How to Properly Set Up the Exhaust Slot in the Injection Mold

How to Properly Set Up the Exhaust Slot in the Injection Mold

In the intricate world of injection molding, the often-underestimated vent slots play a pivotal role in shaping the quality of the final product.

Overlooking the significance of exhaust slots can lead to defects such as incomplete filling, surface blemishes, and even burn marks caused by trapped air.

However, these slots are not just about preventing defects; they are key to enhancing overall productivity, making the molding process smoother, faster, and more reliable.

As we dive into the nuances of setting up exhaust slots, it becomes evident that this seemingly minor component holds substantial power in the realm of injection molding.

The Critical Role of Exhaust Slots

The Critical Role of Exhaust Slots

Defining the Exhaust Slot

Exhaust slots, also known as vent grooves, are precision-engineered channels strategically positioned in the mold design. Their primary function is to serve as an escape route for air and gases trapped in the mold cavity during the injection process.

Functions of the Exhaust Slot

The exhaust slot’s dual functions are crucial:

a. Removing air from the mold cavity during molten material injection.

b. Eliminating various gases generated during the material heating process.

Proper understanding and implementation of exhaust slots are particularly critical for thin-walled or precision parts, as they help avoid surface burns, insufficient injection volume, and eliminate various product defects while reducing mold pollution.

Setting Up the Exhaust Slot

Factors Influencing Design and Placement

  • Mold Size and Complexity: Larger molds and those with complex geometries may require strategically placed exhaust grooves to effectively remove air and gases.
  • Type of Material: Material behavior under pressure and heat influences exhaust groove size and location.
  • Flow Path of Molten Material: The material’s flow path into the mold cavity determines where air is likely to be trapped, guiding the placement of exhaust grooves.

Impact of Mold Cavity Design

Impact of Mold Cavity Design

A well-designed mold cavity ensures efficient exhaust groove placement, reducing the likelihood of defects like air pockets or surface imperfections.

Optimizing Exhaust Slot Placement and Size

  • Guidelines for Size and Position:
    • Size: Large enough to vent air and gases effectively but not so large that it causes material overflow.
    • Position: Typically at the end of the flow path and on the parting lines, depending on mold design and material flow.

Impact of Mold Cavity Design

  • For Product Molds with Complex Shapes:
    • Determine the opening of exhaust slots after several mold tests.
    • Address shortcomings in mold structure design, particularly poor exhaust.

  • Exhaust Methods for Integral Cavity Core:
    • Use grooves or insert installation positions.
    • Utilize side insert joints.
    • Create a spiral shape.
    • Install slotted slat cores in the longitudinal position and open process holes.


Properly setting up exhaust slots is not merely routine design but a strategic decision with a profound impact on product quality, production efficiency, and mold longevity.

In the intricate dance of injection molding, where precision is paramount, exhaust slots play a key role, showcasing that even the smallest details contribute to the pursuit of perfection.

FAQs Section

A1: Proper exhaust slots ensure efficient removal of air and gases, preventing defects and enhancing overall production efficiency.

A2: Mold size, complexity, material type, and the flow path of molten material all influence the size and placement of exhaust slots.

A3: Properly set exhaust slots reduce injection pressure, time, and holding pressure, leading to improved production efficiency and reduced costs.

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