Ejector pins are used in injection molding to forcefully eject the solid part from the mold. They come in various sizes and shapes and can be customized. Three types of ejector pins are available, each with specific characteristics and temperature ranges. Thru-axles are good all-purpose studs, case-hardened pins are suitable for die casting, and black ejector pins are for extremely high-temperature environments. Coatings can enhance the pins’ durability and reliability.
Ejector pins are long pins used in the injection molding industry to push the final molded product out of the mold. They are used forcefully to eject the solid part from the mold and are usually made of high quality steel. They are also known as knockout pins, knock-out pins or KO pins.
Typically, these pins are extended and retracted to force the part out of the molded cavity and are the cheapest means of ejection. Pins may leave marks, so they are usually only applied when the parts have cooled enough, to avoid warping of the parts. Ejector pins are available in various sizes and shapes, such as round, chamfered, straight and cylindrical. They can be customized and precisely engineered to fit the application. Important factors to consider when selecting studs are corrosion resistance, durability, tolerance and tensile strength.
It is important to select the right type of ejector pins for efficient part production in stamping applications. Three different types of ejector pins are available. Each type has specific characteristics and are used in different environments. The most important factor that differentiates these pins is the temperature at which they can be used, because this affects their life and service life. Pins made for low-temperature environments deteriorate quickly when used in a high-temperature environment.
Thru-axles are good all-purpose studs that are heat-treated to be uniformly hard throughout their diameter. They are generally used for plastic injection molding. They are made of steel and can be used in stamping environments below 400 degrees Fahrenheit (about 200 degrees Celsius).
Case-hardened pins are H13 nitride pins suitable for die casting. They can be used in temperatures above 400 degrees Fahrenheit (about 200 degrees Celsius) and are durable enough. They are hard pins that can be drilled or tapped. They chip easily when compared to hard pins, but have a longer life expectancy, even at elevated temperatures.
Black Ejector Pins are special pins developed for extremely high temperature working environments. They can be used in temperatures of approximately 1,100-1,800 degrees Fahrenheit (approximately 600-1,000 degrees Celsius). These pins have a unique protective surface coating which allows them to be used in such extreme temperatures and provides self-lubrication. They are more expensive and are commonly used in automotive injection molding.
The ejector pins can be enhanced by a coating that protects them and makes them more resistant. The coating reduces friction so pins survive wear and tear and the printed part falls more reliably. It also makes the posts more chemically inert and stable and can be applied to treated posts.
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