Sometimes manufacturing moves faster than its customers. Technologies that seemed unthinkable a decade ago are now suddenly part of the mainstream -- or so you hear.
Just when you think you fully understand the benefits of powder metallurgy, along comes the process of additive manufacturing -- better known as 3D printing.
Is it really possible to “print” perfect parts and eliminate some steps in the manufacturing process? Or is there a reason additive manufacturing remains a niche concept?
Here’s our weigh-in on the pros and cons of additive manufacturing vs. powder metallurgy:
Pros and Cons of Additive Manufacturing
What Is Additive Manufacturing?
As with any new technology, there are several pros and cons of additive manufacturing as engineers go through trial and error.
Additive manufacturing (AM) is a die-less process that uses powder to create a component in a way that resembles an inkjet printer. But, instead of printing ink bubbles, the machine "prints" particles of metallic or nonmetallic products that are sintered or laser fused.
These sintering and lasing fusing processes are two distinct methods of additive manufacturing. They are either sintered as a second step or laser fused as part of the process.
AM starts with a bed of powder. A binder is injected in a particular spot that “glues” the powder particles together. This “glued” mass of powder is then sintered to form a PM part. The second process uses a laser to fuse the powder particles metallurgically while still in the powder bed. So, in a sense it's not true "printing," which is 2D.
Where Does 3D Printing Fit With Powder Metallurgy?
For many years, 3D printing has been helpful in the production of prototypes, but its shortcomings are evident when you need large quantities of quickly produced, low-cost items.
Additive manufacturing is instead finding its place in component manufacturing as a complement to conventional pressing and sintering. Home or office versions of 3D printers use plastic to form the end part, but 3D printing can also be achieved in the industrial world using metal in powder form, similar to the process used by powder metallurgy companies.
Decisions about whether to work with powder metallurgy suppliers are often based on the pros and cons of 3D printing. Sure, it’d be neat to jump on board with this emerging technology, but is it really necessary? Or can you get the job done with conventional powder metallurgy mixed with some advanced techniques and materials?
Additive Manufacturing Advantages
Metal additive manufacturing isn’t just technology for technology’s sake. It does have some functional benefits.
1. Rare Shape-Making Ability
Additive manufacturing is very attractive for unusual or complex shapes that can be difficult to manufacture using other processes. Design software makes it possible to create nearly any geometric form, such as hollow spaces or honeycombs, that maintain stability while decreasing weight.
In this regard, think of 3D printing as powder metallurgy (PM) on steroids.
2. Manufacturing + Assembly in 1
An additive manufacturing line can produce multiple components at a time. Instead of creating individual parts and assembling them at a later point, an additive manufacturer can combine manufacturing and assembly into a single process.
This cuts down on what would otherwise be an extraordinary lead time (see more below).
3. Even Less Waste
Additive manufacturing almost always involves less waste material.
Traditional manufacturing processes typically involve removing product from a larger workpiece, while AM actually adds product from scratch to create your component. Using only the material necessary to create a part ensures minimal waste.
Again, this is an area where conventional powder metallurgy excels, but 3D printing takes the elimination of secondary machining to another level -- to a point.
You have a certain amount of ink that spills onto certain particles. In the case of laser, perhaps it isn’t as tightly focused as it should be. So sometimes particles get “glued” where they shouldn't be, so they need to be discarded. If you don’t, you can create a void or defect in a part.
There’s always a small amount of waste in manufacturing, even in AM. And in 3D printing, even a small amount of waste can be an issue due to the high material cost.
Additive Manufacturing Disadvantages
Many of the benefits of additive manufacturing already exist in powder metallurgy, just in lesser form. You’ll have to decide whether modest improvements in those areas are worth the trade-offs below:
1. It’s Almost Always Cost-Prohibitive
Just like metal injection molding (MIM), metal additive manufacturing is rarely the most cost-effective path to an end product.
There are considerable capital costs to purchase the equipment necessary to support additive manufacturing. These costs, whether you’re attempting in-house 3D printing or outsourcing it, are hard to justify compared with traditional processes.
Also, engineers specifying materials for AM frequently look for very fine or small particles or distribution. This can make the raw material cost of your project skyrocket -- even more so if the powder needs to be spherical or gas atomized.
If the part can be pressed in PM and machined (if necessary) later, there’s usually no reason to force AM into your manufacturing process.
2. No Mixing Allowed
The mechanical properties of a finished product are dependent upon the characteristics of the powder used in the process.
Additive manufacturing typically uses a prealloyed material in the base powder. Why? There's no way to successfully introduce additional materials and traits later in the 3D printing process.
If your alloying material isn’t present from Step 1, you’re out of luck. All the materials and characteristics you want in your component have to be in the mix ASAP.
3. It’s Slow, and Niche
Industrial adaptation to additive manufacturing has been slow, and it’s still considered a niche process even in 2019. That’s because after all these years, AM is still not an efficient way of producing a high volume of parts.
Remember how we complimented AM’s ability to produce multiple parts at once? Good thing, because it’s otherwise a snail-like process. Depending on your desired final shape, it can take 2-3 hours to produce a shape that conventional PM could make in 5-10 seconds.
Unless your design is such a unique shape that there’s no other way it can be economically produced, it’s best to stay away from 3D printing. Even in cases where your design is a true unicorn, it may be better to adjust the shape rather than your manufacturing method.
Powder Metallurgy Is Cool, Too
Metal additive manufacturing companies are trying to become more competitive in areas beyond unique automotive parts. But in most cases, it still makes economic sense to use powder metallurgy to meet current and future parts manufacturing needs.
Remember, not all powder metal companies are using decades-old technologies and materials. Check out the resources below to see what powder metallurgy suppliers are doing these days to take PM materials and processes to the next level:
- Beginner’s Look at High-Temperature Sintered Parts
- Powder Metal Materials: A Visual Flow Chart of Possibilities