Key takeaways
Start with the latest part design, expected order quantities, material and appearance requirements. Separate tooling costs from part costs, and agree on sample approval before production.
1. Define what the quotation should include
Begin with a short project overview: what the part does, where it will be used and which stage the design has reached. State whether you need a new custom plastic mold, molded parts from an existing tool, or a complete tooling-and-production proposal.
List each part separately. Include its revision, estimated size, color and relationship to other components. For a housing with a cover, for example, explain how the two parts assemble and which surfaces the user sees. Identify requirements that are fixed and choices that remain open for engineering discussion.
2. Prepare drawings and control the design revision
Ask the supplier which 3D CAD formats it can review. A STEP model is often a useful starting point, accompanied by a dimensioned drawing when particular dimensions or inspection requirements matter. Protolabs' public quoting guide illustrates the use of CAD files and manufacturing analysis; its accepted formats and quoting process belong to that provider. [1]
- Give the model and drawing the same part number and revision.
- State the units and identify critical fits, holes and assembly interfaces.
- Mark cosmetic faces, acceptable gate locations and areas where marks are restricted.
- Flag any differences between the CAD model, drawing and physical sample.
If only a sample is available, describe what should be copied and what should change. Confirm the measurement and design-development scope before assuming the sample is enough to cut a mold.
3. Describe material, appearance and operating conditions
A resin family name alone does not define the complete material requirement. Provide the required grade when it is fixed; otherwise describe the function that material selection must support. Note temperature exposure, impact, outdoor use, contact with chemicals and any documentation requested by your buyer.
Record color references, texture, gloss and appearance expectations separately. Where two materials or a preformed component are involved, include the interface and assembly information when discussing overmolding or insert molding. Ask the supplier to identify its proposed resin and any substitutions in the quotation.
4. Separate quantity planning from tooling assumptions
Distinguish sample quantity, the first production order and an estimated longer-term demand. Treat a forecast as a forecast, rather than a purchase commitment. If demand is uncertain, request clearly labeled quantity scenarios for plastic injection molding.
Ask which tooling assumptions support each proposal: cavity arrangement, expected usage, maintenance responsibilities and whether the mold can be transferred. Avoid choosing solely by the lowest mold price. Compare what is included, what is excluded and which assumptions would require a revised quotation.
Part geometry, wall sections, draft and undercuts need review during mold design and engineering. Published design guidance highlights these factors, but a generic table does not establish a universal tolerance or design rule for your part. [2]
5. Define sample acceptance and compare the whole proposal
Before production, agree on how trial samples will be reviewed. Identify which dimensions require a report, how appearance will be checked, and which assembly or functional checks matter. Define who approves the sample and how design changes will be handled. Your project quality requirements should be visible to everyone quoting the work.
| Quotation item | Question to resolve |
|---|---|
| Tooling | Which mold scope, trials, ownership and maintenance are included? |
| Molded parts | Which resin, finish, quantity and inspection assumptions apply? |
| Additional work | Are inserts, printing, assembly and packaging included or priced separately? |
| Delivery | What starts the lead-time clock, and which transport terms are quoted? |
| Changes | How are revised drawings, material substitutions and rework approved? |
A low headline price is difficult to evaluate when these items are missing. Clarify differences in scope before treating two quotations as directly comparable.
6. A practical RFQ brief you can copy
Use this list in your enquiry. Write “to be reviewed” where a requirement is still open instead of filling the gap with an unsupported assumption.
- Part name, revision and intended application
- 3D model, drawing and available sample information
- Required resin grade or material performance requirements
- Color, texture, visible surfaces and assembly interfaces
- Sample quantity, first order and clearly identified forecast
- Critical dimensions, inspection and sample approval criteria
- Printing, inserts, assembly and packaging requirements
- Tool ownership, storage, maintenance and transfer expectations
- Target milestones, delivery destination and commercial scope
- Project contact, open questions and requested quotation breakdown
For a custom plastic mould project with OPINOX, start by sharing the application, estimated quantity and current design status. Use the enquiry form to describe the project; arrange a suitable drawing-transfer method with your project contact. This website form does not accept file attachments.
Frequently asked questions
Can I request a quote without a finished CAD model?
You can start an initial discussion with sketches or samples, but identify the information that is missing. Confirm the design and measurement work needed before expecting a firm tooling proposal.
Should tooling and part prices be quoted separately?
Request a breakdown so you can compare the initial tooling investment, part pricing and additional work under the same scope and quantities.
Are injection molding and injection moulding different processes?
These are American and British spellings for the same process. Use the spelling your buyer prefers while keeping the engineering requirements consistent.
Bring your brief. Start the discussion.
Share your application, quantities, material requirements and design status with OPINOX to discuss tooling and molded parts.
References and scope
This buyer’s guide uses public engineering references. Referenced suppliers’ guidelines do not establish OPINOX machine capacity, process limits or service commitments. Design, cost, schedule and acceptance requirements are confirmed for each project.