In this series of articles, we are going to offer all the basics that are needed to get introduced to the process of custom plastic injection molding. This very specific skill can be handled by anybody with a penchant for craftsmanship, patience and the right tools. Over the next few lines we are going to explain in a very simple way the basic concepts behind the process, so take a seat and read the info the get started!
The Process of Injection Molding
This is the first thing we need to know. Injection molding is a simple process used to obtain a molded product by injecting plastic base materials that are heated up until they are melted and poured on a mold. After that, the mold is cooled down to make it solid and get a finished product. The original process is rooted in the fierce competition sustained in 1868 by billiard ball makers Phelan and Colander against John Wesley Hyatt and his brother Isaiah. Each entrepreneur was looking to develop a new method to make billiard balls more affordable while retaining their quality.
The Hyatt brothers came up with an injection molding machine that was able to handle melted plastics. The setting of the device was rather crude but very effective. It worked using a plunger of their own design to inject plastic into a mold through a cylinder that was specially crafted to handle enormous amounts of heat. They patented it in 1872. An innovator named James Hendry revamped the machine in 1946 by replacing the plunger used on the original design for an auger inside the cylinder. The new device could mix the plastics before being injected into the mold. The redesign landed him a good patent that became the standard to these days.
The Modern Injection Molding Machine
In modern times, injection molding machines are divided into 2 units that work the same process. The first one is the clamping unit. The second one is the injection unit. The first one handles a die that closes and opens to eject materials. The clamping unit can toggle the materials, or it can place them directly into the injection unit with the help of a hydraulic circle. The second unit is the one that handles the melting process and the pouring of the melted plastics into a mold. The process begins when a screw is rotated to melt the materials and place them into a hopper until it accumulates.
Once there is enough molten plastic in the hopper the injection process can begin. If you are working with an industrial model, you can set up automatic handling of the speed the injection process needs to go. If you are making something a bit more complex, you can handle the injection speed manually to have more control over the pressure applied on the plastic to get to every corner of the mold filled to get a clear finish delivered on your end with no gaps or holes. The key is handling the speed and the pressure in certain positions that will give you a fixed value on your product.