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What are Ejector Pins?

11/8/2013 7:54:40 AM | by Anonymous


Ejector pins are long pins used in the injection moulding industry in order to push the final moulded product out of their moulds. They are typically used forcefully in order to eject the solid parts out of the mould and are usually made of high quality steel. They are also known as knockout pins or in simpler terms KO pins.


Typically, the ejector pins are retracted and extended to force the part out of the moulded cavity. They are also the cheapest means of ejection. However, the downside to ejector pins is that they might leave marks behind. This is so they are usually applied only when the parts have sufficiently cooled down in order to avoid deforming any parts. They are usually available in various shapes and sizes. The shapes can vary from bevel headed, straight, cylindrical and round. They can also be customized and engineered to precision just to suit the application they are for. One important factor is to consider choosing their ejector pins depending on the durability, corrosion resistance, tensile strength and tolerance.


It is important to choose the right type of ejector pins for efficient production of the different mould parts applications. There are three different types of ejector pins that are available. Each of which processes their own specific characteristics that are suited for the different environments they are in. The most important factor that differentiates the pins is the temperature at which they can be used. This is because it affects their durability and life span. The pins are specifically made for low temperature environments. They will deteriorate rapidly when being used in a high temperature setting.


Hard pins are good all purpose pins that are treated with heat to be uniformly hard without their diameter. They are typically used during the injection moulding of plastic. They are generally made of steel and can be used in the moulding environment that are below 400 degress Fahrenheit which equates to 200 degress celcius.


Case hardened pins are also nitride H13 pins. They are suitable for die casting. They can be used at temperatures that are above 400 degress Fahrenheit (200 degrees Celsius) and are also quite durable. They are also hard pins that can be tapped or drilled. They also chip easily when compared to through hard pins. Despite all that, they have a greater life expectancy even at high temperatures.


Black ejector pins are the special pins that are developed for the extremely high temperature working environments. They can be used at temperatures from 1100 – 1800 degrees Fahrenheit that is of about 600 -1000 degree Celsius. These ejector pins however have a more unique protection surface coating which allows them to be used at extreme temperatures and at the same time provides self lubrication. They are also more expensive and commonly used within the automobile injection moulding.


Ejector pins can be enhanced on the outlook by coating it with a layer of coat that protects them from damage and making them more durable and longer lasting. The coating also reduces the friction so that the pins will be able to survive the wear and tear which allows the moulded parts to fall out more reliably and easily. Additionally, it makes the ejector pins more chemically inert and stable. Thus, they are able to apply if over treated pins as well.

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