Central ejector

The central ejector pin b is actuated at an adjustable position of the opening movement or after entry of the robot arm. The ejector pins g which are attached in the ejecting plate are pushing the injection molded part off the core and hand it over to the demolding robot. To avoid bending under the influence of cavity pressure, the ejector box i has to be designed sufficiently stable which means to keep relatively small distances between the support bars k and possibly by means of support pins c. 

The larger rifles such as the familiar military rifle use cartridges of the type shown in Fig. 19.3. The relatively heavy base contains centrally a pyrotechnic percussion igniter (cap) and also a rim on which the ejector mechanism operates. Bullets can be made of various materials, but the detailed construction depends on whether they are to be used for armour piercing, anti-personnel, incendiary or tracer purposes. In operation, the primer is fired by the striking pin of the rifle, the propellant ignites and the... 

Part of the products of combustion from the lower burners rises up the kiln to the upper burners. The remainder is drawn down the kiln and into the central cylinder, together with the cooling air. The necessary suction for this flow is provided by an air-operated ejector. The resulting mixture of kiln gases and cooling air has a temperature of about 900 °C and serves to moderate the flame temperatures in the lower zone to about 1350 °C. 

Ejection of a molded plastic article from a mold can be achieved by using ejector pins, sleeves, or stripper plates. Ejector pins are the most commonly used method because they can be easily fitted and replaced. The ejector pins must be located in position where they will eject the article efficiently without causing distortion of the part. They are worked by a common ejector plate or a bar located under the mold, and operated by a central hydraulic ejector ram. The ejector pins are fitted either to the bottom force or to the top force depending on whether it is necessary for the molding to remain in the bottom half of the female part or on the top half of the male part of the tool. The pins are usually constructed of a hardened steel to avoid wear. 

Finally, another difference fi om Power Leads and Ejectors side is the sensitivity to air stoichs at the Ejectors side at the boundaries they show a not significant effect the same sectors are the ones with the highest sensitivity to overall FC, which could represent a predominant effect. Moreover, the center rows result to be the most sensitive to a variation of the air stoichs this can be linked to the fact that the air is introduced from the piping in the center of a plenum over the stack, and next it is sent to the sectors in this way, the central sectors receive a greater air flow whereas the edge sectors receive less air. This effect is less pronounced in the Power Leads side. 

Ejectors mostly consist of a pole and a plate to reduce the surface pressure to the foam. They can be driven by using the machine movement using starting strips or plates, bowdens with central operation, or pneumatically, using nonsynchronized individual drives. The resetting is obtained with a spring. 

These precision components are centrally located in pairs or eccentrically positioned. They are actuated by a hydraulic machine ejector, the ejectors of the injection mold, and through the opening movement of the machine. Resetting is performed through the ejector hydraulics of the machine or mechanically through back pressure pins. 

The vacuum system is provided independently for each column and usually consists of a mechanical vacuum pump and a steam ejector to achieve the highest vacuum. A centralized vacuum system is not recommended, as a process upset in one stage can readily affect the other stages. The heat source can be a shell-and-tube heat exchanger using thermal oil. 

The mould plates carrying the moulding nest can be thoroughly bent in an area of the central bores and, above all, in the area of the ejector system, rmder the effect of the internal mould pressure. Thus, the mould plates must have sufficiently high flexural strength, if the formation of scratches is to be avoided. This danger is especially great for the mould plate on the ejector side. So, if possible, additional support columns, with an oversize of 0.03-0.05 nun, by comparison with the external supports, should be incorporated. 

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