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: TPU MJF
Hello and welcome to this week’s Insight.
Today we’re going to go into some detail about a new material that is only recently available for multi jet fusion 3D printing. The material in question is thermoplastic polyurethane.
So first I’m going to quickly remind you about MultiJet Fusion, and when you would choose it rather than other 3D printing technologies, before getting onto the new material itself.
So Multijet fusion, or MJF, is a new industrial grade 3D printing technology that has certain advantages over other additive manufacturing processes.
It uses a heated chamber to build a 3D plastic structure by adding successive layers that are just microns thick. Instead of using a laser to fuse these layers together like selective laser sintering, or SLS, it uses an infrared heating element. Neither technology needs support structures for the process.
MJF has a number of advantages over SLS. It has a smaller minimum feature size compared to SLS of 0.5mm compared to 0.75 mm. However, the MJF produced parts are a bit more variable at this fine detail.
It also produces more consistent isotropic material properties. Or in other words it provides more consistent mechanical properties in every direction or axis. If you want great strength and reliability for every bit of your part, then MJF could well be the answer.
If speed is an issue, then MJF also builds parts faster than other 3D printing technologies so it makes sense for a lot of projects for both prototyping and production.
All in all it’s a great choice, except that until recently you could only have parts manufactured from Nylon 12. Nylon 12 is a great general-purpose plastic, but it’s not the solution to everything.
Fortunately, both material science and 3D printing technologies evolve so that new solutions become available. It means that a new thermoplastic polyurethane – Ultrastint TPU01 – is now available using this process.
Before now if you wanted to 3D print TPU you could only use SLS or another technology called fused deposition modelling or FDM.
Anyway this new material means that you can now get a part 3D printed in thermoplastic polyurethane using multi jet fusion technology.
Before now if you wanted a 3D printed material for flexibility then you had to choose a thermoplastic elastomer, but the softness of this makes it more challenging to produce and handle with 3D printing.
The great thing about thermoplastic polyurethane is that it straddles the line between rubber and plastic. It has rubber-like elasticity but it is also very durable, withstands abrasion, tearing, oil, grease and UV light. It is also more rigid and experiences less shrink than a thermoplastic elastomer.
The new material has been developed to optimize lattice structure designs, has a high accuracy and detail resolution and gives a really smooth surface finish.
For those of you who like to dig into the details, and of course you should when looking at material selection, it can achieve tolerances of plus or minus 0.30 mm plus 0.002mm on well-designed parts, although this may change depending on your part geometry. It has a shore hardness of 88A, tensile strength of 9MPa, plus or minus 2MPa on the x-y plane, and elongation at break of greater than 220 percent. In plain English that last point means it’s very stretchy.
What this all means is that you can now bring all of the advantages of multi jet fusion printing to another material, and TPU as we have just seen is not just any material – it gives your part or prototype certain functional advantages.
Its rubber-like elasticity, durability and shock absorption make it ideal for parts in the sports and leisure industry, think about the soles of running shoes for example.
And its chemical resistance to oil and grease, flexibility and high thermal stability make it great for parts in the transportation industry – think about tubes, wheels, ducts, seals and gaskets or other applications where you need high resistance under dynamic loading. It’s also great for hoses and orthopaedic models.
To summarise, thermoplastic polyurethane is a really versatile material. And now that you can use Multi Jet Fusion 3D printing to produce parts in it, you can get those parts even more quickly.
For prototyping it means that you can check your design for functionality and fit using this material before committing to large scale manufacturing. For production it allows you to design complex parts using this material that you can’t achieve using other manufacturing technologies at a comparatively low cost.
It just goes to show that the world of 3D printing is evolving rapidly, allowing you to do more with different materials, more cost effectively.
That’s it for this week. I look forward to seeing you again next Friday.
With special thanks to Natalie Constable.