POM Insert Molding for Industrial Parts with Metal Inserts

This industrial component combines a POM molded body and threaded metal inserts in a compact part approximately 100 × 50 mm. The design includes a deep circular chamber, an angled side port, multiple mounting bosses and metal threaded connections molded into the plastic body.

Unlike a conventional plastic housing, the critical manufacturing work is concentrated around the plastic-to-metal interfaces. The inserts need to be loaded in the correct position, held securely during injection and kept aligned with the surrounding molded features. At the same time, the exposed threads must remain free of unwanted plastic or flash.

The part was produced with a single-cavity injection mold for a customer in the United States. Our insert molding services support this type of custom industrial component from tooling review and mold manufacturing through trial molding and production.

Project Details

Why Insert Molding Fits This Component

The part requires several functional connections within a relatively small molded body.

The large circular chamber forms the main interface, while mounting bosses around the perimeter provide fastening points. An angled plastic port extends from one side, and threaded metal connections are incorporated into other areas of the housing.

These features need to maintain their relationship after molding.

With plastic insert molding, selected metal components are positioned inside the mold before injection. POM then forms the plastic body around the required portions of the inserts.

For a suitable product design, this creates the plastic geometry and metal interfaces as one molded component rather than treating every metal fitting as a completely separate post-molding installation.

Insert Position Matters as Much as the Plastic Part

One of the key challenges in injection molding with metal inserts is keeping the insert where the drawing requires it.

Before each molding cycle, the metal component needs to seat correctly in its locating position. The tooling then needs to hold it securely while the mold closes and POM fills the surrounding cavity.

If an insert shifts or tilts during this process, the plastic body can appear correctly molded while the finished component still fails to meet its assembly requirement.

This is particularly important on a part like this because several interfaces are located around the same body.

The engineering concern is therefore not simply:

Is the metal insert in the plastic?

It is:

Is the insert in the correct position relative to the chamber, mounting points and other connections?

That relationship is one of the main inspection priorities for an insert molded industrial component.

Designing Around Threaded Metal Inserts

The plastic-to-metal interface needs to be considered before the injection mold is built.

Depending on the customer's design, a molded-in insert may use shoulders, grooves, knurls or other retention features. These help the surrounding plastic mechanically engage with the metal component.

The POM geometry around the insert also matters.

Too little surrounding material may not provide the intended support, while excessive local thickness can create unnecessary shrinkage or molding concerns.

For POM insert molding, the review therefore considers:

Insert Geometry → Retention Area → Surrounding POM → Functional Load → Molding Conditions

If the threaded connection will experience specified torque, pull-out or other mechanical loads, those requirements should be identified before tooling.

This allows the insert interface to be evaluated against its actual function rather than assuming that any molded-in metal part will perform the same way.

Controlling POM Flow Around the Metal Components

The metal inserts become part of the cavity during molding, so they influence how POM flows through the part.

Gate location and flow direction need to be considered in relation to the insert positions.

The material needs to fill around the metal components without leaving incomplete areas or unnecessarily disturbing the insert. Where flow fronts divide and meet again, weld-line location may also need attention depending on the functional requirement.

This gives metal insert molding a slightly different mold-design problem from an ordinary plastic part.

The flow path has to work with the metal components already sitting inside the cavity.

Protecting the Threads During Insert Molding

The exposed threaded sections shown on this component are functional interfaces.

They need to remain usable after molding.

The tool therefore has to define precisely where POM should form around the metal component and where the insert must remain exposed.

Accurate seating and suitable shut-off conditions help prevent plastic from entering areas that should remain clear.

After molding, these interfaces can be checked for issues such as unwanted flash, contamination or other conditions that could interfere with mating hardware.

For threaded insert molding, protecting the usable portion of the insert is just as important as forming the plastic around it.

POM for Functional Molded Components

POM is widely used for mechanical and industrial plastic parts where rigidity, dimensional stability, low friction and wear performance are useful.

This component is a good example of a functional rather than purely cosmetic application.

The important characteristics are the relationships between the main chamber, mounting points, molded connection and threaded metal interfaces.

POM also needs to be processed according to its own molding behavior. Material grade, shrinkage, wall thickness and local geometry can influence the finished dimensions.

For that reason, a POM injection molding project should not simply inherit processing assumptions from an ABS or PC housing.

The actual material and part design need to be considered together.

Functional Dimensions Drive Inspection

Checking only the overall 100 × 50 mm size would provide limited information about whether this component will work.

Depending on the customer's drawing, more meaningful inspection points may include:

• position and orientation of threaded inserts;
• center distances between connections;
• circular chamber dimensions;
• mounting boss positions;
• side-port location;
• mating surfaces;
• insert-to-plastic interface condition.

This is where the customer's 2D drawing becomes particularly valuable.

The 3D CAD model defines the complete part, but the drawing tells production and inspection teams which dimensions and tolerances are important to the assembly.

Trial Molding with Production Inserts

The actual inserts are part of the molding process, so they also need to be part of mold validation.

During initial trials, we can evaluate how the POM fills around the metal components, whether the inserts remain in position and whether the finished plastic-metal part meets the relevant drawing requirements.

The trial stage may include checks for:

Insert Position · Thread Condition · Flash · Critical Dimensions · Deformation · Assembly Features

If an insert moves during injection or POM does not form correctly around an interface, the issue can be addressed before repeat production.

Once the insert-loading method, mold and molding conditions are confirmed, the project can move into batch manufacturing.

Custom Insert Molding Services for Industrial Plastic Parts

We provide custom insert molding services for industrial plastic components that require metal features integrated during injection molding.

Depending on the product design, molded-in components can include threaded inserts, bushings, pins, sleeves and other custom metal parts.

Our manufacturing support can cover:

Insert & Part Review → Injection Mold Manufacturing → Trial Molding → Insert Molding Production → Inspection

POM and other engineering plastics can be evaluated according to the component's application and drawing requirements.

For projects where the metal insert also needs to be manufactured or sourced, the insert drawing should be reviewed together with the plastic component so that the two parts are treated as one manufacturing system.

What We Need to Quote Your Insert Molded Part

For an insert molding quote, please provide:

3D CAD + 2D Drawing + Plastic Material/Grade + Insert Drawing + Insert Material + Thread Specification + Production Quantity + Critical Tolerances + Assembly Requirements

Where relevant, also include specified torque, pull-out, sealing or other mechanical requirements for the metal interface.

These details allow us to review not only whether the plastic part can be molded, but whether the insert, tooling and surrounding POM geometry are suitable for the finished industrial component.