Lifter is one of mechanisms of mold. Before designing, make a systematic analysis of product structure. According to product structure, mechanism introduced to deal with some undercuts (mechanism for handling undercuts also has a slider). So what is difference between slider and lifter?
Basic principle of lifter and slider is to change vertical movement when mold is opened to horizontal movement. The biggest difference lies in different driving force sources: lifter mainly moves by movement of ejector plate. It is not like slider is moved by opening and closing of male and female molds. Therefore, design of lifter is related to stroke of ejection pin plate. This is the biggest difference between lifter design and slider design.
Lifter mechanism is composed of following basic mechanisms. Each mechanism is described as follows:

 

Lifter (a mechanism for handling internal undercuts in finished products)
Lifter is one of processing methods of finished barbs,
Types are:
1. Integral
2. Two-stage
3. Lifter of female mold

A. lifter stroke = undercut distance + safety value
(Products with a safety value of 0.8～1.5 can be increased appropriately)
B. lifter angle tanθ(3.～22。)= lifter stroke/ ejection stroke h
C. Check whether there is interference when lifter moves backward.
1.EH>H
2.[endif]EH*tanθ>S
3.[endif]PH-CH>EH
4.[endif]PW=LW+(2～4)mm
5.

 

Design Points:
Lifter is basically a kind of deformation of ejection system, so the first consideration in design of lifter is ejection stroke EJH. Three key items should be considered in ejection itinerary:
1. Ejection stroke EJH must be able to eject finished product out of parting surface, so distance must be greater than height H of finished product
2. Ejection stroke should not be too long, if it is too long, lifter will fall out of mold. Therefore, actual ejection stroke EH must be less than height of lifter. For safety, designer can install a limit block on ejector plate to ensure that ejection distance is only EH when ejecting.
3. Ejection stroke is matched with lifter angle, and finished product must be able to leave undercut position of mold, so actual ejection distance EH * tan (lifter angle θ) must be greater than undercut stroke S.
4. In order to ensure that when finished product is ejected, distance that lifter stays in mold is long enough to prevent lifter from leaving mold, so height of lifter LH must be at least twice height H of finished product.

 

 

Example one (ejection pin type)
When we design lifter, first consideration is which method is more suitable for ejecting undercut. As shown in left picture, there are many undercuts, but stroke of finished product is not large and height of finished product is not deep. Using ejection pin type to occupy a small area on male mold plate and ejection pin plate, will not interfere with lifters, so we can use design method as shown in figure below.
As shown in figure "a":
Finished product size: 240*287*7.4
Lifter: 22
Back hook stroke: 0.65mm

 

Example 2 (ejection pin type)
Use ejection pin-style lifters, which are generally used as guide grooves,
If there is no interference, diameter of ejection pin should be 6 or more, and ejection pin cannot avoid air on male mold plate!

 

Example three (ejection pin type)
As shown below:
A: Width of groove (3～8)mm
B: Width of lifter = width of undercut position + (5～8)mm
C: Depth of upright position (5～10) mm, PL surface should be rounded to the nearest integer!
D: Slope of lifter (3.～8.)

 

Example four (ejection pin type)
Under normal circumstances, lifter designed by us can be extended to bottom surface of mold core, but sometimes due to factors such as insufficient travel, we must extend a section in male mold plate when designing, as shown in left picture:
Product height is 10mm, and actual ejection stroke is 20mm,
When designing lifter, finished surface end is kept in a straight position, which is convenient for processing and coordination!
Straight body depth is generally taken down from parting surface, and ejection pin must be positioned to prevent rotation.

 

If finished product (point A in figure below) has been installed with lifter, try not to install ejection pin on left and right sides of finished lifter (about 20mm). Ejection of finished product at this place is completed by lifter alone.

 

As ejector moves slightly slower than ejector pin, if ejector pin is too close to oblique ejector, part of finished product is pulled by oblique ejector and another part is pushed out by ejector pin, which will easily cause finished product to become white (such as Right picture).

 

Example one (lifter seat type)
Lifter is linked with lifter seat by a pin, and lifter seat is fixed on upper ejection pin plate.
This lifter movement is relatively stable, but lifter seat occupies space of ejection pin plate, which can be used for molds with fewer lifters.

 

Example 2 (lifter seat type)
As shown in the picture on the right: Undercut stroke of this finished product is too long. We use method of extending lifter to ejector plate to increase lifter stroke. Corresponding lifter seat only needs to be made for a short period of time!
When designing lifter, we try not to design lifter on broken surface of finished product and forming position (it will be deformed). For example, drafting angle must be made at forming position!

 

Example three (lifter seat type)

 

Example four (lifter seat type)
As shown in figure "a", this barb is ejected by lifter seat method, but it may interfere with finished rib when it is ejected. Thickness of lifter will be very thin during design. If strength is not enough, it will break!

 

Integral lifter is suitable for finished products with large and deep products, large undercut strokes.
In design, thickness of lifter should not be too narrow, (if it is too narrow, strength is not enough, and it is easy to break).

 

Example 1 (Integral)
In Figure a, "[if !vml][endif] ”means that there is an undercut to remove lifter, number of lifters is so large, you can consider following lifter mechanism,
Finished product size: 400*357*47
Lifter: 19
Back hook stroke: 1.25mm

 

Example 2 (Integral)
1. Lifter is fixed on upper ejection pin plate to save space of ejection pin plate.
2. Straight body position is convenient for processing and positioning.
3. Lifter is too long to add channel block.
At present, most of methods adopted for lifter of LCD rear shell are integral type (or ejection pin type).

 

 

Example 1 (Lifter of female mold)

 

Style of lifter can be various, and it is necessary to select appropriate structure according to characteristics of product, and use it wherever it is.