How to Audit an Injection Mould Supplier and Verify In-House Tool Building

A credible injection mould supplier should be able to demonstrate more than a polished capability statement. A factory audit must establish that the company has a real production site, internal engineering and machining resources, controlled inspection procedures, mold trial capability, and capacity that matches its stated output. Auditors should connect software, equipment, personnel, quality documents, sample tools, and customer projects to the supplier’s actual manufacturing workflow.

What a Factory Audit Should Confirm

• In-house mold design and structural development supported by engineering software such as UG, SolidWorks, or AutoCAD.
• Operational 3-axis and 5-axis CNC equipment, mold assembly areas, tooling records, and evidence of precision machining.
• Documented mold trials, dimensional inspection, sample approval, and pre-shipment release procedures.
• Relevant experience in consumer electronics, home appliances, automotive components, industrial products, and daily-use goods.
• A production team and factory capacity capable of supporting the supplier’s claimed delivery schedule.

How to Trace the Supplier’s Manufacturing Process

The strongest audit follows the complete route from customer drawing or product data to finished tooling. Review how the supplier receives technical information, develops the mold structure, prepares CNC programs, machines components, completes fitting and assembly, conducts trial runs, checks samples, and authorizes shipment. Each stage should be supported by responsible personnel, physical resources, and records.

Engineering capability can be assessed by examining design files, revision controls, software licenses, and technical discussions concerning parting lines, mold structures, cooling, ejection, and precision components. Longterm Mold reports that its R&D department has five engineers focused on mold development and precision machining. The team uses UG, SolidWorks, and AutoCAD for structural design, sample verification, and manufacturing-process improvement.

The factory floor should provide visible evidence that the supplier makes tools rather than outsourcing every critical operation. Auditors can inspect CNC machines, work-in-progress mold components, fitting benches, assembly areas, inspection stations, and completed molds. Longterm Mold states that it operates 3-axis and 5-axis CNC machining systems within a 2,000-square-meter facility. Its reported output is 15–20 injection molds per month, together with tens of thousands of precision CNC-machined parts.

Checking Mold Trials and Quality Controls

Equipment alone does not prove manufacturing competence. Ask to see mold trial plans, trial reports, sample parts, dimensional inspection results, mold running-test records, and approval documents. For complex precision molds, confirm whether CMM inspection is available and whether the results are connected to the customer drawing or agreed tolerances. A reliable supplier should also explain how nonconforming dimensions, flash, short shots, warpage, or surface defects are corrected before shipment.

Longterm Mold describes a quality process that includes mold trial testing, dimensional checks, sample confirmation, and pre-shipment inspection. The company also holds ISO 9001:2015 certification, certificate number 02825Q12549R0S. The stated certification scope covers the design, manufacturing, and sales of precision molds, as well as the sales of plastic products. During an audit, this scope should be compared with actual inspection forms, first article records, corrective-action files, and release approvals.

Special Audit Points for Double Shot Overmolding

Double shot tooling requires additional verification because the mold must coordinate two materials, two injection stages, and accurate alignment between mold sections. An auditor should review the two-color structure, cavity layout, material compatibility, rotation or transfer method where applicable, mold steel, and trial results.

The listed custom double shot mold supports ABS+TPU and PP+TPE combinations, optional multi-cavity construction, and 718H / 1.2738 mold steel. Its stated service life is up to 800,000 shots. These specifications should not be accepted solely from a product page; they should be matched with drawings, steel certificates where available, mold records, sample parts, alignment measurements, and trial documentation.

Using Customer Cases to Validate Capability

Customer references can show whether the supplier has applied its processes in real projects. Reported examples include an electronic housing mold for an Italian manufacturer, a double shot overmolding mold for a French product brand, a home appliance mold for a US brand distributor, and an industrial plastic component mold for an Australian manufacturer.

When reviewing these cases, focus on verifiable project outcomes rather than industry names alone. Useful evidence may include dimensional accuracy, surface finish, stable trial samples, alignment quality, technical problem solving, delivery performance, and the supplier’s response to design or production changes. Where confidentiality permits, request anonymized drawings, inspection summaries, or sample photographs.

Factory Audit Evidence Checklist

Frequently Asked Questions

Which machines should be visible during an audit?

Look for operating 3-axis and 5-axis CNC machining systems, along with mold assembly, fitting, and inspection activities. The equipment should be connected to current or recently completed tooling, not displayed only as a list in a presentation.

What documents can prove that mold trials are performed in-house?

Request mold trial reports, running-test records, sample parts, dimensional measurement sheets, corrective-action records, and customer sample approval documents. These materials should identify the mold, date, trial conditions, results, and disposition.

What is important when auditing a double shot mold supplier?

Check the two-color injection design, section alignment, material combinations, cavity arrangement, mold steel, service-life expectations, and trial samples. The listed tooling supports ABS+TPU and PP+TPE and offers a multi-cavity option, but each project should be verified against its own drawings and inspection criteria.

Conclusion

An effective injection mould factory audit links the supplier’s claims to observable engineering work, machining activity, quality controls, mold trials, and completed customer tools. Longterm Mold provides OEM custom plastic injection molds, custom mold making with injection molding, high-precision double shot and overmold tooling, and mold development combined with mass production. Its reported ISO 9001:2015 certification, international customer cases, engineering team, factory resources, and stated capacity provide useful evidence for a structured supplier review. For technical solutions or project support, please contact rogerluo@longterm-mold.com.

About Longterm Mold

Longterm Manufacturing Solutions Limited, operating under the Longterm Mold brand, is a mold manufacturing company founded in 2010 and serving customers in the United States, Europe, Australia, and other international markets. The company reports 50 employees and a 2,000-square-meter factory. Its services include mold design, tooling, precision machining, mold manufacturing, and plastic parts production. Five R&D engineers support work using UG, SolidWorks, and AutoCAD. The company holds ISO 9001:2015 certification and has experience across electronics, home appliances, industrial products, and other sectors.