Plastic moulding RFQ checklist: what to send and why

Why a moulding quote comes back vague

A moulding quote is only as specific as the enquiry behind it. When a buyer sends a 3D model and a target price, the moulder fills the gaps with assumptions: one cavity, a standard grade, a general tolerance, a packing method chosen for convenience. The number that comes back can look competitive because it describes a slightly different part from the one the buyer has in mind.

A structured RFQ closes that gap without turning into a tender document. It only has to answer the questions that move the price: what the part must do, which dimensions locate it, which material and rating apply, how many cavities the volume justifies, who owns the tool, and how the parts will be packed and inspected.

The checklist below follows the order a moulder uses to build a price. Send the items in that order and the quote arrives in a form you can compare line by line rather than a single number that hides six decisions.

Part data: the model, the drawing and the critical few

Send a STEP file and a 2D drawing. The model gives the geometry; the drawing gives the tolerance, the datum scheme and the surfaces that matter. A model on its own pushes every tolerance decision to the supplier, and the supplier will choose values that suit the tool rather than the assembly.

Mark the critical dimensions instead of tolerancing everything. A housing usually has four or five features that decide whether it assembles: terminal pocket position, cover interface flatness, mounting hole position, a breaker slot width and a sealing face. Tighten those and leave the rest to a general tolerance such as ISO 2768-m or a moulding tolerance standard.

State the cosmetic requirement in words the toolmaker can act on. A visible face with a texture, a class A surface, a laser marking area and a gate position that must not be seen are all tool decisions. Raised after the mould is cut, each one costs steel and time.

• Current revision of the 3D model in STEP or Parasolid
• 2D drawing with datums, critical dimensions and a general tolerance
• Cosmetic surfaces, texture grade and gate restrictions
• Assembly drawing if the part mates with other components
• Any feature the supplier must not change without approval

Material and compliance

Material is the second largest line in most quotes and the easiest to leave vague. A grade name alone is not enough. Two PA66 grades with the same name can carry different flame ratings, different tracking indices and different impact behaviour at low temperature, and the price follows the additive package.

State the rating with the thickness at which it applies. A UL 94 V-0 result at 1.5 mm does not transfer to a 0.8 mm wall. If the housing must meet a glow wire test or a tracking requirement, name the standard and the severity, because a grade that passes one may fail the other. Colour belongs in the same paragraph, since a masterbatch change can move a flame result.

The tool: cavities, steel and ownership

The tool plan is where two quotes for the same part diverge most. A single cavity tool in a standard steel and a four cavity tool with two side actions are different products, and the piece price reflects that. Put the expectation in the RFQ so the supplier prices the same thing.

1. 01

   Cavity count

   Match cavities to annual volume and tool budget. One cavity keeps the tool cheap and the cycle cost per part high; four cavities spread the cycle but need a larger press and a longer tool build.

2. 02

   Steel and life

   Name the steel family and the expected tool life. A soft steel for a pilot is a valid choice; the same steel for a ten year programme is not.

3. 03

   Gating and ejection

   Ask where the gate lands and how the part ejects. Gate position sets weld line position, and weld lines decide where a housing may crack.

4. 04

   Side actions

   Every side action adds tool cost, maintenance and cycle time. List the undercuts and ask which the supplier would remove for the same function.

5. 05

   Ownership

   State who owns the tool, who pays for maintenance and how the tool moves if the supplier changes. Agree it in the RFQ, not after a disagreement.

Volume, schedule and forecast

A piece price without a volume is a guess. Give the annual quantity, the monthly call off, the first year ramp and the expected life of the programme. Suppliers price tooling amortisation and machine time against those figures, and a change in any of them changes the answer.

Say how firm the forecast is and how far ahead you will commit. Many moulders will hold a price for a stated volume band and reopen it below that band. That is reasonable, provided the band is written down.

Add the delivery destination and the Incoterm. A price delivered to a warehouse inland is not the same as a price ex works, and the gap is larger for a bulky part than for a dense one.

The cost of proving the tool belongs in the same conversation. A trial, a correction loop and a first article take machine time that the supplier has to recover, either as a separate line or inside the piece price. Ask which, and ask how many trials the price includes.

Lead time follows the same logic. A tool built in eight weeks and a tool built in twelve are different quotes, and rushing the tool usually costs more in correction than it saves in schedule. Put the required first article date in the RFQ and let the supplier build the plan backwards from it.

Finish, assembly and packing

Secondary operations decide whether the part leaves the moulder as a component or as a finished subassembly. Printing, laser marking, insert fitting, ultrasonic welding and leak testing each need a line in the RFQ, with the acceptance check that goes with them.

Packing deserves the same treatment. Give the parts per bag, per carton and per pallet, and say whether the packaging is returnable. For a light, bulky moulding the packing density often decides the landed cost more than the piece price does.

Finally, name the inspection level. A first article against the drawing, a dimensional report per batch and a visual standard for cosmetic parts are three different commitments, and the supplier needs to cost the one you actually want.

Comparing the quotes you get back

Quotes rarely arrive in the same structure. One supplier bundles the tool into the piece price, another lists it separately, a third excludes the first trial. Normalise before comparing: tool cost, piece price at the stated volume, material assumption, packing, freight and payment terms.

Then read the assumption list. The supplier that writes down its assumptions is easier to hold to the price than the one that sends a single figure.

• Is the tool quoted separately, and is it amortised or paid up front?
• Which material grade and which data sheet revision sit behind the price?
• What cavity count and cycle time does the price assume?
• Which secondary operations and which inspection steps are included?
• What volume band holds the price, and what happens below it?