Metal injection molding (MIM) combines the best aspects of both traditional plastic injection molding and powder metallurgy, offering the design freedom and cost-effectiveness of plastic injection molding, with the strength and durability of metal components.
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In this blog, we explore the advantages and disadvantages of metal injection molding to help you determine if it's the right manufacturing solution for your product.
Advantages of Metal Injection Molding
The main advantages of the metal injection molding process are:
Complex Geometries
Cost-Effectiveness
Consistent Quality
Material Selection
Density & Strength
1. Complex Geometries
MIM parts can be made with intricate internal structures, thin walls, and complex shapes, making it possible to produce functional and aesthetically pleasing components. In addition to complex geometries, MIM also offers tight tolerances, which is important for ensuring the proper fit and function of the component.
2. Cost-Effectiveness
Metal injection molding is considered cost-effective due to several reasons, including reduced labor and reduced waste.
MIM is a highly automated process, which reduces the need for manual labor, compared to traditional metal forming methods. This can result in significant labor savings, especially for high-volume production runs.
The metal injection molding process also generates very little scrap, which reduces the amount of discarded material and the associated costs. The high precision of MIM reduces the need for secondary operations, such as finishing and assembly, which can also result in cost savings.
3. Consistent Quality
Consistent quality is achieved in metal injection molding for the following reasons:
Repeatability
The MIM process is highly automated and repeatable, which ensures that each part produced is exactly the same. This reduces the risk of defects and ensures the parts meet specified design and tolerance requirements.
Consistent Raw Material Quality
The MIM process starts with the creation of a metal powder that's mixed with a binding material to form a feedstock. Metal powders used in the MIM process are highly consistent in composition and particle size, which reduces variability in the final parts and ensures consistent quality.
Controlled Environment
Metal injection molding takes place in a controlled environment, reducing the risk of contamination and defects. The high pressure and heat used in the process also eliminate any porosity or inclusions that might be present in the feedstock, ensuring the final parts are of high quality.
4. Material Selection
A wide range of material options are available with metal injection molding, including stainless steel, titanium, and low-alloy steels. This gives engineers the flexibility to choose the best material for their specific application.
5. Density & Strength
MIM parts are produced with a high degree of density, which results in excellent mechanical properties, including strength and hardness. This makes MIM a great solution for components that need to withstand high stress and wear.
Disadvantages of Metal Injection Molding
Regardless of which metal-forming technology you're using, there will always be disadvantages. The following are some of the disadvantages of MIM technology:
Start-Up Costs
Tooling Lead Times
Design Change Costs
1. Start-Up Costs
The metal injection molding process requires specialized equipment, including an injection molding machine, debinding oven, and a sintering furnace. This equipment can be expensive, especially for companies that are new to the MIM process.
Working with a manufacturer with MIM processes already in place can help alleviate these costs.
2. Tooling Lead Times
The lead time for manufacturing a new mold and producing parts with a new design can be weeks or months, especially for complex parts. This delay can impact production schedules, resulting in increased costs due to the need to meet tight deadlines.
3. Design Change Costs
MIM requires a dedicated mold for each part design and the cost of the mold adds to the overall cost of production. If a design change is required, a new mold must be designed and manufactured, which increases lead times and costs.
Metal Injection Molding in Action
Due to the ability to cost-effectively manufacture large quantities of complex parts, MIM is highly beneficial for many industries, including:
Medical
Metal injection molding is commonly used in the production of medical devices such as orthopedic implants (hip replacements, knee replacements, and spinal implants), surgical instruments (scissors, forceps, and retractors), diagnostic equipment (blood glucose meters, breath analyzers, and pulse oximeters), and dental devices (implants, bridges, and crowns), where precision, reliability, and biocompatibility are critical factors.
Consumer
MIM is also a great option for the production of consumer electronics, such as cell phones, wearable devices, and other electronic components. It's also commonly used in the manufacture of sporting goods (golf club heads, fishing reels, and ski bindings) and jewelry (pendants, earrings, and bracelets).
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Automotive
Metal injection molding is widely used in the production of automotive components such as rocker arms, turbocharger vanes, shift levers, seat components, brake components, injector nozzles, light housings, and numerous fittings and connectors.
Aerospace
MIM is excellent for the production of engine components (turbine blades, nozzles, and combustion chambers), airframe components (hinges, latches, and actuators), avionics components (connectors, switches, and sensors), and spacecraft components (solar panels, antennas, and structural components).
Agricultural
The strength and durability MIM provides make it a popular production choice for agricultural components, such as tractor parts (gears, bearings, and bushings), implement parts (plow shares, cultivator points, and harrow teeth), irrigation components (nozzles, valves, and couplings), and tools (pruning shears, hoes, and cultivators).
Checklist: Is Metal Injection Molding the Right Choice?
Now that you know a little more about metal injection molding and the industries it's thriving in, here's a checklist to help you decide whether the metal injection molding process is the right choice for your production:
If you answer 'yes' to any of these questions, MIM may be a good fit:
Volume of production: Are you producing large quantities of parts?
Part size: Are your parts small and complex in design?
Precision and consistency: Do the parts need to meet strict specifications and tolerances?
Production efficiency: Are you looking for a highly efficient production process?
Complex geometries: Do the parts have intricate designs or functional requirements?
While MIM is a highly efficient and versatile production process, there are some situations where it may not be the right choice.
Frequent design changes: Do you need the flexibility to make frequent design changes? Due to the use of molds, MIM can be expensive to modify once production has started. This makes it an
impractical option for prototyping
.
Lead times: Is quick turnaround an important factor? MIM requires the creation of specialized tooling, including injection molds and binding fixtures.
Tooling can take several weeks or even months
, depending on the complexity of the part.
By considering these factors, you can ensure that you choose the right production process for your specific needs.
Maximize Your Production with Metal Injection Molding
As you can see, metal injection molding offers a number of advantages over traditional metal forming methods, including complex geometries, cost-effectiveness, consistent quality, and a wide range of material options. However, it also has its limitations, including lead time, parts size limitations, material cost, and surface finish.
When considering MIM for your manufacturing needs, it's important to weigh the advantages and disadvantages carefully to determine if it's the right solution for your end-use parts.
Ready to learn more about what metal injection molding can do for your production? Check out our other resources.
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.
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:
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