Custom Low Volume overmolding injection molding + Secondary Assembly

No MOQ (Minimum Order Quantity)

Fast Delivery Time

Consistent Product Quality

Competitive Price

Professional Services (Before & After Sales)

References from our existing customers can be provided upon request.

Competitive Price + Excellent Quality + Outstanding Services = Happy Customers

Starting from product design validation, prototyping, injection mold fabrication, mass production to secondary or finished product assembly, we offer turn-key contract manufacturing services to our customers.

Whether your program requires a simple single cavity, open and shut mold, or a complex, multi-cavity, multiple action mold, Shenghua has the experience to confidently handle your job.

We have 12 injection machines, ranging from 50 ton up to 450 ton, and can mold single part up to 1.5 kilograms in weight. Our injection shop runs on 2 shifts, 7 days a week.

What's Over Molding

Overmolding is an injection molding process where two materials are molded together. Types of overmolding include two shot sequential overmolding, multi-shot injection molding or insert overmolding.

Multi-shot injection molding injects multiple materials into the cavity during the same molding cycle. Insert overmolding uses a pre-molded insert placed into the mold before injecting the second material. Two shot sequential overmolding is where the molding machine injects the first material into a closed cavity, and then moves the mold or cores to create a second cavity, using the first component as an insert for the second shot using a different material.

Materials are usually chosen specifically to bond together, using the heat from the injection of the second material to form that bond. This avoids the use of adhesives or assembly of the completed part. It can result in a robust multi-material part with a high quality finish.

When designing an overmolded part, wall thicknesses of both the insert and the overmolded component should be as uniform as possible to ensure an even and robust bond. Avoid ribs and sharp corners to reduce flow problems.

Overmolded parts take longer to cool than single shot injection molded part, and cooling systems are less effective. The insert acts as an insulator and heat is less efficiently extracted from the part. However, optimising the cooling system can help reduce the cycle time.

Plastic Injection Molded Parts Quality Control Procedures We Follow:

1. Machine Inspection (On-The-Spot Inspection)

Parts are initially inspected directly out of our molding machine. Our machine operators are trained to identify and rectify the following defects:

1.1.Sink marks that form when the outer plastic shell hardens before the internal plastic has had an opportunity to cool.

1.2.Short shots caused when there is an inadequate amount of plastic material to fill the mold.

1.3.Burn marks caused by trapped compressed air during the molding process.

1.4.Flash marks, which is the excess plastic that extends from the end of the molded part

2. Finishing Station Inspection

Parts at the finishing station are inspected for consistent finishes and textures prior to silkscreen or pad printing.

3. Quality Control Department Inspection

Finished parts undergo one final inspection to ensure tolerances are met for every part. Optical projector and digital calipers measure for part accuracy to within =/-.005mm.

-------------------------------------------------------------------------------------------------------------------------------------

Why You Should Also Consider Importing Injection Molds to Your Own Country for Mass Production?

Not ALL plastic injection molds are necessarily cheaper to stay in China for mass part production, otherwise China would not have become the world’s largest mold exporter.

The following conditions will justify your bringing the molds to your own country for mass production:

1. High production volume and the plastic product is bulky, which translates to high transportation cost, even by ocean shipment.
    
2. Plastic products that do not require lots of labor for assembly, or assembly with many other non-plastic components.
    
3. Plastic product that calls for very short delivery time.
    
4. Plastic products that do not require silkscreen printing, pad printing, heat transfer printing or any other secondary treatments.

If the plastic part or product you intend to develop and produce falls under none of the above conditions, the chances are that it’s better to leave the injection molds in China for production.