A Guide to Plastic Molding Techniques
Plastics are compounds that are nonmetallic and synthetically produced. After a molding process that shapes them into whatever a client requests, these products are then hardened to be commercially used.
We are surrounded by plastic products on a daily basis but may not know the process in which they are made. Some examples include:
- Automotive Parts
- Kitchen Utensils
- and much more!
With so many different types of products being made from plastic, it is valuable to know the difference in manufacturing methods.
When a plastic product is produced, it can be formed by 1 of 7 different plastic manufacturing methods including:
- Rotational molding
- Structural foam molding
- Compression molding
- Blow molding
- Injection molding
Let’s take a deeper look at some of these techniques.
The Most Popular Plastic Molding Techniques
During the process of injection molding, a mold cavity is filled with molten resin. This is one of the most common methods of plastic molding, and it is the most often used method when it comes to either mass producing items or prototyping products. Plastic injection molding can be utilized to produce products and components to support a wide variety of industries.
Blow molding is similar to injection molding in many ways, except for the fact that molten resin isn’t injected into a mold; rather, it is vertically poured out of a barrel in a molten tube. The mold then closes in on the tube and forces air into the resin, which causes it to expand outward so that it conforms to the shape of the mold. The hollow part then forms when it is cooled. Some common examples of products made by blow molding include containers, tubes, and bottles.
Compression molding is a little bit different from the previous two. It starts when a hard plastic slug is put between two halves of a heated mold, which are vertically pressed together to mold the part. This is contrary from other types of plastic molding that use a horizontally closing mold press. Once the parts are formed, they are air-cooled. One main benefit of compression molding is that the price for this method tends to be very moderate.
Gas Assisted Molding
Gas injection molding is used to produce plastic parts that have hollow interiors. A mold cavity is partially filled with a shot of plastic. The remainder is then “topped off” with a high-pressure gas-powered injection of plastic. The gas is the “assistant” used to complete the mold.
This method of production involves hollow molds being packed with a powdered plastic. These molds are then secured to spokes resembling pipes which extend outwards from a central hub. The molds begin to rotate on some different axes at once, and the hub is used to swing the mold into a closed-off furnace room. This causes the powder to melt and stick to the insides of the molds.
Structural Foam Molding
With this method, the walls of a part are made thicker by introducing a small amount of chemical foaming agent into the plastic material. Foaming then begins to happen once the mold cavity fills up with the melted plastic material. It’s after this that a thin plastic skin begins to form and solidify against the wall of the mold.
Thermoforming involves sheets of rigid plastic which are pre-extruded. These sheets are then heated horizontally and sucked down into a hollow one-piece mold. Once the hot plastic has solidified, its shape then conforms to the shape of the mold. The tooling costs for thermoforming tend to be on the low end, and piece prices will vary based on the kind of machinery that is used.
As you can see, there are a handful of plastic molding techniques that are used to make products. Some of these molding techniques are perfect for one application but may not be useful in another.
Now that you have read this article, you should have an understanding of the many molding techniques used to form plastic parts.
Learn More from New Berlin Plastics:
- Overview of 3D Printing and Injection Molding
- Cold Runner and Hot Runner Injection Molding: Benefits, Drawbacks, and Applications
- Brief Guide to Tooling Design and Maintenance
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