An injection molding quote is only comparable when suppliers are pricing the same technical and commercial scope. A model alone can start a conversation, but it rarely answers the questions that determine tooling strategy, resin selection, inspection planning, secondary operations and delivery assumptions. This checklist is designed for buyers who want a useful first response without pretending that every detail is already frozen.
A quote-ready RFQ does not need to be perfect. It needs to make open decisions visible, assign priorities, and prevent a supplier from silently filling gaps with assumptions.
01
Why incomplete RFQs create misleading comparisons
Two suppliers can receive the same 3D file and return very different prices for valid reasons. One may assume a single-cavity tool, another may allow for multi-cavity production. One may price a commercial tolerance; another may include a tighter inspection method. One may assume a standard texture and another may price a cosmetic surface with a hidden gate. If these differences are not visible, the lowest first quote may simply be the narrowest scope.
A sound starting point is to separate what is fixed from what is still under review. Core design items—such as the latest CAD revision, critical interfaces, preferred resin and visible surfaces—should be identified. Commercial items—such as annual demand, ramp profile, target market, target timing, packaging and Incoterm—should be stated or marked as provisional. Injection-molding design guidance consistently treats material, wall sections, draft, ribs, tolerances, parting line, gates and ejection as connected decisions rather than isolated fields.[1]
02
The 12 inputs to include before you request a mold quote
| Input | What to provide | Why it changes the discussion |
|---|---|---|
| 1. Revision-controlled 3D CAD | STEP, Parasolid or native CAD, with a clear revision name. | Defines the current geometry and prevents reviews against obsolete files. |
| 2. 2D drawing and CTQs | Dimensions, datum scheme, tolerances and features that are truly critical to function. | Lets the team separate routine dimensions from high-risk interfaces. |
| 3. Resin and grade direction | Preferred resin, grade if known, colour, filler, recycled-content requirement or approved alternatives. | Resin selection influences shrink, flow, finish, stiffness and tool details. |
| 4. Surface requirements | Texture, gloss, colour standard, display surfaces and allowed gate/ejector locations. | Cosmetic expectations affect parting-line, gate and ejection strategy. |
| 5. Mating parts and assembly context | Interfaces, inserts, fasteners, seals, PCB keep-outs or adjacent components. | Helps identify stack-up, access and retention risks early. |
| 6. Volume and ramp | Prototype quantity, bridge quantity, annual demand and expected programme life. | Supports a discussion about cavitation, automation and tool durability assumptions. |
| 7. Tooling intent | New tool, tool transfer, family tool, insert mold, overmold or a concept to be reviewed. | Avoids comparing an assumed tool concept with a different one. |
| 8. Quality expectations | CTQs, visual criteria, inspection frequency, sample requirement and documents needed. | Creates a common basis for sampling and inspection planning. |
| 9. Secondary operations | Assembly, heat staking, printing, ultrasonic welding, insert loading, packing or labelling. | Shows work that may sit outside the molding press cycle. |
| 10. Target market and compliance context | Destination markets and customer-controlled technical or regulatory requirements. | Allows the product owner to identify required records and validations. |
| 11. Target timing | RFQ decision date, sample milestone, production release target and known dependencies. | Makes schedule assumptions visible instead of implied. |
| 12. Commercial and logistics assumptions | Currency, Incoterm, shipment destination, packaging constraints and communication preference. | Prevents late-stage misalignment after the engineering review. |
03
Use DFM as a decision record—not a sales attachment
A DFM review is most useful when it states the decision, the risk and the trade-off. For example: a wall transition may need to change to improve cooling consistency; a gate may need to move away from a visible face; or a snap feature may need more draft or a different release direction. The goal is not to eliminate every compromise. It is to decide which compromise belongs to the product owner and which belongs to the tool design.
Draft is a good example. The appropriate amount depends on depth, resin, shrinkage, texture, finish and ejection approach. Published rules of thumb can help a first review, but they cannot replace part-specific supplier feedback.[2] Ask for screenshots or marked-up views of the affected area, the proposed alternative, and the impact on appearance, assembly or cost.
04
A short pre-submission review for purchasing teams
Before sending the RFQ, ask one practical question: could an engineer who has never seen this programme explain what the part must do, how it will be judged, and what remains undecided? If not, add a one-page project brief. It is usually faster than clarifying a long email chain after quotes arrive.
When comparing responses, normalise the scope before ranking price. Confirm cavity count, resin assumptions, included samples, inspection level, secondary work, lead-time starting point, shipping terms and ownership of any tool or fixture. Then ask suppliers to identify their three largest technical assumptions. That is often more revealing than an unqualified unit price.
Practical takeaway
Before you move
to the next review.
- Latest CAD and drawing revision are named and attached.
- Critical interfaces, cosmetic zones and material direction are explicit.
- Volumes distinguish prototype, ramp and annual demand.
- Sample, inspection, assembly, packaging and shipping assumptions are visible.
- Open decisions are labelled as open rather than left blank.
FAQ
Common questions
Do I need a finished 2D drawing before requesting a quote?
No. A 3D model can start a manufacturability discussion, but a drawing or marked-up CAD view should identify the dimensions and interfaces that matter most. Be explicit about what is still provisional.
Should I ask for tooling and part pricing separately?
Usually yes. Separating non-recurring tooling from recurring part cost helps buyers compare scope, cavities, materials, cycle assumptions and downstream operations more clearly.
What is the most important question to ask after receiving a quote?
Ask which technical and commercial assumptions have the greatest influence on the response. The answer exposes scope gaps that may not be visible in the total price.
References
Source material
- [1] Fictiv, “Injection Molding Design Guide: Best Practices for Molded Plastic Parts.”
- [2] Protolabs, “Draft Angle Guidelines for Injection Molding.”
- [3] 3D Systems Quickparts, “Basics of Injection Molding Design.”
This guide is general information for early procurement and engineering discussion. It does not replace product-specific DFM, qualification, validation, regulatory assessment or legal advice.