Preface：Plastic stuff is used in a lot of different industries, from things in your house to things in hospitals, cars, and more. That’s why plastic injection molding is a big deal in a lot of different fields. If you’re wondering “What is Injection Molding?” then you’re in the right place.In this article, we’re going to go over the basics of the injection molding process. It’s a good process, but you have to control it right to make good stuff. So, we’re going to walk you through the process and give you some tips to make the most of injection molding.

What Does Injection Molding Mean?

Injection molding is a process used to make plastic parts. It works by melting plastic pellets and injecting the molten plastic into a mold. The plastic then cools and solidifies in the shape of the mold. Injection molding is a great way to make a lot of parts at a low cost. You can make parts with all kinds of shapes, including parts with complex shapes.

The Five Major Elements of Injection Molding

Injection Molding Materials

The most important thing in injection molding is the plastic. Different plastics have different properties. Picking the right plastic will make sure your part works and looks good.

Injection Molding Machine

The injection molding machine is the most important part of injection molding. It heats up plastic and then squirts it into the mold to make parts. The machine has a bunch of settings that control how it works. Some of the settings are how hard it squirts the plastic, how fast it squirts the plastic, and how much plastic it squirts.

Mold

The mold is the thing that makes the part in injection molding. If the mold is bad, the part will be bad. The mold is made out of metal and has to be made really good. The metal, how it’s made, and how good it is all matter.

Injection Molding Process Parameters

Process parameters are parameters that affect the key links such as melting, injection, and cooling of plastic materials during the injection molding process, including injection pressure, injection speed, pressure holding time, cooling time, etc. Reasonable process parameters can ensure product quality and production efficiency.

Environmental Factors

Environmental factors include temperature, humidity, air pressure and other factors, which will affect the injection molding process and product quality. For example, injection molding in an environment with excessive humidity may cause quality problems such as air bubbles on the surface of the molded parts. Therefore, environmental factors also need to be reasonably controlled and adjusted.

Injection Molding Working Principle

Injection molding is a plastic manufacturing process where molten plastic material is injected into a mold and then cooled and solidified.

Heating and Melting

Melting plastic particles or powder into a liquid state, usually in an injection machine. The melted plastic becomes thick and runny and can be pushed into the mold by an injection machine.

Filling the Mold

Liquid plastic material is squirted into the mold through an injection machine. The injection machine pushes hard to make the plastic flow and fill the whole mold cavity.

Cooling and Solidification

The plastic in the mold needs to cool down and harden. How long it takes and how cold it needs to get depends on what kind of plastic it is and how thick it is. The way the mold is made can also affect how long it takes to cool down and how good it turns out.

Mold Opening and Removal

After the plastic cools down and gets hard, you open the mold and take the part out. Usually there is some stuff on the mold to help the part come out of the mold easier.

Deburring, Trimming and Processing

After you take out the molded parts, you need to remove the extra plastic and the burrs, and you need to trim and finish the molded parts. You can do this by hand or with a machine.

Inspection and Packaging

Finally, you need to check the finished product to make sure it’s good enough, then put it in a box and send it to the customer.

The principle of injection molding is pretty simple, but if you want to make good parts, you need to know how to do it. For example, you need to control the pressure, temperature, and speed of the injection machine to make sure the injection is accurate and the parts are good. You also need to think about things like what kind of material to use, how accurate the mold needs to be, and how long the mold needs to last.

Injection Molding Process

Injection molding is a way to make plastic stuff. You heat up the plastic until it’s melted, then you squirt it into a mold. It cools down and turns into the shape of the mold. Then you take it out of the mold and you have a plastic thing.Here’s how it works.

Mold Preparation

Before you can make plastic stuff, you need to make a mold. You have to design it, make it, and put it in the machine. The mold has to be the right shape and size for the plastic thing you want to make. You also have to think about what kind of material to use and how accurate the mold needs to be.

Plastic Material Preparation

You need to choose and process plastic materials according to the requirements of the products you want to make. Usually, you heat plastic pellets or powder until they melt, and then you squirt the melted plastic into a mold using a machine.

Injection

Injection is when you squirt melted plastic into a mold using a machine. You have to control the pressure, speed, temperature, and other things on the machine to make sure the injection is right and the stuff you make is good.

Cooling

After you shoot the plastic into the mold, you have to wait for a while to let it cool down and harden. How long you have to wait and how cold it has to get depends on things like what kind of plastic you’re using and how thick it is.

Mold Opening

After the plastic cools down, you open the mold and take the parts out. There are a bunch of ways to open the mold, like by hand, with a machine, or with a hydraulic system.

Slag Removal, Trimming and Processing

After you take the parts out of the mold, you have to do some stuff to them to get rid of extra plastic, make the surface flat, and put holes in them if you need to.

Inspection and Packaging

Finally, you need to inspect the finished product to make sure it’s good enough, then put it in a box and send it to the customer.

Advantages of Injection Molding

Plastic injection molding is really versatile and helps make stuff for all kinds of industries. It’s got a bunch of advantages, like:

High-Volume Production

Injection molding is the most competitive manufacturing method for high-volume plastic part production. Since the mold is set on the injection molding machine, plastic parts can be produced at low cost and at high speed. The minimum injection quantity is 500 units. At this time, the high initial cost of the mold has less impact on the unit price.

Wide Range of Materials

Mold cycle times for injection molding are typically 15 to 60 seconds, depending on the size of the part and the complexity of the mold. Plus, one mold can make multiple parts, which increases the number of parts you can make in a given amount of time. That means you can make thousands of plastic parts per hour.

High Tolerance

Injection molding is a process that can be repeated over and over again with high precision. Molds will eventually wear out, and aluminum molds used for prototypes can usually only make 5,000 to 10,000 parts, while steel molds can make 100,000+ parts.

Excellent Visual Appearance

Injection molding can make finished parts with little or no additional finishing. The mold surface can be polished to a highly mirrored finish, or sandblasted to a textured surface.

High Production Yield

This is one of the most important advantages of this process. The process takes 20 to 120 seconds to complete a cycle, enabling it to manufacture hundreds of parts per hour.

Minimal Labor Costs

The injection molding process is fully automated and can be operated by just one person. So, production costs are reduced because you don’t need as many people.

Design Flexibility

Injection molding lets manufacturers make all kinds of designs, no matter how complicated or fancy.

Quality Consistency

This process follows a step-by-step pattern when making the same part over and over. So, the first one will weigh about the same as the second one, the third one, and so on.

Less Waste

Unlike other production processes, such as CNC machining, which cut off large amounts of parts, injection molding produces very little debris. These small amounts of unused material can be collected and recycled.

Compatible with Multiple Materials

Through the injection molding process, you can use multiple materials and colors at the same time. Since the finished product already comes out with a finish, you don’t have to do any work afterwards.

Disadvantages of Injection Molding

Despite its many advantages, there are some disadvantages to this technology that you need to be aware of before starting your project. They include the following:

High Mold Cost

The main economic constraint of injection molding is the high mold cost. Start-up costs are very high because custom molds have to be made for each geometry.

Costly design changes: Once the mold is made, design changes require a new mold to be made from scratch. So, correct mold design is very important for injection molding.

Long Lead Time

6-10 weeks for injection molding, 4-6 weeks for mold manufacturing, 2-4 weeks for production and shipping. Once the design needs to be changed, this time will increase accordingly.

Not Suitable for Large Parts

Because of the limitations of molds, it is very difficult to make large parts with the same density. Large parts can only be made into several small parts and then put together.

Visible Defects in the Finished Product

Even though the process is extremely accurate, the finished product may still have minor defects that were left over from the injection molding. Please note that this defect does not affect the functionality of the part. Defects include distortion, nozzle drooling, sink marks, flow marks, weld marks, underfill

Injection Molding Applications

Injection molding is a versatile manufacturing technology that is crucial to the development of a wide range of products, including appliances, automotive parts, medical devices, and more. Let’s take a look at some applications of this process.

Automotive Industry

Many car manufacturers prefer plastic injection molding technology because of its strength and precision. For example, plastic components improve the aerodynamic shape of the body and various parts of the vehicle. As industry demands continue to change, injection molding for automotive applications is the first choice for manufacturers.

Packaging Industry

The packaging industry uses components that can effectively develop creative packaging designs that attract customers. In addition to attractive finishes and aesthetics, products must adhere to strict safety and hygiene rules. Injection molding can improve the overall quality of your product without causing any major issues.

Medical Industry

Medical components often require custom plastic parts that are both mechanically superior and highly precise. The healthcare industry is known for its accuracy and sustainability. The manufacturing of medical plastic parts is subject to very strict regulations. Medical components also need to be durable and require the right compounds and structural qualities that can withstand higher temperatures.

Consumer Goods Industry

More and more companies that make stuff for your house are using plastic injection molding.  The reason they use it is because it makes things look good and work right.

Aerospace Industry

The aerospace industry has some pretty strict regulations on how strong and accurate things have to be.  Plastic injection molding is used to make the aerodynamic parts of most airplanes today.  The aerospace industry is changing the way they make parts to use this approach.

Common Defects and Solutions in Injection Molding

There are many problems with injection molded products. Some of the most common ones are short shots, bubbles, warping, edge warping, cracking, shrinkage holes, and so on. These problems can make the product look bad, not work right, or not last as long as it should.

Short Spots

Short shots are small depressions on the surface of the molded part, usually caused by the plastic material not completely filling the mold cavity during the injection molding process. Solutions include increasing injection pressure, increasing injection speed, changing injection position, etc.

Bubbles

Bubbles are gas bubbles on the molded part or in it, usually caused by the air mixing in the plastic material during the injection process. Solutions include increasing the injection pressure, the speed of injection, changing the injection position, improving the material’s dryness, and so on.

Warping and Warping

Warping and warping are the phenomena of bending or bulging on the surface or edges of molded parts. They are usually caused by unreasonable mold design or uneven temperature during the injection molding process. Solutions include optimizing mold design, adjusting injection molding process parameters, increasing cooling time, etc.

Cracking

Cracking is when cracks appear on the surface or inside of molded parts. It usually happens because the plastic material shrinks too much or there’s too much stress during the injection molding process. You can fix this by changing the mold design, moving the injection position, or increasing the holding pressure time.

Shrinkage Cavities

Shrinkage cavities are little dents on the surface or inside of molded parts. They usually happen because the plastic material shrinks too much or because there’s loose material during the injection molding process. You can fix this by making the mold better, holding the pressure longer, making the material drier, and so on.

Conclusion

Plastic injection molding is a good way to make plastic parts. It’s fast, it’s cheap, and it works good. There are a lot of good things about it. But you can’t just know what it is. It sounds easy, but there’s a lot of things that can go wrong. If you don’t do it right, you’ll make a bad part and you won’t make any money.

So, you need to partner with the best injection molding company to consistently outperform your competition. Zetar Mold is the best choice for high-quality injection molding services. With decades of experience, a global presence, and extensive technical expertise, you’re guaranteed to get great results. Zetar Mold’s team of experts will walk you through the entire process from material selection to mold design and part creation.

We make sure we follow strict standards for unmatched quality, performance, and consistency in injection molded parts. Our injection molding quoting platform lets you check DFM analysis and approve mold design before we start production. Zetar Mold offers great solutions to meet your specific needs, no matter how many parts you need. Get in touch with us today and let’s get started!