Defense CNC Parts: RFQ to First Article Inspection

Purchasing defense CNC parts involves more than dimensions and pricing. It also requires control of drawing revisions, material traceability, special processes, inspection methods, and delivery documents. Providing complete information at the RFQ stage helps reduce technical queries, repeat quotations, and first article inspection failures.

For projects involving custom equipment housings, brackets, shafts, flanges, fluid manifolds, optical mounts, and inspection fixtures, Weldo’s defense CNC machining services can be used to review material, machining routes, and inspection requirements. For projects involving controlled technical data, classification and authorization should be confirmed before drawings are transferred.

What Core Information Should an RFQ Include?

A complete RFQ should include the latest drawings, material, quantity, delivery schedule, post-processing, inspection documents, and project applicability information. Missing material conditions, drawing revisions, or inspection requirements can directly affect quotation accuracy and delivery planning.

Purchasers should also specify file formats, quotation currency, trade terms, packaging, and marking requirements to avoid different interpretations of the quotation scope.

What Should 2D Drawings and 3D Models Include?

2D drawings should define tolerances, material, surface finish, and acceptance requirements, while 3D models communicate the complete geometry. The part number, revision, and geometry must be consistent across both files.

A 2D drawing should include:

• Drawing number, part number, and revision.
• Units and projection method.
• Datums, GD&T, and critical dimensions.
• Threads, holes, sealing surfaces, and assembly features.
• Surface roughness and edge-break requirements.
• Material, heat treatment, and surface-finish specifications.
• General tolerances and referenced standards.
• Marking, serial-number, and packaging requirements.

A 3D model can be used independently for manufacturing and acceptance only when the project uses an approved model-based definition process and designates the model as the authoritative design record. The model should also include product manufacturing information such as dimensions, tolerances, datums, material, and surface finish. A standard STEP model usually still needs to be used with a 2D drawing.

How Should Critical Dimensions and GD&T Be Defined?

Critical dimensions should be concentrated on locating, assembly, sealing, and motion features, with a practical inspection method assigned to each requirement. Applying tight tolerances uniformly to every dimension increases machining, fixture, and inspection costs.

Drawings should also specify the measurement condition, clamping condition, and temperature for thin-wall parts. This helps prevent differences caused by the manufacturer and purchaser using different measurement methods.

How Should Material and Supply Condition Be Specified?

Material requirements should include the full grade, heat-treatment condition, product form, and governing standard. Writing only “aluminum,” “stainless steel,” or “titanium” is insufficient for accurate quotation and material acceptance.

Examples include:

• Aluminum 7075-T651
• Stainless Steel 17-4 PH H900
• Titanium Grade 5 / Ti-6Al-4V
• Alloy Steel 4340, quenched and tempered
• PEEK, 30% glass-fiber reinforced

Purchasing documents should also specify:

• ASTM, AMS, EN, or other material standard.
• Material certification type.
• Heat or material lot traceability requirements.
• PMI, hardness, or mechanical-property testing.
• Whether material substitutions are allowed.
• Material origin or approved-source requirements.

If the part will be heat treated after machining, the drawing should specify final hardness, effective case depth, allowable distortion, and subsequent finishing requirements.

Why Must Quantity and Delivery Plans Be Specified?

Quantity determines stock form, fixture investment, programming cost, and inspection frequency. The RFQ should separately state the prototype quantity, quantity for FAI, initial production quantity, annual demand, target date, and delivery location.

Low-volume projects generally use general-purpose fixtures and flexible machining routes. Stable production volumes are better suited to dedicated fixtures, fixed tooling plans, and standardized inspection programs. More complete quantity information supports more accurate unit-price and lead-time estimates.

What Should Be Specified for Surface Finishing and Special Processes?

Drawings should specify the process name, governing standard, target thickness, treated areas, masked areas, and acceptance method. Complete requirements allow the supplier to plan dimensional allowance and arrange qualified special-process providers in advance.

Common processes include:

• Anodizing and hard anodizing.
• Chemical conversion coating.
• Stainless steel passivation.
• Black oxide.
• Electroless nickel and electrolytic nickel plating.
• Zinc plating and project-approved alternative coatings.
• Blasting, painting, and powder coating.
• Heat treatment.
• Shot peening.
• Nondestructive testing.

Purchasers should state whether coating thickness is included in the finished dimensions and whether threads, mating bores, sealing surfaces, and electrical contact areas require masking. Salt-spray, adhesion, coating-thickness, and color requirements should also be confirmed before quotation.

If a designated or approved source is required for a special process, the RFQ should identify the supplier, process specification, and certificate requirements.

What Engineering Reviews Should Be Completed Before Quotation?

Before quotation, the supplier should review the drawings, material, tolerances, machining datums, post-processing, and inspection feasibility. Any issue affecting cost, quality, or lead time should be clarified in writing before the quotation is issued.

Key review steps include:

1. Verify the drawings, models, and revisions.
2. Confirm the material, condition, and certification documents.
3. Identify critical dimensions and machining datums.
4. Assess fixtures, tools, and machining sequence.
5. Confirm special processes and dimensional compensation.
6. Match inspection methods to delivery documents.

Tool interference, inaccessible-to-measure features, unnecessarily tight tolerances, or conflicting requirements found during review should be submitted to the purchaser through an RFI or DFM recommendation.

How Should the Purchase Order and RFQ Requirements Be Kept Consistent?

The purchase order should reference the final approved drawings, models, material standards, quality clauses, and delivery documents. Technical deviations, material substitutions, special processes, and inspection requirements confirmed during quotation should also be included in the order.

The order review should verify:

• Purchase order number and part number.
• Drawing, model, and specification revisions.
• Quantity and delivery schedule.
• Material and approved sources.
• Quality clauses and flow-down requirements.
• Special processes and governing standards.
• Approved technical deviations.
• Inspection documents and retention period.
• Packaging, marking, and shipping requirements.

If the RFQ and purchase order differ, written confirmation should be completed before production to prevent the use of an outdated revision or incorrect quality clauses.

What Quality Documents Should Be Prepared Before Production?

Before production, customer requirements should be translated into process flows, machining programs, and inspection plans. Programming, manufacturing, subcontracting, and inspection personnel should use the same controlled revision.

Depending on project requirements, the following may be prepared:

• Manufacturing process traveler.
• CNC program and program revision.
• Setup and datum instructions.
• Tooling and key machining-parameter records.
• Inspection plan.
• Ballooned drawing or characteristic-numbered drawing.
• Control plan or PFMEA.
• Special-process purchasing requirements.
• Nonconformance and deviation-control procedure.

FAI requirements should be assigned to specific operations at this stage, rather than added after machining is complete.

What Should Be Verified When Raw Material Arrives?

Incoming inspection should confirm that the material grade, dimensions, heat number, supply condition, and certification documents match the purchasing requirements. Traceability to the original heat or material lot must be retained after the stock is cut.

Key checks include:

• Consistency between the material certificate and purchase order.
• Material grade and product standard.
• Heat number or material lot.
• Stock dimensions and surface condition.
• Heat-treatment or supply condition.
• PMI and hardness verification requirements.
• Material marking and storage location.

XRF PMI is suitable for quickly identifying major alloying elements such as nickel, chromium, molybdenum, and tungsten. Carbon, nitrogen, and other critical low-level elements should be verified using OES, combustion analysis, or laboratory chemical analysis, as required by the material specification.

What Records Should Be Kept During Machining?

Process records demonstrate that parts were manufactured using the approved material, programs, and process route. Critical operations, program revisions, inspection results, and corrective actions should be traceable to the specific batch.

Common records include:

• Work order and production batch number.
• Raw material heat number.
• Machine and CNC program revision.
• First-piece setup inspection results.
• In-process data for critical dimensions.
• Tool-change and offset records.
• Outside special-process records.
• Nonconformance, rework, and deviation approvals.
• Operator and inspector records.

The scope of records should match part risk and contract requirements. Noncritical dimensions may be sampled according to the inspection plan, while critical features may require 100% inspection.

What Is First Article Inspection?

First Article Inspection verifies whether the material, manufacturing process, special processes, and inspection methods can produce a part that meets the design requirements. It validates the complete product-realization process, rather than simply measuring one sample.

FAI typically covers:

• Part number and drawing revision.
• Raw material and supply condition.
• All design characteristics.
• Heat treatment and surface finishing.
• Functional testing.
• Marking and packaging requirements.
• Actual inspection results.
• Approved deviations.

The scope and format of FAI are determined by the purchase order, contract, and customer quality clauses. When a project explicitly references AS9102, the specified revision and corresponding forms, ballooned drawings, and supporting records should be used. For projects that do not reference AS9102, a customer-approved FAI format may be used.

What Documents Are Typically Included in an AS9102 FAI?

AS9102 standardizes FAI records for aerospace, space, and defense products. The project should use the standard revision and customer template specified in the purchase order. SAE AS9102

The part number, drawing revision, serial number, and lot in the FAI documents must match the actual part. Certificates verify the applicable material or special process; they do not replace dimensional verification of design characteristics.

Which Design Characteristics Should FAI Cover?

FAI should cover all design characteristics specified in the drawings, models, technical specifications, and purchasing documents. Each characteristic should have an actual result, inspection method, or supporting certificate.

Coverage should include:

• Dimensions and geometric tolerances.
• Material and supply condition.
• Surface roughness.
• Internal and external threads and fits.
• Heat-treatment condition and hardness.
• Coating type, thickness, and color.
• Part marking and serial number.
• Functional, pressure, or leak tests.
• Additional purchase-order quality requirements.

The ballooned drawing should use sequential numbering and correspond one-to-one with Form 3 or the customer’s designated characteristic table.

Which Inspection Methods Are Suitable for Defense CNC Parts?

Inspection methods should be selected according to the characteristic, tolerance, material, and measurement accessibility. The resolution, accuracy, and uncertainty of the measuring equipment should be suitable for the tolerance being verified.

The inspection plan should also specify measurement locations, sampling rates, environmental conditions, and result-record formats.

When Is Repeat First Article Inspection Required?

When a change to the design, material, manufacturing method, or production conditions may affect part conformity, a full or partial repeat FAI should be evaluated.

Typical cases include:

• A drawing or model revision.
• A change in material or supply condition.
• A significant change to the CNC program, tooling, or process route.
• A change in manufacturing location or key equipment.
• A change in special-process supplier.
• An error in the original FAI record.
• A nonconformance indicating that the manufacturing process is no longer stable.
• A production interruption that reaches the period specified in the contract or standard.

For AS9102 projects, the need for repeat FAI after a two-year production lapse, or the customer-defined interruption period, should also be evaluated. The repeat FAI scope should cover the characteristics affected by the change and follow the contract, customer quality clauses, and specified standard.

How Should a Nonconformance Found During FAI Be Handled?

When an out-of-tolerance result is found, the affected parts should be identified and quarantined immediately, and a nonconformance record should be opened. Rework, repair, or acceptance as-is must receive the authorization required by the contract.

A nonconformance record should include:

• Nonconformance report number.
• Affected parts and batches.
• Drawing requirement and actual measurement result.
• Containment action.
• Root cause.
• Rework or repair plan.
• Approval from the design authority or contract-authorized party.
• Reinspection results after rework.
• Corrective and preventive actions.

An out-of-tolerance characteristic may be delivered under deviation status only after written approval from the design authority or contract-authorized party.

Which Documents Should Be Delivered After FAI?

Delivery documents should be traceable to the part number, revision, batch, and serial number. The purchaser should define the electronic file format, submission method, and review timing during quotation.

A typical delivery package includes:

• First Article Inspection report.
• Ballooned drawing.
• Material certificate.
• Certificate of Conformance (CoC).
• CMM or dimensional inspection report.
• Heat-treatment and surface-treatment certificates.
• Nondestructive testing report.
• Hardness, pressure, or functional test records.
• Approved deviation documents.
• Packaging and marking records.

Before delivery, the documents should be internally reviewed to confirm that form numbers, inspection results, and supporting certificates correspond to one another.

How Should Defense Project Drawings and Technical Data Be Protected?

Before transferring technical data, confirm its classification, end user, destination, and applicable authorization. An NDA defines confidentiality obligations, but it does not replace export authorization or controlled-data protection requirements.

The project should define:

• Personnel authorized to access the files.
• Approved transfer and storage methods.
• Download, copying, and revision permissions.
• Drawing revision and change records.
• File retention and destruction requirements.
• Data access for subcontractors.
• Archiving rules after project completion.

U.S. defense projects may involve ITAR, EAR, CUI, DFARS, or customer-specific data-protection requirements. Applicability depends on item classification, technical data, contract terms, end user, and destination. NIST SP 800-171 primarily applies to protecting CUI processed, stored, or transmitted in nonfederal information systems; it does not automatically apply to every defense-part order. U.S. DDTC information on ITAR, NIST SP 800-171

Until classification, authorization, and the transfer method are confirmed, controlled technical data should not be sent through ordinary email or public upload forms.

How Can Repeat Quotations and FAI Delays Be Reduced?

Complete information and early technical review are key to shortening the schedule. These five steps are especially effective in controlling quotation and FAI timing:

• Submit the latest drawings, models, and revisions with the initial RFQ.
• Identify critical dimensions and required inspection reports in advance.
• Confirm material certificates and special processes during quotation.
• Close all technical questions and deviations before production.
• Complete an internal review of the FAI package before shipment.

The recommended process is:

Submit RFQ
→ Review project applicability and documents
→ Confirm DFM and technical questions
→ Confirm quotation and lead time
→ Review purchase order
→ Procure material and perform incoming inspection
→ Prepare process and inspection plans
→ Machine first article
→ Verify dimensions and special processes
→ Compile FAI documents
→ Customer or authorized quality representative review
→ Begin production

How Should a CNC Machining Supplier for FAI Be Selected?

A qualified supplier should have manufacturing, inspection, traceability, and document-control capabilities. Owning multi-axis machines alone does not prove that a supplier can deliver the required FAI package for a defense project.

Check the following:

1. Does the supplier review drawings, models, and revisions?
2. Does it maintain material and heat traceability?
3. Can it match critical characteristics to specific inspection methods?
4. Does it have CMM and other necessary inspection equipment?
5. Does it effectively manage heat-treatment, coating, and nondestructive-testing suppliers?
6. Can it provide a clear and traceable FAI package?

Purchasers should also review the supplier’s actual procedures for handling nonconforming parts, engineering changes, and repeat orders.

Frequently Asked Questions

Must Every Defense CNC Part Have an AS9102 FAI?

No. AS9102 applies when the purchase order, contract, or customer quality clauses explicitly require it. Other projects may be accepted using a customer-approved FAI format.

Can a 3D Model Replace a 2D Drawing?

Yes, when the project uses an approved model-based definition process and designates the 3D model as the authoritative design record. The model must also include complete product manufacturing information; a standard STEP model usually still needs to be used with a 2D drawing.

Does FAI Mean That Later Production Batches Can Skip Inspection?

No. FAI verifies that the manufacturing process can produce conforming parts. Later batches must still follow the approved in-process and final inspection plans.

Can a CMM Report Replace a Complete FAI?

No. A CMM report provides only some dimensional data. A complete FAI also requires material, special-process, design-characteristic, functional-test, and part-accountability information.

How Should an Out-of-Tolerance Result Found During FAI Be Handled?

The affected parts should be quarantined immediately and a nonconformance record opened. Rework, repair, or acceptance as-is requires approval from the design authority or contract-authorized party, followed by reinspection before the issue is closed.

How Long Should FAI Documents Be Retained?

The retention period is determined by the contract, purchase order, customer quality clauses, and applicable regulations. The supplier should confirm the retention period, file format, and customer-access requirements during order review.

Conclusion

A complete RFQ, controlled drawing revision, material traceability, and a suitable inspection plan provide the foundation for a successful first article acceptance of defense CNC parts. Specifying the material, critical dimensions, special processes, and documentation requirements before quotation helps reduce rework, additional inspection, and delivery delays.

Weldo can evaluate machining routes based on project drawings, materials, quantities, and inspection requirements, and provide multi-axis CNC machining, mill-turn machining, grinding, EDM, post-processing, and dimensional inspection. Project technical data should first be classified and its transfer authorization confirmed.