Ejection pin

Other techniques used for venting include very shallow, flat areas machined on the surface of several ejection pins or, for extreme cases, the use of vacuum to exhaust the air just before injection (See Fig. V.3.). If vent holes or channels are made in the mold they should not be over a few thousandths of an inch in diameter, or in depth, to prevent the resin from entering and clogging the vent. 

Sleeve Plates. These are located between the core and cavity plate. It can eject the part itself or contain a number of separately mounted sleeves as required in multicavity molds. Sleeves often are used for circular parts with an undercut in the core section or where core pins prohibit use of ejection pins. The sleeve surrounds the core in a flash free fit. When activated on the opening stroke of the press, the sleeve moves forward beyond the core, stripping the part from the mold. This requires a taper match between the sleeve and core generally about 3-10 deg per side to eliminate wear. 

The hydraulic pressure or mechanical pressure is applied to make sure all of the cavities within the mold are filled. Plastics are allowed to cool within the mold. The mold is opened by separating the two halves of the mold. The product is ejected from the mold with ejecting pin. The runners and sprue are trimmed off and recycled. 

Increasing the size of pins or considering the use of pneumatic air ejection to assist in component release may help to solve the ejection pin marks problem. Flow chart 5.2.17 shows the way to approach the problem of ejector pin marks. 

It is important that a mold can be easily opened and the manufactured part easily ejected from the mold. Ejection pins are built into the mold to... 

Normally, the ejection pin and a sliding sleeve, which are positively connected by segments, drive the first stroke (stroke 1) together. At a defined position, the taper bush strikes and the segments now combine the taper bush and the sliding sleeve with each other and release stroke 2. The initially operated ejector plate is fixed. Both stroke lengths are completely controlled. Also, delayed ejector movement can be implemented without problem. 

At the end of the cycle, when the mold is opened, the remaining polymer solidifies into a disk shape cull). It is removed as a single piece along with the sprue. The part is removed by lifting the middle section of the mold followed by ejection pin action. In the transfer molding method, it is desirable to keep the sprue and the cull attached, contrary to injection molding. 

Increasing the number of the vents (eg. eject pin or inserts) at the vicinity of the weld line will dispel gas from mold cavity more easily. However, these extra vents will leave marks on the product surfaces, especially for... 

Figure 5 shows febricated mold system in this paper. For ejecting the molding product smoothly, 22 ejecting pins are used. Heating cartridge and thamocouple are used to control the mold temperature. 

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