What is Lifter of Injection Mold?

The lifter is a mechanism used in injection molds to solve the problem of product inner concave or undercut structure demolding. Its working principle is composed of an ejector pin and a slider designed with an inclined angle, which is installed on the movable side of the mold.

When the mold is opened, the thrust of the ejection system causes the lifter to move in the inclined direction, completing the two actions of lateral core pulling and ejecting the product at the same time. The main functions of the lifter include:

Lateral demolding

When the product has an inner concave or undercut, the lateral movement of the lifter can avoid structural interference and ensure smooth demolding of the product.

Ejection damage prevention

Eject the product while moving sideways to avoid deformation or damage to the product caused by hard top.

Simplified mold structure

The lifter can replace the complex slider mechanism and reduce injection mold costs. The design of the lifter usually needs to consider its inclination angle, which is generally designed to be 3°-15°. Too small an angle may lead to insufficient movement distance, and too large an angle may easily cause jamming, which needs to be calculated in combination with the product demolding stroke.

Precautions for designing a sloping top

Determine the sloping top area and undercut size.
In general, the ejector is fixed with a 6MM ejector pin.
For high requirements for the export mold, it is fixed with a fixed block, which is convenient for disassembly and assembly.
The top surface of the sloping top is the parting surface, and the sloping top can also be fixed with M8 screws.
For high requirements for the export mold, the sloping top should be designed with 2 guide sleeves, and domestic molds generally do not have this requirement.
For sloping tops with large molding areas, water channels should be designed.
The water channel is generally designed to be connected from the top of the ejector plate.
For particularly large sloping tops, the slide seat should be fixed in the middle of the upper and lower ejector plates.
And design a water channel, the water channel is from the bottom Ejector plate connection.
For integral lifters, an I-shaped seat should be designed.
If the lifter is relatively thin, the I-shaped seat should be raised to increase the strength of the lifter.
The I-shaped seat should not exceed the bottom surface of the movable mold.

Two-stage lifter structure and application occasions
In mold design, if you encounter a situation that is not easy to achieve with a conventional lifter structure, you can consider the two-stage lifter structure to achieve a simple and practical mold structure.

Applicable occasions for two-stage lifter

When the lifter size is relatively small or the space for the lifter movement is insufficient, in some molds with small lifter undercuts and a large number of lifters, such as laptop computer shell molds, it is of great practical significance and can simplify the rear mold ejection mechanism.

Limited scope of use of two-stage inclined top

The lifter angle cannot be greater than 5 degrees to prevent the sliding of the lifter (or inclined top slider) and the ejector head from increasing friction and being unable to be realized.
The undercut of the molded product cannot be greater than 2mm. Due to the limitation of the lifter angle, if the product undercut is too large, the ejection stroke and the sliding distance between the ejector and the lifter will increase, and the lever effect of the ejection force will increase, which will reduce the reliability of the mechanism action.

Commonly used two-stage inclined ejector structure

Application one of two-stage lifter:
This structure is suitable for situations where the size of the lifter is not greater than 5mm.
Pin: There must be a block at the front and rear ends of the pin to prevent the pin from falling off during mold use.
Ejector tube position: It guides and positions the ejector and supports the injection pressure on the lifter.
Ejector: The ejector must be rotated 90 degrees to hook the T-slot of the lifter slider during mold assembly.
Ejector slider: The lifter slider and the lifter are connected as a whole with a pin.
Ejector: The angle of the inclined ejector cannot be greater than 5 degrees, so as to avoid the sliding of the lifter slider and the ejector head due to increased friction.
Application two of two-stage inclined ejector:
When the size of the lifter is relatively large, you can consider sliding the ejector directly in the T-slot at the bottom of the lifter.
① When the size of the lifter is greater than 10MM:
② The lifter can be installed from the bottom of the mold, and the bottom end of the lifter is enlarged.
The third application of the two-stage inclined top:
When the above two structural forms are difficult to implement, the situation of using a spring pin or a reset pin to reset the inclined top can be considered (the ejector pin and the inclined top do not need a T-slot connection).
① When the inclined top and the front mold have a penetration surface:
② When the inclined top and the front mold do not have a penetration surface