Tape, Brims, and Heat: The Secret to Perfect Polypropylene Prints

Although we’re focusing primarily on FDM, if you’re looking for higher volume parts, ones with similar mechanical properties to injection molding, or a smoother surface finish, you can also turn to selective laser sintering (SLS), Multi Jet Fusion (MJF), or Selective Absorption Fusion (SAF) from Stratasys, which are all powder-based technologies and available via 3D printing services if you’re not in the market to own your own industrial 3D printer.

When it comes to FDM, you’d use filament or pellets. In fact, almost any desktop fused deposition modeling (FDM) machine can 3D print with polypropylene filament as long as the nozzle can reach around 265 °C – 275 °C, you can heat the bed to between 80 °C – 100 °C, and you can control the fan speed. The print bed is also important and some manufacturers offer specialized polypropylene print plates to increase the chances of printing success.

To Print PP Your FDM Needs: 

• Nozzle temp to 265 °C – 275 °C
• Heated bed temp between 80 °C – 100 °C
• Polypropylene  print plate or specialized tape/glue
• Enclosure recommended

Industrial FDM machines (MiniFactory, Roboze, Apium, Aon3D, Stratasys, etc.) also process polypropylene as either a filament or pellets. These machines 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.

Large-scale robotic arm 3D printers that use material in pellet form can often 3D print with polypropylene shreds made from post-consumer waste.

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.

Print Profile for PP

Every brand of printer differs, but good starting values are:

• Nozzle: 220 °C – 250 °C
• Bed: 90 °C – 105 °C. If adhesion is weak, increase bed temp slightly. If using bed tape, no heat may be required.
• Chamber temp: 30 °C – 50 °C
• Fan: off or very low (0–20%)
• First layer: slow and hot

Tip #1: Use Tape or Special PP Glue

Polypropylene prints adhere best to polypropylene surfaces. Printing onto a PP sheet or polypropylene packing tape can improve bed adhesion, but tape may degrade at high bed temperatures and results depend on the specific tape used (make sure it’s made of PP). If using tape, you may not need to heat your bed at all but follow the directions that come with your filament.

3D printing adhesive maker Magigoo offers a special glue for your print bed, Pro PP, specifically designed for 3D printing in polypropylene plastics.

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.

First layer brim settings that maximize bonding:

• First layer speed: 15 – 25 mm/s
• First layer height: 0.2 – 0.3 mm
• First layer flow: 105% – 110%
• Wide brim (8–20 lines recommended)

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.

Let parts cool completely before removal. PP contracts strongly during cooling so be sure to wait until bed is near room temperature. This will also help with removal and prevent damage to surfaces.

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

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.