structure from those steps and their work elements, and generated Control Plan rows read the operation number, name and machine from them. Renumbering or renaming a step therefore changes all three, and renaming a step used by a released document flags that document for review.
Yes. Connections are typed as main flow, rework loop, repair branch, return to flow or scrap exit. Checks flag a rework loop with no return, reworked parts that are not inspected before rejoining the flow, and a repair branch that does not return to the operation where the part was removed.
Fourteen flow rules, including duplicate operation numbers, missing receiving or shipping steps, no storage or handling step, unreachable steps, decisions with fewer than two outcomes, outsourced steps without a supplier and transport steps without a movement method. Open errors block the release; several common gaps have a one-click Fix.
Yes. A process flow table with one row per operation can be imported into a process project. Columns for the next operation, rework, return, repair and scrap become connections, and product and process characteristics and incoming materials are linked to the step.
Thirteen ASME-style step types, from operation, inspection, transport, storage and delay to receiving, shipping, rework, repair, outside process, decision and packaging. A tenant can rename the symbol labels shown on screen; standard form exports keep the standard names.
4M work elements are the Man, Machine, Material and EnvironMent behind each process step, the level the AIAG-VDA PFMEA uses for failure causes. Recording them in the flow means the structure analysis is done once, where the process is described, and the PFMEA builds on it.
Each device is registered against the step it protects, with what it detects or prevents, its verification method and frequency, and the master samples used to verify it. Every active device on a step in the Control Plan generates an error-proofing verification row, so the device itself is under control.
A 30-minute discovery call. A 2–3 week pilot on real factory data. Then scale at your pace.
