Additive Supplier Quality Agreement — The 12 Clauses That Decide Who Pays When a Part Fails

Why the Quality Agreement Cannot Live in the Purchase Order

Most additive jobs start with a purchase order that carries a line of boilerplate: "parts to be free of defects, supplied to drawing." That sentence looks protective and is close to useless. When a printed batch arrives with 4% dimensional fallout, the buyer points at "free of defects," the supplier points at a drawing tolerance that was never agreed for the as-printed surface, and both sides discover that nobody wrote down what happens next. The argument then costs more than the parts.

A supplier quality agreement (SQA) is the document that fixes this before the first shipment. It is not a quality certificate and it does not replace incoming inspection. It is the contract section that assigns responsibilities, defines the acceptance rules, and states the remedy when a lot fails. In additive work it matters more than in conventional work, because the process window is wider: two printers running the same profile can still differ on dimensional drift, surface finish and interlayer strength if nozzle condition, chamber temperature or material lot changed between builds.

Below are the twelve clauses that we see decided by argument instead of by document, and what each one is actually written to prevent. The remedy ladder later in the article shows how the clauses connect to money.

What Should a 3D Printing Quality Agreement Contain?

A 3D printing quality agreement should contain twelve clauses covering scope and part identification, drawing and specification control, acceptance sampling per lot, material traceability with a certificate of analysis per lot, process freeze and change notification, sub-supplier flow-down, inspection method and instrument, nonconformance and disposition authority, corrective action timing, right of access and audit frequency, warranty period and remedy ladder, and document retention. Each clause should name a responsible party and a time limit, not just a principle.

That paragraph is the short answer. The rest of this article is the working version, because a clause signed without a time limit is a clause that will be argued about at the worst possible moment.

The Twelve Clauses, and the Failure Each One Prevents

Read the right-hand column first. Every clause in a mature agreement exists because some buyer, somewhere, lost money on exactly that scenario. If your draft agreement has no clause for a failure you can imagine, the failure is unallocated, and unallocated risk lands on whoever has the weaker negotiating position, which is usually the party that has already shipped.

#	Clause	Failure it prevents
1	Scope and part identification (part number, revision, material, process, machine family)	Parts approved on one machine family, then produced on another without the buyer noticing
2	Drawing and specification control, with a named revision date	Supplier builds to Rev B while the buyer's inspection sheet still reads Rev A
3	Acceptance sampling per lot (plan, sample size, AQL or zero-defect rule)	Buyer inspects 100%, supplier inspects 3 pieces, and 8,000 parts are judged on 3
4	Material traceability and certificate of analysis per material lot	A strength shortfall traced to a pigment masterbatch change nobody recorded
5	Process freeze and change notification (PCN) with a defined lead time	Supplier upgrades firmware, prints 40% faster, layer bonding drops, and the buyer finds out from a field failure
6	Sub-supplier flow-down: powder, filament, resin, pigment, plating, heat treatment	Printed in-house but annealed by a job shop with no agreed parameters and no record
7	Inspection method, instrument and environment	Two parties measure the same feature with different instruments and disagree by 0.12 mm
8	Nonconformance handling and disposition authority (who may scrap, rework, accept-as-is)	A supplier "reworks" a part by sanding a critical datum and the buyer accepts it unknowingly
9	Corrective action timing and format (8D or equivalent, response and closure deadlines)	Same defect recurs across three lots because the first report was a phone call
10	Right of access, audit frequency and notice period	Buyer discovers on a site visit that half the order is outsourced to a second plant
11	Warranty period, remedy ladder and liability cap	Credit note issued for part cost while the buyer's assembly line has already stopped
12	Document retention period and record format	A recall two years later with no build record to identify the affected range

Acceptance Sampling: The Clause Buyers Most Often Get Wrong

Additive suppliers get asked for "100% inspection" frequently and it is rarely the right answer. On a printed part, 100% dimensional inspection of every feature on every piece is often economically absurd: a bracket with 22 toleranced features inspected fully with a coordinate measuring machine can consume more hours than printing it. The practical answer sits in a documented sampling plan tied to an agreed acceptance rule.

Three structures work, and the agreement should name which one applies per part family:

• Zero-defect on critical characteristics. Every critical-to-function feature is measured on every piece, usually with go/no-go gauges or a fixture rather than a full CMM program. Typical inspection cycle for a bracket: 40 to 90 seconds per piece.
• Statistical sampling on general characteristics. ISO 2859-1, inspection level II, with the AQL set per characteristic class. A 500-piece lot at AQL 1.0 typically draws 50 pieces; at AQL 0.65 it draws 80.
• Skip-lot after demonstrated capability. Once a supplier shows a Cpk above 1.33 on the agreed characteristics across three consecutive lots, sampling frequency drops to every second or third lot, with a documented trigger that puts full sampling back.

The failure mode to write against is the silent mismatch: buyer assumes full inspection, supplier assumes attribute sampling, and the first real dispute arrives with two incompatible interpretations and no agreed plan to arbitrate. Specify the standard, the inspection level, the AQL per characteristic class, and the reaction when a sample fails, in the agreement, not in an email.

Change Notification: The Clause That Protects Future Batches

Additive processes drift silently. A firmware update that shortens print time by 30% can also change cooling behaviour and layer adhesion. A supplier switching nozzle suppliers or adding a second powder blend can shift the surface finish by more than the print tolerance band. None of these changes shows up on a drawing, and all of them can invalidate a buyer's validation work.

Write the PCN clause with four specifics rather than one principle:

• Trigger list. Machine family or model change, firmware or slicer major version, material supplier or grade change, pigment or additive change, process parameter change above an agreed band, production site change, and any sub-supplier change on a special process.
• Notice window. A common split is 30 days' advance notice for a planned change, 5 working days for an unplanned one, and 24 hours for a change already shipped.
• Approval route. Whether the buyer must approve before the first changed shipment (typical for automotive and medical) or be notified after (typical for industrial and consumer).
• Requalification scope. Which of the buyer's validation activities restart: dimensional re-approval only, or full part qualification with mechanical testing.

Note that the honest position is not "we never change anything." Any supplier running for more than a year will change something. The useful clause is the one that makes the change visible early enough to be tested.

Remedy Ladder: Turning a Failed Lot Into an Agreed Sequence

The most expensive disputes are not about whether parts failed. They are about how far up the ladder the remedy goes. A four-tier ladder with explicit triggers removes most of that argument.

Tier	Trigger	Typical remedy	Decision window
1	Cosmetic or non-functional deviation, drawing tolerance met	Written concession from buyer, lot accepted as-is with a recorded deviation number	5 working days from inspection report
2	Feature outside tolerance but function demonstrably unaffected and buyer agrees	Accept-as-is with price adjustment or 100% sort at supplier cost	10 working days
3	Functional rejection of a lot	Rework to drawing where physically possible, otherwise replacement lot at supplier cost, expedited at supplier cost	48 hours for contain-and-replace commitment
4	Repeated failure, or a supplier-caused line stop	Credit plus documented chargeback for verified consequential cost, capped at an agreed multiple of the lot value	30 days with 8D closure

The cap in tier 4 deserves attention during negotiation. A supplier will argue for a cap at the value of the shipped lot; a buyer will argue for uncapped consequential damages. Neither extreme survives contact with a real contract. A workable middle is a stated multiple of lot value (two to five times is common in industrial work) with an explicit exclusion for defects the supplier reported before shipment, which rewards early disclosure instead of hiding it.

Sub-Supplier Flow-Down: Where Additive Chains Actually Break

A printed part is rarely finished by the printer alone. Powder or filament comes from a materials supplier, colourant from another, plating or vapour smoothing from a finishing shop, annealing from a heat-treatment subcontractor, inserts from a fastener source. Each of those is a place where a requirement can be dropped.

The clause should list every outsourced special process by name and require three things for each: an approved supplier list the buyer can see, the parameters the buyer requires to be recorded (annealing cycle, plating thickness range, vapour smoothing time), and a statement that the supplier remains responsible for sub-supplier performance. That last sentence is often resisted. It is also the only sentence that stops a supplier from pointing at a plating shop when a coating peels.

For automotive work, flow-down expectations sit inside the IATF 16949 external provider control requirements, which we cover alongside the difference between IATF 16949 and ISO 9001 for printed parts. For lot-level material evidence, the practical companion piece is our guide to filament lot traceability and incoming verification.

Where the Agreement Meets the Approval Package

Three documents are frequently confused, and buyers sometimes ask for the wrong one. The agreement sets the rules of the relationship. The approval package proves a specific part is acceptable. The nonconformance procedure governs what happens after a defect.

• The approval package, in automotive terms a full submission with a first article report, is a one-time gate per part and revision. Our PPAP and first article guide walks through the eighteen elements.
• The nonconformance and disposition procedure is the daily operating half. Disposition authority, MRB quorum and rework limits are laid out in the MRB disposition guide.
• The supplier evaluation record, which is how the buyer decides whether to renew, is the scorecard described in our supplier scorecard and audit guide.

If a buyer only has capacity to negotiate one of the three, negotiate the agreement. It is the document that survives staff changes on both sides.

Right of Access and Audit Frequency

Absent a clause, a buyer has no right to walk into a supplier's plant, and a supplier has no obligation to disclose that half the volume runs at a second site. Two numbers make the clause usable: routine audit frequency (annual for a stable part, semi-annual for a new one) and notice period. Ten working days' notice for a routine audit and 48 hours for a for-cause audit is a workable split, and both directions should be written, because a supplier also wants protection from unannounced visits during a peak build.

Pair the access clause with a defined evidence set the audit can check without interpretation: build records per lot, material certificates, calibration status of measuring instruments, training records for operators on the frozen process, and the change log. If the audit can be answered from those five records, the clause is doing its job.

Negotiation Order: What to Concede and What to Hold

Both sides arrive with a template. The productive conversation ranks the clauses by actual cost exposure instead of by how legal they sound.

• Hold firmly: process freeze and change notification, material traceability per lot, disposition authority, warranty period. These four carry nearly all the money at risk.
• Trade: audit frequency and notice period, document retention beyond the statutory minimum, report format and language. These cost time, not margin.
• Concede early: the specific sampling standard named (ISO 2859-1 versus an in-house plan), the liability cap multiple within a reasonable band, and concessional cosmetic criteria. Conceding these builds room to hold the four above.

One practical note for distributors: if you resell printed parts under your own brand, the obligations you sign upstream should mirror what you can enforce downstream. A distributor who accepts a 48-hour contain-and-replace duty from a customer but holds only a 10-day remedy window with the factory has created a liability gap that no amount of quality enthusiasm closes.

For buyers who also audit the visual side of acceptance, the governance half of that work is in our limit sample and visual acceptance guide, and the contract clause that makes limit samples enforceable is clause 7 of the list above.

Reviewed by the Precise3D OEM & quality team. A supplier quality agreement is a commercial contract as well as a quality document; the clause list here reflects common industrial, automotive and medical practice and is not legal advice. Have your own counsel review liability, warranty and remedy language before signature.

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