Injection Molding Quote: How to Prepare an RFQ

An injection molding quote is built from two things a buyer controls before anything is sent: how completely the part is defined, and how clearly the program is stated. A molder prices from geometry, a material, a quantity, and a set of expectations, and wherever those inputs are left blank the supplier fills the gap with an assumption that then shows up as a line in the price. This page walks the whole arc of a molding request in neutral terms: what a complete request contains, what the buyer defines and what the supplier proposes, what a serious quote itemizes, what happens between the approval of a design and the release of production, and which questions are worth asking before accepting a number. It is the commercial companion to the injection molding process guide, and it quotes nothing on purpose, because actual prices and schedules depend on the part, the tool, the supplier, and the market at the time.

The request matters more in molding than in most processes, because the quote prices a tool as well as a part. A machined part can be requoted from a drawing revision at little cost; a molded part commits to steel, and the decisions made in the request, cavity count, tool class, finish, and tolerance intent, shape every part that follows. Guides from molders, quoting platforms, and plastics-industry sources converge on one point: complete, well-structured requests are answered more quickly and priced on fewer assumptions, while thin requests trigger clarification rounds and prices built on guesses. That difference is the entire argument for preparing the request as an engineering document rather than an email with attachments.

What a complete request contains

Across molder guides, request-for-quote templates, and platform quoting flows, the same core package appears again and again. It has two jobs: define what the part must do, and define what the quotation must include. A molding request does not force the buyer to decide every detail of mold construction in advance, which is a common fear; the buyer states requirements and constraints, and the supplier proposes the tool. The fields below are what a serious request carries, and each one exists because its absence has a price.

The model and the drawing

Geometry arrives as a 3D CAD model, with STEP the preferred format and IGES broadly accepted, and with the units written out on the drawing, since mixing millimeters and inches changes the part by a factor of 25.4 and silently ruins the estimate. STL is not a molding input: its tessellated mesh carries no feature-level accuracy to quote from, let alone to cut steel from. The model should be the final revision of the part itself rather than an assembly, and it should represent the part as designed rather than pre-scaled for shrink, because shrink compensation belongs to mold design and follows the stated resin.

Intent lives in the drawing rather than the model. Critical dimensions and tolerance callouts, datum and GD&T references where they govern fit, surface-finish notes, thread calls, cosmetic areas, and any gate or ejector restrictions all live on the drawing, because a model alone does not define them. The model gives the geometry and the drawing gives what matters, and a request carrying only one of the two tends to price a different part than the buyer meant. The conventions behind a complete drawing, from datums to callout placement, are covered on the technical drawing requirements page.

Material: designation or duty

A bare resin name is the classic weak specification, because the grade sets mold temperature, injection pressure, workable wall limits, and shrinkage, and through those the cavity steel and the mold design. A complete request carries the full designation: manufacturer, grade, and color, or a color standard by reference. Buyers who have not fixed a grade should state the duty instead: the environment the part lives in, the loads it carries, the chemicals and temperatures it sees, any UV exposure, and the regulatory needs, and let a qualified molder recommend resin and additives from that. Adding a line that substitutes are acceptable invites alternatives that serve the duty at a different point in the resin range. Certification requirements travel with the material line rather than surfacing after award: flame ratings, food contact, medical use, and compliance schemes such as RoHS or REACH belong in the request. The resin-by-resin depth behind this field lives on the injection molding materials page.

Quantity: the field that shapes the tool

Volume is the input with the most downstream reach, because it drives the two big decisions the supplier makes: cavity count and tool class. Higher volumes justify hardened steel, multi-cavity tooling, and automated inspection; lower volumes may be served by simpler tooling and controls. A complete request states first-order quantity, expected annual volume, program life, and any ramp or phase-in schedule, because those fields point at different tools. Where volumes are genuinely uncertain, suppliers ask for a range rather than silence, since a range lets the molder choose tooling while silence forces an assumption. Buyers may also state a target tool life in shots, conventionally discussed in bands running from the tens of thousands to a million or more, or leave the steel choice to the supplier, and the quote should state which of the two happened. The tooling ladder those decisions draw on, from aluminum through the hardened steel classes, is laid out on the rapid tooling page.

Finish, tolerance, and quality intent

Cosmetic and precision requirements are specified per feature, not per part. Finish callouts follow the SPI letter grades, polish through texture, often alongside a named texture code, and a request that says glossy or smooth is the cited example of a finish no one can quote. Tolerances follow the localize-precision discipline: tight only on mating, sealing, and locating features, and a general class elsewhere, with one widely used request template illustrating the split at roughly ±0.05mm on critical features against a ±0.2mm general default. Blanket precision multiplies inspection and processing effort across every dimension on the drawing and buys nothing on the features that do not need it. The grade systems behind molded tolerance callouts are detailed on the injection molding tolerances page.

Quality expectations belong in the request as well: which dimensions are critical, what inspection documentation is required, a first-article report, dimensional reports, capability studies where the application warrants them, and for regulated work the applicable approval protocols such as PPAP. Stating these up front puts them inside the price rather than on a later invoice.

Application, secondary operations, and program context

Application and environment are not geometry, but they belong in the request because they drive the resin and tolerance choices as much as any dimension does. Secondary operations must be declared: trimming, welding, painting, printing, assembly, inserts, packaging and labeling, traceability. Quotes otherwise assume bare molded parts, and the gap surfaces after award, when the operations are priced as add-ons or sourced separately. For multi-material or insert-molded parts the request changes shape: a bill of materials joins the geometry, specifying inserts by diameter, thread, and material, and the second-shot or substrate material is called out as its own line; the multi-material processes themselves are covered on the overmolding and insert molding page.

Program context rounds out the package. Timeline expectations and, where the buyer chooses to share them, budget constraints let a supplier propose a tooling strategy that fits the program rather than guess at one. And when parts will run from a mold the buyer already owns, the request includes the mold drawings, past production records, and sample parts, because the supplier will want to evaluate the condition, cooling, and machine compatibility of an existing tool before quoting against it.

For example, picture the same enclosure quoted from two requests. One carries a STEP model with units stated, a drawing that marks the critical dimensions and one sealing face, the resin designation with a color standard, the first order and the annual volume, and a note that a texture substitute is acceptable on the hidden surfaces. The other carries photographs, the word ABS, and an instruction to price five thousand. The first is answered with a proposal that names its assumptions and can be judged on them. The second triggers a clarification round, and every question answered loosely becomes an assumption the buyer never chose, priced into a tool that outlives the conversation.

What the buyer defines and what the supplier proposes

The cleanest way to hold a molding request in mind is a division of labor. The buyer defines the volume and the tool-life expectation, the cosmetic restrictions, the tolerance-critical features, the ownership and transfer intent, and the maintenance expectations. The supplier proposes the cavity count and the mold steel, the gate and ejector positions, the runner and cooling design, and the press size. Neither side is expected to do the other side of the split, and most friction in quoting comes from a request that leaves the boundary unclear: a buyer who prescribes tool construction inherits the engineering consequences of it, while a buyer who states intent can hold the supplier accountable for the engineering that answers it.

For example, a buyer who states the annual volume, the cosmetic faces, and a tool-life expectation, and leaves cavitation and steel to the molder, receives a proposal that can be challenged on engineering grounds. A buyer who instead insists on a high-cavity hardened tool against a modest annual volume has made the tooling decision for the supplier and owns the tooling premium that follows. Both paths can lead to a sound tool; only one of them keeps the accountability in the right place.

What a serious quote itemizes

A molding quote has two headline components, and they must be kept separate: a one-time tooling cost and a per-part production price, conventionally shown tiered by quantity at several break quantities. Around those two lines, a complete quote states what the tool is, what the price assumes, and what is included and excluded. A quote that shows only totals has collapsed all of that into one number, which is exactly what makes quotes hard to compare.

Inside the tooling quote

The tooling side of a serious quote names its engineering. It states the mold type and cavity count, including family-mold status if similar parts share a tool; the mold-base and insert steels with hardness and heat treatment; the expected mold life and the warranty conditions attached to it; the runner and gate system, with the hot-runner components named where the design is hot; the side actions and how they are actuated; the cooling design and the cycle time it assumes; and the engineering effort included, meaning the DFM work, any mold flow analysis, and the design reviews. It also states the trial scope: how many sampling rounds, how many sample parts, and what reports come back with them. The mold price itself has an internal structure a buyer can ask to see, conventionally spanning materials, design, processing, tryout, and packing, with tax and shipment where applicable.

The piece price and its assumptions

The per-part price is where unstated assumptions hide. The quote should state the cycle time it assumes, the scrap allowance, the resin price basis, whether material is costed on net part weight or on shot weight including the runner, and who absorbs scrap when a run goes wrong. It should show the price at several quantities, because the per-part figure at the first order and the figure at annual volume are different numbers answering different questions. Where any of these are missing, the price is not comparable to another supplier price; it is only lower or higher.

Inclusions, exclusions, and terms

Fixtures, gauges, texture, packaging, freight, secondary operations, and quality documentation are the classic items some quotes include and others treat as add-ons, and that difference routinely explains a gap between two totals. Commercial terms belong in the quote as well: the payment structure, the price validity window, the terms of sale, the ship-to point, and, for cross-border work, the duties and freight that turn an ex-works number into a landed one. Comparing suppliers on landed cost, particularly across borders, is what keeps that comparison honest. And the warning that recurs across supplier guides deserves repeating: when one quote comes in far below the others, it is probably missing detail, in the form of thinner assumptions, exclusions, or a lighter tool, rather than offering the same thing cheaper.

DFM feedback and the approval arc

Between the request and the release of production sits a sequence of reviews and approvals the buyer owns, and knowing its shape in advance is most of what it takes to run it well. The arc runs design-for-manufacturing review, mold design, steel cutting, T1 samples, corrections, first-article inspection, and production release, and each phase has a deliverable a buyer can check.

DFM feedback arrives in two waves. The first is a preliminary manufacturability review at the quoting stage, which is where a well-prepared request starts paying for itself: the reviewer works from stated intent instead of reconstructing it. The second is the final DFM package, delivered after the tooling order and deposit, which the buyer must approve before steel is cut or tool manufacture begins. The final report conventionally covers the resin and shrinkage review, draft angles, wall thickness and rib ratios, gate location, the parting line and any mechanical actions, ejector-pin mark placement, and the finish definition, and its findings are commonly graded as acceptable, recommended change, or required change. Even an all-clean report needs the buyer acknowledgment before the tool proceeds, because silence is not approval.

The approval that matters most is conventionally summarized as PEG: parting line, ejection, and gate. Those three tooling decisions require customer sign-off before tooling starts, and they earn the gate because all three leave permanent marks on the part. The parting line leaves a witness, ejection leaves pin marks, and the gate leaves a vestige, and once the tool is cut, a change to any of the three moves from a drawing revision to a steel correction. The numeric rulebook behind these findings, draft bands, wall ratios, radii, and feature spacing, appears on the design rules page; at the quote stage the point is that DFM is a deliverable with an approval gate, not a courtesy note attached to a price.

The tool then produces T1 samples: the first parts molded from the new tool, reviewed against the drawing for dimensions, color, finish, and assembly fit. Corrections follow, and T2 and T3 trial rounds follow the corrections, with texture and final polish commonly applied in the last stage once the geometry has settled; some suppliers denote a pre-production mold check as T0. First-article inspection documentation accompanies the approved samples, and for regulated programs the applicable approval protocol runs on top of it; what that documentation typically contains is described on the quality inspection and metrology page. Two allocation questions belong in the quote rather than in a later argument: how many trial and modification rounds the tooling price includes, and which corrections are charged to the tool versus to the part design. A correction caused by a tooling fault and a correction caused by a design change are different events with different owners, and a quote that allocates them in advance is describing a process the supplier has run before.

On timing, supplier guides describe a complete request as typically answered in days rather than weeks, while thin or complex requests take longer because clarification and analysis intervene. The more durable habit is to trade the single duration question for milestone dates attached to the phases: DFM approval, mold design release, steel cut, T1 samples, first article, production release. A supplier willing to commit to milestones is describing a schedule it plans to keep, which is worth more than any headline duration.

Tooling ownership, maintenance, and payment conventions

Tooling can be paid for in two ways, and they differ in more than cash flow. Paid separately, the tool is a one-time item the buyer owns, title transfers on payment, and the buyer can audit it, store it, and move it to another molder. Amortized into the piece price, the tool is supplier-financed, and title commonly stays with the supplier until the committed volume is reached. Tooling described as free is financing rather than a gift; the per-part price and the ownership rights are where it is repaid. Neither structure is wrong. The wrong structure is the one whose ownership terms were never written down.

What should be written down is well established in legal and molder guidance: who holds title and when it transfers; who performs and who pays for scheduled maintenance, unscheduled repair, and end-of-life refurbishment; the buyer right to inspect the tool and reclaim it; whether the molder may run it for anyone else; physical labeling and a tooling inventory record; the mechanics of transferring the tool to another supplier; and ownership of the designs, drawings, and tooling data. Under the common contract-molding arrangement the customer owns the tool and it is housed at the molder, who maintains it, typically as a charged service. Suppliers themselves describe the ownership question as among the most important to settle before signing, alongside who pays for maintenance and repair over the life of the program.

Payments are conventionally tied to verified milestones: order and design freeze, steel progress, T1 sampling, first-article approval, and shipment. The buyer-protection rule that recurs across supplier guidance is never to pay everything before T1 samples exist. Until the tool has made parts, there is nothing to verify against, and a payment schedule that concentrates payment before that point is asking the buyer to carry the execution risk alone.

The questions worth asking before accepting a quote

A short list of questions, condensed from what experienced buyers and molders themselves describe, does most of the work of evaluating a quote:

• What cavitation and tool class is this price built on, and why that combination for the stated volume?
• Who owns the tool, who maintains it, and what happens to it if the working relationship ends?
• What quality documentation is included: first article, dimensional reports, capability studies, PPAP where the industry requires it?
• Could a lower-tier resin or a different grade serve the stated duty, and what would change?
• How many trial and modification rounds are included, and who pays for tooling-fault corrections versus design-change corrections?
• What is excluded from the price: fixtures, gauges, texture, packaging, freight, secondary operations?
• Can milestone dates be attached to the quote instead of a single lead-time number?

The questions do double duty: they produce answers, and they reveal how the supplier behaves when asked. Diligence checks described alongside quote review point the same direction: evidence of the actual production floor, a machine list with tonnage ranges, and a sample part from a comparable past project. Each verifies that the quote describes a real capability rather than an aspiration, and the willingness to provide them is itself information.

Why quotes differ, and how to compare them

Two suppliers quoting the same part can produce very different numbers with both quotes honest, and supplier guides describe the spread for identical requests as running from tens of percent to a multiple. The mechanics behind the spread, how tooling amortizes across quantity, how cavity count multiplies tool cost while dividing machine time, and how resin class and finish move the piece price, are worked through on the injection molding cost drivers page. What the request side adds is the comparison discipline: normalize the assumptions before comparing the totals. Same cavitation. Same steel and tool class. Same release quantities and run pattern. Same tolerance interpretation, same finish, same inclusions, same landed-cost basis. Are all suppliers quoting release quantities the same way, and is the schedule shown for the tool build alone or through production launch? A comparison of totals answers none of those questions; a comparison of assumptions answers all of them.

For example, the same housing quoted by two suppliers can come back far apart with both quotes defensible. One supplier prices a single-cavity tool in a modest steel against the stated first order, keeping the tooling line low. The other prices a multi-cavity hardened tool against the annual volume, on the reasoning that the tooling spreads across the program. Neither miscalculated. They priced different tools for different quantities, and the buyer comparing only totals sees a discrepancy where there is really a decision that belongs to the buyer. The process-generic anatomy behind this, setup versus per-part cost and how quantity shifts the balance, appears on the how quotes are calculated page.

The request checklist

Assembled from the sections above, a molding request reduces to a short checklist, and a request that satisfies every line is one a supplier can act on:

• 3D model: STEP preferred, IGES acceptable, final revision, the part rather than the assembly, units explicit.
• 2D drawing: critical dimensions, tolerance classes, finish and texture callouts, cosmetic areas, gate and ejector restrictions, and the general tolerance stated.
• Bill of materials where inserts or purchased components join the part, each with diameter, thread, and material.
• Material: full designation or the duty, color standard, additives, certification requirements, and whether substitutes are acceptable.
• Quantity: first order, annual volume, program life, ramp, and the tool-life expectation in shots.
• Finish: SPI grade per surface, and the texture code by name where texture is wanted.
• Quality: first-article expectations, dimensional reporting, capability studies, and regulated protocols where required.
• Scope: secondary operations, packaging, labeling, traceability, ship-to, and the terms basis for comparing quotes.

The wider vocabulary of the quoting process is collected in the manufacturing glossary. The stance of this page is deliberate: it quotes nothing, because a number without the part, the tool, and the supplier behind it is marketing rather than information. What a buyer controls is the completeness of the request, the discipline of the comparison, and the quality of the questions, and those three are what turn a pile of quotes into a decision.