How to Compare Injection Molding Quotes Beyond the Unit Price

1. Establish one comparison basis

Use the same drawing revision and the same number of finished parts for the baseline comparison. A quotation for a bare housing is not equivalent to one for a decorated, assembled and packed product. Write the intended deliverable at the top of your comparison sheet, then ask each supplier to identify any difference.

Keep confirmed orders separate from annual forecasts. Ask for an alternative price tier when useful, but do not use a forecast-based price to evaluate a smaller committed order. Injection moulding proposals should also use the same currency and delivery boundary; record the conversion basis separately if currencies differ.

If the project brief is still incomplete, first use the injection molding RFQ checklist. The next step is reconciling the quotations received, rather than sending another general information request.

2. Use a scope-by-scope comparison matrix

For each row, record the quoted scope, any separate charge and an open question. A blank cell does not mean that the item is free or included.

Ask suppliers to revise only the rows that differ. Keep the original proposal and its revision together so a clarification cannot silently replace an earlier condition.

3. Compare the tool proposal alongside the part price

Protolabs identifies tooling, materials and production as major injection molding cost categories. [1] Keep the plastic mold manufacturing charge visible instead of hiding it inside a headline unit price. Ask whether trials, sampling and any setup charges are separate, and how repeat orders are priced.

Tooling proposals can also differ in cavity arrangement and cosmetic work. Protolabs explains that quantity, cavity count and part appearance can affect tooling and part costs. [2] A lower part price therefore needs its tool and volume assumptions beside it. More cavities are not automatically the right choice for every geometry or demand pattern.

Discuss open design assumptions through mold design and engineering review. For a plastic mould proposal, record the agreed ownership, storage, maintenance and transfer responsibilities. Do not infer these arrangements from who pays the initial mold charge.

4. Check what happens after molding

Printing, insert installation, assembly and packaging are distinct requirements. Protolabs lists these among its secondary-operation options, with their own inputs and project conditions. [3] Treat that as a reason to specify your required scope, not as proof that any supplier includes every operation.

For an illustrative LED night-light enclosure comparison, one proposal might cover only the molded shell. Another might include the shell, logo application and a specified packing method. Before ranking their prices, ask both to quote the same deliverable. This example describes a comparison method, not an OPINOX customer order or a published price.

Also distinguish a cosmetic mold finish from decoration applied to the finished part. A smooth molded surface does not by itself specify printed artwork, its location or acceptance criteria. Put those requirements into the comparison row that pays for them.

5. Calculate the total for the order you will actually place

Build a comparison total using the same order quantity and delivery boundary:

Comparison total = one-time tooling + quoted setup or sample charges + ordered quantity × part price + separately priced finishing or assembly + packing + delivery costs within the agreed boundary.

Add only charges not already included elsewhere. List unknown charges separately instead of assigning them zero. State whether the total excludes taxes or destination charges; an incomplete delivery price should not look like a complete delivered cost.

For repeat orders, make a second comparison that excludes tooling only when no new tooling charge is expected. Evaluate a larger-volume option separately. Spreading a one-time mold fee over more parts lowers its allocated cost per part, but does not reduce the upfront invoice or make an unconfirmed forecast an order.

6. Resolve the differences before selecting a proposal

Ask each supplier to confirm the revised scope and the conditions that would change its price or schedule. Check the trigger for each milestone: design approval, material confirmation, mold trial, sample acceptance and production release. A production date measured after sample approval cannot be compared directly with a date measured after payment.

• All proposals refer to the same revision and finished-part scope.
• Quantity tiers and forecasts are clearly separated.
• One-time fees, repeat-order costs and exclusions are visible.
• Sample approval, inspection and delivery boundaries are agreed.
• Open questions have named owners and written answers.

Use the matched comparison to discuss your custom injection molding project with OPINOX. Share the application and the scope differences you need to resolve; agree on a suitable drawing-transfer method with your project contact. The website enquiry form does not accept attachments.

Frequently asked questions

Should I choose the quotation with the lowest part price?

First match quantity, material, tooling, finishing, acceptance and delivery scope. Only then can the price difference be evaluated. Missing scope is a clarification item, not an assumed saving.

Can I compare quotes based on different cavity counts?

Yes, as separately labeled alternatives with their own tooling charge, order quantities and operating assumptions. Ask the supplier to explain suitability for the part and demand; cavity count alone does not establish the better proposal.

How should an unspecified cost be entered in the comparison?

Mark it as unresolved and request a written inclusion or exclusion. Do not record zero unless the supplier explicitly confirms no additional charge for that scope.

Should a first order and a repeat order use the same total?

Use separate totals. A repeat-order comparison may exclude previously paid tooling if no new tooling work is required, while setup, decoration, packing or delivery charges may still apply.