Vertical vs Horizontal Injection Molding for Plastic Components

By Kevin Allison Jan 04, 2021

Vertical vs horizontal injection molding operates according to the same general principles of injection molding (injecting liquid plastic into a mold to take the form of the mold cavity as the material hardens), each one offers unique benefits and application suitability.

The primary difference in vertical vs. horizontal injection molding is the configuration and movement of the mold. In the vertical injection molding process, the mold clamping action occurs vertically, up-and-down. The clamping mechanism and injecting mechanism are located along the same vertical plane. In the horizontal injection molding process, the mold clamping action occurs horizontally, with each half of the mold moving sideways to join. We will now take a closer look at each type of process and the pros and cons.

The Vertical Injection Molding Process

In vertical injection molding, the two halves of the mold move vertically, up and down, to open and close. The injection mechanism is typically located at the top of the mold. Gravity plays a significant role in filling the mold cavities and the injection pressure. This can help with filling time and consistency.

Vertical injection molding equipment is designed with open clamps and rotary tables. This allows for work with multiple molds and simultaneous operations—pre-molding, injection molding, and post-molding. As a result, there is less need for manual operation and intervention, higher efficiency, increased productivity, and reduced costs.

One key difference between a vertical and horizontal mold is that pieces do not automatically fall out of the mold after being ejected (as is the case with horizontal molds). In vertical molds, pieces must be extracted by hand or robotic arm.

Use Cases

Multiple concurrent operations: The design of vertical molds and their use of rotary tables means two bottom halves and one top half can be used in tandem so that pre- and post-molding operations can occur while parts are being filled. This is especially useful in operations such as insert molding or over-molding, where inserts or substrates must be loaded prior to resin injection.
Insert and Overmolding: Vertical molds are ideally suited to insert molding and overmolding due to the configuration of the mold. Inserts are naturally held in place by gravity rather than having to be built into the cavity or use other methods to remain in position.

Pros

More consistent material flow and temperature distribution
Advantageous for insert molding, especially when compared with older or more basic horizontal molding machines
Can easily be manually operated and used with revolving tables to create inlays and combination parts
Machine footprint is half the size of typical horizontal molding machines
Pressure and clamping force required are lower due to the role of gravity in the process

Cons

Manual part removal can be more time-consuming
Parts may be damaged during removal by robots or human operators
Removal timing must be precise, which is more difficult in a manual process
Manual removal step can make for inconsistent cycle times

The Horizontal Injection Molding Process

Horizontal injection molding has historically been the more commonly used type, though that does not mean it is inherently superior. As we continue to examine, each method has distinct applications, pros, and cons.

In horizontal injection molding, the mold opens and closes along a horizontal axis. Due to this configuration, consistent, correct injection pressure is required to fill the mold cavities and help ensure proper packing and cooling. Horizontal molds are typically built with more cavities than their vertical counterparts and are thus able to produce more parts per cycle. In addition — thanks to the horizontal separation of the mold halves — parts from these molds naturally fall out of the cavity upon ejection, and do not need to be manually extracted.

Use Cases

Ideal for cylindrical parts
Typically used for higher-volume production runs
Advantageous for standard molding that does not require inserts or overmolds

Pros

Efficiency in parts produced per cycle
As a more common type of machine, more options are available, such as hydraulic or electric options
Consistent cycle times and continuous operation

Cons

Insert molding is much more complex and inefficient
Machines take a larger footprint than vertical molding machines

As you can see, each process has unique strengths and scenarios for which it is ideal. For example, for insert molding, vertical injection molding will almost always be the right choice.

To learn more about injection molding product from these presses contact Crescent Industries or reference the Complete Guide for Plastic Injection Molding.