What Technical Information Should an Injection Molding RFQ Include?

An engineering RFQ for injection molding needs controlled CAD and drawings, the resin specification, part function, volume assumptions, tooling scope, quality documents, and delivery terms. Anything still unknown should be marked TBD rather than left blank. With that package, a molder can quote the same part you intend to buy, and differences between quotes become explainable.

What Is an Injection Molding RFQ?

An RFQ is a written request that asks suppliers to price a defined scope. The term covers two rather different documents.

A preliminary inquiry asks whether a supplier could do a job at all, and roughly what it might cost. An engineering RFQ asks for a quote a buyer can rely on, so it carries revision-controlled data.

A tooling quotation and a molded-part quotation also answer different questions. One prices building the mold, the other prices making parts from it. State which you want, or both, since a supplier can otherwise assume one and price accordingly.

Then separate what you know from what you do not. A specification you know goes in as a requirement. An unknown goes in labeled as unknown.

Engineering Drawings and CAD Files

3D CAD formats

STEP is a neutral exchange format, and Parasolid is another exchange option. Ask which the supplier prefers. A 3D model lets a supplier check draft, wall thickness, projected area, and part volume.

2D dimensioned drawings

A 2D drawing, which may be issued as a PDF, carries what a model alone may not convey: tolerances, datums, material callouts, surface finishes, and notes. A supplier should not have to infer a tolerance from a solid model.

Drawing revision and document control

List a revision letter and date for each file, and say which document controls if they disagree. An RFQ stating “Rev C” gives the supplier a way to check that it quoted the right geometry, and gives you a way to tell when a quote is out of date.

Critical-to-quality dimensions

Mark the dimensions that matter to function. If every dimension carries a tight tolerance, the supplier cannot tell where to spend inspection and tooling effort, and the part may be priced accordingly. ISO 20457:2026, the second edition of the plastics moulded part tolerance standard, is one reference a drawing can name for general tolerances. If your drawing cites the 2018 edition, decide whether that is still intended.

Material Specifications

• Resin family: for example, PP, ABS, or PA66
• Manufacturer and grade: the exact commercial grade, when one is required
• Reinforcement: glass or mineral content, if any
• Color and appearance: a color standard and the surface finish or texture
• Chemical, temperature, and mechanical requirements: the environment the part must survive, which lets a molder suggest a grade when none is fixed
• Approved alternatives: which substitutes, if any, are acceptable without a new approval

The RFQ checklist from Precision Molded Plastics also asks about regrind percentage allowed, additives, whether an equivalent is allowed, and whether certificates and lot traceability are required. Regrind is worth stating, since a supplier that assumes it can use regrind will price differently from one that cannot.

Part Function and Assembly Requirements

A supplier reviewing a drawing without context cannot tell which features are structural and which are decorative.

Describe mating components and how the part joins them: snap-fit, threaded, or welded interfaces each impose their own constraints on resin and tool design. Identify the critical dimensions at those interfaces, and state functional testing criteria if the part has to pass a test.

A short paragraph explaining what the part does and what failure looks like can prevent a costly misunderstanding. It also helps the supplier raise concerns about feasibility while the design can still change.

Annual Volume and Ordering Assumptions

Volume drives cavity count, automation, and resin buying, so a quote is only as good as the volume it assumes.

• Estimated annual quantity
• Initial order
• Normal batch or release quantity
• Program lifetime
• Forecast uncertainty, including any planned ramp

State whether figures are firm or estimates. A forecast is not an order commitment, and labeling it as a forecast keeps both sides clear on who carries the risk if the volume does not arrive.

Tooling Scope

New tool

Say whether the supplier should design and build a tool, and give any requirements: cavity count if fixed, target mold life, steel requirements, and hot or cold runner preference. Precision Molded Plastics’ checklist also lists mold classification (Class 105 to 101), side actions, water lines, ejection method, and cycle counter.

Existing customer-owned tool

If a mold already exists, the supplier needs to know that, because the job becomes one of fitting that tool into its press and process.

Tooling drawings and existing mold data

Provide what you have: mold type and dimensions, number of cavities, runner type, cold runner weight, gate type, side actions, year built, estimated cycles run, and photographs of the mold. These are RFQ data fields only. Moving a mold from one molder to another is a separate process with its own risks and is outside what an RFQ can settle.

Quality and Documentation Requirements

• Inspection: which features, by what method, and how often
• Material certification, if required
• Part traceability: lot marking and records
• Sampling expectations: first article, mold qualification samples, and ongoing plans
• Relevant customer specifications, attached or named by document number

Quality requirements affect price directly, so a supplier that discovers them after award has a basis for reopening the quote.

Packaging, Delivery, and Schedule

Add the shipping destination, delivery frequency, and packaging requirements, plus any assembly or secondary operations such as printing, insert installation, or kitting. Timeline milestones complete the picture: the award date, the first-article date, and the desired production start.

What to Mark as TBD

An unfinished design does not disqualify a buyer from preparing an RFQ. It means the RFQ has to be honest about status. Open items can include:

• A resin grade not yet selected
• Draft CAD that may change
• An estimated volume
• Tolerances not yet finalized

Label each one, and ask suppliers to state in writing what they assumed for each and how the price would change. That turns an unknown into a tracked assumption. It also tells you whether a low quote rests on a favorable guess.

How to Check Published Supplier Capabilities Against RFQ Requirements

A supplier’s public capability page can screen candidates, as long as you treat what it shows as a starting point.

Check sheet: tick each point as you work through it

• Machine capacity: does the published tonnage range cover your clamp estimate?
• Mold envelope: does the press range imply your mold will fit? Tie bar spacing and platen size may not be published
• Material compatibility: are your resin family and any special handling mentioned?
• Quality system evidence: are certificates shown, and do they cover the site doing the work?
• Process capabilities: secondary operations, tool repair, and warehousing

As an example of what such a page can contain, SPF Groups’ injection molding capabilities lists clamp sizes along with items such as an in-house tool repair shop and daily QC programs. A page like that gives you questions to ask. It does not confirm that any given job fits.

Published information and written confirmation are two separate levels of evidence. Ask the supplier to confirm in writing the machine it would use, the capacity available, and the certificates that apply. Machine sizing questions at this stage can be checked with how to calculate shot size against barrel capacity.

Injection Molding RFQ Checklist

What a field needs depends on the answer you are asking for. A budgetary response can rest on stated assumptions, while a firm production quotation needs those assumptions closed or priced as exceptions. Status shows where each field stands today. The split below is an editorial guide rather than a rule every molder follows, so ask each supplier what it needs for each type of quote. The example values are hypothetical.

Field	Example data	Status	For a budgetary response	For a firm quotation
Part number	AB-102	Confirmed	Stated	Stated
CAD revision	Rev C	Confirmed	Preliminary CAD, labeled	Released revision
2D drawing	Rev C, with tolerances	Confirmed	Can follow, with gaps noted	Issued with tolerances
Resin	PP, exact grade TBD	Open	Family, with grade TBD	Grade or material specification confirmed
Regrind allowed	Not stated yet	TBD	Stated assumption	Stated rule
Annual volume	100,000 estimated	Preliminary	Estimate	Price breaks and release assumptions stated
First order	10,000	Preliminary	Estimate	Confirmed or priced as an assumption
Critical tolerance	Drawing reference	Confirmed	Risks and gaps flagged	Dimensions and tolerances set
Mold ownership	Customer-owned	Confirmed	Stated	Responsibility and contract terms set
Existing mold data	Dimensions, cavities, runner	Open	What you have	Provided, with gaps listed
Quality documentation	Customer to specify	Open	Draft list	Included scope confirmed
Secondary operations	None expected	Preliminary	Stated assumption	Confirmed
Shipping destination	Named site	Confirmed	Site or region	Named site

In this example, the open resin grade, regrind rule, mold data, and quality documents would limit a supplier to a budgetary response or a quote with stated assumptions.

RFQ Preparation FAQ

Can an engineering RFQ be submitted with preliminary CAD?

Yes, if it is labeled preliminary and the revision is stated. Ask for a budgetary response or a quote that lists its assumptions. The supplier can flag moldability concerns early, and you can avoid treating that number as firm until the model is released.

Which documents should control if a 3D model and 2D drawing disagree?

State the answer in the RFQ, because no universal rule settles it across every buyer. A buyer may name the drawing as controlling for tolerances and the model for geometry not dimensioned on the drawing. Without a precedence note, two suppliers can reasonably quote two different parts.

Before You Send It

Check the whole package against one plain question: could two suppliers read this and quote the same part? If a reader would have to guess the resin grade, the regrind rule, or the volume basis, mark that field and ask for a stated assumption. Send the same revision to every supplier, keep a record of what went to whom and when, and hold back no requirement you intend to enforce later. Once the replies arrive, the task changes from describing the part to reading the answers, and how to compare quotes built on different pricing assumptions picks up from there.