What are Plastic Injection Moulding Advantages and Disadvantages ?

Plastic injection moulding advantages centre around great precision and high repeatability, combined with speed, a low cost per part and a huge choice of available plastics. Disadvantages include a higher initial cost and lead time than some other processes.

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Plastic Moulding Advantages

1. Precision

Plastic injection moulding is perfect for very intricate parts. Compared to other techniques, moulding allows you to incorporate more features at very small tolerances. Have a look at the image to the right. You can hold this moulding in the palm of your hand and it has bosses, ribs, metal inserts, side cores and holes made with a sliding shut off feature in the tool. That's an awful lot of features on a small part! It would be impractical to make using plastic fabrication and impossible to make using the vacuum forming process.

2. High repeatability

Once your mould tool is made, identical products can be made over and over again. And again. A decently made mould tool has a very long mould tool life, as long as it's treated well by the moulding machine setters !

3. Low cost per part

Whilst there is an initial high investment for the plastic injection moulding tool, after that the cost per part is very low. Other plastic processing techniques may require multiple operations, like polishing, whilst injection moulding can do it all at once. If you chose to CNC machine the part above, it would cost hundreds of pounds per part. If you're looking to go into full production, injection moulding is the way to go.

4. Fast

Cycle times can be as low as 10 seconds. Combine that with a multi-impression injection moulding tool and you get a LOT of products very quickly. That part above takes a bit longer as it's a specialist material and has a lot of features to be moulded correctly, but at about 50 seconds you'd still get 70 parts per cavity per hour. CNC machining a one-off would take half a day - 3D printing it even longer!

5. Material choice

There's a vast amount of materials available for plastic injection moulding. A range of more common materials, but also things like antistatic plastic, thermoplastic rubber, chemical resistant plastics, infrared, biocompostable...and with colour compounding or masterbatch colouring you have an endless choice of colours as well. The moulding above is boring black, but it's made out of PPO - poly(phenylene oxide) - which is an extremely rigid and flame-retardant material.

6. Special Surface Finishes, Engraving & Printing

In addition to a range of colours, the injection moulding tool can be made with a special finish which will show on the moulding. Just about any finish you like, for example leather look, soft touch, sparked, high shine, you name it. You can also have logos or other text engraved in the tool. Finally, you can have your mouldings printed, as a range of inks are available that will print well on plastic.

7. Little plastic waste

Part repeatability is very high for injection moulding. Even the sprues and runners (the leftover bits of plastic created by the 'tunnels' through which the plastic material reaches the actual mould) can be reground and the material reused. You can explore this in more detail on our environmental impact of injection moulding page.

Plastic Moulding Disadvantages

Sounds amazing doesn't it ? Of course there are also some disadvantages:

1. High Initial Cost

Often, several rounds of designing and modelling are needed before the go-ahead or production is given. Then, the injection moulding tool needed to make the mouldings will need designing & manufacturing. The mould tool is an intricate piece of work which costs manpower, material and many machining hours to make and represents the largest cost in getting injection mouldings. Of course, once it's all done, part cost is very low and repeatability very high for hundreds of thousands of mouldings.

2. Initial lead time

From product conception to final part can take months of design, testing and tool manufacturing. That said, if you know what you want, you can have the finished mouldings within 6 weeks. (Toolcraft's Chinese Mould Tools Flowchart shows how that could work). And as mentioned under advantages, once the tool exists, it takes very little time to run the mouldings, especially when you have a multi-impression mould tool. (Here's a list of Mould Tool Types).

3. Large Part Size Limitations

Huge machines are needed to make plastic injection mouldings. Very large parts need an enormous mould tool and become very expensive to make, in which case a process like Plastic Fabrication may be a better choice, depending on the tye of product needed.

4. Careful design needed

Plastic mouldings need very careful design to avoid tooling issues like undercuts (which will send up tooling cost significantly), locked-in features and not enough draft (What Draft Angles for Plastic Mouldings ?). The material and temperature will need to be taken into account in wall design, otherwise the mould may not fill fully. The placement of ejectors and cooling lines will need to be considered to ensure the product is aesthetically pleasing.

Should I choose plastic moulding for my product ?

Well, it depends on so many factors: design considerations, material, size, quantities needed, your budget. An expert will have to assess each product idea to decide the most effective and economically viable way of manufacturing it.

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Toolcraft offer plastic injection moulding, vacuum forming and plastic fabrication, including a range of finishing, printing & packing services. Our longstanding experience allows us to help you choose the best manufacturing process for your new project. We also share our knowledge on our plastic moulding advice pages. Or just:

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Top 6 Major Advantages of Plastic Injection Molding

Plastic injection molding involves injecting molten plastic into a mold to create different shapes and parts. This cost-effective process is extensively used in the manufacture of plastic parts. Plastic injection molding produces an extensive range of high-quality, complicated plastic parts cost-effectively. 

1. Geometry & Design Flexibility

Design flexibility is one of the main advantages of plastic injection molding. Extremely high pressure is applied to the injection molds, which forces the plastic into the mold. Injection molding can create complex and intricate designs that are usually too difficult and expensive to produce using other methods. 

2. Faster Production & High Efficiency

Computer-aided design (CAD) and computer-aided manufacturing (CAM) methods create the injection mold. The designs are made to the customer&#;s specifications, and the mold is used to make the parts. The plastic injection molding technique is fast and allows many pieces to be produced from a single mold. 

Plastic injection molding is efficient, cost-effective, and has a high production output. The speed varies depending on the intricacy and size of the mold, but each cycle takes roughly 15-120 seconds.

3. Enhanced Strength & Perfect Finishing

Fillers are used in materials and can change the plastic&#;s physical and mechanical prperties, increasing the item&#;s strength.  

There are tens of thousands of injection molding materials, including high-performance blends and hybrid materials.

Most injection-molded products have a smooth surface finish close to the desired final appearance. Injection molding allows for surface treatments that don&#;t require further procedures, such as engraving, matte finishes, and distinctive textures

4. Flexibility to Change Color & Material

Various color and material choices are diverse, and various color procedures are available. Colors can be matched to a variety of sources such as mating parts, PMC color book, and even everyday items. 

5. Reduced Waste & Lower Labor Costs

Plastic injection molding produces little waste and is environmentally friendly. The exact quantity of plastic required for a product is pressed into a mold, making it a low-waste procedure. Product design and manufacturing processes can assist in reducing waste by recycling and planning production runs to maximize efficiency and conserve energy. 

Machines and robotics execute most of the injection molding process, which one person controls. Automation reduces production costs by lowering labor costs and overhead, which reduces the cost of producing parts. 

6. Multiple Plastic Types can be Used at the Same Time

Injection molding can produce simple and complex items, and some techniques alter mold designs. A single mold can be used for a variety of parts or products. Complex part designs frequently necessitate the use of components comprised of several materials. 

Multi-shot injection molding, or twin-shot injection molding, is a method that involves injecting two or more colors and materials into a mold. Thermoplastics, thermosets, and liquid silicone rubber are popular materials utilized in this method. The materials must have the same adhesive grade to guarantee the finished components are securely attached.

Find the Best Plastic Manufacturing Company

Injection molding has a broad range of applications and quickly generates large quantities of components. A professional plastic molding company can take your concept and make it a reality.  
Universal Plastic Mold (UPM) is the best plastic injection molding near me in California. We produce accurate, durable, cost-effective plastic manufacturing services in California.

For more information, please visit plastic injection mold design.