Lifter is a common term for mold industry in Pearl River Delta region, which is dominated by Hong Kong-funded mold factories. It is a mechanism used to form internal barb of product in mold design. .

For flat-shaped plastic parts with flanges, if they are ejected with a push plate, they will adhere to mold, and a push block ejection mechanism should be used. Because push block is an integral part of cavity, it should have high hardness and low surface roughness.
There are two forms of its reset: one is to rely on plastic pressure, the other is to use reset rod.

Due to relationship between structural shape and plastic used, some plastic parts should not use ejector mechanisms such as ejector rods, ejector tubes, push plates, and push blocks. At this time, molding inserts or female molds can be used to bring out plastic parts. Ejection block mentioned above belongs to ejection mechanism of molding insert.

It refers to combination of several ejector mechanisms mentioned above to achieve purpose of ejection. Commonly used are ejector and top plate, jacking pipe and top plate.

Compressed air passages and valves are required for air pressure demoulding, which is relatively simple to process, is suitable for light and thin soft plastic demoulding.

When there are inner and outer holes or undercuts on plastic part that are different from mold opening direction, which hinder direct demoulding of plastic part, inclined slider demoulding mechanism must be used. Part that is to be formed with side holes or undercuts is made into a movable core. When plastic part is demolded, movable core is first pulled out, then plastic part is ejected from mold, mechanism that completes extraction and reset of movable core is called core-pulling mechanism.

Principle is same as that of oblique guide post core-pulling mechanism, difference is that oblique guide post is replaced by a curved pin with a rectangular section in structure. Its advantage is that oblique angle can be made larger.

   1. Determine core-pulling distance from shape of product: S-pull = S-barb + (2~3)mm.
   2. According to ejection stroke, calculate angle α of lifter (tgα = S extraction / S top). Value of α should not be too large. If it is too large, bending force of lifter will be large, which will easily lead to breakage. Generally, 3≦ α≦8˚.
   3. Confirm that position of reference point P of lifter in mold is an integer.
   4. Confirm thickness L1 of lifter. L1 depends on actual situation, but this value should not be too small, otherwise strength of lifter cannot be guaranteed.
   5. Break distance H between lifter and mold core is generally 5~10mm (depending on thickness of mold core).

   1. lifter cannot damage other parts of product when product is ejected.
   2. Stealing holes of lifter in body plate should be able to fully accommodate lifter.
   3. Size and direction of sliding groove of lifter seat on upper ejection plate are determined. To make lifter work smoothly, that is, to meet smooth movement of lifter on upper ejection plate and sufficient movement space. Therefore, we need to make sure that space on the side of movement direction of lifter seat should be large, and ensure that L2>S pumping.

 

1. Basic parting (as shown in Figure 1 and Figure 2)
2. R angle processing (Figure 3)
3. Interference 1: Insufficient travel space (as shown in Figure 4)
Solution: (1) Finished product shift or cut meat; (recommended for customers) as shown in Figure 5

 

(2) Make thickness of lifter smaller; (guaranteed strength)
(3) Change direction of core pulling; (lengthen stroke) as shown in Figure 6
4. Interference 2: Along core pulling direction, finished product has a descending arc, and lifter cannot retreat.
Solution: (1) Glue reduction in finished products, (recommended for customers) as shown in Figure 7

 

       (2) Make slope b at the bottom of sloping roof seat to make the sloping roof come out with a delay, as shown in Figure 8
   Requirements: b≧a˚ c≧b˚
5. Demolding angle is ≧2. Due to small core pulling force of lifter, demoulding is difficult.

<4>. Lifter cooperates with male mold

 

1. Basic match (as shown in Figure 9), male mold core is cut with oblique holes.
2. Increase guide (as shown in Figure 10).
    When lifter is wider or mold core (guide) slope is too short, lifter will incline to finished product when it is ejected, which will shorten design stroke and make demolding difficult. Guide should be increased in following forms:
a. Side (single) side plus T-shaped hook;
b. Hook or dovetail slot on the back;
3. Mold inserts (picture 11)
When male mold core is too thick (eg > 150mm), wire cutting machining accuracy (wire bending) will be reduced, processing time will be long, and threading hole will be difficult to drill, so inserts should be considered.

 

Key points: a. Priority is given to round holes, followed by square holes, and then special-shaped holes;
    b.1KP Size and position of stealing holes are checked by double-section method
       (As shown in Figure 12);
   c. Stealing hole must be drawn on assembly plane for inspection
        Whether it interferes with sealing ring, water pipe, thimble, screw, etc.;
    d. Location and size of stealing hole will be rounded first.

<6>. Connection between lifter and ejector plate

Connection 1: lifter and lifter seat are connected with a T-shaped hook (as shown in Figure 13).
        If thickness of lifter is too small, use a single-sided hook; bottom of male mold needs to be added with a wear-resistant plate;
        Reserve 1~2mm at the bottom of top seat for adjustment during assembly.
Connection 2: Lifter dome is connected to lifter seat, and rest are same as before (as shown in Figure 14).
Connection 3: Lifter is lengthened, and lifter is shortened (increased rigidity). Male mold does not need to add wear plates (as shown in Figure 15).

 

 

 

 
Connection 4: Use a round pin with a hook as lifter seat (as shown in Figure 16).