Most established manufacturers can quote from a 2D drawing, a 3D CAD file or both. Quoting from a physical sample is less common, because it usually needs measuring or 3D scanning first. Which input you send affects the accuracy of the quote, how many questions come back, and how much hidden risk ends up in the price.
This guide explains what each input gives a supplier and where each falls short. It also covers what to check before choosing a supplier, what to ask about standards, and what decides price and lead time.
What does it mean to quote from a drawing, a CAD file or a sample?
A quote is a supplier's estimate of tooling cost, unit price and lead time for your part. To produce it, the supplier needs to know the part's geometry, material, tolerances, finish, quantity and any secondary operations. Each input carries a different part of that information:
- 2D drawing (PDF, DWG, DXF): shows dimensions, tolerances, geometric dimensioning and tolerancing (GD&T), material callouts, surface finish, notes and inspection requirements. It is the document that usually defines what "acceptable" means.
- 3D CAD file (STEP, IGES, Parasolid, or native formats): shows the full geometry, including curves, ribs, bosses, wall thickness and undercuts. It lets the supplier check moulding or machining feasibility, estimate volume and weight, and judge tool complexity.
- Physical sample: shows the real part, including feel, colour, texture and fit. It carries no tolerances or material certificates, so the supplier must measure it, scan it, or both, and then infer the intent.
In practice the best quote package combines a 3D model for geometry with a 2D drawing for tolerances and requirements.
Common types and how they differ
| Input | What it tells the supplier | What it leaves out | Typical use | Quote accuracy |
|---|---|---|---|---|
| 2D drawing only | Dimensions, tolerances, material, finish, notes | Complex surfaces and full 3D shape can be ambiguous | Simple parts, legacy parts, turned or sheet-metal parts | Good for simple shapes; weaker for complex ones |
| 3D CAD only | Complete geometry, volume, features | Tolerances, critical-to-quality features, material, finish | Early-stage quotes, rough budgeting, prototypes | Good for geometry, but tolerances must be assumed |
| 3D CAD + 2D drawing | Geometry plus requirements | Little, if the two agree | Production tooling and series parts | Highest |
| Physical sample only | Real shape, appearance, fit | Tolerances, material grade, design intent, draft | Replacement of an existing part with no documents | Lowest until measured and documented |
| Sample + drawing or CAD | Reference for appearance and fit plus defined requirements | Little | Matching an existing part while improving it | High, if the sample is representative |
Which manufacturers can quote from 2D drawings, 3D CAD files, or physical samples?
2D drawings. Almost every contract manufacturer, including injection moulders, CNC machine shops and sheet-metal fabricators, can quote from a clear drawing. This is the traditional route. For plastic parts, though, a drawing alone leaves gaps. A moulder needs the 3D shape to judge parting lines, draft, gate position and tool complexity.
3D CAD files. Most moulders, tool rooms and machine shops accept STEP files, which are a neutral format that opens in nearly any software. Online instant-quote platforms usually require a 3D file, because they calculate price automatically from geometry. These platforms tend to suit prototypes and low volumes. Production tooling with tight tolerances, multiple materials or assembly steps usually needs an engineer to review the quote.
Physical samples. Fewer suppliers do this well. It requires in-house or partnered measuring equipment, such as a coordinate measuring machine (CMM) or 3D scanner, and engineers who can turn the scan into a usable model. Ask directly whether the supplier does reverse engineering, and whether the quote covers only the measurement or the whole part.
Capability depends on the supplier's set-up, not on its size. A supplier with in-house tool design can usually take any of the three inputs. One that outsources tooling may only quote after another party has reviewed the files. If your part is a moulded plastic part, the plastic injection moulding page shows the kind of process and tooling information a supplier should be able to describe.
What should a buyer check before choosing a supplier?
Before you send files, check the following with each shortlisted supplier:
- Accepted formats. Confirm which 3D formats (STEP, IGES, native) and 2D formats (PDF, DWG, DXF) they take. Ask whether they want both.
- Quoting process. Find out whether an engineer reviews the files or an automated tool produces the price. Ask whether a design-for-manufacturability (DFM) review is included, and whether it is free or charged.
- Reverse engineering. If you only have a sample, ask how it will be measured, who owns the resulting model, and whether the quote is fixed or subject to revision after measurement.
- Tooling in-house or outsourced. This affects lead time, communication and accountability for design changes.
- Quality system and inspection. Ask for the certificate and what measurement equipment and reports (first-article, dimensional) are supplied with parts.
- Material sourcing. Ask how the supplier confirms grade and traceability, especially for reinforced or engineering polymers.
- Confidentiality. Ask whether an NDA is signed before files are shared.
Which standards and certifications apply?
The standards that matter depend on the part and the industry:
- ISO 9001 is the general quality management standard. It shows a supplier has a documented system, but it does not guarantee any particular part's quality.
- IATF 16949 is typically requested for automotive supply chains, and ISO 13485 for medical devices. Confirm whether your customer requires them rather than assuming.
- ISO 2768 gives general tolerances for machined and metal parts when none are stated. ISO 20457 (which replaced DIN 16742) sets tolerances for moulded plastic parts. State which one your drawing refers to.
- UL 94 (flammability), RoHS and REACH may apply to electrical and consumer parts.
How to choose
What decides the choice is how complete and how critical your information is. A decision table:
| If you have… | Send… | Why |
|---|---|---|
| A new design in CAD with defined tolerances | STEP file plus a dimensioned PDF drawing | Gives geometry and requirements together, so there are fewer assumptions |
| Only a 3D model, for early budgeting | STEP file, with material and quantity noted | Enough for a rough estimate; tell the supplier tolerances are not final |
| An old part with a drawing but no CAD | The drawing plus the sample if available | The supplier can build a model and check it against the part |
| Only a physical part | The sample, and ask for reverse engineering | The supplier must measure it first, so expect extra time and cost |
What decides the price and the lead time, in most cases:
- Tooling cost: the number of cavities, the steel grade, part size, undercuts, textures and tolerances all drive tool complexity.
- Material: commodity resins cost less than reinforced or high-temperature engineering polymers.
- Cycle time and part weight: thicker walls cool more slowly, which raises the unit price.
- Volume: tooling is a fixed cost spread over the quantity, so the unit price usually falls as volume rises.
- Tolerances and finish: tight tolerances, cosmetic surfaces and extra inspection add cost.
- Secondary operations: assembly, inserts, plating, printing or machining add time and cost.
- Lead time: it typically includes DFM review, tool design, tool build, first samples, approval and production. Tool build is usually the longest step, and design changes after approval extend it.
Common mistakes to avoid
- Sending a 3D file without tolerances. The supplier must assume them, and the real cost appears later. Add a drawing that marks critical dimensions.
- Mismatched drawing and model. If they disagree, ask which governs and fix it before quoting. State this on the drawing.
- Sending a worn or modified sample as the reference. Wear, shrinkage and repairs distort the measurements. Say which features are critical.
- Leaving out material and finish. A quote for "plastic" is not comparable across suppliers. Name the grade, colour and texture, or ask for options.
- Comparing quotes with different scope. Check that each includes the same tooling, samples, inspection and packaging.
- Ignoring annual volume. Quote for the realistic quantity range, not only the first order.
- Skipping the DFM feedback. Draft angles, wall thickness and gate position suggestions can lower cost, so read them rather than treating them as delays.
Summary
Choose the input to match what you know. Send a 3D model and a 2D drawing together when you have both, because that gives the most accurate and comparable quote. Use a model alone only for budgeting, and a sample only when no documents exist, accepting extra measurement time. When you compare suppliers, check accepted formats, who reviews the files, tooling capability, quality certificates and inspection reports, and make sure every quote covers the same scope. If you want to discuss the files you have, use the contact page to see what a supplier asks for.