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.
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:
Plastic injection molding is an extremely versatile method of producing plastic parts and has multiple advantages over other methods of plastic molding. Not only is the process simpler and more reliable than others methods, but it is also extremely efficient.
Want more information on Injection Mold Tooling? Feel free to contact us.
Let's take a look at the top six advantages of this process:
1. High Efficiency- Fast Production
There are several good reasons that plastic injection molding is known as the most common and most efficient form of molding. The process itself is extremely fast compared to other methods, and the high production output rate makes it even more efficient and cost-effective. Speed depends on the complexity and size of the mold but only about 15-120 seconds pass between each cycle time.
With the short period between cycles, a greater quantity of molds can be produced in a limited amount of time, thus increasing possible revenue and profit margins. At Rodon, we run parts 24/7 using an MRP system (Material Requirement Planning System). While the MRP system can&#;t replace the input and experience of manufacturing managers, it does help improve efficiencies within the factory and this, in turn, creates savings for the customer.
2. Complex Part Design
Injection molding can handle extremely complex parts, and uniformity, as well as the ability to make millions of virtually identical parts. To optimize the effectiveness of high-volume injection molding and maximize the precision and quality of your parts, key design elements should be taken into account. The part design must be developed to maximize the efficiency inherent in high-volume molding. With the right design, parts can be made consistently and with quality. Without a good design, costly processing mistakes can be made.
Around the industry, most molding professionals agree that there are fundamental design elements that must occur during the injection process to work correctly. They include wall thickness, rib design, boss design, corner transitions and weld lines and gate placement, and properly placed vents. You can learn more about all of these elements here.
3. Enhanced Strength
Strength is one of the key factors that need to be determined when designing a plastic injection molded part. The designer will need to know if the part needs to be flexible or rigid so that he/she can adjust the integrating ribs or gussets. Understanding how the customer will be using the part and what type of environment the part will be exposed to is also important.
Finding the proper balance of design considerations will help address your part&#;s need for strength and stability. Material selection plays another key role in the strength of the part. See below for more information on the types of resins used in the process.
4. Flexibility- Material and Color
Choosing the right material and color for a project are two of the essential factors in creating plastic parts. Due to the wide variety of both, the possibilities are almost endless. The advances in polymers over the years have contributed to the development of a large selection of resins from which to choose. It is important to work with an injection molder that has experience with a variety of resins and applications including resins that are compliant with FDA, RoHS, REACH and NSF. To ensure you select the right resin for your project, keep in mind the following variables: impact strength, tensile strength, a flexural modulus of elasticity, heat deflection and water absorption.
Plastics can be colored using various coloring systems, each of which offers its own unique properties, benefits, and drawbacks. Masterbatches,&#;salt and pepper&#; blends, Liquid Color, and precolored resins are four of the most common coloring techniques. To learn more, check out our recent article on how plastic resins get their color.
Intro to Plastic Injection Molding eBook
Explore the World of Plastic Injection Molding with Confidence
Download our eBook, &#;An Introduction to Plastic Injection Molding.&#; Inside we cover:
- Types of plastic molding, their benefits & applications
- Types of presses and their capabilities & advantages
- How to determine plastic injection molding costs
- Common mistakes to avoid
Download Your Free Copy5. Reduced Waste
When looking for a high-volume injection molding partner, it&#;s important to consider companies&#; green manufacturing initiatives, as these signify a commitment to quality, sustainability, and optimal safety. During the molding process, excess plastic is generated. You want to look for a company that has a system in place to recycle its excess plastic. The most eco-friendly plastic injection molding companies employ state-of-the-art machinery to assist them in minimizing waste, transportation, and packaging.
At The Rodon Group, we&#;re committed to nurturing an ethos of environmental sustainability in everything we do. Over the years, we&#;ve instituted many green initiatives, all of which have helped us become one of the most sustainable leaders in the injection molding industry. Visit our Sustainability page to learn more about these initiatives.
6. Low Labor Costs
Labor costs are typically relatively low in plastic injection molding, in comparison with other types of molding. The ability to produce the parts at a very high level with a high output rate helps with its cost efficiency and effectiveness.
The molding equipment typically runs with a self-gating, automatic tool to keep operations streamlined and production ongoing, requiring minimal supervision.
Automation abounds at Rodon, from our 3D computerized design capability and automated tool fabrication processes to our computerized and automated plastic injection molding machines and robots. The entire Rodon facility is setup to produce the highest quality most economical plastic injection molded components in the industry.
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