Plastic injection molding presses are used to create an assortment of products. In order to create these products, the right machine has to be selected. For injection molding, there are two types of presses: horizontal and vertical. There are similarities and differences between the two that we will evaluate below.

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Keeping Up With Standards

Horizontal injection molding presses are the most standardized machines used today. The mold opens and closes on a horizontal path as well as the injection unit. In order for these presses to maintain heat stabilization, the sprue bushing stays in contact with the injection unit. Maintaining heat stabilization is key for an ideal injection. This reduces the amount of excess material as well as reducing the common defects. Once the molten plastic has been injected into the mold and is ready for ejection, the horizontal press helps. Since the mold is on a horizontal path, once open, gravity assists with ejecting the part causing it to fall from the mold. Because horizontal injection molding presses are the most common, there is a larger employee base available. In addition, there is more information readily available to educate individuals as well as help trouble shoot any mechanical problems.  



Standing Out From the Rest

In comparison to horizontal presses, vertical injection molding presses are less commonly used. The two presses are similar in the fact that the injection unit is on a horizontal path. Where they differ though, is a vertical press has the mold opening on a vertical path. Vertical injection molding machines are primarily used for products that utilize the concept of overmolding. Overmolding is the process of molding a softer more malleable material over an insert that’s generally a rigid plastic. An example of overmolding is displayed below. There are three different types of overmolding which are insert molding, two-shot molding, and co-injection. These methods vary in the technique at which the parts are molded. The technique of overmolding helps reduce cycle times, which factor into the overall cost. With the mold opening on a vertical path, the machine operator has easier access to the finished parts. Instead of having the pieces fall to the floor, they are handled with more care, which is beneficial especially if there are fragile components. Even though there isn’t a surplus of information on vertical presses, there is still plenty to educate users and help with any mechanical issues that arise.



The Overall Picture

When choosing between a horizontal injection molding press and a vertical one, there are common characteristics to keep in mind. Injection molding presses are characterized by their clamping force and the shot size. Clamping force is the amount of pressure needed to keep the mold closed during the injection process. Generally injection molding presses range from seven tons of clamping force to three thousand tons. The shot size refers to the amount of molten plastic being injected into a mold. This amount normally ranges from an ounce of material to three hundred ounces. There are many factors that influence the decision of using a horizontal injection molding press over a vertical one and vice versa. When choosing a press, make sure that these considerations aren’t being overlooked during phase one of project development.