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Our 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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Insight: SLS Materials
Hello and welcome to this week’s Insight.
Today we’re going to take a close look at some of the materials that you can use with selective laser sintering or SLS.
If you go back to some of our past Insight videos you will see that there are a number of different types of 3D printing technologies, and which you choose will depend on what you want to achieve.
Where SLS really does well is if you need functional parts that have a greater toughness and higher impact strength than parts produced using stereolithography. On the other hand stereolithography does produce a better surface finish than SLS, so it’s up to you to balance the pros and cons.
But let’s delve a bit deeper and look at some of the more common materials used with SLS and why you would pick them for your project.
I’ll start with one of the most popular choices: PA12 white. You might’ve already guessed that this nylon has a white finish, but it’s not just its colour that makes it a good choice. It is cost effective, very durable and stable under a wide range of environmental conditions. It also has high impact and temperature resistance.
It's one downside is that it has a slightly rougher surface texture compared to other nylons.
But it’s a good solid choice for applications such as jigs, fixtures, housings and other functional parts.
Next up is PA 11 black. And as the name suggests, this one is black. You would use this nylon if you want excellent ductility and temperature resistance without sacrificing tensile strength. It has one of the highest elongation break thresholds of any nylon, which makes it perfect for functional moving parts such as snap fits and living hinges.
Also, because it’s black, it’s a good choice for optical applications due to its low reflectivity.
Okay let’s move onto PA 12 40% glass filled. Now you may know that if you add or blend materials together it is because you want to achieve a certain functionality. This is a polyamide powder that’s loaded with glass spheres to increase stiffness and dimensional stability. The glass also gives it a higher thermal resistance than other polyamides and it has very good long-term wear resistance.
There is a downside, however, in that it has a lower impact and tensile strength compared to other nylons.
Its stiffness and temperature resistance mean it is well suited to high heat environments such as for automotive engine components or perhaps tooling applications.
Now let’s turn our attention to one of the most popular plastics in the world, polypropylene. Popular, but it’s only recently that this plastic could be 3D printed at all.
There’s a good reason why it is so widely used. It’s very durable and is both tough and flexible. When you combine this with its low weight compared to other plastics, its excellent chemical resistance, electrical insulation and low moisture absorption, then you can see why it’s so popular. It’s a good general-purpose plastic that is also well suited for moving parts with features like snap fits.
Now what happens if you mix PA12 with polypropylene? You get a material that we call PA 12 Flex Black. Its strength and stiffness are like PA 12, while its elongation is comparable to that of polypropylene. On top of that it has a high temperature resistance and has a good surface quality and smoother finish than other SLS nylons.
We’ve seen it used a lot for interior parts in the automotive industry, but I’m sure you can think of plenty more applications.
The next material is PA12 Carbon filled. Again, it’s a blend, where the carbon fibre filler provides different mechanical properties to PA12. It’s extremely stiff, has good electric conductivity and is lightweight.
All of this makes it ideal for mechanically stressed parts; think about highly rigid components in automotive applications for example, as well as jigs, fixtures and gauges.
While the next material is the last on my list, but it’s certainly not the least. Thermoplastic polyurethane, or to give it the rather catchy name that we use, TPU 88A Black, combines rubber-like elasticity and elongation with good abrasion and impact resistance. If you are looking for a material that has a superb resistance under dynamic loading, then take a closer look at TPU.
Its rubber like quality makes it perfect for things like seals, gaskets, grips or hoses.
Right that’s plenty of SLS materials covered. But selecting the right material for the project that you are considering is vital.
Whoever you use for 3D printing or indeed any other manufacturing technology, you should certainly take a closer look at the datasheets for the materials that you are considering.
That’s it for this week. I look forward to seeing you again next Friday.
With special thanks to Natalie Constable.