Best Injection Molding Supplier in China


At Plus Proto, we also provide Injection Molding services from low volume to mass production for customers. Our experienced specialists can give you the best solutions whether you need rapid tooling or mass production mold making or end-use plastic molding with tight tolerances.


We use aluminum molds for injection molding(Steel is also available). It’s cost-efficient tooling, it also can accelerate manufacturing cycles. Meanwhile, there are more than 200+ metal materials in stock at Plus Porto, we can easily meet all kinds of your applications and industries.


Let’s help you make your idea into reality from your drawings now.

Rapid Prototyping Manufacturer Injection Molding

Additional Injection Molding Options


We also supply 2 variants on the process:  overmolding and insert molding. They are both useful in many industries.




Overmolding is a multi-step injection molding process in which two or more parts are molded on top of each other. Therefore, overmolding is sometimes called two-shot molding which makes injection molding reality to create parts from multiple materials. Compared with other manufacturing methods that require separate creation and assembly of component material parts, overmolding methods are generally cheaper and more effective.


First, the basic component (also called the substrate) is molded and cured. The overmolding substrate is usually made of plastic. Then, the second layer is molded directly on top of the first layer to form a single solid piece. Overmolding is often used to make plastic parts with rubber handles. For example, a toothbrush,  pliers, etc.

insert molding

Insert Molding


Insert molding is another form of injection molding, It is similar to overmolding.  The secondary parts are formed on a substrate.

The difference between insert molding and overmolding is that insert molding is performed using a pre-existing substrate (base or internal components). A prefabricated part (usually produced in a completely different factory or purchased from another company) is inserted into the mold, and then a second layer is formed around it.


Common products manufactured by insert molding such as Electrical sensors, gears, fasteners, and other automotive parts.

SPI Mold Classes


Standard molds are defined by the Plastics Industry Association (formerly known as the Society of Plastics Industry or SPI).  There are 5 classes as following:


ClassCyclesLevel of ProductionUsesCosting
Class 101≥1 millionExtremely highVery high production and fast cycle times The highest cost and made with only the highest quality materials
Class 102< 1 millionMedium to highSuit for parts with abrasive materials and/or tight tolerances  high priced and made with materials of high quality
Class 103<500,000MediumA very popular mold for low to medium production partscommon price ranges
Class 104<100,000LowIdeal for limited production parts with non-abrasive materials low to moderate price ranges
Class 105<500Very LowPrototypes ONLYinexpensively to produce a very limited quantity of prototypes

Injection Molding Materials


  • ABS (Acrylonitrile Butadiene Styrene)
  • HDPE (High-Density Polyethylene)
  • LDPE (Low-Density Polyethylene)
  • PARA( Polyaryl Amide)
  • PBT (Polybutylene Terephthalate, Valox)
  • PC (Polycarbonate)
  • ASA (Acrylonitrile Styrene Acrylate)
  • CA (Cellulose Acetate)
  • COPO (Copolyester)

Injection Molding Finishes Options


  • Mold Standard Fishes: SPI A-1 , SPI A-2, SPI A-3, SPI B-1, SPI B-2, SPI B-3, SPI C-1, SPI C-2, SPI C-3, SPI D-1, SPI D-2, and SPI D-3
  • Polishing
  • Pad printing
  • Silk screening
  • Painting
  • Laser finishing
  • Heat staking
  • Texture finishing
  • Or Other Custom

If you can NOT find your custom materials above, please contact us freely.

Benefits of Cooperation with Plus Proto


  • Rich Experience: Our core team has more than 20 years of Injection Molding experience. We can give professional guidance to you from prototypes to mass production.



  • One-Stop Service: We can give clients the best injection molding solutions whether prototypes or high volume production and any Post-processing, assembling and Sheet Metal Fabrication, etc.



  • Quality Worry-Free: We cooperate with Fortune 500 companies in the world, such as  BMW, TESLA, HP, Samsung, The quality is recognized by them. Our injection molding parts used for many industries.

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