The Protolabs Insight video series will help you master digital manufacturing.
Every Friday we’ll post a new video – each one giving you a deeper Insight into how to design better parts. We’ll cover specific topics such as choosing the right 3D printing material, optimising your design for CNC machining, surface finishes for moulded parts, and much more besides.
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Hi and welcome to this week’s insight video. Today I’m joined by Tasos Pantelis who is an Application Engineer here at Protolabs.
We’re going to talk about selecting materials for 3D printing. Now we all know how great 3 D printing is for producing parts in pretty much any shape you want and as a rapid prototyping technology, but Tasos, what do I need to think about when it comes to material selection?
The first thing that you need to be aware of is that it’s the combination of both the material and how it is produced that will determine a part’s characteristics.
Now 3 D printing is completely different to all other manufacturing processes so the characteristics of parts that it produces are different, even if you are using a nearly identical thermoplastic or metal alloy. This does not mean that it is any better or worse, it’s just that the results for things like tensile strength, elongation and heat deflection can differ.
Okay. I know that material science is really advancing in 3 D printing, can you tell me what this means as far as a designer is concerned?
That’s certainly very true and it’s a great time to be involved with this technology. For one thing it means that many more materials than you might think can now be 3 D printed. A good example is that we can now print parts out of a copper alloy. It also means that this technology has moved beyond models and prototypes to producing functional parts for testing, shop floor use and production.
When you are seeking a direct replacement for a part produced using another technology it pays to experiment to see what is possible.
So, sticking with material selection and properties are there any disadvantages when it is compared to other production technologies?
Each production technique brings its own advantages and disadvantages as we have talked about in these videos before.
One thing that you do need to consider when designing a part for 3 D printing is that the process produces anisotropic properties.
This means that a characteristic’s values can differ in the X and Y versus the z axis. This does vary depending on which additive technology you use, so it’s less with direct metal laser sintering than for selective laser sintering or stereolithography.
Unfortunately, it can be hard to find out how much of an affect this will have, because material suppliers might not publish how properties change between the different axes.
The good news is that we can overcome this by adjusting the build orientation, but it does mean that you need to design the part specifically for the 3 D printing process. I’d suggest that you work closely with your chosen supplier because you can use all of their experience from past projects.
Okay so how do you go about selecting a material for prototyping and production parts?
What we tend to find is that one or two material properties distinguish an additive material from others.
This means that you need to define what mechanical or thermal properties are critical for your part or prototype. You can then review the different material options to find a fit and then narrow this down further by looking at the other properties that are acceptable for your project.
Let me give you an example. If you need to have the average tensile strength of polyamide or PA 11, then a stereolithography photopolymer is probably a better option than a part produced from PA using selective laser sintering. And if you want to mimic the heat deflection temperature of an ABS then your best option is a sintered nylon.
So don’t try and find a perfect match to a cast, moulded or machined material, but find out what options satisfy the most critical requirements.
So can you give me an example of how a material alters between different manufacturing technologies?
Sure. Let’s take take a look at Aluminium. An aluminium part produced using direct metal laser sintering is broadly comparable to a 3000 series alloy that is used in casting and die casting, but there are differences.
The tensile strength and yield strength for the DMLS aluminium are far greater than those for a comparable die cast part. But when it comes to elongation at break then the die cast aluminium is way better.
And what about plastic parts? I know for example that we often use 3 D printing to prototype parts for injection moulding.
Absolutely, if you are prototyping then you need to select the material based on the most critical property that you are testing for.
For example polyamide parts produced using selective laser sintering have similar heat deflection temperatures to those from their injection moulded counterparts, but can sometimes have lower values for mechanical properties.
With stereolithography you get a much wider selection of materials, which gives you a larger range of tensile strengths and elongation to break values, but impact strength and heat deflection temperatures tend to be far lower.
Okay thanks Tasos. I know we’ve deliberately avoided going into too much detail about individual materials because we could be here all day. Have you got any final tips for our viewers?
Yeah. 3 D printing is an amazing technology both for rapid prototyping and also to produce parts. This means there’s now loads of metals and plastics to choose from. While you can’t exactly match something from another process, we can generally meet the most important requirements.
The best thing to do is work with a supplier who really knows the technology, because there’s an awful lot that you can do with 3 D printing that is simply not possible with other manufacturing technologies.
That’s great. Thanks for your time today Tasos. I think it’s time to sign off now so have a great weekend and I hope you can join me again next Friday.
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