What is insert molding?

insert molding

What is insert molding

Insert molding is a molding process in which resin is injected into a mold after pre-prepared inserts of a different material are loaded into the mold. Out-sert molding (out-sert molding) is a molding process in which injection molded parts are embedded locally in a sheet metal surface.

The characteristics of these two molding processes:

  1. Manufacturing of complex products: Using the resin’s ease of molding, bending and metal’s rigidity, strength and heat resistance combined with each other to make complex and delicate metal-plastic integrated products.
  2. Electrical product needs: Using the combination of the insulating property of resin and the electrical conductivity of metal, the molded products can meet the basic functions of electrical products.
  3. Rationalization of post-processing: The combination of multiple inserts in pre-molding makes it possible to rationalize the post-processing of the product unit combination.
  4. Multiple options for inserts: The options for inserts are not limited to metal, but include cloth, paper, wire, plastic, glass, wood, coils, and electrical parts.
  5. Simplified post-processing: For rigid molded products and rubber gaskets with curved elastic molded products, injection molding on the substrate to make an integrated product eliminates the need for complex operations to arrange seals, making it easier to automate the combination of post-processing.
  6. High reliability: Due to the joining of molten material and metal inserts, compared with the press-in molding method, the gap between the metal inserts can be designed to be narrower, and the reliability of composite product molding is higher.
  7. Sealing and fixing: For products that are easy to deform and break (such as glass, coils, and electrical parts), sealing and fixing can be realized by selecting the appropriate resin and molding conditions.
  8. Fully encapsulated design: By choosing the appropriate mold structure, the inserted products can also be fully encapsulated in the resin.
  9. Hollow groove design: After insert molding and core hole removal, products with hollow grooves can also be made.
  10. automated production: vertical injection molding machine and robot, inserts, such as the combination of the whole series of devices, insert molding project can be realized mostly automated production.insert molding

Automatic insert molding system design selection considerations

  1. Molding shrinkage test: metal insert molding is prone to molding shrinkage is not uniform, should be carried out in advance of the important parts of the shape, dimensional accuracy of the limit test.
  2. Mold design: metal inserts are easy to deform and shift during the injection process, the mold composition and the design of the mold shape that can easily keep the metal inserts should be considered.
  3. Product quality effect: the contact between metal inserts and the contact between inserts and vibration ball will make the surface of the inserts to produce subtle damage, affecting product quality, the quality of the permissible limit range should be confirmed in advance.
  4. stamping processing effects: should be determined in advance metal inserts due to stamping processing and caused by the amount of jaggedness, warpage, material thickness difference, diameter difference, and so on.
  5. mold structure: mold gate location, molding cycle and other constraints on the mold structure of the predictable matters, as far as possible to solve or have the corresponding improvement measures.
  6. Preheating or drying treatment: It should be confirmed whether metal inserts need preheating or drying treatment to ensure product quality and molding stability.
  7. Use of detection devices: Various detection devices are set up in the mold to ensure the stability of the molding action, and it should be confirmed whether to use them or not.
  8. Anti-accumulation design: In order to avoid the accumulation of metal inserts and fine pieces of molded products in the mold cavity, an air blowing device can be assembled.
  9. Production volume of equipment operation: Due to the high investment price of the system equipment, it is necessary to consider whether to ensure the production volume of the equipment after operation.
  10. Product fixed assets recovery: the use of general-purpose machines, need to confirm the number of varieties of small batch inserts have how many combinations of production, in order to avoid difficulties in the recovery of product fixed assets.
  11. technical decisions: to determine the insert molding rate, productivity and molding cost conditions of a variety of factors and technical decisions.
  12. System combination: the effective combination of injection machine, mold, automation devices and how to function in a short period of time is the key to determine the automatic insert molding system, it is recommended to consult with manufacturers with considerable track record and experience to discuss the choice.insert molding


If your products need to put nuts into plastic parts or need to use insert molding production process, welcome to browse and visit Grand éclat‘s website or factory, we will provide you with professional insert molding production services.

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