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Welded Fabrication Drawing and Inspection Plan for RFQs
A useful welded-fabrication RFQ makes the drawing, weld definition, distortion-sensitive datums, acceptance method, finish sequence, assembly interfaces, and evidence owner explicit before a supplier quotes the job. A model that shows the final shape is not enough when the weld symbol, joint preparation, inspection stage, or post-weld dimensional requirement remains open.
Establish drawing authority before discussing the process
List the governing 2D drawing, 3D model, specification, revision, units, and order of precedence. Mark which document controls weld location, size, length, contour, intermittent pattern, joint preparation, backing, finishing, and inspection. ISO 2553:2019 explains how welded-joint symbols can carry geometry, manufacturing, quality, and testing information on drawings. The buyer still has to select the applicable system and project requirements.
Identify base material by the controlled grade and condition, not by a family name alone. State thickness at each joint, cut-edge condition, any coating at the weld zone, filler or process restriction when contractually required, and surfaces that must remain free of weld spatter, grinding marks, or heat tint. If an item is supplier-proposed, label it as a proposal that requires approval rather than presenting it as a released requirement.
Separate weld acceptance from assembly dimensions
| Control layer | RFQ question | Evidence to define |
|---|---|---|
| Joint definition | Which symbol, size, length, contour, side, sequence, and preparation apply? | Released drawing and approved clarification record. |
| Fabrication datums | Which surfaces locate parts during cutting, forming, fit-up, welding, and final inspection? | Datum scheme, fixture concept, and inspection setup. |
| Distortion limits | Which flatness, position, angle, gap, or alignment values matter after welding and after finishing? | Post-weld drawing limits and measurement method. |
| Visual acceptance | What is checked before, during, and after welding, and which visible conditions are rejectable? | Named criteria, viewing conditions, stage, and record. |
| Additional examination | Is any project-specific penetrant, magnetic, radiographic, ultrasonic, leak, pressure, or destructive test required? | Applicable method, area, timing, acceptance rule, qualification, and responsible party. |
| Finish and assembly | What happens after welding, and which interfaces must still fit? | Grinding/coating sequence, masked areas, final dimensions, and assembly check. |
Do not use a weld appearance statement as a substitute for dimensional acceptance. A visually acceptable joint can still leave holes, flanges, covers, or mating surfaces out of position. Conversely, an assembly that fits does not by itself prove that the specified weld and examination requirements were met.
Plan distortion control around the features that matter
Ask the supplier to review restraint, tack sequence, weld sequence, access, heat concentration, part symmetry, and the timing of critical measurements. The goal is not to prescribe a universal technique; it is to identify which dimensions can move and where the quotation needs an agreed control or trial plan.
Place datums on stable, inspectable features. If a datum surface is created or altered after welding, explain which operation establishes it and when dependent dimensions are measured. For a welded frame, record diagonal, twist, flatness, mounting-hole position, and interface checks as separate characteristics when each affects assembly.
Use an inspection ladder instead of one final check
- Incoming and preparation: verify material identity records, thickness, cut features, bevel or edge preparation, cleanliness, and drawing revision as required by the project.
- Fit-up: verify joint gap, alignment, orientation, fixture location, tack condition, and restricted areas before access is lost.
- In-process: retain only the process and sequence records required by the approved plan; do not invent a universal record set.
- Final visual and dimensional: inspect the specified weld characteristics and post-weld datums with named tools, access, and acceptance limits.
- Finish and assembly: verify grinding, coating, masked areas, cleanliness, identification, mating interfaces, and packaging after the operations that can change them.
ISO 17637:2016 covers visual testing of fusion-welded joints and can also apply before welding. ISO 5817:2023 provides quality levels for specified fusion-welded materials and joint types. Neither reference makes one inspection plan or acceptance level correct for every assembly; the contract, design responsibility, material, load, service environment, and governing requirements decide what applies.
RFQ package for a reversible supplier decision
- released drawings/models, revision, units, precedence, weld-symbol system, and open technical questions;
- material grades/conditions, thicknesses, joint preparation, coatings, restricted areas, and supplied-part condition;
- critical datums, post-weld dimensions, assembly interfaces, cosmetic zones, and finish sequence;
- required procedure or personnel qualifications only when the project actually requires them;
- visual, dimensional, additional examination, sample, and record requirements with acceptance ownership;
- prototype, pilot, production and forecast quantities, packaging, traceability, change notification, and nonconformance route.
Use the welding and fabrication commercial page for service scope, review quality-control context, or send the controlled drawing package for RFQ review.
Questions sourcing and engineering teams ask
Is a 3D model enough for a welded assembly quote?
Usually not. The quotation also needs the governing drawing, weld definition, material condition, datums, post-weld limits, finish sequence, inspection requirements, quantity, and open-responsibility list.
Should every weld use the strictest imperfection level?
No automatic rule makes the strictest level correct for every joint. The responsible design and contract parties should select requirements that match material, joint, load, service, regulation, consequence of failure, and verification method.
When should final dimensions be checked?
Specify the stage. Welding, stress-relief when applicable, straightening, machining, grinding, coating, and assembly can each change a feature. The drawing or inspection plan should identify the condition in which acceptance is measured.
Does visual inspection replace project-specific NDT?
No. Visual testing and any additional examination answer different questions. Use only the methods, areas, timing, acceptance criteria, and qualified responsibilities required by the project.
Authorship and evidence boundary
Published by Zhengna Technology on 2026-07-21. This guide is a procurement and drawing-review framework. It does not claim a universal welding procedure, welder qualification, NDT capability, certification, material range, fixed tolerance, test result, code compliance, or finished-assembly approval.