If you want to 3D print polypropylene on your own 3D printer, there is a wide variety to choose from in three different technologies.

The three top 3D printing methods used to produce polypropylene parts are:

• fused deposition modeling (FDM), with filament and pellets
• selective laser sintering (SLS)
• binder jetting, including Multi Jet Fusion (MJF) from HP, High-Speed Sintering (HSS) from Voxeljet, and Selective Absorption Fusion (SAF) from Stratasys.

Almost any desktop fused deposition modeling (FDM) machine can 3D print with polypropylene filament as long as the nozzle can reach around 205 °C – 275 °C, you can heat the bed to between 80 °C – 100 °C, and you can control the fan speed. Some manufacturers offer specialized kits like polypropylene print plates to increase the chances of printing success.

Industrial machines also process polypropylene as either a filament, pellets, or a fine powder.

Industrial FDMs (MiniFactory, Roboze, Apium, Aon3D, Stratasys, etc.) typically offer more control of the print parameters and established print profiles for polypropylene. Some industrial FDM 3D printer makers also offer their own polypropylene material tuned to their machines. As 3D printing with recycled polypropylene becomes more common, it’s a popular choice in pellets or scrap form used with large-scale robotic arm 3D printers.

SLS and binder jetting methods (MJF, HSS, SAF) both use polypropylene in powder form. We take a closer look at these printers in the section below: Powder Bed Fusion 3D Printing with Polypropylene.

Merging the versatility of FDM 3D printing with polypropylene’s material characteristics is ideal for a wide range of products, such as orthopedic devices, auto parts, and sports equipment.

PP filament is widely available in a range of formulations, but the opportunity to 3D print with PP in pellet form is gaining traction as a far more economical alternative for larger projects. In most cases, you can 3D print with the same PP pellets used in the injection molding industry with a pellet 3D printer.

Whether filament or pellets, the semi-crystalline structure of polypropylene comes with its own challenges. High warping stresses are generated as it cools down, often peeling off any first layers that might have had the luck of sticking to your print bed. As bed adhesion and warping are our primary enemies, we’ll run through how you can address them for printing success.

When 3D printing polypropylene, keep in mind that varying the extrusion temperatures can result in different properties within a single 3D printed part. If this is not the desired effect, use an enclosed chamber 3D printer to ensure consistent temperature and no drafts.

Tip #1: Use Clear Packing Tape

Tape is often used as an adhesive aid on print beds, with Kapton tape and blue painter’s tape being classic choices. Unfortunately, these classic options won’t work well here, as PP doesn’t like sticking to other materials.

Thankfully, PP loves to stick to itself, and most packing tapes are made of polypropylene. Therefore, instead of using the above tapes, try printing onto some clear packing tape. (Make sure it’s made of PP.) You’ll likely see a dramatic improvement in bed adhesion.

Tip #2: Use a Large Brim

Try printing with a large brim or raft to combat polypropylene’s high warping stresses. Both methods increase the surface area of the first layers of your prints, reducing concentrated points of warping stresses and increasing the likelihood of your prints succeeding. After printing, they simply snip or peel off.

With PP, you may have to increase the brim or raft size beyond what you might typically use for other materials. Generally, the two can be used interchangeably, though you may find yourself preferring one over another.

Tip #3: Turn Up the Heat

Another way to mitigate warping is to turn up the bed temperature. This will prevent the PP from cooling down too much, thus reducing the amount of contraction. By keeping contraction down, you can reduce the warping stresses that are generated.

A good place to start is your printer or filament manufacturer’s default settings for PP, if available. Otherwise, start at 85 °C and turn up the bed temperature 5 °C at a time until you find an optimal temperature. The sweet spot should be somewhere between 85 °C and 100 °C.

Powder bed fusion (PBF) encompasses the two 3D printing technologies we mentioned above (selective laser sintering and binder jetting) and is often preferred to FDM 3D printing for end-use parts for a few reasons. First, powder bed fusion has better interlayer adhesion than layers of filament. Although this varies with the printer and the process, generally speaking, PBF technologies will produce parts with a better surface finish and more consistent mechanical properties than FDM parts.

The binder jetting processes (MJF, HSS, SAF) are often preferred over SLS for even better interlayer adhesion. In fact, SLS 3D printing with polypropylene is relatively rare since the material has a low melting point and tends to warp or shrink during the cooling process. Many top SLS brands, such as EOS and 3D Systems, do not offer 3D printers compatible with polypropylene powder (opting instead for nylon and other engineering-grade polymers).

Even though these BPF processes use polypropylene powder, all polypropylene powders are not the same. Varying material compositions and parameters often mean these powders are restricted to a specific technology or even a specific brand of 3D printer.

Process-specific advantages of PP include its very high powder refresh rate and comparatively low melting temperature. Similar to FDM however, warpage is a significant concern that not only affects dimensional accuracy but may also lead to print crashes, making polypropylene a particularly difficult PBF material to work with.

If you’re just getting started with polypropylene 3D printing, ordering a few parts from a third-party 3D printing service is a great way to evaluate if the material fulfills your requirements. It’s also the obvious choice if you’re not yet prepared to invest in your own 3D printers.

Services, such as Craftcloud, offer several types of materials in all the relevant technologies so you can compare. For example, upload the digital file of your factory fixture to a service provider, select one printed in polypropylene using FDM and another printed in SLS with glass-filled polypropylene, then put both to the test.

Top 3D Print Services Offering Polypropylene

What do polypropylene parts cost at a service? 

To give you a rough estimate of what some polypropylene parts cost at a 3D printing service, we uploaded several digital models to Craftcloud for an instant quote.

As we mentioned polypropylene is made from fossil fuels, a finite resource with a tremendous impact on the environment, but that doesn’t mean you should write off the material as an unsustainable option because progress is rapid on recycled polypropylene as a 3D printing material.

Polypropylene has the resin recycling code 5 and theoretically offers good chemical and mechanical recyclability relative to other plastics, meaning products made from recycled PP have excellent mechanical qualities. Chemical or solvent-based recycling of polypropylene is known as the Dissolution / Reprecipitation Technique and yields more homogonous recyclate due to the improved capability to remove contaminants. On the downside, this technique is quite energy-intensive, resulting in higher costs and making it difficult for the recyclate to compete with the low price point of virgin material.

US-based PureCycle Technologies is a start-up company with a production facility in Ironton, Ohio, that is developing recycled PP pellets made from post-industrial recycled material, such as reclaimed consumer packaging and other discarded products traditionally destined for a landfill. Once fully operational, the company’s facility will produce 107 million pounds Ultra-Pure Recycled PP pellets that are easily colorable and 3D printable. PureCycle will be offering multiple PureFive grades to customers that include a blend of PureCycle resin and varying levels of post-industrial recycled material or virgin polypropylene.

In fact, recycled pellet materials for extrusion FDM 3D printing, typically with a robotic arm 3D printer, are far more widely available than just five years ago.

The priority, however, when it comes to using polypropylene, or any polymer for that matter, is to think before you 3D print and always keep the waste hierarchy (reduce, reuse, recycle) in mind to avoid unnecessary waste.