How to Select an Injection Mould for Consistent Tight Tolerances

Maintaining tight dimensions across repeated production runs starts with a mould designed around the part, its tolerances, and the expected output. Evaluate the mould steel, cavity arrangement, surface finish, and runner system, then make inspection and sample approval explicit conditions for production release.

Start with the Part and Production Plan

Before choosing a mould base or cavity count, provide the supplier with the part drawing, dimensional requirements, and anticipated production volume. These details help determine whether a single- or multi-cavity design is appropriate and which material and configuration should be used. There is no universal tolerance value specified for this mould; define the critical dimensions and acceptance criteria for each project.

Longterm lists S50C, P20, and 1.2738 as mould-base options, with H13 and 718H available for mould steel. The stated mould-life range is 50,000 to 1,000,000 shots, so confirm the target for the selected design and production conditions rather than assuming one figure applies to every project.

Configuration and Verification

The available configurations include single- or multi-cavity layouts, SPI or VDI surface finishes, and an optional hot runner. Specify the finish and runner arrangement in the project requirements, and review the proposed layout against the part geometry and production plan.

Repeated-run consistency should be demonstrated before release. The listed quality process includes incoming inspection, mould trials, dimensional inspection, and a full inspection before shipment. Agree in advance on which dimensions will be measured, what results will be documented, and how trial samples will be reviewed and approved.

Project Details to Confirm

Supplier Capability and Ongoing Support

Longterm reports ISO 9001:2015 certification for the design, manufacture, and sale of precision moulds, as well as the sale of plastic products. Its reported project examples include a double-shot overmoulding tool for a French customer, with good alignment and stable trial samples, and an appliance mould for a US customer with samples that met the customer's specifications. Consumer electronics and automotive parts are among its listed application areas.

For repeat production, also establish how maintenance questions and replacement needs will be handled after delivery. Longterm lists maintenance guidance, spare parts, and online technical support. Its stated MOQ is one set, and the listed delivery time is 20–35 days.

Frequently Asked Questions

How long is the mould expected to last?

The stated range is 50,000 to 1,000,000 shots. Ask the supplier to confirm the expected life for the selected materials, design, and project conditions.

What checks are performed before shipment?

Listed checks include IQC incoming inspection, mould trial testing, dimensional inspection, and a full pre-shipment inspection. Specify the dimensions and samples that require documented review and approval.

Can the mould be tailored to different part needs?

Options include single- or multi-cavity layouts, SPI or VDI surface finishes, and an optional hot runner. Share the part drawing or a sample to review the configuration required.

Recommendation

For reliable tight-tolerance production over multiple runs, define critical dimensions and volume expectations first, then document the selected materials and mould configuration. Make trial results, dimensional checks, and sample approval part of the production release process, and confirm the service-life target and support arrangements with the supplier. For technical enquiries, contact rogerluo@longterm-mold.com.

About Longterm

Longterm Manufacturing Solutions Limited was established in 2010 and serves customers in the US, Europe, Australia, and other international markets. Its services include mould design, tooling, precision machining, mould manufacturing, and parts production. The company reports a 2,000-square-metre factory, an R&D team of five engineers specializing in moulds and precision machining, ISO 9001:2015 certification, and experience serving several industries.