Dongying (Suzhou Dongying Electronic Technology Co., Ltd.) is a mold maker and injection molder in Suzhou, China. We build precision molds and run injection molding and insert molding for overseas teams. Our drawing preparation guide describes the brief we normally start from; this article covers the case where that drawing does not exist yet.
Can you get an injection molding quote without a drawing?
Short answer: you can get a budgetary discussion from a sample or photos, but a firm tooling and part price needs a drawing or 3D model that both sides have agreed on.
A mold is built to a defined geometry, material and set of critical features. Without a drawing, the molder has to guess wall thickness, draft, hidden features and which dimensions matter. Those guesses move cost, so an early number should be read as a range for planning, not as a commitment.
The common starting situations are:
| What you have | What it is good for | What is still missing |
|---|---|---|
| Physical sample part | Size, shape, visible features, surface finish | Design intent, tolerances, confirmed material grade |
| Photos with a scale reference | First feasibility talk, part family | Hidden geometry, wall thickness, internal features |
| 3D scan (mesh) | Overall form, freeform surfaces | Clean CAD, datums, functional dimensions |
| Old 2D drawing, no 3D | Dimensions and notes | Current revision, 3D model for tooling |
| Mating parts only | Interface fits | The part geometry itself |
What to send when there is no drawing
Short answer: send the best physical evidence you have plus the facts only you know: how the part is used, what it mates with, and how many you need.
A sample shows the shape. It does not show why the shape is that way. These inputs close most of the gap:
- Samples: two or more if possible, ideally from different lots or with different wear. One sample can hide a warped or damaged feature.
- Mating parts: the shaft, housing, bearing, connector or metal insert the part fits with. Fits are often better defined by the mating part than by a used sample.
- Photos: several views, with a ruler or reference in frame, including the gate mark, ejector marks and any text molded into the part.
- Function and environment: load, temperature range, chemicals or fluids it touches, outdoor exposure and any appearance surface.
- Volumes: sample quantity separate from expected annual demand, because they lead to different tooling decisions.
- Supply scope: whether you need the mold, molded parts, or both, and whether the mold will run at another site. See tooling and supply scope.
- Any old documents: even a partial or outdated drawing, a specification sheet or a material callout on a bill of materials helps.
If the part carries a metal insert, busbar or terminal, list it as a separate item with its supplier and plating. Our insert molding inputs page explains why metal processing and the molded body are defined together.
What a sample cannot tell you
Short answer: a sample records how one part turned out, not what the designer intended, so tolerances, datums and the exact material grade must be decided, not copied.
Reverse-engineering references make the same point: a scan captures the part as it exists, including wear, deformation and manufacturing variation, while a production CAD model often needs to represent nominal geometry and design intent (QuickSurface, 3D Scan vs CAD Model). If a worn bore is copied as-is, the new part inherits the wear.
Three gaps come up on almost every sample-based project:
- Tolerances and datums. A sample has no tolerances printed on it. Plastic parts vary more than metal parts in size, form and location, and ISO 20457 expects functionally required tolerances to be defined by the part designer and confirmed against what the molding process can achieve (ISO 20457:2026). Someone has to decide them.
- Material grade. Lab methods such as FTIR can identify the polymer family of a sample, but fillers, blends and additives often need further tests such as DSC or TGA, and the exact commercial grade usually cannot be read from the part (Infinita Lab, Polymer Identification Testing). Treat a lab result as evidence for choosing a grade, not as the original specification.
- Hidden geometry. Ribs inside a closed housing, undercuts and core-out pockets may need sectioning a sample, which means sending a spare.
From sample to an approved drawing
Short answer: the sample is turned into a CAD model and drawing, the customer reviews and approves it, and only then is the mold designed against that approved revision.
A typical sequence looks like this:
| Step | Output | Who approves |
|---|---|---|
| Review samples, photos and use conditions | List of open questions and assumptions | Customer answers |
| Measure and model the part | 3D model to nominal geometry | Customer reviews |
| Mark critical features and datums | Draft 2D drawing with key dimensions | Customer engineering |
| Agree material | Grade selected against function and datasheets | Customer |
| Freeze revision | Approved drawing and 3D model | Customer signs off |
| Quote tooling and parts | Price against the frozen revision | Both sides |
Who creates the CAD model is agreed for each project. Some customers have their own engineers rebuild it; others ask the molder or a third party to model it. Either way, the approved drawing belongs in the project record, and later changes go through a new revision. For neutral 3D data exchange, STEP files are widely used, and ISO 10303-242 covers managed model-based 3D engineering data (ISO 10303-242). For drawing notation, many teams use ASME Y14.5 dimensioning and tolerancing (ASME Y14.5).
Once the drawing exists, inspection is planned against it, not against the old sample. Our inspection and approval guide covers how methods, datums, sample quantities and acceptance criteria are agreed.
Ownership and confidentiality
Short answer: confirm you have the right to reproduce the part before asking anyone to copy it, and agree confidentiality before sharing samples or scans.
Replacing a part from a discontinued supplier is common. Copying a design owned by someone else is a different matter, so confirm that your company owns the design or has permission to have it reproduced. If the samples, scans or use data are sensitive, agree a confidentiality arrangement before sending them, and state who will own the new drawing and the mold.
How to keep the first conversation productive
Short answer: label what is fact and what is a guess, so open questions are resolved before price, not after tooling.
A short brief that separates "known" from "assumed" saves rounds of questions. For example: "Material believed to be glass-filled PA66, not confirmed. Bore fits a purchased bearing, part number attached. Outer cosmetic face matters; inside does not." When you are ready, you can prepare a project brief and send it with your photos.
FAQ
Can I get a mold price from photos only?
Photos with a scale reference are enough to discuss part family, rough size and likely mold type, and to list the questions that need answers. They are not enough for a firm tooling price, because wall thickness, hidden features, draft and critical dimensions cannot be confirmed from images. Expect a planning range at most, followed by a request for samples or a CAD model.
Is a 3D scan the same as a CAD model?
No. A scan is a mesh of measured points that records the part as it is now, including wear, warpage and scanner noise. A CAD model for tooling should describe nominal geometry, with clean surfaces, datums and functional features. The scan is a useful input for rebuilding the model, especially for freeform shapes, but someone still has to interpret it into design intent.
How many samples should I send?
Send at least two where possible, and more if parts come from different lots or show different wear. Multiple samples help separate design features from damage or molding variation. If hidden internal features matter, include a spare that can be cut open. Add the mating parts too, because fits are often easier to define from the part they assemble with.
Can the material of my sample be identified?
A lab can usually identify the polymer family with FTIR, and further tests such as DSC or TGA can indicate fillers, crystallinity or blends. The exact commercial grade, additive package or supplier is usually not recoverable from the part. Use the lab result to shortlist grades, then choose one against your function, environment and datasheets, and record it on the approved drawing.
Who owns the drawing created from my sample?
That should be agreed at the start, in writing. In many projects the customer owns the approved drawing and the part design, and mold ownership is agreed separately as part of the tooling terms. Settle both points, plus confidentiality for samples and scans, before modeling begins, so there is no dispute when the mold is built or transferred.
What if my old part was made by a supplier who closed?
That is a common reason for sample-based projects. Collect every document you still have, such as old drawings, purchase specifications or material callouts, and send them with the samples and mating parts. Confirm you have the right to reproduce the design. The part is then rebuilt into a new drawing, approved by your team, and tooled against that revision.
References
- ISO 20457:2026, Plastics moulded parts — Tolerances and acceptance conditions
- ISO 10303-242:2025, Application protocol: Managed model-based 3D engineering
- ASME Y14.5, Dimensioning and Tolerancing
- QuickSurface, 3D Scan vs CAD Model: Accuracy and Design Intent
- Infinita Lab, Polymer Identification Testing (FTIR, DSC & Raman)