What to Send With an Injection Moulding RFQ (and Why Each Item Matters)

Why enquiries get requoted

A supplier quoting a moulded part has to estimate the tool, the cycle, the machine it will run on, the material consumption and the inspection effort. Every missing piece of information forces an assumption, and assumptions are made conservatively. That is how the same part attracts quotations that differ by a wide margin: the suppliers are not quoting the same job.

The list below is roughly in order of impact.

1. A 3D model

A native CAD file or a neutral format such as STEP or IGES is the single most useful thing you can send. It lets the supplier assess wall sections, identify undercuts, judge whether side actions are needed, estimate projected area for machine selection and calculate shot weight.

A PDF drawing alone is not enough to do any of that reliably. If the model is confidential, say so and ask for an NDA rather than withholding it. Quoting without geometry helps nobody.

2. A 2D drawing with tolerances

The 3D model describes the shape. The drawing states what matters. It should identify:

• Which dimensions are critical and what tolerance applies to them
• Datum references
• Surfaces that are cosmetic and surfaces that are not
• Any geometric tolerancing that controls assembly

Applying one blanket tolerance to every dimension is counterproductive. It either forces the supplier to price for the tightest interpretation across the whole part, or invites them to ignore the tolerance block entirely. Neither serves you.

3. Material grade, not just the family

"Nylon" is a family. "PA66 with 30% glass fibre, this grade, from this supplier" is a specification. The difference matters because shrinkage, processing window, mould steel wear and cycle time all change with the specific grade.

If you have not selected a grade, say what the part has to do (operating temperature, loads, chemical exposure, whether it is outdoors, whether it needs a flame rating) and ask for a recommendation. That is a far better enquiry than naming a grade you are not committed to.

4. Volumes: annual and per batch

State the expected annual quantity, the likely batch or call-off size, and the expected life of the programme. These drive cavity count, steel selection and therefore tooling cost.

Be realistic rather than optimistic. A tool specified for volumes that never materialise is money spent for nothing; a tool specified too light for volumes that do materialise becomes a maintenance problem.

5. Surface finish and cosmetic requirements

Specify whether the part is visible in use, which faces are cosmetic, and whether you need a polish, a bead-blast or a defined texture. State where the gate witness mark and ejector marks are acceptable.

Finish is a genuine cost driver in tool making, and it is one of the most common causes of dispute at sampling: the part meets every dimension but is rejected on appearance because nobody wrote down what appearance meant.

6. Inserts, threads and secondary operations

If the part carries metal inserts, say whether they are moulded in or fitted afterwards, and supply the insert drawing. Insert moulding changes the cycle, the tool design and the handling, and it needs to be priced as part of the job rather than discovered at sampling.

The same applies to threads, printing, pad marking, ultrasonic welding, sub-assembly and any testing you expect the supplier to perform.

7. Packaging and delivery expectations

Packaging is routinely left out of enquiries and then becomes a problem at first dispatch. State whether parts can be bulk packed or need individual protection, whether you require specific labelling or barcoding, and what the delivery destination is. For export consignments, moisture protection and crate specification are part of the cost.

8. Compliance and documentation

List any documentation you will require: material certificates, first-article inspection reports, certificates of conformity, or any industry-specific requirement. These carry real effort and should be quoted, not assumed.

What you should expect back

A considered quotation should separate tooling from piece price, state the cavity count and expected cycle, identify which machine class the part will run on, and note any design features the supplier believes will cause difficulty. That last point is the most useful part of any quotation: a supplier who raises draft, wall thickness or gate location concerns before cutting steel is telling you something valuable.

If a quotation arrives with no questions and no observations about the part, it is worth asking how thoroughly the geometry was reviewed.

A note on lead time

Tooling lead time is driven by mould complexity, not part size. Undercuts, side actions, tight tolerances and demanding finishes all extend it. Sampling and correction cycles then follow, so it is sensible to plan for at least one round of adjustment after the first trial rather than assuming the first samples will be production-ready.

When you are ready, our enquiry form accepts part details, volumes and material specifications directly.