Injection molding is a process that involves making molten products. Producers usually melt plastic materials before injecting them into a mold and then exposing the molten plastic to extremely low temperatures to cool and solidify them. Injection molding is an area of plastic processing and is suitable for mass production of products, especially those with complicated shapes for complex functions.

What are the six significant steps involved in injection molding?

Injection molding is a repeating cycle. There are six steps involved in plastic injection molding:

  • Clamping
  • Injection
  • Dwelling
  • Cooling
  • Mold opening
  • Removal of products

What machine performs injection molding?

Injection molding is a complex procedure requiring the use is specialized machinery for the production of seamless products. The injection molding machine has a role throughout the process. The two units of an injection molding machine include:

  • The clamping unit
  • The injection unit

What is the role of the clamping unit in an injection molding machine?

The function of this part of an injection molding machine is to open and close a die and eject products. The clamping process leverages two methods:  toggle type and straight hydraulic type.

What does the injection unit of an injection molding machine do?

The function of the injection unit is straightforward. This part of the injection machine works by melting plastics and injecting them into a mold. Plastics melt upon exposure to extremely high temperatures.

A screw in the injection unit allows heat to melt the plastic. Rotating the screw also allows molten plastic to move inside and accumulate in front of the screw.

One critical role of the injection unit is to control the speed by which the screw rotates. Controlling the injection speed is crucial in managing dwell pressure after molten plastic fills out spaces in the mold.

There is a specific fixed value of screw position or injection pressure. This fixed value influences the position of change from speed to pressure control.  

What is a mold?

Manufacturers achieve a product’s fixed shape using a mold. This hollow metal block receives molten plastic, which conducts temperatures during cooling. Afterward, the plastic solidifies, taking the shape of the mold. Temperature control is necessary to manage the solidification process. To achieve temperature control, manufacturers drill holes in the mold.

The only route of molten plastic into a mold is via a sprue. Runners and gates direct the filling of molten plastic into cavities. Moldings are ejected after molds open when the ejector rod pushes the ejector plate. 

Understanding the molding process

There are multiple cavities involved in one injection molding shot. Mass production would not be efficient if cavities were filled one after the other. For this reason, one mold usually has different holes to enable the production of multiple products simultaneously. It is necessary for injection molding to adapt simultaneous filling techniques and manufacturers achieve this by making the length of runners for each cavity equal.

What is the significance of reprocessing in injection molding?

Moldings form after the solidification process. After the ejector plate eliminates the products from the mold, they come attached with sprues, runners and gates. However, these materials do not make up parts of the finished products. Some manufacturers discard these parts after molding ejection. However, most manufacturers prefer a reprocessing approach where the sprues, runners, and gates undergo fine regrinding for reusing as a molding material.

Reprocessing is an excellent source of molding material. Plastics are a limited resource. Therefore, reprocessing spires, runners, and gates is a sustainable business model. However, manufacturers should be keen on how much reprocessed material is involved in production. It is essential to ensure reprocessing materials do not take up more than 30% of the total raw materials to prevent the loss of the original properties of the intended plastic.

Optimal molding conditions to observe

Manufacturers must set specific conditions in an injection molding machine to control production. Molding conditions include cylinder and mold temperature and injection speed. Molding conditions are particular to end products’ desired appearance, dimension, and mechanical properties.

Manufacturers should rely on injection molding machines that leverage the best technology to guarantee the production of desired products. Collaborating with a trusted injection molding provider is key to enhancing the predictability of the process and ensuring top-notch products that will satisfy customers. 

By Manali