Molded ejection mark

This arrangement has the added advantage Aat Ae rib can be ejected from to lowest point, and it should ensure Aat Ae rib will not remain stuck in Ae mold at ejection. On Ae down side, Ae addition of Ae stud will fractionally add to Ae molding cycle because of the increased mass and to possibility of a sink mark, but it is better to mold somewhat slower Aan to be uncertain wheAer Ae piece, as designed, can be molded at all. 

Ejector pins often leave compression marks on the molded article. They should not be used on the visible part of the article, if this can be avoided. Another example of an ejector is the sleeve-ejector (Figure 4-12), which is able to transmit greater ejection force. Slccvc-ejectors are primarily employed with moldings, which are axially symmetrical. 

Ejector locations. Ejection devices for plastic parts can range from screwdrivers used to pry parts out of a hand mold to mechanized stripper plates and elaborate mechanisms which also retract collapsible cores. All of them share one common characteristic they exert pressure on a newly formed part. That pressure can distort the part to the point of disturbing its function or appearance if it occurs while the part is still too soft to withstand it. Therefore, the processor must delay ejection until the moldment can endure it. The more ejectors there are, the more ejection surface there is to distribute that pressure and the sooner the part can be removed from the mold, thereby shortening the molding cycle. However, ejectors cost money and leave marks on the surface of the moldment. Therefore, there is a mold cost associated with a faster molding cycle. (Differences between bidders on a project are often based on variations in cooling and ejection systems.) Additional ejectors leave more marks on the surface and their number and location may be limited by functional and appearance concerns. 

A diagram of the injection molding process is shown in Figure 6.22. The extruder is similar to other fabrication techniques where the granular resin enters a hopper, where the material is transferred to a heated barrel and a reciprocating screw moves the molten plastic to the molding cavity. The molding cavity is unique to this process. The molten polyethylene is forced xmder pressure into a closed mold that is continually cooled. After the molded part cools, the mold opens and the fabricated part is ejected from the mold. An injection molded article can usually be identified by the ejector pin marks that are usually present on the molded part. 

The spectrum ranges from pre-defined molds in various panel specifications and steel grades to guide eiements, components for marking of plastic components and their traceabiiity, various eiements of ejection from simple to complex geometries and special temperature connections, and many other parts for tool and mold making. 

Ejection is the name given both to the process of removing the molding from the mold and to the means by which it is done. Ejectors inevitably leave witness marks on the molding, and this alone may determine the disposition of the part in the mold. Once that basic choice has been made, there is usually not much further freedom to position ejectors in cosmetically acceptable positions. The choices are much constrained by other features in the mold and the need to put ejectors where they are most needed to overcome the resistance of the molded part. 

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... 

The breakdown of the timing for each step is illustrated in FIGURE 2 by plotting temperature and pressure inside a flat plate mold against time. FIGURE 2 also shows that the part sticks to the side of the mold on which the thermocouple is located therefore no sudden temperature drop is observed when the mold separates. Two small bumps on the pressure curve represent mold separation and the part being ejected (21 second and 28 second mark). 

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