Ejector bushings, also known as the guided ejector bushings, are specifically designed to hold the ejector assembly along with the ejector pins in injection molding, to prevent the ejector plates from potentially cocking. In short, a guided ejection system improves the longevity of a mold.
It is often recommended that a minimum of four ejector bushings are used. Solid aluminized bronze, steel, and self-lubricating ejector bushings are able to reduce wear on ejection mold components.
Following the above, a guided ejection system (which involves the use of guided ejector bushings) basically holds the ejector assembly in alignment and support the weight of the ejector plate through molding cycle, which in turn reduce wear on ejection components significantly.
The aforementioned system can typically be of two configurations. For the first one, the ejector housing can be removed from the mold without removing ejector plates when ejector pins are installed in the support plate. This enable easy access to service the guided ejector system.
As for the other alternative, ejector pins are installed in the ejector housing to allow faster installation. The complete ejector assembly is removed as the ejector housing is removed from the mold base.
Despite the seemingly insignificant look, guided ejection bushings actually have many great features. Ejector bushings are often characterized by the superior strength, attributed by the steel body and the non-scoring lubricity of bronze plating. The internal oil grooves and the lubrication hole are able to ascertain smoother moulding operation. A handful of ejector bushings’ key features are listed in line below:
● Ejector bushings are able to hold the ejector assembly in alignment, along with all of the ejection pins of all standard sizes in the injection assembly system.
● Ejector bushings are capable of supporting the weight of the ejection assembly throughout the whole cycle.
● Ejector bushings, especially the ones that are lubricated, or made of aluminized bronze or steel, to minimize the potential wear on ejection mold components in an ejection assembly.
● Ejection mold components of different sizes may cause the displacement of ejection plates. Ejector bushings are useful in this respect as to preventing the ejector plates from cocking.
As mentioned above, you should always have at least four ejector bushings installed in your injection assembly. The size of the ejector bushings is typically determined by the size of the injection mold. Ejector bushings, as a part of the guided ejection system, is extremely inexpensive yet possessing the superior capability to protect the ejection mold components against wear, which can save you from the potentially significant cost due to mold damage during the production.
To elaborate further, when guided ejector bushings and guided pins are installed within the ejector housing, it is referred to as the guided ejection system. Although guided ejection systems involving guided pins and guided ejector bushings can significantly increase the lifespan of a mold, the cost increase respectively, too. So, as a common question posed by many: when are the guided ejector bushings needed and when are they not?
To answer the above question, we need to first understand the advantages of a guided ejection system. Simply put, the components along with the guided pins and guided ejector bushings inside offer substantial support, guides and aligns the many connected components including ejector pins, sleeves, return pins, blades, lifters and so on.
Again to break this down into a simple-to-understand language, the answer to when a guided ejection system should be used can be broken down into four key factors:
1. You need to determine the expected or desired longevity of the mold.
2. You need to determine the weight of the ejector plates in order to evaluate the desired weight capacity.
3. You need to evaluate the complexity of the ejection configuration, including the quantity and arrangement of the ejection components.
4. You need to determine how hard the core inserts are.
It is imperative that you assess whether or not a guided injection system is needed based on the factors we provided above because there have been many reported cases in which unguided aluminum molds have flash and ejection issues within a very short period of time. In other words, the resulting lifespan was a disaster because the possible need of a guided injection system is neglected. Based on reliable sources, wear problems of mold can typically start to occur after around 25,000 cycles. Therefore, it is always better to deal with the upfront cost than having to deal with the repair cost later on. Because in most cases, the former will outprice the latter.
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