Aerospace Drafting and Design for Manufacture Reviews
Engineering support for aerospace parts means making your design data complete and buildable: drawings cleaned up to ASME Y14.5 and Y14.100, design for manufacture reviews that show what drives cost and risk, models exported with usable PMI, and change requests written up for your approval. You stay the design authority. Aerospace Sourcing coordinates qualified engineering and drafting suppliers and routes every decision back to you.
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What engineering support covers, and who decides
The supplier proposes and documents; your engineering decides. Nothing in a drafting or DFM job changes the released design until your engineering, or the design authority behind you, approves it in writing.
| Work | What you send | What comes back | Who approves |
|---|---|---|---|
| Drawing cleanup and drafting | Legacy drawings, sketches, models, marked up prints | Drawings to your format and ASME Y14 practices, with open questions listed | Your engineering, then your release process |
| Design for manufacture review | Model, drawing, quantity, material and finish callouts | A written findings list: each feature, the cost or risk it carries, a proposed change and its effect on function | Your engineering, finding by finding |
| Tolerance stack analysis | Assembly model, mating part drawings, functional requirement | A stack report showing the chain, the method and the margin | Your engineering |
| Model based definition and STEP export | Native CAD with PMI | Annotated model and STEP AP242 files checked against the native data | Your engineering and configuration management |
| Redlines and engineering change requests | The drawing at its current revision and the problem found | A redline and an ECR package ready for your change board | Your change board, and the customer or government where the contract requires |
We are a sourcing service and do not hold design approvals. If you need a design built from performance requirements rather than help with your own, say so, because that is build to spec work with different ownership and approval terms, explained on our build to print page.
Drawing cleanup to ASME Y14.5 and Y14.100
Drawing cleanup turns a drawing a shop has to ask questions about into one it can quote, make and inspect as is. The work is mostly finding what the drawing leaves unsaid and asking you to decide it.
Two standards anchor the work. ASME Y14.5 is the GD&T language; ASME lists Y14.5-2018 as the current edition, reaffirmed in 2024 and on stabilized maintenance. ASME Y14.100 sets the essential requirements for preparing and revising engineering drawings and associated lists; ASME lists Y14.100-2017 as current and also on stabilized maintenance. If your company standard names other editions, the drafter works to yours.
Typical cleanup findings:
- No Y14.5 edition stated, or an old edition stated on a drawing being redrawn in new CAD where the default template quietly changed
- A datum scheme that does not match how the part is located in its assembly, so a part can pass inspection and still not fit
- Features controlled only by a title block tolerance when they carry a functional requirement, and the reverse
- Material called out by alloy name instead of a specification with temper and form
- Finish notes with no class, type or sequence, or a cancelled specification with no replacement named
- Missing marking, thread, edge break or surface texture callouts
- Drawing and model that disagree, with no note saying which governs
Every finding goes to you as a question with a recommended answer, not as a silent edit. How an edition change affects inspection is covered in our inspection and metrology guide.
Have a part like this?Send it in under a minute. A person replies within 1 business day.What a design for manufacture review looks at
A DFM review tells you which features of your design cost the most to make or carry the most scrap risk, and what you could change without hurting function. It is a list of options for your engineer, not a redesign.
| What the reviewer checks | Why it matters | Typical proposal for your decision |
|---|---|---|
| Internal corner radii against standard cutter sizes | Small radii in deep pockets force small tools and slow cutting | Open the radius where the mating part allows it |
| Wall thickness and pocket depth | Thin, tall walls chatter and move after unclamping | Thicken a wall, add a rib, or accept a stress relief step |
| Hole depth, thread length and thread type | Deep small holes and full depth threads add cycle time and breakage risk | Thread only the engagement length the fastener needs |
| Tolerances and GD&T against function | Tight controls on non-functional features add inspection and scrap | Move non-critical features to the title block tolerance |
| Surface texture callouts | Fine finishes on every surface add finishing passes | Apply the fine finish only to sealing or bearing surfaces |
| Number of setups and access | Features on many faces mean more fixturing and more stack up between setups | Relate features to datums reachable in fewer setups |
| Stock size and form | Odd thicknesses or forms can be slow to buy with certs | Adjust an envelope dimension to a common stock size |
| Process sequence in the notes | Machining after a finish, or a finish that adds thickness to a tight fit, causes rework | Mask, re-sequence or adjust the pre-finish dimension |
A useful review states the reason for each finding and what it does not know, such as the load path or the mating part, so your engineer can accept or reject it quickly. Cost drivers in general are explained on our machining cost guide; the DFM review applies them to your specific part.
Tolerance stack analysis
A tolerance stack checks whether a fit, gap or alignment that matters still works when every part in the chain is at its tolerance limits. It is the analysis that tells you whether a tolerance can be opened safely, or whether it has to stay tight.
The two common methods give different answers and suit different situations:
- Worst case adds every tolerance in the chain at its limit. If the stack passes, every combination of conforming parts assembles. It is the conservative choice for low quantities, safety related fits and flight hardware where you cannot sort parts at assembly.
- Statistical, usually root sum square, combines the tolerances as independent variations. It allows wider part tolerances for the same assembly result, but it rests on assumptions: that each dimension is produced by a stable, roughly centered process and that the variations are independent. With small lots from one setup, those assumptions may not hold.
A stack report should show the loop of dimensions from one mating surface back to the other, the value and tolerance of each link with its drawing reference, the method, the result against the requirement, and any assumption about process capability. If the statistical result is what lets a tolerance open up, put that assumption in writing so it can be checked against inspection data after the first lots.
GD&T matters here. Position, profile and datum shifts change how links combine, so the stack has to be read to the same Y14.5 edition as the drawing.
Material and finish choices in the review
The material and finish callouts often drive lead time more than geometry does, and a DFM review should test them against what can actually be bought with certs and processed by an approved source.
- Form and temper availability. A specification may allow plate, bar, extrusion and forging, while the drawing quietly needs one of them. The review says which forms fit and whether they are commonly stocked with mill certs.
- Specialty metals. On DoD work, titanium, certain steels and nickel alloys bring melt source rules. See our DFARS specialty metals page before changing a material.
- Finish compatibility. Anodize, plating and conversion coatings change dimensions or conductivity and need masking plans. The review checks that pre-finish dimensions and masking are stated. Our surface finishing guide and plating and cadmium alternatives page cover the options.
- Dissimilar metals. Fastener, insert and mating part materials are checked for galvanic pairs the finish callouts do not address.
- Heat treat sequence. Where the part is machined before and after heat treatment, the notes should say which dimensions are final after treatment.
A material substitution is a design change. The review can propose one with reasons; only your engineering can approve it, normally through a drawing revision.
Model based definition and STEP AP242
If your model carries the tolerances instead of a drawing sheet, the file you send has to carry them in a form the shop can read, and the order has to say the model governs. STEP AP242, published by ISO as part 242 of ISO 10303, is the neutral format built for that: it carries geometry together with product and manufacturing information (PMI).
The distinction that matters is between two kinds of PMI. NIST describes semantic PMI, also called PMI representation, as dimensional tolerances, geometric tolerances and datum features stored so software can interpret them, and graphic PMI as the visual appearance of the annotations, which is not meant to be machine interpretable. A model that only carries graphic PMI can be read by a person but not used directly by CAM or CMM software. The CAx Implementor Forum publishes recommended practices for representing and presenting PMI in AP242; version 4.1 is dated June 2024.
What to settle before sending a model based package:
- Which ISO 10303-242 edition your CAD exports, and that the shop's software reads it. Confirm the current edition with ISO before writing it into a contract.
- Whether the export carries semantic PMI, graphic PMI or both, checked on a sample part before the real job
- That ASME Y14.41, the digital product definition data practice, or your company equivalent, is named in the package
- That the native file and the STEP file are compared, so nothing is lost in translation
- Whether a reduced drawing sheet still exists for notes, marking and the parts list
MIL-STD-31000B, the DoD technical data package standard, treats CAD models as part of a data package, so model based definition on defense work is a contract question, not just a file format choice.
Redlines and engineering change requests
A redline shows a proposed change on a copy of the current drawing; it is never a build authority on its own. The change becomes real only when your change board approves it and a new revision is released.
An ECR package a change board can act on contains:
- The drawing number and current revision, with the redline marked on that revision
- The problem in one or two sentences: a nonconformance, a manufacturing difficulty, an obsolete material or a DFM finding
- The proposed change and the alternatives considered
- Effect on form, fit, function, interchangeability and the next higher assembly
- Effectivity: from which serial, lot or date, and what happens to parts in work and in stock
- Effect on qualification, first article inspection and any approved processor lists
On defense contracts, changes are classified as major or minor, often still called Class I and Class II. An Air Force tailoring document for SAE EIA-649-1 notes that the standard equates major with Class I and points to the DD Form 1692 instructions for the Class I definition. The classification decides whether the customer or government must approve before the change is made, so your configuration manager, not the supplier, sets it.
After release, the new revision is recorded under ASME Y14.35 practices, and the part usually needs a new or partial first article. See our first article inspection page and records and change control guide.
Data rights and design authority
You remain the design authority, and the purchase order should say who owns every file the engineering supplier produces. Write that down before work starts, because drawings and models created under the order are design data with value.
- State that drawings, models, analyses and redlines produced under the order belong to you, or to your customer if your contract says so
- Require native CAD files, not only PDFs or STEP, if you will maintain the drawings yourself
- Require your drawing numbers, title block and proprietary legends on every sheet
- Prohibit reuse of your data for other customers and require return or destruction at the end of the job
- If the data belongs to a prime or the government, confirm your contract lets you share it with a subcontractor before it goes out
On DoD contracts, DFARS 252.227-7013 sorts technical data into rights categories that control who may use it and how. That clause, and how it bears on copying an existing part, is covered on our reverse engineering page. We do not give legal advice; your contracts team decides the rights language. Every supplier signs a flow-down NDA before seeing your files, as described on our confidentiality page.
Export control on technical data
Drawings and models are export controlled data in their own right, so an engineering review can be an export even when no hardware moves. Under the ITAR, 22 CFR 120.33 defines technical data to include information required for the design, development, production, repair, testing or modification of defense articles, including drawings. Under 22 CFR 120.56, data is released by visual or other inspection by foreign persons and by oral or written exchanges, in the United States or abroad.
For engineering work that means:
- A screen share or design review with a foreign person engineer can be a release, not just a file transfer
- A redline or DFM markup of a controlled drawing is controlled to the same degree as the drawing
- Cloud CAD and file sharing tools must keep controlled data with authorized U.S. persons
- EAR controlled designs carry their own rules for technology; your export compliance team sets the classification
Do not upload controlled drawings or models through our website. Tell us the jurisdiction on the request form and the data moves by secure transfer to U.S. persons only, as set out on our controlled programs page.
What to send for a DFM review
A DFM review is only as useful as the context behind it. Send the design and enough about its job for the reviewer to tell a functional requirement from a habit.
- Native model and STEP export, plus the drawing at its current revision
- Mating part drawings or an assembly model for any fit you want checked
- Functional notes: which surfaces seal, bear load, locate or carry current
- Expected quantities: prototype lot, first production lot and annual rate
- Material and finish callouts, with any approved processor or source lists that apply
- Inspection plan or key characteristics, if they exist
- The questions you want answered, for example "can this be one setup" or "can we drop the 32 microinch callout"
- Export classification of the data and any customer flow-downs on sharing it
The review comes back as a numbered findings list you can accept or reject line by line. Accepted findings become a redline and an ECR for your change board, then a released drawing ready for CNC machining or sheet metal fabrication. Our aerospace RFQ checklist covers what the final package needs.
How Aerospace Sourcing handles engineering work
We do not do the engineering ourselves. We match the job to drafting and engineering suppliers whose experience and tools fit it, and keep the decisions with you.
- One quote, one point of contact and one purchase order, including when a DFM review leads straight into manufacture
- Your drawing standards, Y14.5 edition, CAD format, data ownership terms and export requirements flowed down to every supplier in writing
- Every design question sent to your engineering, logged with the answer and who gave it
- Deliverables checked against your request before release to you
We cannot promise a supplier for every scope, and we will say so if a job needs a capability we cannot match.
Request drafting or a DFM review
Use the engineering and DFM request form to describe the part, the scope you want (cleanup, DFM, stack, MBD export or an ECR package) and your drawing standards. Telling us the decisions you need from the review lets the reviewer focus on the features that matter to your cost and schedule. A person replies within one business day. If the data is export controlled, say so on the form and leave the files off.
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
Who owns the drawings when a supplier redraws my part?
Whoever the purchase order says owns them, so write it down before work starts. For design support the normal term is that drawings, models, analyses and redlines produced under the order belong to you, carry your drawing numbers and legends, are delivered in native format, and may not be reused for anyone else. If the design belongs to your customer or the government, your contract decides, and your contracts team should set the language.
Does a DFM review change my design?
No. A DFM review produces a list of findings and proposals, each with the reason and the effect on function. Your engineering accepts or rejects each one. Accepted findings become a redline and an engineering change request for your change board, and only a released drawing revision changes what gets built. The supplier never edits a released drawing on its own.
Should I use worst case or RSS tolerance stacks?
Use worst case when every combination of conforming parts must assemble, such as low quantity flight hardware or safety related fits. Statistical methods such as root sum square allow wider part tolerances but assume stable, roughly centered and independent processes. For small lots from a single setup those assumptions are weak, so if a statistical result is what justifies opening a tolerance, record the assumption and check it against inspection data.
Can a shop machine directly from a STEP AP242 model with no drawing?
Yes, if the model carries semantic PMI the shop's software can read, the order says the model governs, and the shop can inspect to model based definition. Check a sample export first, because many exports carry only graphic PMI that a person can read but software cannot use. Name ASME Y14.41 or your company equivalent in the package and keep a sheet for notes and marking if you need one.
Which ASME Y14.5 edition should my drawings use?
Use the edition your company standard and your customer require, and state it on every drawing. ASME lists Y14.5-2018 as current, reaffirmed in 2024 and on stabilized maintenance, but many legacy drawings still use 2009 or 1994, and some rules differ between editions. When a drawing is redrawn, do not let a CAD template change the edition without an engineering decision.
Is a design review with a foreign national engineer an export?
It can be. Under 22 CFR 120.56, ITAR technical data is released by visual inspection, oral or written exchange with foreign persons, in the United States or abroad, so a screen share of a controlled drawing can count. Your export compliance team decides jurisdiction, classification and any authorization. Keep controlled engineering work with authorized U.S. persons unless your compliance team has an authorization in place.
Related
Sources
- ASME: Y14.5 Dimensioning and Tolerancing
- ASME: Y14.100 Engineering Drawing Practices
- ASME: Y14.41 Digital Product Definition Data Practices
- ISO: ISO 10303-242 Managed model based 3D engineering
- CAx-IF / MBx-IF: Recommended Practices for PMI in AP242, version 4.1 (June 2024)
- NIST: STEP File Analyzer and Viewer (semantic and graphic PMI)
- EverySpec: MIL-STD-31000B Technical Data Packages
- EverySpec: SMC-T-007 tailoring of SAE EIA-649-1
- Cornell LII: 22 CFR 120.33 Technical data
- Cornell LII: 22 CFR 120.56 Release
- Acquisition.gov: DFARS 252.227-7013 Rights in technical data
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