Insert molding is key across industries, integral in the production of electrical switches, vehicle dashboards, power tools and surgical appliances. For any product that is intended to connect with another through the use of a connector pin or alternative insert, insert molding is the process used to add that metal mating pieces to a plastic design during the manufacturing of that particular part.

The insert can be placed either manually or automatically onto a mold core and then plastic is poured into the mold, forming around the insert’s retention feature, locking it into place. As it hardens, the result is a customized part that takes less time to make and weighs less than an all-metal alternative.

When to Use Insert Molding

Any two components that require mating pieces to hold these parts together would benefit from insert molding. However, it is important to know what kind of inserts would work best for your mold. Here are some things to consider:

What material is recommended for my product?

Standard molded inserts are made of brass, steel, and sometimes ceramic. These can be closed holed or open-ended. They should be rounded with no sharp edges. When choosing materials for your product, use a stress chain chart to better understand the pros and cons of each insert.

Your insert will not shrink during the molding process. Therefore, it’s important to measure the shrink rate of your material. Nylon and polycarbonates are two materials with low shrink rates, whereas polypropylene and polyethylene have high shrink rates.

What length does my insert need to be?

When inserted to your product, your insert should have a depth of ⅙ the insert diameter to avoid sink. The boss diameter should be 1 ½ the insert diameter.

What kind of custom inserts are there?

Connector pins, female or male, alignment pins, bushings, needles, tubing, and magnets are all custom insert options. However, these each follow standard design considerations. Special considerations need to be made for the shut-off, which needs to have a tight grip with the cavity and core. Custom inserts can be made of any material that can endure the pressure and temperature of the molding process.

Can I use contact pins as inserts?

Contact pins are commonly used as metal inserts. Depending on what application you need from your connector, contact pins are an especially easily customizable insert. Pins can be designed to your exact specifications, making them a versatile option to serve as a connector.

Contact pins can have a number of different retention features to keep them in place once placed in a mold and dried. These include flat, serrated, collar, and star. Depending on the product, and how much space you have between the pin and the circumference, you may want to leverage a narrower option, or one with a collar for a larger, heavy-duty product.

The contact pins above are two commonly used examples of an all-metal insert with varying retention features. Bead Electronics offers both retention and anti-rotation, as well as a number of other custom options, to offer the best one to suit your DFM needs. Reach out to find out what connector solutions support your applications.

What are the Benefits of Insert Molding

First and foremost, insert molding reduces assembly and therefore, is a cost-effective and efficient production. Customization is another huge advantage, especially for DFM in the medical and automotive industries.

The reliability of products that have undergone insert molding are usually more durable than products fastened together using alternate molding processes. Furthermore, the inserts are overmolded by plastic, they’re locked in due to the retention feature, which is stronger than a pin that is inserted after the plastic housing is molded.

Not only does the insert stay in place, but anti-rotation features can also keep the insert locked in. Quality control is easier managed as imperfections like cracking or stripping are preventable due to the simplicity of the bonding that occurs between the plastic material and the (oftentimes) metal insert. And that simplicity also means more design flexibility.

Regulations do exist around insert molding, especially as this process pertains to its use in medical equipment. The type of plastic needs to be compatible with the material of your insert and testing may need to be done before that insert is implemented. Occasionally, and despite the increased design flexibility, designs may not be suitable for insert molding, resulting in cosmetic imperfections or functional issues.

How to Use Insert Molding in Your Designs

Insert molding provides an opportunity to think outside the box. With components that can be mass-produced as a sub-assembly, like Right Angle Pin Headers, these products are easier to place into the molding machine, eliminating the need to individually place every contact pin. This results in a one-step insert process for an easier overmold, saving time and money.

But because there are endless possibilities in the realm of DFM, regardless of how you plan to leverage insert molding, you need to make sure you’ve got all your files ready for an engineer or designer to reference.

The final design must include insert CAD to see how much space the inserts occupy. This way, you get a comprehensive understanding of how your product’s structural integrity was affected by these inserts. Any DFM required for the part will also need to be recorded so that the product’s quality is properly evaluated before its creation.

About Bead Electronics

Bead Electronics is proud to be a manufacturer of pins for dispensing and isolating solenoid valves - particularly those used in ventilators and other life-saving medical devices. As a global manufacturer of electronic connector pins, Bead Electronics has been manufacturing end-to-end, wire and tubular contact pins over 100 years. The award-winning company carries over 500 patents and is best known for inventing its manufacturing process called swaging. This process is a high-speed, virtually scrap-less, cold-forming process capable of producing a wide size range of metal electronic components that are consistent and cost-effective. The family-owned business is led by its fifth generation. Click here to speak to a connector pin specialist today.