Manufacturing FAQs

Engineering and sourcing teams often ask the same questions when qualifying a new process, supplier, or part family—especially in defense and aerospace where material pedigree, repeatability, and controlled workflows matter as much as geometry. Below are 25 practical manufacturing questions that come up in RFQs, design reviews, and supplier audits, with answers written for engineers, procurement teams, and program managers.

Additive questions

1) Q: When is additive manufacturing (AM) the right choice versus machining or casting?

A: AM is typically a strong fit when value comes from geometry rather than raw production speed: internal channels, lattice/lightweighting, part consolidation, difficult-to-machine features, or when you need fast iteration without hard tooling. For production, AM can be competitive when it reduces assembly labor, eliminates brazes/welds, improves performance (thermal management, weight), or avoids long lead-time castings/forgings. If the part is a simple prismatic bracket with wide tolerances, CNC machining is usually cheaper and lower risk.

2) Q: What’s the practical difference between DMLS and SLM for procurement and qualification?

A: In many procurement contexts, DMLS and SLM are used interchangeably to describe metal powder bed fusion (PBF). The practical differences are less about the label and more about the machine model, parameter set, powder specification, and the qualified build/heat treat/HIP route. When writing an RFQ, specify the alloy/standard, required density/mechanical properties, inspection plan, and whether the supplier must be qualified to a specific machine and parameter set (a “frozen process”).

3) Q: How should we design parts for powder bed fusion (PBF) to reduce risk?

A: Start by designing for stable builds and predictable post-processing. Common best practices include: (1) orient critical surfaces to minimize supports and stair-stepping; (2) avoid thin, tall walls that can distort; (3) add machining stock on datum surfaces and tight-tolerance features; (4) design internal passages with powder removal in mind (escape holes, accessible paths); (5) consider distortion compensation only after first builds prove the trend; and (6) plan for how features will be inspected (CMM access, CT scanning needs). The goal is a design that can be built, densified, machined, and inspected without heroic rework.

4) Q: What should an engineer include in an AM RFQ to get consistent quotes and parts?

A: A high-quality RFQ reduces ambiguity. Include: CAD + drawing, material/spec (e.g., Ti-6Al-4V, Inconel 718, 17-4PH), target mechanicals if applicable, surface finish requirements, critical-to-quality (CTQ) dimensions, GD&T, inspection method expectations (CMM, CT, dye penetrant), heat treat/HIP requirements, required certification pack contents (powder lot traceability, CoC, build travelers, heat treat charts), any required standards/flowdowns (AS9100, DFARS clauses, ITAR handling), and quantity/forecast. If the supplier must use a specific machine family or parameter set, say so.

5) Q: How do we handle support removal and post-processing without damaging the part?

A: Treat support strategy as part of the manufacturing plan, not an afterthought. A robust approach is: (1) design supports to be accessible and removable; (2) define which surfaces are “as-built” versus “machined”; (3) use controlled removal methods (wire EDM, band saw, machining) depending on material and geometry; (4) stress-relieve per the qualified route before aggressive removal when distortion risk is high; and (5) finish with machining and surface conditioning (bead blast, abrasive flow, hand finishing) that is compatible with inspection and fatigue requirements.

HIP questions

6) Q: What is Hot Isostatic Pressing (HIP), and why is it used after AM?

A: HIP is a high-temperature, high-pressure process (typically inert gas) that closes internal porosity and improves fatigue performance by densifying the material. For metal PBF parts, HIP is frequently used to reduce lack-of-fusion voids and improve consistency across builds. HIP does not “fix” every defect—large inclusions, unmelted powder trapped in cavities, or gross process issues still require upstream control—but it can materially improve density and fatigue reliability when properly qualified.

7) Q: What does a real additive + HIP + machining workflow look like in defense/aerospace?

A: A controlled end-to-end workflow typically looks like this:

Step 1: Contract review and flowdown capture (ITAR/DFARS, drawing revision, inspection plan, serialization needs).

Step 2: Material control: powder lot receiving, verification (as required), and traceability setup.

Step 3: Build preparation: orientation/supports, parameter set selection, and traveler generation.

Step 4: Printing (PBF): in-process monitoring and build record capture.

Step 5: Depowdering and initial stress relief (if part risk warrants) using the qualified schedule.

Step 6: HIP cycle per approved procedure, with recorded time/temperature/pressure charts.

Step 7: Heat treatment/aging (if specified) to achieve final mechanical properties.

Step 8: Rough machining to establish datums, then semi-finish/finish machining on 3-axis or 5-axis machining centers.

Step 9: Inspection and NDE (CMM, CT scanning, dye penetrant, etc.), followed by final documentation package and CoC.

8) Q: What is PM-HIP and when is it preferable to AM?

A: PM-HIP (powder metallurgy + HIP) produces near-net shapes by sealing powder in a can (or tooling), evacuating, then HIPing to full density. It can be attractive for larger, simpler geometries or when you want high density and homogeneous properties without the layer-by-layer build constraints of PBF. PM-HIP is also used when supply chain needs a scalable route for certain alloys or when internal features aren’t required. Compared to AM, it generally offers less geometric freedom but can provide excellent material quality and repeatability when properly controlled.

9) Q: Does HIP change dimensions, and how should we tolerance parts that will be HIPed?

A: HIP can cause small dimensional changes due to creep and pore closure, especially in thin sections. Treat HIP as a process step that influences final geometry: (1) leave machining stock on critical surfaces; (2) avoid specifying final tolerances on “as-HIP” surfaces unless proven; (3) establish datums after HIP whenever possible; and (4) validate distortion trends during first article to set realistic stock allowances and machining plans.

10) Q: What documentation should we expect for a HIP’d part?

A: At minimum, a procurement-ready pack includes: HIP provider identification, HIP cycle parameters (time/temperature/pressure) and charts, furnace/load traceability, part/lot traceability, and a certificate of conformance (CoC) stating the cycle met the required procedure/specification. If mechanical properties are required, include test results tied to the lot (often via coupons or witness samples) and any post-HIP heat treat records.

Machining questions

11) Q: Why do AM parts often still require CNC machining?

A: PBF excels at complex geometry, but it typically cannot hold tight tolerances or surface finishes on all critical features. CNC machining is used to: establish precise datums, achieve GD&T requirements, control fits/sealing surfaces, and ensure repeatable assembly. For flight and defense hardware, expect a hybrid approach: AM for the near-net “performance geometry,” machining for interfaces and CTQs.

12) Q: When is 5-axis machining worth it for post-processing AM parts?

A: 5-axis machining is often the most efficient way to finish AM parts with complex angles, organic shapes, or multiple faces requiring tight positional tolerances. It reduces setups (and therefore stack-up error), improves access to features, and can be essential for maintaining datum relationships across non-prismatic geometry. If a part requires 3+ setups on a 3-axis mill, 5-axis frequently reduces risk and total lead time.

13) Q: How much machining stock should we add to an AM part?

A: Stock depends on material, build size, and expected distortion, but a practical approach is: (1) identify datum surfaces and CTQ features; (2) add enough stock to clean up surface roughness and any minor distortion; (3) avoid excessive stock that increases cycle time and tool wear; and (4) validate with first-article results. Many teams start with conservative stock on critical faces and refine after proof builds. The key is to plan stock by feature, not as a blanket offset.

14) Q: What are common post-processing steps besides machining?

A: Common steps include stress relief, HIP, heat treatment/aging, support removal, surface finishing (bead blast, tumble, abrasive flow for internal channels where appropriate), coating (if specified), and cleaning/passivation depending on alloy and end use. Defense/aerospace programs also frequently require controlled cleaning and packaging to prevent FOD and corrosion, plus serialization/marking requirements.

Inspection questions

15) Q: What inspection methods are most common for AM + HIP + machined parts?

A: Expect a combination of dimensional inspection and NDE. Common methods include: (1) CMM for GD&T and datum-controlled features; (2) optical scanning for form/fit trend checks; (3) CT scanning when internal geometry, porosity evaluation, or trapped powder risk must be assessed; and (4) surface NDE such as dye penetrant (PT) for crack detection on machined surfaces. The inspection plan should be tied to CTQs and failure modes—not performed “because it’s AM.”

16) Q: When should we require CT scanning, and what should we specify?

A: CT scanning is most useful when internal features are critical (cooling channels, manifolds), when porosity limits are contractually defined, or when you need objective evidence of internal integrity on early builds. In an RFQ/drawing note, specify: the region of interest, minimum voxel resolution (or acceptable detection threshold), acceptance criteria (e.g., maximum pore size in critical zones), and deliverables (3D volume, slice images, porosity report). Also be realistic: higher resolution increases scan time and cost, especially on dense alloys and larger parts.

17) Q: How is first article inspection (FAI) typically handled for these parts?

A: A robust FAI approach includes: (1) contract review to confirm all drawing requirements and flowdowns; (2) a ballooned drawing with measurement plan; (3) complete dimensional results (CMM + manual as needed); (4) material and process certs (powder lot, HIP/heat treat, NDE); and (5) clear traceability from raw material through each operation traveler. Many aerospace programs expect an AS9102-style package even if not explicitly called out.

18) Q: What does “material traceability” mean in practice for AM and PM-HIP?

A: Material traceability means you can connect the finished part to its input material lots and processing history. Practically, that includes: powder lot ID(s), receiving records, storage/handling controls, build ID and machine/parameter set, any recycling rules used for the powder, HIP/heat treat load IDs, machining work orders, inspection records, and final CoC. For PM-HIP, traceability includes powder lot, can/billet identification, HIP cycle records, and subsequent processing. Traceability is what makes audits and root-cause investigations survivable.

Compliance questions

19) Q: What’s the difference between being “ITAR compliant” and having good export-control practices?

A: ITAR (International Traffic in Arms Regulations) requires controlled handling of defense articles and technical data. In practice, good export-control operations include: access controls for technical data, visitor management, controlled communication and file sharing, employee training, and documented procedures. Many customers expect suppliers to demonstrate these controls during audits. For procurement, specify whether the work is ITAR-controlled and require the supplier to confirm how they handle controlled data and physical parts.

20) Q: What is DFARS compliance, and why does it show up in RFQs?

A: DFARS clauses are contract requirements tied to U.S. Department of Defense purchasing. Depending on the program, DFARS requirements can affect sourcing of materials (e.g., specialty metals restrictions), cybersecurity expectations, and documentation/flowdowns to subtiers. From a manufacturing perspective, DFARS matters because it can limit where material is melted/produced and can impose additional recordkeeping. The actionable step: ask for the applicable DFARS clauses up front and ensure your supplier’s purchasing and traceability system can support them.

21) Q: What does AS9100 mean for an AM/machining supplier?

A: AS9100 is a quality management system standard used in aerospace. For an AM and machining supplier, it typically means: documented processes, risk-based thinking, calibrated measurement systems, controlled nonconformance and corrective action, configuration management, and traceable records. It does not automatically guarantee technical capability, but it significantly improves the predictability of how issues are captured and resolved—critical for program execution.

22) Q: When is NADCAP relevant for post-processing and inspection?

A: NADCAP is a special-process accreditation used widely in aerospace. It may be required for heat treating, NDE (PT/MT/UT/RT), chemical processing, welding, and other special processes. If your part requires NADCAP-controlled operations, specify it clearly in the RFQ and confirm whether the prime expects in-house NADCAP, approved subtiers, or both. Also ensure the certification pack includes NADCAP certificates and process records tied to the part/lot.

Cost/lead time questions

23) Q: What typically drives cost in metal AM parts?

A: Major cost drivers are: build time (laser hours), powder/material cost, support strategy and removal labor, post-processing (HIP, heat treat, machining), inspection/NDE (especially CT scanning), and documentation/QA overhead. A part that looks “simple” can be expensive if it requires extensive CT, tight GD&T on many surfaces, or multiple NADCAP processes. To manage cost, focus requirements on true CTQs and avoid over-specifying non-critical surfaces.

24) Q: How can we shorten lead time without increasing risk?

A: Lead time improves when decisions are made early and requirements are unambiguous. Practical levers include: (1) provide a complete RFQ package (drawing, models, standards, inspection expectations); (2) align on the qualified process route (AM parameters, HIP/heat treat) before release; (3) allow machining stock and avoid “as-built” tight tolerances; (4) pre-approve subtiers for HIP/NDE if required; (5) use a phased approach—prototype/first article, then production—so learning is captured without schedule surprises; and (6) avoid last-minute revision churn by controlling configuration.

25) Q: What should a “procurement-ready” certification pack include for regulated manufacturing?

A: While requirements vary by contract, a strong baseline pack often includes: final CoC, material certs (powder or feedstock), traceability records linking part to lots and process travelers, build record (machine ID, parameter set, build ID), HIP and heat treat certifications with charts, NDE reports (if required), dimensional inspection results (CMM report, ballooned drawing), calibration evidence for key gauges (as required), nonconformance documentation (if any) and disposition approvals, and any required serialization/marking records. For defense/aerospace, this pack is as important as the hardware because it proves the part was made under a controlled, auditable workflow.

Closing note: The fastest way to de-risk advanced manufacturing is to treat the process route, inspection plan, and documentation as a single integrated system. When engineering and procurement align on CTQs, flowdowns (ITAR/DFARS), and a qualified additive/HIP/machining workflow, suppliers can deliver predictable quality and lead time.