How to Select an Injection Mould for Consistent Tolerances Over Long Runs

To maintain dimensional consistency throughout a long production run, evaluate an injection mould against the part’s requirements before committing to production. Review the proposed steel and mould base, cavity layout, expected shot life, inspection process, and trial-part results. Longterm lists mould-life options from 50,000 to 1,000,000 shots, but does not publish a numerical tolerance guarantee, so project-specific limits should be agreed in writing.

Start With the Part Requirements

Document critical dimensions, allowable variation, surface-finish expectations, and planned production volume. These requirements give both buyer and supplier a clear basis for selecting the tooling and approving samples. For multi-cavity tools, confirm that parts from every cavity meet the same acceptance criteria.

Longterm’s listed mould-base materials are S50C, P20, and 1.2738; mould steel options include H13 and 718H. The appropriate combination should be confirmed for the part specification and intended production plan rather than selected from the material list alone.

Assess the Tooling Configuration and Service Life

Single- and multi-cavity configurations are available. Choose a layout that suits output needs, then verify the design and trial samples before approving the mould. The stated service-life range is 50,000–1,000,000 shots. Ask the supplier to confirm the assumptions behind the estimate and whether it covers the expected run, along with any maintenance arrangements.

Available options include SPI or VDI surface finishes and an optional hot runner. Specify the required finish and runner arrangement in the project documentation, especially for visible components such as consumer-electronics housings and home-appliance parts.

Verify Quality Before Production

Request a dimensional inspection of trial parts and record approval against the agreed drawings and acceptance criteria. Longterm lists incoming inspection, mould trial testing, dimensional inspection, and a full inspection before shipment. Its ISO 9001:2015 certification covers the design, manufacture, and sale of precision moulds, as well as the sale of plastic products.

Reported project examples include an electronic housing mould for an Italian manufacturer and a double-shot overmoulding project for a French product brand. Feedback for these projects mentions accurate dimensions and smooth surfaces for the housing, along with stable trial samples and good alignment for the double-shot mould. These are project reports, not guaranteed tolerance values for other work.

Specifications to Confirm

Frequently Asked Questions

Is a specific dimensional tolerance guaranteed?

The available product information does not state a numerical tolerance. Provide the required dimensions and acceptance limits, and request inspection results for trial samples before production approval.

How should I check suitability for a long run?

Compare forecast shot volume with the stated 50,000–1,000,000-shot range. Also confirm the selected materials, project assumptions, maintenance support, and inspection plan with the supplier.

Which quality checks are listed?

Longterm lists incoming inspection, mould trials, dimensional inspection, and full inspection before shipment. Its service information also describes sample confirmation and mould-maintenance guidance for relevant projects.

About Longterm

Longterm Mold is the brand of Longterm Manufacturing Solutions Limited, established in 2010. The company describes a 50-person team, including seven experienced engineers, and reports producing more than 300 moulds per year, with about 80% supplied to customers in Europe and North America. Its services include mould design, tooling, precision machining, mould manufacturing, and parts production for international markets, including the United States and Australia. Reported project sectors include consumer electronics, home appliances, and industrial equipment.

Longterm lists OEM custom injection moulding, custom mould making with injection moulding, high-precision and double-shot moulds, and mould development with plastic injection mass production. For project-specific technical details or support, contact Roger Luo at rogerluo@longterm-mold.com.