Key facts
- 2D drawings: DWG, DXF and PDF; 3D models: STEP, IGES, STL, 3MF and native formats
- Laser and plasma cutting usually need only a 2D DXF profile
- CNC machining, injection moulding and 3D printing work from 3D geometry
- Tolerances and inspection requirements are still usually communicated on a 2D drawing
- STEP AP242 can carry 3D product and manufacturing information (PMI) inside the model
- dijitul CAD time is £45 an hour + VAT, or a fixed quote for a defined pack
What each one is for
| 2D technical drawing | 3D CAD model | |
|---|---|---|
| What it shows | Orthographic views, sections, dimensions, tolerances, notes | Complete solid or surface geometry |
| Typical formats | DWG, DXF, PDF | STEP, IGES, STL, 3MF, native CAD |
| Best for | Quoting, inspection, flat profiles, planning, simple parts | CNC programming, moulds, 3D printing, assemblies, renders |
| Tolerances | Clearly shown and the usual contractual reference | Possible via PMI, but not every supplier reads it |
| Standards | BS 8888, ISO 128, ISO 129, ISO 2768 | STEP (ISO 10303) for exchange |
| Changes | Simple edits quick; geometry changes need care | Change the model and update linked drawings |
When a 2D drawing is enough
Plenty of work only needs 2D. Laser, plasma and waterjet cutting run from a flat DXF profile. Many simple turned or milled parts can be made from a clear dimensioned drawing. Floor plans, site layouts, signage fixings and planning drawings are naturally 2D. And for paper or scanned drawings that need bringing into CAD, a clean 2D DWG is often the first and most useful step.
A good drawing follows BS 8888, the UK framework for technical product specification, which references ISO 128 for presentation and ISO 129 for dimensioning. It states the projection method, first angle or third angle, a general tolerance standard such as ISO 2768, material, finish and a revision. See 2D CAD drafting and technical drawings.
When you need a 3D model
Anything with complex or curved geometry needs 3D. CNC machinists program toolpaths from 3D models in their CAM software. Injection mould toolmakers design the tool around the part model. 3D printers slice an STL or 3MF. Assemblies need 3D to check that parts fit, clear each other and can be assembled. Renders for sales, crowdfunding and packaging come from the model too.
We build 3D CAD models from sketches, samples, measurements or existing drawings, and export to STEP for most suppliers, STL or 3MF for 3D printing, and native formats where a supplier asks. Sheet metal parts are modelled in 3D and supplied with a flat pattern DXF.
Do you still need a drawing if you have a model?
Usually, yes. A model defines nominal geometry, but it does not tell a supplier which dimensions are critical, what tolerances apply, how surfaces should be finished or what will be inspected. Model-based definition aims to put all of that into the 3D model: the STEP AP242 standard, ISO 10303-242, can carry product and manufacturing information (PMI) such as dimensions and tolerances. Plenty of suppliers still quote, inspect and contract against a 2D drawing, so the safe default is a 3D model plus a drawing that references it.
Make it clear which document controls. If the model and drawing ever disagree, the supplier needs to know which one wins, and that is normally stated in a note on the drawing or in your purchase order. Keep revision letters in step: when the model changes, the drawing should be updated and reissued with the same revision, so nobody machines a part from an old file.
Neutral formats help too. Sending a STEP file rather than a native file means a supplier using different software can still open it, though features and history are lost in translation. If a supplier needs to edit the model rather than simply read it, ask which native format they use and we can supply that as well.
Choosing for your project
- Flat profile for cutting: 2D DXF, plus a PDF with material and thickness.
- Simple machined part: 2D drawing; add a STEP file if the machinist prefers.
- Complex machined, moulded or cast part: 3D STEP plus a 2D drawing for tolerances.
- 3D printed prototype: 3D model exported as STL or 3MF.
- Assembly or product launch: 3D assembly, drawings for each made part, renders for marketing.
dijitul's CAD design is £45 an hour + VAT, or quoted as a fixed price for a defined pack. Send a sketch, photo or sample and tell us what the supplier has asked for.
Frequently asked questions
What file does a laser cutter need?
Usually a 2D DXF of the profile at 1:1 scale, with cut lines on their own layer, plus a note of material and thickness. Bend lines for sheet metal go on a separate layer. dijitul prepares cutting DXFs and flat patterns at £45 an hour + VAT.
Do I need a 2D drawing if I have a STEP file?
In most cases, yes. A STEP model defines geometry, but suppliers usually need a drawing to show critical dimensions, tolerances, finishes and inspection points. STEP AP242 can carry this information in the model, but many workshops still quote and inspect against a 2D drawing.
What is BS 8888?
BS 8888 is the British Standard framework for technical product specification. It sets out how engineering drawings and specifications should be prepared, referencing ISO standards such as ISO 128 for presentation and ISO 129 for dimensioning. dijitul lays out drawings following these conventions.
Can you turn my 2D drawings into a 3D model?
Yes. dijitul builds 3D CAD models from existing 2D drawings, sketches, photos or physical samples, and supplies them as STEP, STL, 3MF or native formats. Any conflicting or missing dimensions are flagged before modelling. CAD work is £45 an hour + VAT.
First angle or third angle projection?
Both are allowed under BS 8888. First angle is traditional in the UK and Europe; third angle is standard in North America. The drawing must show the projection symbol. dijitul uses whichever you or your supplier specify.
Related
Get a fixed price
Send a rough brief. You'll know exactly what it costs before we start.