3D Printing Polypropylene

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Protolabs’ Insight video series

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: 3D Printing Polypropylene


Hi, it’s Friday which means it’s time for another Insight video from me.

Each week we take a look at a different aspect of additive manufacturing. In this week's video we look at Polypropylene, a thermoplastic addition polymer made by combining propylene monomers.

This week I’m going to turn my attention to one of the most popular materials used in manufacturing, polypropylene and a recent breakthrough which means that it can now be 3D printed using selective laser sintering.  I’m going to explore what this means for both design and how it could substantially reduce your product development times.

But first the sciency bit.  Polypropylene is a thermoplastic addition polymer made by combining propylene monomers.  Today it is one of the most commonly produced plastics in the world and its use is increasing rapidly.  By 2026 production is estimated to reach 88 million tonnes. That’s a lot of plastic.

And there’s a good reason for its popularity.  It’s tough, semi rigid and has excellent heat, chemical and fatigue resistance.  It’s also easy to use in injection moulding.

Did you know for example that 32% of the plastic used in a typical car is polypropylene?

All of this sounds too good to be true. And until recently it was too good to be true, because you could not 3D print it. Due to its high crystallinity, it tends to shrink and warp.

So, let’s step back, if you wanted a part in polypropylene you faced limitations in getting a cost-effective rapid prototype and you could forget about designing complex geometries.

Of course, you had options you could still protype using CNC machining or injection moulding, but this limits you in what you could achieve, both cost wise and in design.

Another possible solution was to use a polypropylene like thermoset resin that was UV cured, but it’s not the same material and it does not have the same properties; so, while you could test the design, it would not always perform the same way as the actual material.

Far from ideal really. Just like those Elvis impersonators, you know that it’s not really the real thing.

But you can take the brakes off as far as this fantastic material is concerned because 3D printing is now possible.

Let’s just stop a minute and think about that.

It means that a whole new world of complex geometries opens up.  Your engineering design world for polypropylene has just got a whole lot bigger.

Perhaps even better, you can now prototype and perfect your design using this material more cost effectively and faster than ever.  There are no compromises, you can now test your design for function in its actual operating conditions as well as its form.

And let’s not forget its never been more important to get new concepts and designs to market quickly.  But against this has always been the fear that if the product or component is not spot on, then the complaints will quickly pile up.  And in today’s era of social media that can really damage your brand.

In this race to market where being first really counts and you don’t want to be a ‘me too’ left in the wake, where else can you shave days, weeks or even months from that development cycle?

Well for polypropylene the development cycle would probably take you from a 3D printed prototype to injection moulding.  As we have already covered in a previous video hopefully your prototype was developed with mass manufacture in mind because this will save you time in the long run.

Regardless of that, your injection moulding supplier should be able to do a design for manufacturability analysis and if needed suggest some areas that could be improved.

But here’s a good tip for you, why not simply find a supplier that can take you through the whole process – from 3D printing and testing the prototype through to injection moulding. Such suppliers do exist, and you will have the benefit of their knowledge for the entire process.

Want another time saving idea?  Why not see if you can get bridge tooling developed in aluminium moulds so that you can start production even while you are waiting for your permanent steel moulds?

Suddenly you can get that polypropylene part or component, designed, tested and produced far more quickly than ever before.  To pinch that cliché, you can now succeed far faster.

So that’s a big tick for mass production parts, but what about something bespoke or a little bit special?

While injection moulding and CNC machining are great for mass production, they do have their limitations.

If you really want to let your imagination go, then you can design anything that you want using 3D printing.  From organic shapes to honeycomb structures to save weight, there are no limitations.

To conclude, polypropylene is a fantastic material with numerous applications.  Now that the technology allows it to be 3D printed a whole new world has opened up for you, both to get product to market faster than ever before and to design components or parts that were previously impossible. 

I bet you can’t wait to get back in front of your CAD!

And with that I’ll leave you until this time next week. 


With special thanks to Natalie Constable

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