Finished product sticky mold (difficult to demold) refers to a phenomenon in which molded product cannot be taken out of mold.
Depending on conditions such as size and temperature of molded product, poor demoulding will occur when demould resistance increases. Although it is also affected by characteristics of resin and molding conditions, main reason is still shape of molded product and structure of mold. Special attention should be paid to situation when slender reinforcement ribs, wheel hubs and plastic hole bolts are tightly hugged.
When molding shrinkage around plastic hole bolt is too large, holding force of plastic hole bolt will become larger, which is prone to poor demolding. In terms of molding conditions, when mold temperature is low and holding pressure is high, it is easy to cause poor demolding.
When overfilling occurs in erected moldings such as long ribs or hubs, these ribs or hubs will become difficult to fall off, resulting in poor demolding. In terms of molding conditions, when mold temperature is low and holding pressure is high, it is easy to cause poor demolding. This is opposite of holding tightly plastic hole bolt.
If demolding angle of cavity product part is too small, demolding resistance is too large, so demolding failure is likely to occur. Position of ejector pin also has a great influence (it is better to set ejector pin where ejection resistance is too large). In addition, smoothness or damage of surface of mold cavity also affects demoulding resistance, resulting in poor demoulding.
During injection molding, finished product will stick to mold. The first thing to consider is whether injection pressure or holding pressure is too high. Too much injection pressure will cause over-saturation of finished product, which will cause plastic to be filled into other gaps, which will make it difficult for finished product to get stuck in mold cavity and mold sticking is likely to occur when it is taken out.
When temperature of material pipe is too high, two phenomena usually occur. One is that temperature is too high to decompose plastic and lose its original characteristics; and it will break or tear during demolding process, resulting in mold sticking. Second is that rubber material is not easy to cool after being filled into mold cavity, and cycle time needs to be increased, which is not economical. Therefore, it is necessary to adjust its operating temperature according to characteristics of rubber material.
As for problem of mold, if feed port is not balanced, it will be easy to stick to mold when finished product is demolded. At this time, improvement measures must be made on mold.

 

(1) Filling is too full, reducing injection dosage, time and speed
(2) Injection pressure or barrel temperature is too high, reduce injection pressure or barrel temperature
(3) Holding time is too long, reduce holding time
(4) Injection speed is too fast, reduce injection speed
(5) Uneven feed makes part too full, change size or position of overflow
(6) Insufficient cooling time, increase cooling time
(7) Mold temperature is too high or too low, adjust mold temperature and relative temperature on both sides
(8) There is an undercut in mold, repair mold to remove undercut
(9) Unbalanced feed inlets for multi-cavity molds, or unbalanced feed inlets for single-cavity molds; limit plastic flow, as close as possible to main runner
(10) Poor design of demoulding and exhaust of probe tube, providing sufficient escape air passage
(11) Screw advance time is too long, reduce screw advance time
(12) Mold center is misaligned, adjust mold center, and use "back dial" angle to lock it
(13) Surface of mold is too rough, polish surface of mold cavity and spray a release agent

1. Runner is too large, modify mold
2. Runner is not cooled enough, extend cooling time or reduce temperature of material pipe
3. Demoulding angle of runner is not enough, modify mold to increase angle
4. Concave arc of runner and nozzle are not matched properly, readjust and match
5. Inner surface of runner is not polished or has demoulding angle. Check and repair mold
6. Outer hole of runner is damaged, check mold
7. No sprue grab lock, add grab lock
When demoulding resistance caused by tightness of plastic hole bolt is too large, method of suppressing molding shrinkage by increasing holding pressure and mold temperature is also effective.
On the contrary, if size increases due to overfilling and is embedded in cavity, holding pressure and mold temperature should be reduced to increase amount of molding shrinkage. When demoulding resistance caused by tightness of plastic hole bolt is too large, method of suppressing molding shrinkage by increasing holding pressure and mold temperature is also effective.
Increase demolding slope at periphery of mold cavity, hub and ribs. Especially in the case where it is already firmly embedded, it is necessary to add ejector pins and other methods to configure ejector pins for parts that need to increase ejection strength.