Plastic Injection Molding Overmolding

Due to the popularity among consumers, the application of dual materials has become a major trend in recent years, with a wide range of applications, from toothbrush handles, comb handles, cleaning brush handles, knife handles, scissors handles and other daily necessities to flashlight handles, hair dryer handles, electric iron handles, electric toothbrushes and other small household appliances. Manufacturers have tried their best to add a layer of TPE to make the products more diversified. The market is constantly expanding and its application will also be more extensive.

Generally speaking, TPE dual-material injection molding can produce the following functions in product design:

Make the product surface soft and comfortable
Make the product anti-slip
Improve the product’s impact resistance
Add value to old products and improve product grades

Processing methods

1. Multiple Material Molding

Multiple Material Molding is processed by a multi-material co-molding injection molding machine (Overmolding for injection molded parts). The two-color machine is generally divided into two different designs, such as right-angle shooting table arrangement and balanced shooting table arrangement.

The right-angle two-color machine can be used with a variety of two-color mold operation methods, such as: turntable type, core rotation, core sinking, valve separation, core sliding, etc. Two (or more) plastics are injected into different cavities at the same time to achieve multi-color or multi-material effects.

Its advantages are briefly as follows:

Short production cycle and higher output than traditional methods

More stable product quality, low scrap rate,
Stronger material bonding and fewer defects on the bonding surface,
Can manufacture more complex dual-material products.

2. Overmolding and Insert Molding

Insert Molding is also called the two-step method, which is processed using a general horizontal or vertical injection molding machine. This method requires the use of two sets of molds and two injection molding machines to fix the prefabricated hard plastic parts in the mold cavity of the second set of molds in the form of inserts, and then inject TPE into the hard plastic parts to achieve multi-color and multi-material effects.

In the application of dual-material co-molding, different products will use different hard plastics, such as brushes will use PP materials, while home appliances will use ABS, PC or PA (nylon) materials.

Since the characteristics of each specification or variety of TPE are different, and a single specification of TPE cannot have good bonding ability with every hard plastic, different specifications of TPE are needed to achieve the best bonding effect when matching soft materials and different hard materials.

What materials can be co-molded with TPE?

Polyolefins PP, PE
ABS, PC, ABS/PC
Nylon PA66, PA+GF
SAN, PS, HIPS, PMMA