Solutions for Plastic Injection Moulding
Brass threaded inserts and insertion technologies for creating durable metal threads in moulded plastic components.
Injection-moulded components frequently need to be screwed together, connected to another assembly or reopened during maintenance.
In these applications, relying directly on the polymer to form the threaded connection may not provide the required performance, particularly where repeated assembly or defined mechanical loads are involved.
Metal threaded inserts provide a permanent thread inside the plastic component and allow the fastening point to be engineered as part of the product.
A.T.S. supplies brass inserts for mould-in, heat insertion, selected ultrasonic insertion applications and press-fit installation, together with self-tapping threaded inserts for plastics and other soft materials.
Insert selection should consider polymer type, wall and boss geometry, mechanical load, required assembly cycles and installation process.
How should a threaded insert for plastic be selected?
Polymer type, boss design, wall thickness, pull-out and torque requirements, assembly cycles and installation method all affect selection. Mould-in, heat, ultrasonic and press-fit installation require different insert and component configurations.
Why Use a Metal Thread in a Plastic Component?
A screw driven directly into plastic relies on the polymer itself to form and retain the thread.
Where a component is repeatedly assembled or exposed to higher loads, a metal insert can provide a more durable fastening interface.
A brass threaded insert transfers load into the surrounding plastic through its external geometry.
Knurls, grooves and other retention features help resist pull-out and rotation.
The insert therefore needs to be considered together with the moulded hole, boss geometry and direction of the applied load.
Mould-In Inserts Integrated During Injection Moulding
Mould-in inserts are positioned inside the mould before the plastic is injected.
The polymer flows around the external retention features and the metal thread becomes an integral part of the component as it is produced.
This removes the need for a separate post-mould insertion operation.
A.T.S. supplies brass inserts specifically designed for mould-in applications, including through-thread and blind configurations.
The insert, locating method and surrounding part geometry should all be considered during mould and component design.
Heat and Ultrasonic Insertion for Thermoplastics
Threaded inserts can also be installed after moulding.
During heat insertion, the brass insert transfers heat into the surrounding thermoplastic while being pressed into a prepared hole. The softened polymer flows around the insert features and locks it in place as it cools.
Selected A.T.S. insert geometries can also be used with ultrasonic installation, where high-frequency vibration generates local heat at the plastic-to-insert interface.
Both methods require the insert geometry, polymer, pilot hole and boss to be designed for the installation process.
Press-Fit Inserts for Different Plastic Materials
A.T.S. also supplies threaded inserts designed for mechanical press installation.
Different configurations are available for softer and medium thermoplastics as well as applications involving thermosetting materials.
The insert is pressed into a correctly dimensioned receiving feature without a thermal insertion cycle.
Hole geometry, material behaviour and insert design therefore directly influence retention.
Self-Tapping Inserts for Plastics and Soft Materials
Self-tapping threaded inserts provide another method of creating a durable internal metal thread.
During installation, the insert forms its own receiving thread in the surrounding material.
A.T.S. offers ENSAT self-tapping inserts for applications involving plastics and other soft materials.
They provide an alternative where the manufacturing process or material does not favour a heat-set, press-fit or mould-in solution.
Designing the Plastic Boss Around the Fastening Point
The performance of a threaded insert depends on more than the insert itself.
Boss diameter, hole depth, distance from edges, polymer type, reinforcement, loading direction and tightening conditions all influence the joint.
Installation timing also matters: mould-in and post-mould processes place different demands on production.
A.T.S. supports insert selection according to the component, material and assembly requirements so that the fastening point becomes part of the design rather than a secondary operation considered too late.
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