10 Advantages And Disadvantages Of Injection Moulding

Moulding, or molding, is a process of manufacturing parts and products by filling a rigid frame called mould (mold) with raw materials in liquid or pliable forms. There are several types of moulding processes, mainly for rubber or plastic manufacturing, and injection moulding is one of them. In injection moulding, molten raw materials are injected into the mould where they are cooled to form the final product. 

While injection moulding is an excellent way to produce diversely shaped parts quickly and pretty much continuously, there are some pros and cons you should consider to determine whether it is the right choice for your project. To make things more explicit, below are 10 advantages and disadvantages of injection moulding. 

Advantages of Injection Moulding

Injection moulding is a versatile process that allows manufacturers to produce high-quality parts while saving some costs. 

The advantages of injection moulding include manufacturing complex parts with high precision and strength, being fast and time efficient, compatibility with various types of raw materials, being ideal for high-output production runs, and producing little to no waste. 

Here are the pros of injection moulding: 

#1. Can Manufacture Complex Parts with High Precision

One of the main reasons injection moulding is so popular is that it can produce complex parts with high precision and therefore, is perfect for manufacturing small but intricate parts. As injection moulding accuracy is within ±0.005 inches, it is considered one of the most precise processes in manufacturing. 

Besides, with injection moulding, you can achieve part tolerances of ±0.002 inches (tight tolerance) and ±0.001 inches (very tight tolerance). While tight and very tight tolerances for injection moulding are more expensive, they might be useful for manufacturing tiny parts with complicated details.  

Although manufacturing parts with high precision is essential, you may not always need to achieve tight or very tight tolerances. Ideally, you should determine the optimal precision and accuracy for the parts you want to produce before choosing the suitable tolerance. This will make the manufacturing process less expensive without affecting the overall quality of the produced parts. 

#2. Is Pretty Fast and Time-Efficient

Another factor that makes the injection moulding process so remarkable is its speed and high repeatability. As the machine uses the same mould, the products are identical and can be made over and over again. As long as you use a high-quality mould, you should not have to worry about its lifetime. 

While manufacturing products, in general, can take just a few minutes or even several hours, the majority of injection moulding machines take only 10 to 60 seconds to produce parts. According to Injection Moulding Excellence, the whole injection moulding cycle may only take 2 seconds. Impressive, right?

If your project involves parts with complex geometry, it may take around 1-2 minutes for the machine to complete the cycle. But still, injection moulding is one of the most time-efficient processes for manufacturing large amounts of small parts repeatedly. 

#3. Is Compatible with a Broad Range of Materials

When it comes to injection moulding, there is a broad range of materials you can choose from. In order to produce complex parts with desired properties, it is critical to select the right materials. And believe it or not, material selection is just as important as part design. So, the fact that injection moulding machines are compatible with numerous materials makes the process even more advantageous. 

As noted by Fast Radius, more than 25,000 engineered materials are compatible with injection moulding and the list includes resins, silicones, plastics, rubber, and thermosets. Since the range of materials that can be used for injection moulding is pretty broad, the process allows you to produce parts while modifying the mechanical characteristics of the parts. 

Besides, injection moulding enables you to achieve the desired strength, flexibility, color, and finish by adding glass fibers, colored resins, liquid colorants, or other additives. 

#4. Is Ideal for High-Output Production Runs

Ideally, you should consider using injection moulding if your polymer project production run is in thousands. This is because designing the part and creating the mould can be expensive, but once you have the mould, the cost per part is pretty low. So, if you are interested in high-output production runs, injection moulding may be the best option for you. 

In addition, as the machine uses the same mould during the manufacturing process, you can obtain as many parts as your mould is capable of producing. The Society of the Plastic Industry (SPI) classifies injection moulds into 5 major categories. 

The mould categories and their life expectancies are as follows:

  • Class 101 – 1,000,000 cycles
  • Class 102 – 500,000 to 1,000,000 cycles
  • Class 103 – 100,000 to 500,000 cycles
  • Class 104 – Less than 100,000 cycles
  • Class 105 – Around 500 cycles

While creating the mould with a higher life expectancy can be expensive, it will allow you to produce more parts at a lower cost per part.

#5. Produces Minimal Waste

It takes many years for plastics to decompose and undoubtedly, plastic pollution has a significant impact on our environment. Therefore, minimizing plastic waste by following more sustainable practices is crucial for building a greener world and protecting our planet.

The fact that injection moulding produces much less waste than other manufacturing processes is another factor making it so popular. That is because injection moulds utilize a higher percentage of the raw material compared to other processes. 

Along with producing minimal waste, the small amount of excess plastic produced throughout the injection moulding process can be melted and reused. Clearly, by reusing the excess plastic pieces for manufacturing some extra parts, you can minimize plastic waste and reduce the costs too. 

Another reason why injection moulding is more sustainable is that most injection moulding machines are energy-efficient, meaning that they do not require oil. By eliminating the need for oil disposal, you create even less waste during the injection moulding process. 

Disadvantages of Injection Moulding

While injection moulding offers plenty of benefits, it might not always be the most optimal choice for your polymer project. Therefore, considering the disadvantages of injection moulding will allow you to select the right manufacturing process for your project.

The disadvantages of injection moulding include high initial costs, long lead times, unsuitability with low-output production runs and large parts, the need for careful designing, and costly design changes and repairs.

Below are the cons of injection moulding:

#1. High Initial Costs and Long Lead Times

When it comes to the disadvantages of using injection moulding, we should note how high the initial costs typically are. While the machine itself is quite expensive (around $10,000), designing and manufacturing the mould also comes with a cost. 

On average, simple moulds with a single cavity cost around $1,000-2,000. However, according to Rex Plastics, you may need to invest approximately $70,000 or even more for moulds with 10 or more cavities for manufacturing complex parts. 

Besides, you will need to hire professionals to create the mould as its quality and design will have a significant impact on how the final product looks and functions. So, although the cost per part may be low, the initial costs of manufacturing parts using an injection moulding machine are high. 

In addition to that, manufacturing parts via injection moulding can take months. That is because you will need to design, test, and manufacture the parts first. So, if you are looking for a way to produce parts quickly, injection moulding might not be the best option. Still, you can have the finished products within a couple of weeks if you know exactly what you want. 

#2. Not Quite Suitable for Low-Output Production Runs

If you are thinking of manufacturing just a few hundred parts, injection moulding might not be the best choice for you. This is because the initial costs and lead times are so high that there would be no point in designing a mould to produce 100 or even 200 individual items. 

So, if your production runs are in the hundreds, injection moulding will not be the cost-effective option. Instead, you should consider 3D printing or CNC machining to manufacture the parts as the cost per part will be lower and you will not have to spend extra resources on setting up the injection moulding machine. This will not only save you thousands of dollars but also allow you to obtain the parts a lot faster. 

#3. Requires Careful Designing

Another drawback of using injection moulding is that it requires very careful designing while considering the design limitations and restrictions. To manufacture parts that look aesthetically pleasing and function properly, you should control wall thickness as well as avoid undercuts and sharp edges. 

Besides, you should consider the material and temperature to ensure that the designed mould fills properly during the moulding process. You should also take into account the placement of ejectors and cooling lines so that the final product looks flawless. 

As designing products for injection moulding and creating suitable moulds require plenty of time and financial resources, the process might not be suitable for every polymer project. So, before you invest in designing and creating the injection mould, make sure it is what you really need to manufacture the parts for your project. 

#4. Design Changes and Repairs Are Expensive

When manufacturing parts with 3D printing, you can easily upload new files whenever you want to make some changes to the design. However, design changes for injection moulding require starting everything from scratch. Oftentimes, you need to design and create a new mould to keep going. 

Obviously, creating a new mould will not only take your time but also your financial resources. And this is another reason why you should design your product and the mould carefully. By doing so, you will minimize the need for changing even the tiniest details in your product or mould design. 

In addition to that, repairing your injection moulding machine or the mould itself can be pretty expensive. Undoubtedly, expensive machinery and parts are expensive to repair. While using high-quality materials can solve the issue, wear and tear are pretty much inevitable, especially if your project involves high-output production runs. 

#5. Not the Best Option for Producing Large Parts

Although injection moulding is a remarkable process allowing you to produce even the most complex parts, not all items can be manufactured using this technique. Typically, large parts or those with thick and uneven walls cannot be produced using an injection moulding machine. Besides, you should also avoid manufacturing parts with sharp corners as injection moulding is characterized by certain design limitations. 

While it may be possible to manufacture larger parts, large moulds are quite expensive to make, so injection moulding might not be the best option. Depending on the type of product you want to produce, consider using other manufacturing processes for larger parts to save both your time and money. 


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