PPAP for small suppliers: what a customer needs before approving your parts

A small manufacturer wins its first order from a larger industrial or automotive customer. Then the supplier quality engineer asks for a PPAP submission, and the owner opens a list of requirements that seems longer than the order: design records, flow diagrams, failure mode analyses, control plans, measurement studies, capability results, sample parts and a warrant to sign. It looks like paperwork designed to keep small suppliers out.

It is better understood as a structured argument. The production part approval process, PPAP, asks a supplier to show, with evidence, that it understands everything the design requires, has planned a process to meet those requirements, has identified what could go wrong and put controls in place, can measure what matters reliably, and has actually made parts on the real production process that meet every requirement. A customer about to depend on your parts is entitled to ask for that.

This article explains what PPAP is trying to prove, how its elements fit together, what reviewers check, how to handle changes after approval and how a small supplier can prepare without disrupting the business. It is general information. PPAP originated in the automotive industry and is published by the Automotive Industry Action Group (AIAG); many customers in other industries use it or their own version. Always work from your customer’s requirements and the edition they specify.

What PPAP is trying to prove

Strip away the forms and PPAP answers five questions:

Do you understand the requirements? Every dimension, note, material property and performance requirement on the drawings and specifications.
Have you planned the process to meet them, and thought through what could go wrong?
Are controls in place to prevent or detect problems in normal production?
Can you measure what matters reliably?
Have you shown it works on real production equipment, with real operators, at a meaningful rate?

The elements of a PPAP package are the evidence for those answers. Seen that way, they connect rather than pile up.

The main elements, grouped

Group	Typical elements	What they show
Design	Design records, approved engineering changes, customer engineering approval, design failure mode analysis where you are responsible for design	You are working to the right, current requirements
Process planning	Process flow diagram, process failure mode and effects analysis, control plan	You have mapped the process, assessed risk and planned controls
Evidence	Measurement system analysis, dimensional results, material and performance test results, initial process studies, laboratory qualifications, appearance approval where relevant	The process works and the measurements can be trusted
Physical	Sample production parts, a master sample, checking aids	Real parts and the tools used to accept them
Records	Customer-specific requirements, part submission warrant	Everything required has been addressed and is signed for

The customer decides how much is submitted and how much is retained at your site for review. This is usually expressed as a submission level. Ask early which level applies and which elements are needed for your part, rather than assuming.

The documents must tell one story

Reviewers do not just check that each document exists. They check that the documents agree. Two kinds of tracing are common:

Trace a requirement across the documents. Pick a critical dimension on the drawing. It should appear in the process failure analysis, where the risk of getting it wrong is assessed; in the control plan, with a measurement method, frequency and reaction plan; in the measurement system study for the gauge used; and in the dimensional results, measured on the sample parts.
Trace a process step down the documents. Pick an operation on the process flow diagram. The failure analysis, control plan and work instruction for that operation should describe the same step, equipment and controls.

Mismatches are the most common reason for rejection: a different drawing revision on the dimensional report, an operation in the control plan that is not on the flow diagram, a gauge in the control plan that was never studied. A readiness review by someone who did not prepare the documents catches most of them.

Special characteristics deserve the closest attention

Customers often mark some characteristics as special, because they affect safety, regulatory compliance or critical function. These need an unbroken chain: identified on the drawing, assessed in the failure analysis, controlled with an appropriate method in the control plan, measured with a proven gauge and shown to be capable in the initial process studies. If your customer specifies a minimum capability level for special characteristics, plan the process and measurement to meet it from the start.

Measurement comes before capability

A capability study is only as good as the measurements behind it. Before running a capability study, check that the gauge or method can tell good parts from bad reliably, through a measurement system study. A gauge that varies too much can make a good process look poor, or hide a poor one. The proving a process is ready for production article covers measurement systems, stability and capability in more depth.

Samples must come from the real process

PPAP samples should come from a production run using the actual tooling, equipment, operators, materials, settings and environment that will be used for ongoing supply, at a meaningful rate. Parts carefully made by the best toolmaker on a prototype setup do not prove that the production process works. If several tools, cavities or machines will make the part, the evidence needs to cover each of them.

Checking aids need control too

Fixtures, go/no-go gauges, templates and other checking aids used to accept parts are part of the evidence. Keep a register of every product-specific aid, give each an identity number, link it to the control plan where it is used, check or calibrate it where wear or damage could affect acceptance, and include it in measurement studies where required. A worn fixture that still says “pass” is one of the quieter ways a good PPAP turns into a bad shipment.

Sub-suppliers and outside processes

Many parts pass through outside processes such as heat treatment, plating, coating or testing. These are part of your process, and your PPAP must cover them. Pass the relevant drawing requirements and special characteristics to your sub-suppliers in writing, ask for their certificates and test results, and check their capability for anything critical. If a sub-supplier changes its own process or site, that can be a change your customer needs to know about. The quality starts before the specification article covers setting clear requirements with suppliers.

Interim approval and deviations

Sometimes a submission is nearly ready but one item is outstanding, such as a long lead test. Customers may grant interim approval, allowing limited shipments while the gap is closed. Treat it as a temporary, bounded arrangement: state what is missing, the action plan and the date for full resubmission. Similarly, any deviation from the drawing must be formally approved by the customer and limited in quantity or time, not left open.

After approval: changes need control

Approval applies to the part as made by the approved process. Many changes require you to notify the customer and, often, to resubmit, such as moving production to a different machine or site, changing a material source or sub-supplier, changing the process, or making the part with new or refurbished tooling. Keep a simple change control: before changing anything that affects how the part is made, check whether the customer must be told. Unapproved changes are a common cause of lost business.

Preparing as a small supplier

Start at the quote stage. Ask what PPAP level, customer-specific requirements and capability levels apply, and price the work accordingly.
Name one owner for the PPAP package.
Talk to the customer’s quality engineer early, and agree expectations before the due date.
Build the package alongside development, not afterwards. Failure analysis and control planning should shape the process, not describe it after the fact.
Keep a register listing each element, its status, owner and where the evidence is stored.
Check revisions everywhere: part number, drawing revision and engineering change level should match across every document.
Hold a readiness review with someone who did not prepare the package.

The inspection and test plans for supplier work article covers agreeing inspection and test evidence with customers more generally.

A worked example

This is an illustration. A 15-person CNC machining business wins an order for a steel bracket from an agricultural equipment manufacturer. The customer requires a full PPAP submission, and two bore diameters and their positions are marked as special characteristics because they affect a safety-related linkage.

The owner appoints the quality lead as PPAP owner and arranges a call with the customer’s supplier quality engineer, who confirms the submission level, sends the customer-specific requirements and the required capability level for special characteristics.

The team builds the process flow, then a process failure mode analysis focused on the two bores. The main risks are tool wear and fixture clamping errors. The control plan specifies in-process gauging of both bores at a set frequency, a first-off and last-off check, and a reaction plan that quarantines parts back to the last good check if a bore is out of tolerance.

The measurement system study on the existing bore gauge shows too much variation relative to the tolerance. The business buys a more suitable gauge, repeats the study and gets an acceptable result. A capability study on a production run then meets the customer’s required level for both bores. Dimensional results cover every characteristic on the drawing for parts from both fixtures used in production, and material certificates from the steel supplier are included.

The readiness review, done by the production supervisor, finds that the dimensional report refers to the previous drawing revision. It is corrected before submission. The customer grants interim approval because a surface finish test at an external laboratory is still pending; the result arrives two weeks later, and full approval follows.

Six months on, the business wants to move the job to a newer machine. Its change-control checklist flags this as a change requiring customer notification. The customer asks for a partial resubmission, covering dimensional results and a new capability study, which is approved before the move.

How this applies to a small Australian business

Ask about PPAP requirements at the quote stage, and price them in.
Treat PPAP as evidence, not paperwork.
Name a PPAP owner and keep an element register.
Make the documents agree, especially revisions and special characteristics.
Prove measurement before capability.
Use the real production process for samples.
Control changes after approval, and notify the customer when required.
Review readiness with fresh eyes before submitting.
Flow requirements down to sub-suppliers and outside processes.

Signals worth watching

Documents prepared after the process is already running.
Different drawing revisions across the package.
Capability studies on gauges nobody has checked.
Samples made on prototype setups.
Open-ended deviations.
Process or supplier changes made without checking customer requirements.
Checking aids with no identity or calibration record.

Common mistakes

Underestimating the effort when quoting.
Filling templates instead of using them to plan.
Missing special characteristics in the control plan or work instructions.
Submitting before an independent readiness review.
Treating interim approval as final.
Changing the process after approval without notifying the customer.
Leaving outside processes out of the evidence.

Frequently asked questions

Is PPAP only for automotive suppliers? It began there, but many industrial, agricultural and other manufacturers use PPAP or similar approval processes. Aerospace customers often use a related approach called first article inspection.

How long does a first PPAP take? It depends on the part and the level, but plan weeks rather than days, and start alongside process development.

Do we need specialised software? No. Spreadsheets and well-controlled documents work for small suppliers. What matters is consistency and evidence.

What if we cannot meet the required capability? Talk to the customer early. Options include improving the process, better measurement, tighter controls such as full inspection while improvements are made, or discussing the tolerance.

Does every change need a new PPAP? Not every change, but many do require notification or resubmission. Check the customer’s requirements before changing anything that affects how the part is made.

Questions to ask

What PPAP level and customer-specific requirements apply to this part?
Which characteristics are special, and can we trace each across our documents?
Have we proved our measurement systems?
Were our samples made on the real production process?
Who checked the package who did not prepare it?
What changes would require us to notify the customer?
Do our sub-suppliers know which characteristics are critical?

Bringing it together

PPAP is a structured argument that you can make the customer’s part consistently, backed by evidence. Understand the requirements, plan and risk-assess the process, put controls in the control plan, prove your measurements, and show it works on real production equipment. Make the documents agree, give special characteristics an unbroken chain of evidence, review readiness before submitting and control changes after approval. Approached this way, PPAP improves the process rather than just documenting it, and builds a customer’s confidence.

Source: KEVOS notes, drawing on earlier KEVOS manufacturing handbooks on PPAP submission assessment, including the part submission warrant, control plans, special characteristics, measurement systems analysis, checking aids, customer-specific requirements and engineering change approval. Examples and figures in this article are illustrations. This article is general information; always follow your customer’s requirements and the edition of the PPAP manual they specify.