When an automotive Tier-1 or Tier-2 supplier decides to buy CNC parts from Turkey, the first technical question is: "Can you prepare a PPAP, and at which level?" PPAP is a standard file proving that the part is produced not only to the right dimensions but by a correct and repeatable process. This guide explains the structure of PPAP and the role of the CNC contract manufacturer; it can be read as the automotive-specific continuation of our quality assurance article.
What Is PPAP?
PPAP is the process published by AIAG (Automotive Industry Action Group) and used in the automotive sector for the approval of series production parts. Its purpose is to show that the supplier has understood the customer's design and specification requirements and that the production process can consistently meet these requirements at the specified production rate. PPAP is requested again in situations such as a new part, a design change, a process change, a sub-supplier change or relocation of the production site.
The 18 Elements of PPAP
- Design records (technical drawing, CAD, customer specifications)
- Authorised engineering change documents
- Customer engineering approval (if required)
- Design FMEA (DFMEA) — if the supplier is design-responsible
- Process flow diagram
- Process FMEA (PFMEA)
- Control plan
- Measurement system analysis (MSA) — Gage R&R
- Dimensional results (full inspection report)
- Material and performance test results
- Initial process study (Cpk/Ppk)
- Qualified laboratory documentation
- Appearance approval report (AAR) — for appearance parts
- Sample production parts
- Master sample
- Checking aids (gauges, fixtures)
- Customer-specific requirements
- Part Submission Warrant (PSW)
The 5 Submission Levels
| Level | Submitted to the customer | Typical use |
|---|---|---|
| 1 | PSW only (with AAR for appearance parts) | Low risk, approved supplier |
| 2 | PSW + samples + limited supporting data | Minor changes |
| 3 | PSW + samples + full supporting data | Default level; new parts and suppliers |
| 4 | PSW + elements defined by the customer | Customer-specific |
| 5 | PSW + samples + full data, review at the supplier's site | Critical parts, new-supplier audit |
If no level is specified, Level 3 is assumed. All elements are prepared and retained at the supplier at every level; the level determines which ones are sent to the customer.
Which Elements Is the CNC Contract Manufacturer Responsible For?
In machining, design responsibility usually lies with the customer; DFMEA is therefore mostly out of scope. The core elements prepared by the contract manufacturer:
- Process flow, PFMEA and control plan: every operation from raw-material receipt to shipment, potential failure modes, prevention/detection controls and inspection frequency. These three documents must be consistent with each other.
- Dimensional results: every dimension on the drawing numbered on a ballooned drawing and measured, usually on 3–5 parts; the CMM report is attached.
- Material test results: EN 10204 3.1 certificate, hardness and coating-thickness reports if required.
- Initial process study: on special characteristics (marked with a symbol on the customer drawing), a target of Ppk ≥ 1.67 (new process) or Cpk ≥ 1.33 (stable process) on 100 parts from at least 25 subgroups or a quantity agreed with the customer.
- MSA: Gage R&R for the instruments measuring special characteristics (below 10% ideal, conditionally acceptable up to 30%).
- PSW: the summary of the file and the supplier's formal declaration.
Common Challenges
- Ambiguity of special characteristics: if the customer has not marked them on the drawing, the manufacturer does not know which dimension to run the Cpk study on; clarify in the RFQ.
- Small series and Cpk: a 100-part capability study may be meaningless for a part with an annual volume of 300; a reduced sample is agreed with the customer.
- Plating and heat-treatment sub-suppliers: these processes must be included in the PFMEA and control plan, and sub-supplier certificates added to the file.
- Document language: for German customers, German or English templates are commonly used.
The VDA 2 (PPF) Difference
Instead of PPAP, the German automotive industry mostly uses the PPF (Produktionsprozess- und Produktfreigabe) process from VDA Volume 2. The content overlaps to a large extent; the differences lie in the submission template, the evidence matrix (Nachweisführung) and the naming of the approval levels. A request from a German customer for "PPF-Unterlagen" or an "Erstmusterprüfbericht (EMPB)" means a file close to PPAP Level 3. We touch on this terminology in our guide for Germany.
The PPAP Approach at Tornelle
For automotive parts, the process flow, PFMEA, control plan, full inspection report based on a ballooned drawing, material certificate and PSW are prepared as standard; the Cpk/Ppk study is carried out on the special characteristics marked by the customer. The PPAP level and customer-specific requirements are clarified at the quotation stage; preparation time and cost are shown as a separate item in the quote. For the effect on price see our 12 factors article.
Frequently Asked Questions
Is IATF 16949 certification mandatory for PPAP?
Certification is not mandatory to prepare a PPAP file; however, many OEMs and Tier-1s require IATF 16949 or at least ISO 9001 from series suppliers. Check your customer's supplier requirements.
How long does PPAP take?
File preparation after sample production typically takes 1–3 weeks; the number of parts required for the capability study determines the duration.
Who pays for the PPAP?
It varies by practice; usually sample and file preparation is priced as a separate item or spread over the series price. Clarify at the quotation stage.
Are FAI and PPAP the same thing?
No. FAI (first article inspection) covers only dimensional and material results; PPAP adds process evidence (PFMEA, control plan, Cpk, MSA).
Conclusion
PPAP is the entry ticket to series production for automotive CNC parts; what is expected from the contract manufacturer is consistent process evidence beyond the inspection report. Send your technical drawings for your automotive parts via our quote form, stating the PPAP level and special characteristics; receive a quote that includes the PPAP preparation plan together with the series price.
