# PPAP Submission for CNC Automotive Parts: 18 Elements

> PPAP for CNC automotive parts: which of the 18 AIAG elements apply, common rejection reasons, submission levels 1–5 and material cert requirements.

https://www.sinbo-machining.com/wiki/quality/ppap-submission-cnc-automotive/

---

## On This Page

- What PPAP Is — and Why Getting It Wrong the First Time Is Expensive
- The 18 PPAP Elements — Which Ones Apply to CNC Machined Parts
- Submission Levels 1–5 — What Your Customer Actually Expects
- The Documents That Get Rejected Most Often
- Process Flow Diagram — How to Map Your CNC Process for PPAP
- Material and Performance Test Results — What the Lab Report Must Show
- Initial Process Studies — Cpk / Ppk and What the Numbers Mean
- Standards & Sources
- Need help preparing a PPAP package for a CNC machined part?

# PPAP Submission for CNC Machined Automotive Parts: A Practical Guide to the 18 Elements That Actually Apply
The Production Part Approval Process (PPAP) is the automotive industry’s standard gate between prototyping and serial production. AIAG’s PPAP manual lists 18 elements; not all of them apply to a CNC machined part, and submitting the wrong set is the single most common reason for rejection. This page walks through the elements that actually matter for a CNC shop, what the customer’s SQE opens first, and what to fix before re-submitting.
## What PPAP Is — and Why Getting It Wrong the First Time Is Expensive
PPAP (Production Part Approval Process) is defined in AIAG PPAP 4th edition. It is the package of evidence a supplier submits to a customer to prove that the production process can make parts that meet all design and specification requirements, consistently, at the quoted rate. The customer reviews the package and either approves the part for serial production, returns it for correction, or rejects it. The standard defines 18 elements (see the table below). The supplier must show evidence for every element that the customer has marked as “required” on the customer-specific PPAP checklist — most German and US OEMs require all 18 by default, with exceptions noted in the customer’s PPAP requirements document. The cost of a rejection. A first-time PPAP rejection can delay a project by 4–12 weeks. If the part is on the critical path for a vehicle launch, that delay is measured in lost OEM production days — easily five to six figures of OEM-internal cost. The customer remembers the supplier that delayed the launch, which is why the typical PPAP re-submission rate is the metric German procurement watches most closely on new suppliers. For a CNC machined part, the PPAP package is built around your process flow diagram, PFMEA, control plan, dimensional report, material certificate, and process-capability study. The challenge is that the AIAG manual is generic — it covers stamped parts, cast parts, machined parts, electrical assemblies, and assemblies of all of them. Knowing which of the 18 elements actually require evidence for a CNC part is half the work.
## The 18 PPAP Elements — Which Ones Apply to CNC Machined Parts
The table below marks each element as Required (must submit evidence for almost any CNC part), Conditional (depends on customer-specific requirement or part characteristics), or Rarely required (typically N/A for a single-piece CNC machined part).
|  # |  Element |  CNC applicability |  What you actually submit
|  1 |  Design Record |  Required |  Customer drawing (or your drawing if you own the design), with revision number and date
|  2 |  Authorized Engineering Change Documents |  Required if any |  Any ECNs since the last sample, with sign-off
|  3 |  Customer Engineering Approval |  Required if applicable |  Customer sign-off if design is owned by the customer and the part deviates from drawing
|  4 |  Design FMEA |  Required if you own design |  DFMEA per AIAG-VDA DFMEA Handbook (2019); N/A if customer owns the design
|  5 |  Process Flow Diagram |  Required |  One-page flow from incoming raw material to shipping, with each step identified
|  6 |  Process FMEA |  Required |  PFMEA per AIAG-VDA PFMEA Handbook (2019), covering every step in the process flow, including outsourced operations
|  7 |  Control Plan |  Required |  Control plan covering prototype, pre-launch, and serial production, with reaction plan for every special char
|  8 |  MSA (Measurement System Analysis) |  Required for special chars |  Gauge R&R, bias, linearity for every gauge measuring a special characteristic
|  9 |  Dimensional Report |  Required |  100% of drawing dimensions measured on at least 30 parts from a documented production run; layout per customer template
|  10 |  Material / Performance Test Results |  Required |  Material cert per EN 10204 3.1 (or 3.2 for PED parts), mechanical properties, chemistry
|  11 |  Initial Process Studies |  Required |  Cpk / Ppk for every special characteristic, typically from 30 consecutive parts; Cpk ≥ 1.67 long-term target
|  12 |  Qualified Laboratory Documentation |  Required |  Lab accreditation (ISO 17025 preferred) for any external lab doing chemistry, mechanical, or metallurgical testing
|  13 |  Appearance Approval Report (AAR) |  Conditional |  Required for parts with customer-specified surface appearance (paint, texture, color); N/A for raw machined surfaces unless specified
|  14 |  Sample Production Parts |  Required |  Number of sample parts per customer requirement, usually 5–30, from the actual production run that produced the dimensional report
|  15 |  Master Sample |  Required if requested |  Customer-retained sample; required for some OEMs (e.g. VW, BMW) as a visual / dimensional reference
|  16 |  Checking Aids |  Conditional |  Custom gauges, fixtures, or optical-comparison masters if used in production; often not required for CNC parts but listed for completeness
|  17 |  Customer-Specific Requirements |  Required |  Compliance with any additional customer requirements (e.g. VW Q-Steps, Ford Q1, BMW Group Standard)
|  18 |  Part Submission Warrant (PSW) |  Required |  Signed warrant that all other 17 elements are complete and accurate; signed by your quality manager
For a CNC machined part from a customer drawing, you can usually mark elements 4 (DFMEA) and 13 (AAR) as N/A, and elements 3, 15, 16 as conditional. The remaining 13–14 elements are your real workload. Always confirm with the customer’s PPAP checklist — the German OEM´s PPAP requirements document will tell you which level to submit and which elements to fill in.
## Submission Levels 1–5 — What Your Customer Actually Expects
AIAG PPAP defines five submission levels. The level is set by the customer, not by the supplier.
|  Level |  What you submit |  When it is used |  Typical for CNC parts?
|  Level 1 |  Warrant only (PSW) |  Customer has all other evidence already (e.g. re-approval after design change) |  Occasional, for re-approvals only
|  Level 2 |  Warrant + product samples + limited supporting data |  Customer wants a quick re-look |  Occasional
|  Level 3 |  Warrant + product samples + full supporting data |  Default for new part submissions |  Default — most common for CNC parts
|  Level 4 |  Warrant + customer-defined requirements |  Customer specifies what they want beyond Level 3 |  Common at German OEMs with extended requirements (e.g. VW Q-Steps)
|  Level 5 |  Warrant + full supporting data + samples retained at supplier |  Customer wants to audit the package on-site rather than receive it |  Rare for CNC parts; more common for assemblies
Level 3 is the default. Level 4 is what most German OEMs actually use. If the customer hasn’t told you the level, ask before you prepare the package — a Level 3 package is a few hundred pages; a Level 4 package with VW Q-Steps or BMW Group Standards can run into the thousands.
## The Documents That Get Rejected Most Often
From our PPAP experience (we are running PPAP for six parts on a German Tier-1 program right now) and from peers in the supplier network, these are the rejection reasons that show up in 80% of failed first submissions.
|  # |  Rejection reason |  How to avoid it
|  1 |  Dimensional report missing key characteristics or special-characteristic symbols |  Use the customer’s dimension layout; mark << / K rows explicitly; measure on the customer-specified inspection equipment
|  2 |  PFMEA actions do not match control plan rows |  Reconcile after every revision — every PFMEA action must appear in the control plan, and vice versa
|  3 |  Material cert missing heat number / batch traceability |  Request EN 10204 3.1 cert from the mill with heat number, not the generic 2.1 compliance statement
|  4 |  Cpk < 1.33 with no improvement plan |  Run capability study before submitting; if Cpk is low, attach a documented improvement plan with target and timeline
|  5 |  Sample parts not from a documented production run |  Tag the run on the production router; have the operator and QA sign off; the sample submission must be traceable to that run
|  6 |  Outsourced process (heat treat, plating, coating) not in your PFMEA |  Include every external process step in the process flow, PFMEA, and control plan; attach the sub-supplier certs
|  7 |  MSA / Gauge R&R not done for the actual gauge used in production |  The gauge on the PPAP MSA must be the same gauge (same ID, same calibration) used in serial production
|  8 |  PSW signed by someone without authority |  PSW must be signed by the quality manager or someone explicitly authorized in your quality manual
|  9 |  Revision mismatch between drawing, DFMEA, PFMEA, control plan |  Lock revisions before PPAP — any change after submission invalidates the package
|  10 |  Customer-specific requirements (CSR) checkboxes unchecked or unmarked |  Walk the customer’s CSR form row by row; missing checkboxes are an automatic reject
The single most common rejection on first submission: the dimensional report doesn’t include all special characteristics, or measures them on a different gauge than the one used for MSA. This is item 1 and item 7 above. Fix both before you submit anything else.
## Process Flow Diagram — How to Map Your CNC Process for PPAP
The process flow diagram is the spine of the PPAP package. Every other element (PFMEA, control plan, MSA, capability, sample selection) refers back to a step on the flow. A one-page flow that anyone in the plant can read is the goal. For a CNC machined part that goes through outsourced heat treatment and surface finishing, the flow looks like:
|  Step # |  Operation |  Workstation / supplier |  Inspection / control |  PFMEA link
|  10 |  Incoming raw material (bar / billet / forging) |  Goods-in |  Material cert (EN 10204 3.1), dimensional check, heat-number trace |  PFMEA row 10
|  20 |  CNC turning OP10 (rough) |  Cell 1 — Citizen L20 |  In-process: OP10 dimensions per WI |  PFMEA row 20
|  30 |  CNC turning OP20 (finish) |  Cell 1 — Citizen L20 |  In-process + final dimensional check at OP20 |  PFMEA row 30
|  40 |  Deburr / chamfer |  Manual bench |  Visual per WI |  PFMEA row 40
|  50 |  Wash |  Wash station |  Visual cleanliness |  PFMEA row 50
|  60 |  Heat treatment (sub-supplier) |  External — approved sub-supplier |  Sub-supplier cert + incoming hardness check |  PFMEA row 60
|  70 |  Surface finishing (sub-supplier) |  External — approved sub-supplier |  Sub-supplier cert + visual check |  PFMEA row 70
|  80 |  Final inspection |  CMM room / inspection bench |  100% dimensions per drawing, 100% visual |  PFMEA row 80
|  90 |  Pack & label |  Pack bench |  Per customer packaging spec, label check |  PFMEA row 90
Sub-supplier steps must be in your flow. A common rejection: the supplier’s process flow stops at the cell door and the heat treatment / plating step is not in the PFMEA. The customer’s SQE will read the flow, ask “where does the part go after OP20?”, and if the answer is “to a sub-supplier we didn’t list”, the package is rejected on first review.
## Material and Performance Test Results — What the Lab Report Must Show
For a CNC machined part, the material evidence is the EN 10204 3.1 mill certificate from the raw material supplier. (For PED / pressure-equipment parts, you need 3.2 instead — see the EN 10204 wiki page for the difference.) The cert must show: 1- Heat number — the unique identifier that links this batch of raw material to the chemistry and mechanical test results.
1- Chemistry — actual measured values for C, Mn, Cr, Ni, Mo, etc. (per the material spec), with the spec range and pass/fail.
1- Mechanical properties — yield strength, tensile strength, elongation, hardness (or impact for some specs), per the material spec.
1- Authorized signature — the mill’s authorized inspector (not a sales rep, not a quality manager — the person specifically authorized per EN 10204 3.1).
The performance test results (element 10) are typically the same document for a CNC machined part. If the part is heat-treated by you or by a sub-supplier, attach the heat-treat cert and the post-HT hardness report.
|  Test |  Standard |  Typical for
|  Tensile test (yield, UTS, elongation) |  ISO 6892-1 / ASTM E8 |  All metallic parts
|  Hardness (Brinell / Rockwell / Vickers) |  ISO 6506 / 6507 / 6508 / ASTM E10 / E18 / E92 |  All metallic parts
|  Impact (Charpy) |  ISO 148-1 / ASTM E23 |  Parts with impact requirement
|  Chemistry (optical emission or XRF) |  ASTM E415 / E1086 |  All metallic parts
|  Grain size (when specified) |  ASTM E112 |  Austenitic stainless, aerospace alloys
|  Ferrite content (when specified) |  ASTM E562 or Schaeffler diagram |  Austenitic / duplex stainless welds
Lab accreditation matters. Element 12 (Qualified Laboratory Documentation) is automatic if the mill is ISO 9001 / IATF 16949 and the test lab is ISO 17025-accredited. If you do the testing in-house and you are not ISO 17025-accredited, you need to either get accredited or send the testing to an accredited sub-supplier. Most German OEMs will not accept a non-accredited lab result.
## Initial Process Studies — Cpk / Ppk and What the Numbers Mean
Element 11 (Initial Process Studies) is the capability study, typically calculated from 30 consecutive parts measured at the production rate. The two indices are Ppk (initial, before any process adjustment) and Cpk (long-term, after the process is stable). The customer will look at both, and the minimum acceptable values are usually defined in the control plan or the customer’s CSR.
|  Index |  Typical minimum |  Interpretation
|  Ppk ≥ 1.67 |  Common automotive target for new parts |  Process is capable; the customer usually accepts the PPAP
|  Ppk 1.33–1.67 |  Conditional |  Acceptable for non-critical characteristics; for special chars, requires improvement plan and 100% inspection until Cpk ≥ 1.67
|  Ppk < 1.33 |  Reject |  Process is not capable; PPAP will be rejected; root-cause and corrective action required
Capability is calculated per special characteristic, not per part. If a part has three special characteristics (e.g. Ø10 H7, Ra 0.8, concentricity 0.02), you need three capability studies. Use a software package (Minitab, JMP, or the open-source R qcc package) and report the Ppk, the mean, the sigma, and the control chart alongside the histogram. Common mistake: submitting a Cpk value calculated from a hand-picked sample. The customer will ask for the raw data (the 30 measurements) and re-calculate. If the data doesn’t look random — if the first 10 are all at the high end and the last 10 are at the low end — the customer will suspect cherry-picking and reject the package. Run the study on consecutive parts from a single documented run.
## Standards & Sources
Primary standardAIAG PPAP 4th edition Production Part Approval Process. Defines the 18 elements, the 5 submission levels, the Part Submission Warrant (PSW), and the customer-supplier responsibilities. Related standardsAIAG-VDA DFMEA / PFMEA Handbook, 1st edition 2019 Joint AIAG-VDA reference for DFMEA and PFMEA structure (replaces the older AIAG FMEA 4th ed.).AIAG APQP 3rd edition Advanced Product Quality Planning — the framework PPAP sits inside.AIAG CQI-23 Soldering process assessment (referenced for outsourced processes).IATF 16949:2016, Clause 8.6.2 Requires PPAP (or equivalent) before serial production.EN 10204:2004 / EN 10204:2017 Types of inspection documents for metallic products — 3.1 vs 3.2 distinction.ISO 17025:2017 General requirements for the competence of testing and calibration laboratories. Customer-specific PPAP requirements (common at German OEMs)VW: Q-Steps (Q-Steps 1–5), formal PPAP cover sheet, VDA 6.3 process audit before PPAP.BMW: BMW Group Standard 95000 (former GS 95000), QPNR (Quality Part Number Release).Daimler: Mercedes-Benz Special Approval Process, formal MBN certs.Ford: Q1, Advanced Product Quality Planning.GM: BIQS (Built-In Quality Supply). Frequently Asked Questions How long does PPAP approval take for a CNC machined part? From first submission to customer approval: typically 4–8 weeks if the package is clean on the first try. Rejection and re-submission adds 2–6 weeks per cycle. The customer’s review time is the bottleneck — 2–4 weeks for first review at a German OEM, 1–2 weeks for a re-submission. If you can hand the customer a clean package with all 18 elements and no missing signatures, expect 3–4 weeks end-to-end. What is the single most common reason for PPAP rejection? In our experience and from peers in the supplier network, the top reason is the dimensional report missing key characteristics or special-characteristic symbols. The customer’s SQE opens the dimensional report first, checks that every << / K on the drawing has a row in the report with measured values, and rejects the package if any are missing. Second-most-common: PFMEA actions not matching the control plan. Both are easy to prevent with a one-hour reconciliation walk-through before submission. Do I need a new PPAP for every material change? Yes, for any change in material grade, material supplier, or country of origin — AIAG PPAP requires a new submission. The trigger list also includes changes in sub-supplier (for outsourced processes), production location, tooling (for tooling that affects form / fit / function), and inspection method. For a minor change within the same material grade from the same mill (e.g. a new heat within the same spec), a re-submission is usually not required but should be documented in your change-control system. What is the difference between PPAP Level 3 and Level 5? Level 3 = warrant (PSW) + product samples + full supporting data, sent to the customer. Level 5 = warrant + full supporting data, with samples retained at the supplier’s site for the customer to audit on demand. Most German OEMs default to Level 3 (sometimes extended to Level 4 with customer-specific requirements). Level 5 is rare for individual CNC parts; it is more common for assemblies or for long-term retention of historical PPAPs. Can I submit PPAP before serial production starts? Yes — PPAP must be approved before serial production starts. The whole point of PPAP is to prove the production process is capable before parts ship in volume. Submitting PPAP for prototype parts (before the production process is stable) is a common mistake. IATF 16949 clause 8.6.2 requires validation of products and services before serial production; AIAG PPAP is the automotive industry’s interpretation of that requirement. A customer who finds out you are shipping serial parts without PPAP approval has grounds to issue an SCAR and put new business on hold. How do I handle PPAP for outsourced processes like heat treatment? You own the PPAP, not the sub-supplier. The sub-supplier’s process must appear in your process flow, PFMEA, and control plan, and you must collect the sub-supplier’s certs (heat-treat cert, plating cert, etc.) as part of your PPAP package. Element 12 (Qualified Laboratory Documentation) applies to the sub-supplier’s lab as well. Many German OEMs will not accept PPAP from a supplier whose sub-supplier is not on the OEM’s approved-sub-supplier list — confirm the sub-supplier status before starting the PPAP clock. Sources & Standards Referenced 1- AIAG PPAP 4th edition: Production Part Approval Process — 18 elements, 5 submission levels, Part Submission Warrant (PSW), requirement for Cpk ≥ 1.67 long-term / 1.33 short-term for special characteristics (Element 11, Initial Process Studies)
1- AIAG-VDA DFMEA / PFMEA Handbook, 1st edition 2019: Joint AIAG-VDA reference for PFMEA structure and special-characteristic symbol (PPAP Elements 6 and 7)
1- AIAG APQP 3rd edition: Advanced Product Quality Planning — the framework PPAP sits inside
1- IATF 16949:2016, Clause 8.6.2: Validation of products and services before serial production (the IATF clause that requires PPAP or equivalent)
1- EN 10204:2004 / EN 10204:2017: Metallic products — Types of inspection documents 3.1 / 3.2 (PPAP Element 10 material evidence)
1- ISO 17025:2017: General requirements for the competence of testing and calibration laboratories (PPAP Element 12)
1- ISO 6892-1:2019: Metallic materials — Tensile testing at room temperature (commonly cited on 3.1 cert)
1- AIAG SPC 2nd edition (Statistical Process Control): Reference for Cpk / Ppk calculation method, control-chart interpretation, and capability indices used in PPAP Element 11

## Need help preparing a PPAP package for a CNC machined part?
We are running PPAP for a German Tier-1 automotive program right now. We can review your 18-element package against AIAG PPAP 4th edition, reconcile your PFMEA and control plan, and run the capability study for you. [Request a Quote ](https://www.sinbo-machining.com/quote/)