Start with the clearest available part definition
A complete technical package usually combines a controlled 2D drawing with a 3D model. The two files serve different purposes and should agree on revision.
2D drawing
Use the drawing to define dimensions, tolerances, datums, threads, surface finish, material, treatment, notes and inspection requirements.
3D model
Use the model to communicate nominal geometry, complex surfaces, pockets and features that are difficult to interpret from orthographic views alone.
If only one file is available, identify which information remains controlling. A model without tolerances does not fully define acceptance, while a drawing without complex geometry may leave the manufacturing route unclear.
Define material and condition
State the material grade and any relevant condition, temper, hardness or heat-treatment requirement. Material descriptions such as “aluminum” or “steel” are often too broad for quotation because grade and condition can affect sourcing, machining, finishing and inspection.
- Material specification and grade
- Temper, hardness or supplied condition where relevant
- Required certificates or traceability records, if applicable
- Any approved substitutions or a clear instruction that substitution is not permitted
Separate critical tolerances from general tolerances
Identify dimensions that control fit, sealing, alignment, motion or assembly. Applying a tight tolerance to every dimension can introduce unnecessary process and inspection effort without improving function.
Include the applicable general-tolerance standard or title-block tolerance, then call out critical features individually. Define datums and the intended measurement basis when geometric controls depend on assembly relationships.
Specify surface finish and downstream treatment
Distinguish functional surface-roughness requirements from cosmetic expectations. For anodizing, plating, passivation, heat treatment, coating or other downstream operations, provide the governing specification, finish designation, color, masking and appearance criteria where they matter.
State quantities and supply pattern
Provide the prototype quantity, anticipated production quantity and expected repeat pattern separately. This helps distinguish a first-part route from a repeat-production route and prevents a quotation from being based on the wrong batch assumptions.
Define inspection and documentation needs
Identify the features that require recorded results and the documents expected with delivery. Inspection planning should match the drawing, part function and purchasing requirements rather than relying on an undefined standard package.
- Critical dimensions or characteristics to be reported
- First-piece or first-article expectations
- Material, treatment or conformity documentation
- Customer forms, sampling instructions or measurement-method constraints
Include packaging and part-protection requirements
Identify surfaces, edges, threads or finishes that must be protected during handling and shipment. Note any individual wrapping, separators, caps, corrosion protection, labeling or cleanliness expectations needed for the application.
When no complete drawing exists
Send the information that is available: photographs from several angles, overall dimensions, critical interface measurements, material information, functional context and a physical sample if appropriate. This can support a preliminary assessment, but open design intent and acceptance criteria must still be clarified before production.