Build to Print Aerospace Manufacturing
Build to print means the supplier makes exactly what your released drawings, models and specs define, and changes nothing without your written approval. Aerospace Sourcing matches build to print work to qualified shops, flows down your data package and revision, routes every question back to your engineering, and delivers the parts with FAI and a cert package.
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Build to print versus build to spec
In build to print, you own the design and the supplier owns only the making of it. In build to spec, you state what the item must do and the supplier designs something that meets it. The difference decides who answers design questions, who carries design risk, and what paperwork proves the part is right.
| Question | Build to print | Build to spec |
|---|---|---|
| What the buyer provides | Released drawings, models, specs and notes that fully define the part | A performance or interface specification |
| Who designs | The buyer, or the design authority behind the buyer | The supplier |
| Who answers design questions | The buyer's engineering | The supplier's engineering, within the spec |
| What proves conformance | Inspection against the drawing, FAI, material and process certs | Qualification and acceptance testing against the spec, plus the supplier's design data |
| Who owns the design data | Usually the buyer | Usually the supplier, subject to the contract |
DoD's technical data package standard, MIL-STD-31000B, draws a similar line between a fully defined data package that gives the detailed design and a performance based package that describes the item by its required performance. Most machined, sheet metal and fabricated aerospace parts are bought build to print.
What a complete data package contains
A build to print package is complete when a qualified shop could make and inspect the part without asking you anything. In practice that means the following, at matching revisions:
- The detail drawing, prepared to the ASME Y14 drawing practices your organization uses, with every dimension and tolerance, datums, material, finish, marking and notes
- The 3D model, and a statement of whether the model or the drawing governs where they disagree
- Referenced specifications: material specs, process specs for heat treat, finishing, welding or NDT, and any company specs the notes call out
- Associated lists: parts lists for assemblies, and the approved sources where the drawing limits them
- Inspection and acceptance requirements: key characteristics, FAI requirement, sampling, and any test the drawing requires
- Marking and packaging requirements
- Export classification of the data
MIL-STD-31000B describes a fully defined package as one that details the design through drawings, specifications and CAD models, covering dimensions, tolerances, materials, finishes, inspections and packaging. That is a good test for any build to print package, defense or not. Our aerospace RFQ checklist covers how to send it.
Have a part like this?Send it in under a minute. A person replies within 1 business day.The drawing standards behind the package
Most US aerospace drawings are prepared to the ASME Y14 series, and the standards a drawing invokes affect how the shop reads it. The ones that come up most often in build to print work:
| Standard | What it covers | Why it matters to the buyer |
|---|---|---|
| ASME Y14.5 | Dimensioning and tolerancing, including GD&T | The edition on the drawing changes how some tolerances are interpreted, so it must be stated |
| ASME Y14.100 | Engineering drawing practices | Sets the general rules for drawings and works alongside the other Y14 standards |
| ASME Y14.24 | Types and applications of engineering drawings | Defines drawing types and the minimum content for each |
| ASME Y14.35 | Revision of engineering drawings and associated documents | Sets how revisions are identified and recorded |
| ASME Y14.41 | Digital product definition data practices | Governs annotated models and model based definition, with or without a drawing sheet |
If your part is defined by an annotated model with no drawing, say so in the request and confirm the shop can work and inspect to model based definition. Our inspection and metrology guide covers how the drawing standard affects measurement.
Configuration control and revision letters
The part must be built to the revision on the purchase order, and nothing else. Configuration control is how both sides make sure of that. Revisions to drawings are identified and recorded under ASME Y14.35 practices, normally as a revision letter on the drawing with a revision block describing each change.
What to do on the buyer side:
- Put the drawing number and revision on every PO line, and the revision of each referenced spec where your program requires it
- Send the drawing at that revision, not the latest one in your system if they differ
- When a revision changes after the order is placed, issue a PO change that names the new revision and says what happens to parts already built
- Ask for the revision to appear on the certificate of conformance and the FAI report
Across defense and aerospace, configuration management is now organized around SAE EIA-649, the consensus standard DoD adopted in place of the cancelled MIL-STD-973, with SAE EIA-649-1 adding the defense contract requirements. Your contract decides which applies. Our records and change control guide covers supplier change notification in more detail.
Deviations, waivers and variances
When a part cannot be made or delivered exactly as the drawing says, the supplier asks the buyer for written permission before shipping it. It does not decide on its own that the difference does not matter. The older terms come from MIL-STD-973, which was cancelled on 30 September 2000 but still shapes how contracts and supplier forms use the words.
- Deviation: a request, made before manufacture, to depart temporarily from the approved configuration for a specific quantity of units or period of time. It does not change the drawing.
- Waiver: a request, made during or after manufacture, to deliver items that do not conform to the requirements as they stand.
- Request for variance: the current DoD form for both, DD Form 1694, is titled Request for Variance and lists SAE EIA-649-1 as its authority.
Many primes still use the deviation and waiver wording on their own forms, so use the terms your contract uses. Whatever the name, the request should give the part and serial numbers affected, the requirement, the actual condition, the cause, and the corrective action. Approval belongs to your engineering and, where the contract requires it, the design authority or government.
A permanent change to the design is not a deviation. It goes through your engineering change process and results in a new drawing revision.
How questions get resolved without changing the design
Every question from the shop goes back to your engineering in writing, and the answer comes back in writing before work proceeds. Nobody on the supplier side reinterprets a drawing to make it easier to build.
Typical questions on build to print work:
- A dimension or tolerance that conflicts between the drawing and the model
- A note that calls out a spec revision the shop cannot obtain, or a cancelled spec
- A material form or temper that is hard to source, where an equivalent spec might be acceptable
- A feature that the shop proposes to make by a different process, such as EDM instead of milling, where the drawing is silent on method
- A finish or process sequence that seems out of order
The useful answer is one of three: a clarification that does not change the design, a deviation for a set quantity, or a drawing revision. Questions are logged with the date, the question, the answer and who answered, and the log travels with the job so the FAI and the cert package reflect what was agreed. That record is also what protects you when a part is inspected a year later.
First article inspection
First article inspection proves the supplier's process can make the part to the drawing, and it is the normal acceptance step for new build to print work. In aerospace it is usually performed and documented to SAE AS9102, which records design characteristics, material and process data, and the measured results for every characteristic.
A new FAI, or a partial one covering the affected characteristics, is normally required when the drawing revision changes, the manufacturing process or location changes, or production has lapsed for a period your contract defines. Our first article inspection page explains the AS9102 forms and what to check in a report.
Special processes on a build to print part
Most build to print aerospace parts need at least one outside process: heat treat, anodize, conversion coating, passivation, plating, paint, NDT or welding. The drawing names the spec, and often the class, type and sequence. Those processes go to processors approved for that spec, and if your program requires it, to Nadcap accredited or prime approved sources.
The processor's cert must name the spec and revision the drawing calls out. A cert for a different revision or a different class is a nonconformance, even if the part looks right. Our special processes page covers how processors are selected and certs are checked.
Package gaps that cause rejects and delays
Most build to print problems trace back to the package, not the machining. The common gaps:
- Revision mismatch between the PO, the drawing sent and the model sent, so the shop builds to one and inspection checks to another
- Unstated Y14.5 edition, leaving a GD&T callout open to two readings
- Company specs referenced but not supplied, so the shop cannot quote the finish or marking
- Cancelled or superseded specs in the notes with no direction on the replacement
- No statement of model authority for undimensioned geometry
- Missing approved source lists for processes the prime controls
Each one either stops the job for a question or shows up later as a nonconformance. Checking the package against this list before release is cheaper than either.
Data rights and export control
Sending a build to print package means sending your design data to a shop, so the data needs protecting. Every supplier signs a flow-down NDA before seeing your files, and suppliers do not learn the end customer unless you approve. Our confidentiality page explains the terms.
If the drawings are ITAR or EAR controlled, or carry CUI markings, do not upload them through the website. They move by secure transfer to US persons only. See our controlled programs page. If the data belongs to someone else, such as a prime or the government, make sure your contract lets you share it with subcontractors before it goes out.
How Aerospace Sourcing handles build to print work
We are a sourcing service. We do not run machines. We match your package to shops whose equipment, approvals and processors fit it, and we manage the job through delivery.
- One quote, one lead time, one point of contact and one purchase order, including outside processing
- Your drawing revision, specs, FAI, material traceability, specialty metals and special process requirements flowed down to every supplier
- Every technical question sent to your engineering in writing, logged, and answered before work continues
- Certs and FAI reports checked against your drawing and PO before shipment
- A certificate of conformance with every order, plus the certs your request requires
Build to print covers most made parts, including CNC machining and sheet metal fabrication. If the drawing does not exist yet because the part is obsolete or undocumented, start with our reverse engineering page.
Send a build to print package
Upload the drawings, models and spec list through the build to print quote request, with the revision, quantity, need date and FAI requirement. A complete package gets a firm quote instead of a list of questions, and any questions that remain go straight to your engineering in writing. A person replies within one business day. If the data is export controlled, say so on the form and leave the files off.
Where buyers source this
Send the job. A person replies within 1 business day.
Part, quantity and date are enough to start. Drawings and the mutual NDA follow by reply, and controlled programs never send technical data through this site.
We have it.
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Questions
What does build to print mean in aerospace?
It means the supplier makes the part exactly as your released drawings, models and specifications define it, and does not change the design. The buyer, or the design authority behind the buyer, owns the design and answers design questions. The supplier owns the manufacturing process and proves conformance through inspection, first article inspection, and material and process certs.
What is the difference between build to print and build to spec?
In build to print, the buyer supplies a complete design and the supplier only manufactures it. In build to spec, the buyer supplies a performance or interface requirement and the supplier designs the item to meet it. Build to spec puts design responsibility, and usually design data ownership, on the supplier, and conformance is shown by qualification and acceptance testing against the spec.
What is the difference between a deviation and a waiver?
Under the older MIL-STD-973 terms many contracts still use, a deviation is requested before manufacture to depart temporarily from the approved configuration for a set quantity or period. A waiver is requested during or after manufacture to deliver items that do not conform. The current DoD form, DD Form 1694, calls both a request for variance. Neither changes the drawing, and both need the buyer's written approval.
Can the shop change a tolerance or process if it makes the part easier to build?
Not on its own. On build to print work, any proposed change goes to your engineering as a written question or a request for deviation. Your engineering can clarify, approve a deviation for a set quantity, or revise the drawing. Where the drawing is silent on method, the shop may choose the process, but if a process choice affects a characteristic or a spec callout, it still needs approval.
Do I need a new first article inspection when the drawing revision changes?
Usually a full or partial FAI is required for the characteristics the revision affects. SAE AS9102 and most purchase order clauses also call for a new FAI when the manufacturing process or location changes, or when production has lapsed for a period the contract defines. Check your PO clauses for the exact triggers, and put the FAI requirement on the order.
Does the model or the drawing govern if they disagree?
Whichever your drawing notes or company standard says governs. Many drawings state that the model is the authority for geometry not dimensioned on the sheet, while others make the drawing the only authority. If the package does not say, the shop should ask before cutting metal. Stating it on the drawing or in the request avoids a question that can stop the job.
Related
Sources
- ASME: Y14.35 Revision of Engineering Drawings and Associated Documents
- ASME: Y14.24 Types and Applications of Engineering Drawings
- ASME: Y14.41 Digital Product Definition Data Practices
- ASME: Y14.100 Engineering Drawing Practices
- EverySpec: MIL-STD-31000B Technical Data Packages
- NIST: MIL-STD-31000 technical data packages in acquisition (2024 MBE Summit)
- EverySpec: MIL-STD-973 cancellation notice
- DoD Executive Services: DD Form 1694 Request for Variance
- DLA Defense Standardization Program Journal: configuration management standards
- Lockheed Martin RMS: Request for Deviation / Waiver supplier form
- ANSI Webstore: SAE AS9102C First Article Inspection Requirements
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