Try it while you read
Open the free Turtle Diagram Generator tool and click Load sample: it reproduces the case study below.
Theory: one page that describes how a process is controlled
The turtle diagram puts the process in the middle. Inputs come in at the head, outputs leave at the tail, and four legs answer the questions an auditor asks about every process:
| Part | Question | Examples |
|---|---|---|
| Inputs | What comes in? | Material, orders, drawings, programs, requirements |
| Outputs | What goes out? | Products, records, data for the next process |
| With what? | Which resources? | Machines, tools, gauges, software, infrastructure |
| With whom? | Which people and competences? | Roles, qualification level, training |
| How? | Which methods? | Work instructions, control plan, procedures, reaction plans |
| Results | How is it measured? | KPIs with target and actual: scrap, Cpk, OEE, on-time delivery |
Suppliers and customers (internal or external) and the risks and opportunities of the process complete the picture. In IATF 16949 terms, the turtle shows the process approach of clause 4.4 and links to the risk-based thinking of clause 6.1.
Key point
Step by step
- Scope: in the turtle diagram generator enter the process name, owner, department, revision, start and end.
- Inputs and outputs: one item per line, concrete (“Bar stock C45, certified”, not “material”).
- Legs: resources, people with qualification level, documents with their numbers.
- Results: KPI | target | actual, one per line. The diagram marks KPIs that miss the target.
- Risks: the top risks with a reference to the PFMEA or risk register, plus opportunities.
- Labels: choose English, German or Slovak labels if the plant works in that language, and download the A3 or A4 PDF.
Case study: CNC machining of shafts
The Load sample describes the turning process of a gearbox shaft plant, from released bar stock to shafts released to heat treatment.
| KPI | Target | Actual | Status |
|---|---|---|---|
| Scrap rate | ≤ 1.5 % | 1.3 % | Met |
| Bearing seat Cpk | ≥ 1.33 | 1.62 | Met |
| OEE | ≥ 85 % | 81 % | Not met |
| On-time to next process | ≥ 98 % | 99 % | Met |
The legs list three CNC lathes, a tool presetter and calibrated gauges (with what), operators at qualification level 3, a setter per shift, the process engineer and inspector (with whom), and work instruction WI-210, control plan CP-0412, the tool change procedure and the reaction plan (how). The risks name the wrong offset after an insert change (PFMEA action priority High), a single-source tool supplier and operator turnover on the night shift; automatic in-process probing is noted as an opportunity.
Result
Common mistakes
- Generic content that fits every process (“machines”, “employees”, “procedures”).
- KPIs without targets, or targets that are never compared with actual results.
- Risks that do not match the PFMEA or the risk register.
- Diagrams made once for the certification audit and never updated.
- A turtle for every work step instead of one per process in the process map.
Use the turtles to plan the internal audits with the IATF 16949 or ISO 9001 audit checklist, and scope new processes first with a SIPOC.
Frequently asked questions
Is a turtle diagram required by IATF 16949?
No. IATF 16949 and ISO 9001 (4.4) require that processes are determined with their inputs, outputs, resources, responsibilities, methods, criteria and risks. The turtle diagram is a common way to show exactly that on one page, which is why auditors like it.
What is the difference between a turtle diagram and SIPOC?
SIPOC lists suppliers, inputs, process steps, outputs and customers and is used to scope a process. The turtle diagram adds the resources, people, methods, KPIs and risks, so it describes how the process is controlled.
How many turtle diagrams do I need?
One per process in the process map: typically 10 to 25 for a plant, from customer-related processes to production and support processes.